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Aspects of Eucalyptus waferboard Ngusya, Musyoka 1988

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ASPECTS OF EUCALYPTUS WAFERBOARD by MUSYOKA NGUSYA B.Sc, University of Nairobi, 1984 A THESIS SUBMITTED IN PARTIAL FULFILMENT THE REQUIREMENTS  FOR THE DEGREE OF  MASTER OF SCIENCE  in THE FACULTY OF GRADUATE STUDIES FACULTY OF FORESTRY  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA August 1988 ® Musyoka Ngusya, 1988  In  presenting  degree freely  at  this  the  available  copying  of  department publication  of  in  partial  fulfilment  University  of  British  Columbia,  for  this or  thesis  reference  thesis by  this  for  his thesis  and  scholarly  or for  her  Department  DE-6(3/81)  Columbia  I further  purposes  gain  the  requirements  I agree  shall  that  agree  may  representatives.  financial  permission.  The University of British 1956 Main Mall Vancouver, Canada V6T 1Y3  study.  of  be  It not  is  that  the  Library  permission  granted  by  understood be  for  allowed  an  advanced  shall for  the that  without  make  it  extensive  head  of  my  copying  or  my  written  ABSTRACT  Eucalyptus species is already well established in the pulp and paper The species  noted  fast  growth, especially in the  industry.  tropical regions, provides a  special resource for utilization in providing shelter in these regions, which have some of the highest growth in population rates. Waferboard industry, though well established in most developed countries, is rare in most developing countries. The fact that waferboard requires relatively low quality wood, as opposed to plywood, is an important factor and makes it more appealing for development in these regions.  Technical information on utilization of Eucalyptus for waferboard most aspects,  is lacking in  and most of the experimentation has mainly been conducted on  preliminary levels only. The study was carried out to fill that gap and provide data which can lead to increased utilization of the species in the  waferboard  industry. This was achieved by the making of panels under standard conditions and performing standard tests on the specimens cut from the laboratory made panels.  ii  ACKNOWLEDGEMENT  The  author  guidance  wishes to express  he  encouragement  provided  in  the  great appreciation to Dr. L . Paszner for project,  the  late  L.  Valg  for  the  the  initial  and A. Anderson of Forintek Corp, Vancouver, Wood Composite  Lab, for the technical assistance he so generously gave.  Special  thanks  MacMillan  are  Bloedel  to for  the the  people use  at  their  Forintek laboratory  Corp,  CAE Machinery and  equipment.  Generous  advice  received from Ebo Andoh, Drs S. Avramidis and P. Cho is greatly appreciated.  iii  TABLE OF CONTENTS ABSTRACT  ii  ACKNOWLEDGEMENT  iii  Table of Contents  v  List of Tables  :.. vi  List of Figures  vii  1. INTRODUCTION  1  2. SCOPE AND OBJECTIVE OF THIS STUDY  5  3. LITERATURE 3.1. Effect 3.2. Effect 3.3. Effect 3.4. Effect 3.5. Resin  REVIEW of pH on Wood Gluing of Wood Specific Gravity of Extractives of Wettability Type  7 7 8 10 14 16  4. MATERIALS AND METHODS 4.1. Wood Furnish 4.2. Extraction 4.3. Blending and Pressing 4.4. Bending Strength Tests  18 18 19 20 21  5. RESULTS AND DISCUSSION 5.1. Wafers 5.2. Bending strength 5.2.1. Modulus of Rupture 5.2.1.1. Effect of 5.2.1.2. Effect of 5.2.2. Modulus of elasticity 5.2.2.1. Effect of 5.2.2.2. Effect of 5.2.3. Internal Bond 5.2.3.1. Effect of 5.2.3.2. Effect of  24 24 28 28 29 30 31 31 32 32 34 34  Extractive Removal Resin Increase Extractive Removal Resin Change Resin Change Extractive Removal  6. CONCLUSIONS  41  7. REFERENCES  42  8. APPENDICES 8.1. APPENDIX 1 : Statistical Analysis of the Data 8.2. APPENDIX 2 : Comparative data from another species 8.3. APPENDIX 3 : Phsical and chemical properties of the wood used  46 46 64 65  iv  LIST  OF  TABLES  Table 1: Analysis of variance for MOR data  35  Table 2: MOR treatments and their F values  35  Table 3:MOR mean (Mpa) values for all treatments  36  Table 4: MOR range and standard deviation for each treatment  36  Table 5: Anlysis of variance for MOE data  37  Table 6: MOE Treatments and their F values  37  Table 7: MOE mean (Mpa) values for all treatments  38  Table 8: MOE range and standard deviation for each treatment  38  Table 9: Analysis of variance for IB data  39  Table 10: IB treatments and their F values  39  Table 11: IB mean (Kpa) values for all treatments  40  Table 12: IB range and standard deviation  40  v  LIST  OF  FIGURES  Figure 1: Pattern for cutting testing specimen for panel I  21  Figure 2: Pattern for cutting testing specimen for panel II  23  Figure 3: Sample of the Wafers produced  27  Figure 4: Wafer Distribution by Width  27  vi  1. INTRODUCTION  In most parts of the world, increasing attention is being paid to the material resource  required to maintain and generate  the  energy  necessary  to  sustain  community and other activities. In countries where the standards of living remain low,  limited resources now demand greater attention. The use of a particular  resource will depend on several factors. These include the resources' availability and  renewability, and  the  disturbance  to  the  environment  entailed  in their  extraction and harvesting. The amount and type of energy required in production and subsequent processing, application, and disposal is also quite important.  Wood-based materials are more attractive in this respect than most alternative materials. The amount of raw material required and the cost of protecting the environment at all stages, up to the processing of products, is much less with wood  than  with  aluminium,  steel,  or  concrete  (2). The energy  required for  conversion of raw material into products of comparable use such as sawn wood, reinforced concrete, cast iron and aluminium alloys is in ratio of 1:8:16:39 (2). The  energy  required to  extract  logs, to  manufacture  and  to  transport  the  materials to a building site and to construct some house sections, is much less for  wood based materials than for common alternatives (2), in most situations.  Thus, due to these advantages and the rising energy costs, it is justified to predict that the worlds' dependence on forest products will increase. Some of the data used in earlier calculations for projection of global requirements of industrial wood by year 2000, were collected during a period of rapid economic growth and thus neglected the full impact of the energy crisis (33). There is neverthless, an  1  INTRODUCTION unmistakable upward the  rise  may  turn  trend  out to be more modest than some projections. A  increase in the demand considerable do  Admittedly, very  large  for paper and allied products is expected, followed by a  increase in demand for wood based panels. These are products which  not require  emphasis  in the consumption of all forest products.  / 2  will  large be  quantity  placed  on  and/or  growing  high  quality  smaller  logs  logs.  In the future  in shorter  more  rotation and the  utilization of wood waste for reconstituted products.  Future food,  supply water,  of forests is a controversial issue. Certainly, increased and  living  space  will  reduce  the availability  of land  needs for for wood  production. There are three ways in which greater efficiency can be attained: 1. By per  growing more  unit area  wood  of the required  and time.  2. By utilizing the tree more  3. By  properties  taking  other  more  completely.  active  steps  essential needs of the end-user with  to meet the  minimum  amount  of raw material.  This last approach may of use of wood efficient may  through greater  methods of pulping,  be achieved  building  take the form of modifying  codes,  utilization of Eucalyptus  quality control and by using  different and more  paper making, and flaking. Further,  in the other wood  and rationalizing the patterns  the same  goal  industries by modification of construction methods,  protection  methods,  etc. The  is approached from this view.  investigation, of  increased  INTRODUCTION / 3 The forest products industry, in most parts of the world, is facing a decline in both quality and quantity  of available logs, to  satisfy  the  growing domestic  demand, for ' producing lumber and plywood. However, the total wood supply is such that the industry can be maintained at present operating levels and can, perhaps,  be  expanded.  This will  necessitate changes  in using the  total  raw  material base. Production lines will have to be modified or changed altogether to use new types of raw material or other species, particularly for panels.  Eucalyptus species are not usually considered for most structural applications (4). They are used in particleboard plants in Brazil and Australia, either partly or exclusively (18). Further, this species has been shown to be ideally suited for composition board and composite materials. Studies conducted in Zambia, using Eucalyptus grandis, indicated that the species forms satisfactory waferboard panels (18).  Investigation  using  species  of  similar  density  Washington State University showed that flakeboards  range made  carried  from  out  at  alder (Alnus  rubra) had excellent bending properties (24). There is an increased acceptance of Eucalyptus paper and panel products in the forest products markets today (18).  Eucalyptus  has  many  characteristics  which  make  it  suitable  flakeboards, particularly those of structural panels, therefore, conducted panels.  to  determine  the  production  parameters  for  for  use  in  research should be  manufacturing  Short rotation Eucalyptus trees provide wood of lower density,  suitable which  makes it possible to produce a lower density panel product than can be obtained with available conifers. Older trees, with much higher density, higher extractive content and poor bonding by conventional adhesives, present challenges which are  INTRODUCTION / 4 responsible  for the limited  use of Eucalyptus  at the present time  and therefore  must be addressed, too.  Eucalyptus converted because is  grows into  with  wafers.  of lower  expected  a relatively Boards  straight bole. For this reason, it is readily  made  from  material requirement,  to have  better  Eucalyptus  ease  structural  are expected  of cutting  properties  to cost less  and nailing. The product  than  waferboards  made of  comparable species.  There  are several  waferboard studied  rapidly  be  production is concerned.  Suitability  grown trees. The performance  assessed,  using  structural  applications.  Canadian  Standards  building  as far as the successful  use of Eucalyptus for  of the material has to be  carefully. Excessive shrinking and drying defects are common  of young will  panel  unknowns  industry. A  conditions  will  development waferboards  of  These  thorough  base  of Eucalyptus waferboard  to determine  and property  series  CAN  investigation  it possible data  tests  tests  Association,  make a  standard  assess and  with wood  if they  of the boards the potential  performance  are suitable for  requirements,  3-0188-M  panels  formulated  are accepted made under of this  information  in the controlled  product. on  by  The  structural  of Eucalyptus, will greatly aid in the species' utilization. This panel  product could supplement presently inadequate plywood supplies in Kenya. Because of the shrinking raw material base, development of such make it possible for manufacturers an  increased level. The new  applications in Kenya .  to continue to operate  panel product  Eucalptus panels would at the present or at  should fit in with the current panel  2. S C O P E  AND OBJECTIVE  O F THIS  STUDY  One of the major challenges faced in wood utilization is the great variation in properties between and within species. This necessitates a proper understanding of the  properties  of individual  species  before  it  can  be  utilized  for commercial  purpose.  Eucalyptus  spp is currently one of the most promising species for planting in  sub-tropical and tropical countries. Its utilization in the pulp and paper industry is well recognised and documented. In the panel board industry however, the use of Eucalyptus species is quite limited. Problems indicated with its utilization for composite  boards  include: high shrinkage,  poor  gluing properties,  high energy  consumption for processing due to high density, and poor flaking properties (18). With the increasing importance of these species in the tropics, there is a need to  provide  a  data  base  which  can  increase  its  utilization  in  the  growing  composite board industry.  This study was undertaken in an effort to contribute to the data base, which can lead to enhanced  utilization of Eucayptus  species  in the  relatively young  flakeboard industry, and particularly in structural waferboard panel industry for tropical applications.  The following steps were carried out in this study:  5  SCOPE AND 1.  Literature  production waferboard  OBJECTIVE OF THIS STUDY / 6  review parameters  panels from  to  determine for  the appropriate  producing  structural  Eucalyptus sp,  2. preparation of experimental structural panels,  3.  investigation  panels and,  of the strength  properties of these  3. L I T E R A T U R E R E V I E W  3.1. E F F E C T OF P H  ON  Generally,  are  known  most  species  materials, wood  also and  acidic.This  (4). Certain  for instance  has  Kitahara  wood  WOOD G L U I N G  been  woods, have  corrosion shown  Mizumo  (22)  were correlated with pH  has  to  been  cause  utilization  the  wood chips  for  Goto and glue  joint  Onishi  (15)  strength  and  strength  with a change in wood  on  and  other hand, observed  pH  were  properties  wettability and  increased  the  pH  showed  that the  significant.  that  of the  extractives  amount it was  of  cold  observed  or that  hot both  Rather  specific  Goto (34)  affected.  7  study  by  acid in  time  gravity  a  and  and  indicated that  pH  0.8.  improved  tested. The  (27).  With  pH  of the  the  gelation  were added, increased  extractives  gelation  A  relationship between  wood in all species  water  other  of particleboard  removal of extractives  time of urea formaldehyde to which wood extractives increased  to  Gray (8) reported  affected wettability of wood having specific gravity lower than  study of tropical woods (27)  damage  of  pH.  wettability were more important factors. Sakuno and  A  number  that in some cases, the  the  not  a  problems.  wood is sufficient to precure urea resin adhesive. Chugg and change of joint strength  for  western red cedar (23). Acidity in  other  that  demonstrated responsible  of metals, by  indicated  of the  been  cold wood  with water were  LITERATURE  REVIEW  / 8  3.2. E F F E C T OF WOOD SPECIFIC G R A V I T Y  Extensive  work has been carried  of wood. A casein  out on the effect of specific  gravity  on gluing  study done on gluing of fifteen species using urea formaldehyde  adhesives, showed  that  urea  formaldehyde  adhesive  was  and  less sensitive to  specific gravity variations than casein (8).  Troop  and Wangaard  their  gluing  formaldehyde increasing  (38) investigated  characteristics.  Resorcinol  adhesives were used  specific  gravity  twenty-nine  formaldehyde  for gluing. They  the joint  tropical  American  and  woods  phenol  generally, observed  strength increased but the amount  on  resorcinol that with of wood  failure decreased. Interference of the glue curing, as evidenced by high variability of bond strength values, was noted. This was attributed to probable wood surface defects  or the nature  of chemical  components, such  as gums, resins, oils, and  waxes which occured at various levels in the wood extract. They concluded that, due  to  variations  in  specific  gravity  within  the  species,  interference  from  extractives was partly obscured in the shear strength data.  On  the effect  joints, Freeman  of specific  gravity, p H  (10) found  that  and wettability  specific  gravity  was  on the strength of glue of prime  importance.  High  specific gravity woods were found to give higher bond strength.  Carstenen  (5) working  variation  of  density,  with both softwoods grain  and hardwoods observed that the wide  configuration,  characteristics were well reflected in gluability.  moisture  content  and  surface  LITERATURE Goto  and  Onishi  (15)  studied the  percentage of extractives on high  degree  glue joint  of correlation  strength  effect of specific gravity, wettability, pH,  gluability  between  increased  as  investigated, specific gravity was  REVIEW / 9  of eighteen  glue joint  specific  tropical woods. They  strength  gravity  and  increased.  specific Of  the  and  found  gravity.  a The  four factors  shown to have the greatest effect on  glue joint  strength, followed by wettability.  Yagishita  and  Karasawa  (40), in their investigation of fourteen hardwood species,  reported that the correlation between bond strength and that, the  higher  formaldehyde  density  adhesive  species  and  showed  higher  specific gravity was  values  melamine  formaldehyde.  Goto  attemped  of strength  with  Urea-formaldehyde  such phenol  did  not  show a similar trend.  In  their  specific  study, gravity  studied thirty glues.  Their  effect on  Sakuno ceases  and to  six species using conclusion  was  found to be  opposite trend. There was values  of  0.8  and  no  significant both  that, up  the joint strength. At  specific gravity was  for  have  (34)  urea to  specific  effect  on  find  the  glue  joint  formaldehyde and 0.8,  specific  gravities  point  which  strength.  They  phenol formaldehyde  gravity had  higher  at  than  0.8,  a the  significant effect of  insignificant. Wood failure, however, showed the  correlation between wood failure and  lower. However, wood  showed significant correlation  to  at the  Moriya (26), working with red lauan  5%  with  specific  gravities  level. Similar results  sawn boards.  specific gravity above  0.8  were obtained  by  LITERATURE REVIEW  3.3. E F F E C T OF  /  10  EXTRACTIVES  Numerous studies have shown that extractives significantly affect gluing properties of wood. However, little these and  extractives. The quantity vary  species may  Troop which  problem  within  not be  and  shed  among the  surface  some  in  their  light  on  Vitae  review this  to improve  caustic  soda  minutes and This  test  to  improve  combination  the  study  gluability  solution  then removed an  of sanding  shear strength and  A  the  (NaOH)  showed  carried  and  the  fact  a  mode of action of that  extractive type one  by  increase and  of  the  subject, cited investigations Rappt  studied  the  gluing  (Guaiacum officinale L.), a species which is known investigated the possibility of various  gluing  performance  of the  wiped  removal  of, at  least,  solvents used included  ethyl alcohol. None of these  solvents  specimen. However, application of  on  the  washing with in both  by  in the wood. The  tetrachloride, benzene, acetone, and  seemed  by  matter.  most difficult to glue. He  treatments  nature  individual trees therefore findings with  part of the resinous extractives contained carbon  the  is compounded  species and  (38),  characteristics of Lignum to be  about  universally applicable to others.  Wangaard  have  is known  the  caustic soda  surface,  allowed  water, improved shear  strength  treatment  gave  to the  and still  react bond  for  10% 10  strength.  wood  failure.  A  higher  values  of  wood failure.  out  by  Gamble  Brother  Inc,  indicated  surface of teak, which contains oily extractives, with  that  washing  of  the  acetone improved joint shear  t original not seen, cited from Troop and Wangaard (38)  LITERATURE REVIEW strength  and wood  hand reported  failure  substantially. Troop  and Wangaard (38), on the other  that Burma teak does not necessarily require  when glued with resorcinol adhesive, but may and  maximum  bond  strength  is needed,  / 11  preliminary  treatment  require pretreatment if permanence as  in high  quality  furniture  and  plywoood.  In his review of extractives effect on wood, Narayanamurti (27) pointed the  distribution of extractives  bole. Extractives  varies  both  affect the hygroscopicity,  vertically swelling,  and horizontally  out that in a tree  and shrinkage of wood. The  effect of extractives in gluing of wood is of special importance. Nayanamurti (27) reported  that  different researchers  observed,  sapwood which has a lower extractives conditions  and  with  gluability of Diospyros which  in turn  considerable  treated  than  is improved with  testing  of glue joints,  that  content, can be glued better under some  adhesives  melaxylon  were  glue joint  Narayanamurti  certain  during  heartwood.  He  found  by extraction. Further,  extractives  from  Dispyros  that  other  the  species  melaxylon  lost  strength.  et al (28) studied  adhesives. Wood extractives  the effect  of extractives  on  the setting of  affect the bonding of wood but their effect may  vary  from glue to glue. Viscosity and rigidity of the glue was found to be affected by the  presence of extractives. The effect of extractives  and  time of gelation in adhesion was investigated, using  with  animal  increased  and  urea  the gelation  depended on the species  formaldehyde time  and  glues.  lowered  They  on the modulus of rigidity teak and Acacia  found  the rigidity  that  of glues  the  Catechu  extractives  but the effect  being glued. Teak extractives were more inhibitory than  LITERATURE REVIEW  / 12  those of the Acacia.  Chugg and surface  Gray  and  (8) reported  reduce  that extractives lower surface  wettability, which  wood species contain traces of low could  easily  refractory  migrate  surface  This  molecular  surface  during  if the  strong  weight fatty drying  surface  or  glue  acids or  hot-pressing  tension  of  the  surface  so  is more likely  that they with  glues  remain  completely  possessing  a  resins which  wood  form  a  becomes  of contact of  free from  high  wood  bond. Most  and  glue tends to display a definite receding angle  of the  behavior  the  layer. Thus,  sufficiently low, the some parts  to  is essential for a  tension of the  surface  the  glue.  tension  such  as cold setting phenol formaldehyde or urea formaldehydes.  Hancock  (16)  reported  that Douglas  fatty acids concentrated the  at the  wettability of veneer and  glue. In  a  microsections removed by catalysts  study  on  surface  of  white  spruce  time periods  temperatures,  had  acids were shown to reduce  to affect the rate and  depth of penetration of the  inactivation (Picea  for oxidation. Wood  dried at high  surface. These fatty  varying degrees, Chow  for prolonged  fir veneer  of wood  glauca  at  Moench  to temperatures  temperatures,  Voss) that  (7) found that the  exposed  high  had  extractives  extractives may over  suffered additional oxidation and  180  using  serve  as  degrees Celcius  pyrolytic  degradation,  particularly at the surfaces.  Goto  and  relationship by  Onishi between  (15)  in  the  cold or hot water was  their  glue joint not  study  of  strength  tropical and  woods  percentage  reported  that  the  of extractives either  significant. However, glue joint  strength  increased  LITERATURE with  the  decrease  effect of specific pH than  and  of percentage gravity  percentage  wettability  observations  was  excluded. They  extractives  and  in their  of extractives  specific  were  less  gravity.  investigation  in the  solubles  when  Sakuno  on  and  the  glue joint strength  Goto  six tropical  (34)  made  species. They  similar reported  that specific glue joint strength (shear strength of glue joint/ specific gravity) significantly correlated adhesive  to the percentage  (for woods of specific gravity  correlation at the 5 %  of ether extracts for urea 0.8  and  below). There  was  Chen (6), using eight tropical woods studied  solution  and  wettability.  (10%), acetone  formaldehyde improved  and  the  increased  pH  of  existed  formaldehyde.  formaldehyde; pH  formaldehyde no  significant  used  for extraction  formaldehyde  adhesive the  used.  wood  between  due  in  no  to the  by  such fact  species  and  joint  the  joint  10%  than  A  observed  resorcinol  hydroxide with  strength  urea was  the others,  wettability positive  strength of blocks was  on  solution of sodium  improved  examined.  correlation that  glued  treatment  removal  tolerant than that of the urea formaldehyde  Imamura et al (20), observed  the  sodium  were  Glue  species. With  more  all the  were  woods  adhesives.  Extractive  wettability  However,  possibly  affected  0.8.  the effect of extractive removal  alcohol-benzene. The  species were  of  urea  and  resorcinol  regardless  correlation  Solvents  by all treatments for all, but one  hydroxide, some  was  level of significance between glue joint strength and percent  ether extractables of wood species with specific gravity higher than  adhesion  the  further reported that the value of  important  of thirty  ether  R E V I E W / 13  glued  and linear with  for resorcinol  condensation  is more  system.  that phenol formaldehyde  adhesive was  inhibited in  LITERATURE {Dryobolanops  kapur  wood  curing  of paint  study  also  films  showed  sp). These  with  that  extractives  unsaturated  only  certain  polyester fractions  inhibitory effect while the rest of the extractives and cold  Goto (29) investigated water,  boiling  water  and  alcohol-benzene  results showed that  increase For  gelation  found  resin varnish  wood  on  the gelation  it was  an  strength  time  of urea  of the glued  material.  time of urea formaldehyde  extractives,  exerted  isolated with the aid of  observed  that  decreased with decreasing pH. Alcohol-benzene extractives  also  on  water  type. The same  had no inhibitory effect. Onishi  increased  of added amounts of cold and boiling water extractable  the cold  / 14  to inhibit the  of the extractives  the effect of wood extractives  formaldehyde resin and the resulting compressive The  were also  REVIEW  with the  wood extractives. the gelation exhibited  time  an effect  the gelation time of urea formadehyde though to a lesser extent than did the  soluble water extractives.  In  summary, previous work on the effect of extractives  indicates, that  extractives  in general  affect gelation  time  on the resin chemistry and the ability  of the  adhesive to wet the wood surface. Hence, with high extractive content woods the resin chemistry has to be adjusted in order to maintain optimum condition the  during  resin polycondensation process.  3.4. E F F E C T OF WETTABILITY  The  intended function of an adhesive cannot be fully realized unless the adhesive  spreads  effectively over  minimized  and good  the wood  chemical contact  surface.  Surface  with the wood  irregularities substrate  have  to be  made, so that  a  LITERATURE REVIEW permanent, high physical the  strength bond is developed between the glue and the wood. The  quantities which  surface  adhesive  / 15  tension  determine  effectiveness of spreading  of the wood  surface  and  interfacial  and adhesion are  tension  between the  and the wood.  It has been clearly demonstrated that glue bond strength is correlated to surface wettability been  (1, 2, 3, 6). The adhesion  studied  extensively  theory  relating  to surface  (10). The concept of equilibrium contact  energetics has angle  and the  methods of measuring it on wood surfaces have been developed (10). Most of the wettability  measurements  on  wood  have  been  made  using  homogeneous liquids,  such as water. A n investigation on wetting of wood by liquids of varying surface tension, pointed wetting,  out the probability that bond  spreading,  ascertained content,  that  bond  and wood  increase  more  and  surface  tension  of  quality is signficantly  surface  rapidly  in  characteristics  strength the  is closely dependent upon  adhesive  (15). Thus,  it is  influenced by the wettability, resin  (18). Viscosity  woods  of  high  in wettability are caused  by  contamination  of glue  was  found to  than  those  showing  wettability  non-wetting behavior (12).  Changes  active chemicals of low molecular the  of the wood  which reduce surface tension (19). The chemicals weight fatty or resin acids which migrate,  may  surface  by  be traces  from the interior, to  surface and lower the surface tension and reduce wettability. Tests based on  wet-shear shown  strength,  that  a  quality (25). .  percent  of wood  positive correlation  failure  and  percent  of delamination  have  exists between  contact  angle  bond  and glue  LITERATURE REVIEW / 16 In some cases, extractive  removal has  improved wettability  and increased pH  (33). At the same time, a reverse correlation has been demonstrated with specific gravity. Wettability decreased with increasing specific gravity. Further glue joint strength increased with increase in wettability when the effects of specific gravity are excluded (30).  The  interaction  of specific (35).  gravity,  Sakuno  and  Goto  Specific  gravity)  and  wettability were  wettability  glue joint  and  adhesive  strength  was  (shear  significantly correlated  at  the  studied  strength  /specific  5% level for all  species with specific gravity of 0.8 and below for both urea formaldehyde phenol formaldehyde  resins.  No correlation  was  observed  by  between  and  specific glue  joint strength at the 5% level for species having specific gravity higher than 0.8.  3.5.  RESIN  TYPE  Although the possibility of using phenol formaldehyde recognized at the end of nineteeth century,  resin as an adhesive was  it was not until the  1930's  liquid phenolic resin were used commercially (24). Presently, phenolic resins  that are  the most widely used adhesives in plywood, waferboard, glulam beams production as well as, boat construction.  Most commercial phenolic resins  are  prepared  by the  with specific phenols. The phenolic resin is manufactured  reaction  of  formadehyde  in two basic ways: an  initial addition reaction between phenol and formaldehyde to form alcohols, and a subsequent condensation  reaction  in which a phenol alcohol reacts either with  LITERATURE REVIEW / 17 itself or with another phenol. Then, in turn, these products react with each other by further condensation reactions.  In the initial step, if the phenolic resin is prepared with excess of formaldehyde at high pH (10-12), the product will be a phenol alcohol with a number of methylol groups. When this resin is subjected to heat or acid, it is capable of further  polymerization. The process can be slowed down at any stage between  the addition reaction and final cure, by cooling. The reaction can be accelerated by  increasing  the  temperature  or  adding  an  acid  catalyst.  Thus,  the  polymerization of this resin is continuous and whereby it bears the name "one stage resin" or resole.  On the other hand, if the phenolic resin is prepared with an acidic catalyst and less than one mole of formaldehyde per mole of phenol, the resin will be a linear,  structure  similar  to  dihydroxydiphenylmethane and  the  chains  will  be  phenol terminated. The limited amount of crosslinking in the structure of this resin makes it permanently fusible and soluble; it will cure only upon addition of a curing agent, consequently it is normally referred to as a "two stage resin" or novolac. The resin used in this experiment was a one stage resin, PF-IB947  4. M A T E R I A L S A N D  METHODS  4.1. WOOD FURNISH  Eucalyptus  globulus  logs  were  secured  for the  experiment  Forest Products Laboratory in Richmond, California. Two cm  in diameter  billets. The  and  billets  approximately  measured  15 cm  4  65%.  cm  The  from  attributable using  billets,  to the  their  disc  water  cm  and  width of 0.5  dimensional  drum  Total  their  Wafers weight  were of  cm.  A l l wafers  of wafers  1/100  mm,  were  facilitate  had  were  with  weight). After drying to 7%  This  (determined  removed by  most  weighing)  of the  of the  Richmond  cm  and  into  30  quarter  waferizing, the billets  30%  weight  produced  at the  CAE  was  particles furnish,  wafers were used for the extractive procedure.  18  all  plant,  about  34  an average length of  equal thickness  determined  was  using  of 0.76 a  mm.  vernier  All  calipers  sampling of all the wafers  moisture content in an electrically  fine  wood  which  produced  wafers had  random  cutting sample of  gain,  dryer; the wafers were screened to remove fines using  screen.  split  a cubed  wafers  moisture content. The  measurements  capable of measuring (based on  65%  logs of 20  in length  determined by  determining  absorbed.  waferizer.  Kilograms at around 2  and  the  days, then air-dried to a moisture content of  moisture content was  the  cm  in length. To  were soaked in warm water for 30 about  60  from  which  heated  a of 6-mesh plate  constituted  (Fig 3). About  50%  about  12%  of these  MATERIALS AND METHODS / 19 4.2.  EXTRACTION  TAPPI 12 SO-75 (41) procedure for removal of extractive was used, with slight modification  due  ethanol-benzene  to the  size of the  (50:50) to extract  particles involved.  waxes, fats,  This  involved  use of  and some resin and posssibly  some of the wood gums. Hot-water was used to extract tannins, gums, sugars, starches and colouring matter.  Five grams of wafers were wrapped with a nylon cloth material and placed in a paper thimble positioned in the Soxlet apparatus. Extraction with 200 cc solvent was carried out for 48 hours, with  the  liquid kept boiling briskly to  effect  siphoning from the extractor of no less than two times per hour.  After extraction with ethanol-benzene, each sample was transferred to a Buchner funnel  to remove excess solvent with suction and both the  thimble and the  sample were washed with ethanol to remove the excess ethanol-benzene. The sample was then returned to the thimble for further extraction with 95% ethanol until the siphoning solvent turned colorless. Again, the sample was transferred to a Buchner funnel to remove the excess solvent with suction and washed with distilled water to remove the ethanol. The wafers were then transferred to 100 cc Erlemeyer flask containing water and heated for 12 hrs in a hot-water bath. The water was kept boiling before the sample was added and the flask  was  surrounded by boiling distilled water. After this process, each sample was filtered and washed with 500 cc of boiling distilled water. This was followed by drying the wafer sample to 7% moisture content. Moisture content was determined by  MATERIALS  AND METHODS  /  20  drum,  at  use of a M o i s t u r e Teller.  4.3. BLENDING AND PRESSING  Powdered  phenolic resin  the  Composites L a b of F o r i n t e k C a n a d a  Wood  was  applied first at  and  6%.  Mats  were  pressed using This  a  time  Pressing found  was the  time  to be  panels.  by  hot-press  pressure  throughout  the  a  wax  1% level  formed  in  and  with  of 3 8 x 3 8 4133  found  to  Kpa  Corp.  (15x15  (600  psi).  boards  for  all  i n s u r i n g full  However, optimum  wafers  resin was  to  closing  relatively  proportioned at  randomly.  in), heated  of  rotary  i n V a n c o u v e r . W a x emulsion  oriented  Press  in a  205  time  Boards  degrees was  uniform  45  3%  were  Celsius,  seconds.  density  profile,  board.  minutes  adequate for  the  cm  produce  thickness of the  five  applied separately  (2% solids) while the  hands  of  was  were  pressing  boards.  This  r e s i n cure  and  conditions  time  was  experimentally  m i n i m u m heat damage  were  not  established  for  on this  experiment.  In  a l l , eight  wafers trimmed length.  and  panels four  size; 1.27  were  with  made  by  unextracted  this  process.  wafers.  cm(7/16 in) i n thichness,  F o u r were  A l l the and  panels  made were  34.56 c m (14  with of  extracted the  same  in) i n w i d t h and  MATERIALS AND METHODS / 21 4.4. BENDING STRENGTH TESTS  Fig 1 and 2 show the test specimen cutting pattern used for each treatment. Testing included modulus of rupture  (MOR), modulus of elasticity (MOE) and  internal bond (IB) for both panel types. All tests were done in accordance with CSA  Standards  CAN3-0188.0-78,  for  Waferboard. Computation of strength shown in the standards.  Mat-Formed  Wood  Particlesboards  values was in accordance  with  procedure  Dimensions for each bending test specimen were  mm in thickness, 75 mm in width and 254mm in length (span). bending and IB tests were carried out.  and  11.1  Only dry  22  Fig 1. Pattern for cutting testing specimen for panel  23  Fig 2. Pattern for cutting testing specimen for panel II  MOR/MOE  MOR/MOE  MOR/MOE  MOR/MOE  -i  r  5. RESULTS AND  DISCUSSION  5.1. WAFERS Figure  2 shows  an  example  of  the  wafers  produced  and  used  for  board  preparation. Average dimensions were about 72 mm in length, 22 mm in width and 0.76 mm in thickness. Thickness and length were kept roughly constant for all the particles produced. Width varied greatly as shown in Fig 3.  The particle dimensions conform with the recommended standards which indicates that wafer thickness may range from 0.254 mm to 1.5 mm. The width be 5 to 60 times the size of thickness, and length be 40 to 100 times the size of thickness (24). The average ideal wafer dimensions are thickness 0.64 mm, width 20 mm, and length of 68 mm (25).  Wafer length-to-thickness ratio is a better measure of the effect of wafer length and thickness on bending strength and stiffness than either of the two considered separately  (26). The average  this experiment characteristics  was  wafer value, computed as a slenderness  98.6. This value is related to an array  such as  contact  area  in the mat,  ratio for  of vital board  mechanical properties  of the  finished board, and consumption of the binder per given set of board properties. Since this value is lower than values encountered with other species, , eg aspen = 100, a high resin requirement was indicated.  Another  parameter,  known  as  flatness  ratio,  a  factor  of wafer  width and  thickness has a great influence on board separately (26). It is a better measure 24  RESULTS of  the  effect  stiffness  than  flatness  ratio  of  wafer  either  width  and  of the two  computed  for  thickness  dimensions  the  wafers  on  board  considered  used  AND  in  D I S C U S S I O N / 25  bending  strength  separately.  this  The  experiments  and  average was  30,  representing a rectangular cross section (w/t>l).  Wafer surface area per unit weight is a highly important parameter, which must be  considered  surface  in resin  application  if adequate  bonding  is to be  area per unit weight of a given wafer not only depends on  of the wood species from which it is produced, but also on Geimer  achieved. The  (28) identifies  wafer  size  the density  the wafer  as having enormous influence  on  size (27).  surface area  per unit weight.  The  average  length  to width  provide orientation (27). M O E and in  geometry waferboard  ratio and  was MOR  in boards with randomly is also  affected  by  3.3, slightly  higher than  are highly dependent  on  arranged wafers. Water  wafer  geometry  3  required to  the wafer absorption  (28). Its effect  on  size (WA)  water  adsorption can probably be related to the change in surface area covered by the resin and by  its bulking effect. Geometry may  also affect water  causing mechanical restraint in the board from  and density variation.  absorption indirectly  stresses induced by  crushing  RESULTS AND DISCUSSION / 26  Fig. 3 :  Sample of Wafers produced and used f o r p a n e l p r e p a r a t i o n .  FIG 3 . W A F E R D I S T R I B U T I O N  RESULTS 5.2. B E N D I N G  Two  This  are  (MOE).  stress i n the  extreme  i n pascals  bending  strength  stiffness  of the  of  properties  M O E , as  MOE  and  strength, to  upper  and  and  and  flexural  material are  as  was  extractive  to  siding  rigidity.  In  4  from  subflooring,  most  specimen under  test.  under  elasticity  the  range  boards  face  to  and  applications, waferboard  Standards  give the  model  perpendicular  fiber  test and  for this parameter  i n pascals.  sheathing,  M O R i n the  removal  reported  for  Tables  and  also  of  p a r t i c u l a r l y important  of  evident  it is  Modulus  maximum  product  used interchangeably  strength.  determined  5.2.1. M o d u l u s  is  and  of the  and modulus of  computed  fibers of the  the b r e a k i n g strength  (Pa). Other terms  Canadian  1 to  and lower surface  is the  (MOR),  ( M O E ) refers  In  waferboard,  of the  is are to  both  panel. M O R  indicated earlier, were determined by centre loading.  such  plywood.  MOE  as  M O R are  application,  modulus of rupture  T e c h n i c a l l y , modulus of rupture  reported  and  u s u a l l y measured:  value is regarded  these  / 28  STRENGTH  properties  elasticity  A N D DISCUSSION  Association  used  industrial is used  recommends  of 4,000 M P a and  be  for  structural  parts  requiring  as  an  alternative  m i n i m u m values  of d r y  18.6 M P a , respectively.  Rupture  Table  statistical analyses 3,  the  of extractives  significant at  the  r e m o v a l accounted  effect  had  of c h a n g i n g resin  significant  5% level. for  of M O R of the  The  60% of the  influence  panels  content,  on  tested.  from  M O R . Thus  combined effect  3% the  A s it to  design  of resin change  total M O R increase  as  6%,  and  indicated by  RESULTS  AND  DISCUSSION / 29  the coefficient of determination of 0.600. Variation throughout  the experiment  quite  of  moderate  as  indicated  by  analysis of the data, Table pronounced effect than the higher F  an  coefficient  4, showed  was  no  of  variation  that removal  increase in the  value. There  content change and  a  16.407. Further  of extractives  had  a  more  amount of resin. This is explained by  significant  resin change. It was,  was  interaction  between the  extractive  therefore, possible to analyze the effect  of each individual treatments.  5.2.1.1.  Effect of Extractive  Tables  3  MOR  and  was  4  show  statistically  Removal  the  effect  insignificant  considerable increase in MOR resin level, the average  of extractive at  the  values namely  5%  removal. . Although level,  46%  there  at 3 %  increase being 44.5%. As  was,  the increase neverthless  resin level, 4 3 %  it is observable from  a  at  6%  Table  6  however, the standard deviations for all the means did not differ very much.  The  increase  between  in  individual  MOR  values  wafers.  phenomenon, extractive  is an  Since  removal  to some extent, though it was observed by Troop and  bonding was  the chemical effect. Tables 3 and  indication is both  expected  to  of  improved a  physical  reduce  the  strength  and  chemical  a  negative  extent of  4 show that a reduction in inhibition did occur  statistically  insignificant. Similar observations were  Wangaard(38), using teak wood. The  be dependent on other factors.  bonding  effect therefore must  RESULTS AND DISCUSSION / 30 5.2.1.2.  Effect  of Resin  Increase  Tables 3 and 4 show the effect board  MOR. There  was  some  of doubling the amount of resin applied on increase  wafers,  3.4% for unextracted  wafers  increase  in MOR values attributable  in MOR values:  and an  average  to doubling the  2.3% for  increase  extracted  of 4.3%. The  resin content  showed no  significant effect at the 5%, or 1% level.  Ideally, an increase in resin level should increase MOR values as it provides more bonding sites. There is, however, an optimal level beyond which, increased levels of resin would have a negative effect on the strength properties of board, as well as being wasteful. For most commercial operations (40), with low density hardwoods and softwoods as sole source of raw material, a resin level of 3% is common. Recommended level is at 5% (40). As can be observed from Tables 1 to 4, the optimal application level for powdered resin is lower than 6%. The expected level for liquid resin should be less, since it flows easily.  RESULTS AND DISCUSSION / 31 5.2.2. Modulus of elasticity  Table 8 shows the effect of both extractives removal and resin change on MOE values of the experimental board. Generally, the mean values were quite high, three to four times higher, as compared to other commonly used species like aspen (Appendix 4). This difference is explained by fact that the species used is a particularly high-density hardwood species. Tables 7 and 8 list these values. The combined effect of both treatments had a considerable effect but statistically insignificant increased  at the  5% level. The treatment accounted for about  MOE values  whereas  the  coefficient  of  determination  58% of the was  0.575.  Cofficient of variance was 16.612.  5.2.2.1.  Effect  of Extractive  Removal  Absence of extractives had the same effect on both MOE and MOR. An increase of 23% was realized at 3% resin content and a 36% increase was found for MOE values for the 6% resin level application. Both changes were statistically insignificant at the 5% level. There was a higher MOE increase at the high resin level compared to the lower one. Removal of extractives had the same effect on MOE values as the change of resin content.  RESULTS 5.2.2.2.  Effect of Resin  Doubling  of  MOE  of the  made  of  wafers. from  resin  Table  from  specimen.  The  7, the  3%  There  wafers,  average  and  increase  increase  strength  indication  properties  that  higher t h a n  the  to  was  6%  a  was  resulted  39%  25%  increase  increase  32%  in  notable  increase  i n M O E values  for  ( see  a  32  boards  Tables  7  made and  for  of  8).  of  than  of resin level removal  o p t i m a l level  of  had  a  more  extractives  of application for  this  the  boards  unextracted  As  is  evident  i n M O E values, though considerably substantial,  statistically insignificant. Increase the  /  Change  level  extracted  A N D DISCUSSION  were  pronounced effect  (Table  8).  This  on  is  an  particular e x p e r i m e n t  was  3%.  5.2.3. Internal Bond  Tensile  strength  perpendicular  to  long time, a n d is also referred of  the  bond  quality between  indicates  the  preparation;  It  adequency  boards  is  an  of  the  blending, forming,  surface  of the  board has  been  used  to as internal bond. It is the best single  of manufactured flakes.  the  because  important  and  three  it  test  most  pressing.  include:  4.  board density,  5.  board thickness,  indicates  for  quality  fundamental Factors  which  the  processes affect  a  measure  strength  control  for  of  the  because for  internal  it  board bond  RESULTS AND  DISCUSSION / 33  6. orientation of the flakes, 7. density profile,  8. moisture content,  9. resin type, distribution and level.  Both  resin  increase and  shows that both board  at the 5 %  removal  treatments  had  level. The  of extractives  affected  found  for all the  treatments  data.  accounted  for about  This  is an  indication  the combined effect of both treatments was  IB was  treatments  did not seem  values. Interaction  significant, separately. compared  of the strength  16.6122, a constant  of consistence  in the  statistically siginificant  significant. The total increase in  49%.  Individual bond  57%  about  experiment. Thus, it can be concluded that the model was and  12  a significant effect on the internal bond of the  increase (R-squared = 0.57). Coefficient of variation was value  internal bond. Table  thus, the The  between  effects  average  to have  extractive  of the  values  of  a  significant  removal  individual internal  and  treatments bond,  effect resin  obtained  3 to 4 times as high.  the internal  change  could  to those obtainable with other species as evidenced  8.3. Sometimes the former were  on  be  were  was  not  investigated quite  in Table  high  appendix  RESULTS AND DISCUSSION / 34 5.2.3.1.  Effect of Resin  Change  The increase of resin level from 3% to 6% had the same effect on the IB as it had on MOE and MOR. There was a substantial increase on the boards IB strength values with increased resin level (Tables 11 and 12). The increase was more pronounced with boards  made  of extracted  wafers.  A l l the  changes  in  strength values were not statistically significant.  5.2.3.2.  Effect  of Extractive  Removal  Tables 11 and 12 show the effect of extractive removal on the internal bond. Among the three strength properties investigated here, internal bond is the most sensitive indicator of the bonding strength and hence, the adhesion between resin and wafers. As indicated in the Table 11 removal of extractives did not change the internal bond value significantly. Viewed in percentage  change, the increase  was considerable at both resin levels; 22% increase at 3%, and 35% at 6% resin level. It was observed that removal of extractives had a more pronounced effect at the high resin level than at the lower levels. It is probable that the removal of extractives means that less resin is used in combating the negative extractive effect, and hence the amount applied is directly available for bonding the wafers together.  Troop and Wangaard (38) did observe increased strength values with  extractive removal.  RESULTS Table  1. A n a l y s i s of variance  Source  DF  Model Error Corrected Total  3 28 31  Source Resin  Wafer Resin* Wafer  for M O R data. S u m of Squares 3552.25 2363.75 5916.00  Table 2. M O R Treatments DF 1 1 1  A N D DISCUSSION  Mean  Square  + F  1184.08 84.42  Value  14.03  a n d their F Values ANOVA 190.133 3362.00 0.125  SS  + F Value 2.25 39.82 0.00  /  RESULTS AND DISCUSSION / 36 Table 3. M O R mean (Mpa) values  for a l l treatments.  +  Resin 3 6 Wafer Ext Unx Resin  Sample size 16 16  Mean 53.56 58.44  16 16 Wafer  66.25 45.75 Sample size  MOR  3 3 6 6  Ext Unx Ext Unx  8 8 8 8  63.75 43.38 68.75 48.13  MOR  +  Table 4. M O R range and standard deviationfor each Resin Specimen level (%) N O Wafers extracted 3 8 6 8 Wafers unextracted 3 8 6 8  Mean  Std  63.75 68.75  43.38 48.13  Dev  treatment.  +  Std E r r o r  Minimum  Maximum  7.722 9.407  2.730 3.326  52.00 58.00  74.00 84.00  10.528 8.871  3.722 3.136  27.00 35.00  59.00 60.00  RESULTS AND DISCUSSION / 37 Table 5. A n a l y s i s of variance M O E data. Source  DF  Model Error Corrected Total  3 28 31  Sum of Squares 277939991.60 238482904.63 516422896.22  +  M e a n Square  F Value  92264666.86 8517246.59  10.88  Table 6. M O E Treatments a n d their F Values Source Resin Wafer Resin* Wafer  DF 1 1 1  A N O V A SS 144461752.53 122415800.78 13062438.28  + F Value 16.96 14.14 1.53  RESULTS A N D DISCUSSION / 38 Table 7. M O E mean  (Mpa) values for all treatments.  +  Resin 3 6 Wafer Ext Unx Resin  Sample 16 16  Mean 53.56 58.44  16 16 Wafer  66.25 45.75 Sample  3 3 6 6  Ext Unx Ext Unx  8 8 8 8  size  MOE  size  MOE  +  Table 8. M O E range Resin Specimen level (%) N O Wafers extracted 3 8 6 8 Wafers unextracted 3 8 6 8  and standard  12778.44 17027.88 16843.00 12963.31  deviation  for each  treatment.  Dev  Std E r r o r  Minimum  Maximum  Mean  Std  14079.38 19606.63  2505.800 3089.76  88.934 1092.400  10007.00 15620.00  18223.00 23250.00  11477.50 14449.13  2160.640 3684.422  763.900 1302.3.640  9916.00 10849.00  16277.00 22802.00  R E S U L T S A N D D I S C U S S I O N / 39 Table 9. A n a l y s i s of variance for IB data. Source  DF  Model Error Corrected Total  3 28 31  Table  Sum of Squares 279400.38 209490.50 488890.88  Mean Square  F Value  93133.46 74.81  12.45  10. IB treatments and their F V a l u e s  Source Resin Wafer R e s i n * Wafer  DF 1 1 1  A N O V A SS 2926.13 276396.13 78.1  + F Value 0.39 36.94 0.01  RESULTS A N D DISCUSSION / 40 Table 11. IB mean (Kpa) values for a l l treatments. Mean Resin Sample size 16 511.125 3 6 16 530.25 Wafer 613.50 16 Ext Unx 16 427.75 Wafer Sample size Resin Ext 3 8 Unx 3 8 Ext 8 6 Unx 8 6  Table  12. IB range  and standard  IB  + IB 602.50 419.75 624.75 435.75  deviation.  + Resin Specimen level (%) N O Extracted Wafers 3 8 6 8 Unextracted Wafers 3 8 6 8  Mean  Std Dev  Std E r r o r  Minimum  Maximum  602.50 624.75  72.016 79.430  25.461 28.083  510.00 507.00  686.00 750.00  419.75 435.75  109.514 80.240  38.719 28.369  200.00 295.00  509.00 553.00  6. CONCLUSIONS  This  study  was  done  on  limited  therefore  do not  sampling  is reqiured on a l l the  can  made.  under  this  quantity  necessarily reflect the  General  wood  material  behavior of the  species  conclusions,  of  provenances  however,  can  and  species as  before  made  the  results  a whole. M o r e  a n y definite conclusion  from  the  tests  conducted  study. 1.  Eucalyptus  MOR,  spp  M O E and  can IB  provide  to  be  suitable  used  in  dry  the  bending  waferboard  industry. 2. T h e r e  is need  to develop a  for high- extractive-content, to  obtain  adhesives 3.  research  utilization  of  of  the  on gluability  costs  of productions, but  this  hardwoods products,  specific  species  reduces  is a  species  to  possibility. the  easy  adhesive  species i n order  and  not  w h i c h were m a i n l y developed for  Treatment  i n the  enhance  quality  effect  the  To  high  more  use  softwoods.  reduce This  to  extractives  may  and fast  the  extent  of extractive  many  other  tropical  increase  g r o w t h of occurence  species .  species,  and  species,  should be directed at s t u d y i n g the gluing phenomenon on these  41  future  species.  7. R E F E R E N C E S Bodig, J . 1962. Wettability related to gluabilities of five Philippine Mahoganies. Forest Prod. J . 12(6):265-270. Boyd, C. W., Koch, P., Mckean, H. B., Marschauser, C. R., Preston, S. B., Wangaard, F. F. 1977. Highlights for wood for structural and architectural purposes. For. Prod. J . (27): 10-20 Bryant, B. S. 1968. Studies in wood adhesion interaction of wood surface and adhesive variables. Forest Prod. J . 18(6):57-62. Campbell, W. G., Packman, D. F. 1940. Woods, no. 5, 99-101 Carstensen, J . P. 1961. Gluing characteristics of softwood veneers and secondary hardwoods. Forest Prod.J. 10:313-315 Chen, Chia Ming 1970. Effect of extractive removal on adhesion and wettability of some tropical woods at high temperature. Wood Science and Technology (5):27-31 Chow,S-Z. 1971. Infra red spectral characteristics and surface interaction of wood at high temperatures. Wood science and Technology 5:27-31 Chugg, W. A., Gray, V. R. 1965. The effect of wood properties on strength of glued joints Black oak, Chipkapin, Madrone and Tanoak. University of California School of Forestry: 45-47 Dane, C. W. 1972. The hidden environmental costs of alternatives materials available for construction. J . For. 70:734-736. Freeman, H . 1959. Relation between physical and chemical properties of wood adhesion. Forest Prod. J . 9(12):451-458. Freeman, H . , Wangaard, F. F. 1960. Effect of wettability on glue line behaviour of two urea resins.Forest. Prod. J . 10(6):311-315. Gary, V . R. 1962. The wettability of wood. Forest Prod. J . 12(9):452-461. Geimer, G. C , 1981. Predicting shear and internal bond propeerties of flakeboard. Roh-Werkstoff 42  R E F E R E N C E S / 43 39:409-415. Geimer, G. C, 1982. Dimensional stability of flakerboard as affected by board specific gravity flake alignment. Forest Prod. J. 32(8): 40-45  and  Goto, T., Onishi, H. 1967. Studies on the wood gluing I.On the glubility of tropical woods 1. Shimane Agr. Coll. Matsue Japan.Bull. No. 15(a):53-60 Hancock, W. V. 1964. The influence of native fatty acids on formation of glue bonds with heat treated wood. Ph.D Thesis. Faculty of Forestry University of B.C. Vancouver,B.C. 176pp. Herczeg, A. 1965. Wettability of wood. Forest Prod. J. 15(ll):499-505. Hillis, W. E., Brown, A. G.,1978. Eucalyptus for wood production.CSIRO, Australia, Griffin Press Limited, Adelaide, South Australia. Hse, C. Y. 1972. Wettability of Southern pine veneer by phenol formaldehyde wood adhesive. Forest Prod. J. 22(l):37-56. Imumara, H., Takahashi, M., Yasue, M., Yagishita, H., Kawamura, J. 1970 Effect of wood extractives on gluing and coating of kapur wood. Govt. For. Exp. Sta.,Meguro,Tokyo,Japan. Bull. no. 232(l):65-96. Johnanson, F. E., Watkins, W. L. 1975. U.S. Patent 3,899,559. Chemical Technology Review No. 84 Particle Board Manufacture. Kitahara, K. Mizumo, Y. 1961. Relationship between tree species and properties of particleboard. Relation between acidic substances of wood and delamination resistance. J. Japan wood Res. Soc. 7:239-241 Lambuth, A. L 1977: Bonding tropical hardwoods with phenolic adhesives. I U F R O conference On utilization of tropical hardwoods 55. o4-70, Venuezela. Maloney, T. M. 1977. Modern Particleboard and Dry process Fibreboard:34-56. Manufacture. Miller Freeman Publications Marian, J. E., Stumbo, D. A. 1962. Adhesion in wood II. Physical-Chemical surface phenomena and the thermodynamic approach to adhesion. Holzforschung 16(6):168-180.  REFERENCES / 44 Moriya, K . 1971. Gluing faculties of laminated wood made of red launa sawn boards from the Philippine. Govt. For. Expt. Station, Meguro, Tokyo, Japan. Bull. 234: 94-104. Narayanamurti, D. 1957. The role of extractives in wood. Holz als RohWerkstoff 15 1957 Herf (95):370-380. Narayanamurti, D., Gupta, R. C , Verm, G. M . 1962. Influence of extractives on setting of adhesives. Holzforschung und Holzverwetung 14 (5/6):85-88. Onishi, H . , Goto, T. 1971. Studies on wood gluing. The effects of wood extractive on the gelation time of urea-formaldehyde resin adhesive. Shimane Agr. Coll. Matsue, Japan Bull. 5:61-65. Patton, T. C. 1970. A simplified review of adhesion theory based on surface energetics Tappi 53(3):421-429. Post. P. W., 1961. Relation of flake size and resin content to mechanical and dimensional properties of flakeboard. Forest Prod. J . ll(l):317-322. Rayhan, E. A. 1976. Forest products:an assured future. Commonwealth For. Review. (55):341-345 Sakuno, T., Dietrichs, H. H. 1957. Foreign substances cause the specific nature of timbers. Die Umschau in Wissenschaft u Technique 57(7): 197-200 Sakuno, T., Goto, T. 1970. Studies on wood gluing Vii on the gluiability of tropical woods. Part II. Faculty of Agriculture, Shimane University.Matsue, Japan. Bull. 4:103-109. Sakuno, T., Goto, T. 1970. Studies on the wood gluing IV. On the wettability of tropical woods. Faculty of Agr., Shimane University,Matsue Japan. Bull. 4:97-102. Sakuno,T.,Onishi,G.(1970). Studies on the wood gluing. On the gluibility of tropical woods. Part II. Faculty of Agri. Shimane University, Matsue Japan Bui. no. 4:103-109. Stone, R. N , Saeman, J. F. 1976. Future wood demand and costs of supply of timber products X V I IUFRO World Congress Oslo, Division V. 11-23. Troop, B. S., Wangaard, F. F. 1950. The gluing  REFERENCES / 45 properties of certain tropical American woods.Office of Naval Research,Yale university school of Forestry,New Haven Connectut. Techn Rep. no 4. lOpp Vital, B. R., Wilson, T. C. 1980. Water adsorption of particleboard and flakeboard. Wood and Fiber 12(4): 264-271. Yagishita, M . , Karasawa, H . 1969. Adhesion Faculty in veneers of fourteen species of kalimantan woods. Govt. For. Expt. Station, Meguro Tokyo Japan Bull. 218: 273-285 Tappi. 1981. Preparation of Wood for Chemical Analysis (including procedures for extractive Removal and Determination of Moisture content). Fibrous Materials and Pulp Testing, Official Testing Methods. T 12 os-75.  8. APPENDICES  8.1. APPENDIX  1 : STATISTICAL ANALYSIS OF T H E D A T A .  46  14:18 TUESDAY, NOVEMBER 3, 1987  1  ANALYSIS OF VARIANCE PROCEDURE CLASS LEVEL INFORMATION CLASS  LEVELS  VALUES  RESIN  2  3 6  WAFER  2  EXT UNX  NUMBER OF OBSERVATIONS IN DATA SET = 32  4^  SAS  14:18  A N A L Y S I S OF VARIANCE DEPENDENT  TUESDAY,  NOVEMBER  3,  1987  2  PROCEDURE  V A R I A B L E : MOR  SOURCE  DF  SUM OF SQUARES  MEAN SQUARE  F VALUE  PR > F  R-SQUARE  C.V.  MODEL  3  3552.25000000  1184.08333333  14.03  0.0001  0.600448  16.4072  ERROR  28  2363.75000000  84.41964286  CORRECTED TOTAL  31  5916.00000000  DF  ANOVA SS  VALUE  PR > F  1 1 1  190.12500000 3362.00000000 0 . 12500000  2.25 39.82 0.00  0.1446 0.0001 0.9696  SOURCE RESIN WAFER RESIN'WAFER  ROOT MSE  MOR MEAN  9.18801626  56.00000000  oo  SAS  14:18 TUESDAY, NOVEMBER 3,  ANALYSIS OF VARIANCE PROCEDURE MEANS RESIN 3 6 WAFER EXT UNX  N  MOR  16 16  53 .5625000 58 .4375000  N  MOR  16 16  66 . 2500000 45. . 7500000  RESIN  WAFER  N  3 3 6 6  EXT UNX EXT UNX  8 8 8 8  MOR 63. 43. 68. 48.  7500000 3750000 7500000 1250000  4^  to  1987  3  SAS ANALYSIS  14:18  NOVEMBER 3,  1987  OF VARIANCE PROCEDURE  CLASS L E V E L CLASS  TUESDAY,  INFORMATION  LEVELS  VALUES  RESIN  2  3 6  WAFER  2  EXT UNX  NUMBER OF OBSERVATIONS  IN DATA SET  =  32  cn O  4  SAS  14:18  A N A L Y S I S OF VARIANCE DEPENDENT  TUESDAY,  NOVEMBER  3,  1987  5  PROCEDURE  V A R I A B L E : MOE  SOURCE  DF  SUM OF SQUARES  MEAN SQUARE  F VALUE  MODEL  3  277939991.59375000  92646663.86458330  10.88  ERROR  28  238482904.62500000  CORRECTED TOTAL  31  516422896.21875000  SOURCE  DF  ANOVA SS  1 1 1  144461752.53125000 120415800.78125000 13062438.28125000  RESIN WAFER RESIN'WAFER  F  VALUE  PR > F  16.96 14.14 1.53  0.0003 0.0008 0.2258  PR > F  R-SQUARE  C.V.  0.0001  0.538202  19.5826  en  SAS ANALYSIS  14:18 OF VARIANCE  TUESDAY,  NOVEMBER  3,  1987  PROCEDURE  MEANS RESIN 3 6  WAFER EXT UNX  N  MOE  16 16  12778 . 4 3 7 5 17027 . 8 7 5 0  N  MOE  16 16  16843..0000 12963 . 3 1 2 5  RESIN  WAFER  N  MOE  3 3 6 6  EXT UNX EXT UNX  8 8 8 8  14079. . 3 7 5 0 11477, . 5 0 0 0 19606..6250 14449. . 1250  N3  6  1 4 : 1 8 TUESDAY.  SAS ANALYSIS CLASS CLASS  OF VARIANCE  LEVEL  NOVEMBER 3 .  1987  PROCEDURE  INFORMATION  LEVELS  VALUES  RESIN  2  3  WAFER  2  EXT UNX  NUMBER OF OBSERVATIONS  6  IN DATA SET  =  32  en CO  7  SAS ANALYSIS DEPENDENT  14:18 OF VARIANCE VARIABLE:  SOURCE  3,  1987  8  IB SUM OF SQUARES  MEAN SQUARE  F VALUE  MODEL  3  279400.37500000  93133.45833333  12.45  ERROR  28  209490.50000000  CORRECTED TOTAL  31  488890.87500000  DF  ANOVA SS  1 1 1  2926.12500000 276396.12500000 78.12500000  RESIN WAFER RESIN'WAFER  NOVEMBER  PROCEOURE  DF  SOURCE  TUESDAY,  F  VALUE  PR > F  0.39 36.94 0.01  0.5368 0.0001 0.9193  PR > F  R-SQUARE  C.V.  0.0001  0.571498  16.6122  SAS ANALYSIS  14:18 OF VARIANCE  TUESDAY. NOVEMBER  3, 1987  PROCEDURE  MEANS RESIN 3 6  WAFER EXT UNX  N  IB  16 16  51 1. 125000 530.250000  N  IB  16 16  613.625000 427.750000  RESIN  WAFER  N  IB  3 3 6 6  EXT UNX EXT UNX  8 8 8 8  602 . 5 0 0 0 0 0 4 1 9 .. 750000 6 2 4 ..750000 4 3 5 ..750000  Ol  9  SAS  14:18  TUESDAY.  NOVEMBER 3,  1987  10  RESIN=3 TTEST  PROCEDURE  V A R I A B L E : MOR WAFER  N  MEAN  EXT UNX  8 8  63.75000000 43.37500000  STD DEV 7.72287881 10.52802383  STD ERROR  MINIMUM  2.73044999 3.72221852  52.00000000 27.00000000  MAXIMUM 74.00000000 59.00000000  VARIANCES UNEQUAL EQUAL  T 4.4137 4.4137  DF  PROB > | T |  12.8 14.0  0.0007 0.0006  PROB > F ' = 0 . 4 3 2 4 FOR HO: VARIANCES  ARE E Q U A L , F ' =  1.86  WITH  7 AND 7 DF  V A R I A B L E : MOR WAFER EXT UNX  N 8 8  FOR HO: VARIANCES  RESIN=6  MINIMUM MEAN 68.75000000 48.12500000 ARE E Q U A L . F ' =  STD DEV 9.40744386 8.87110075 1.12  STD ERROR 3:32603367 3.13640775  WITH 7 AND 7 DF  58.00000000 35.00000000 PROB > F ' =  MAXIMUM 84.00000000 60.00000000  VARIANCES UNEQUAL EQUAL  T 4.5115 4.5115  DF 14.0 14.0  PROB  > |T| 0.0005 0.0005  0.8809  <7>  SAS  14:18  TUESDAY,  NOVEMBER 3,  1987  RESIN=3 TTEST  PROCEDURE  V A R I A B L E : MOE WAFER  N  MEAN  EXT UNX  8 8  14079.3750000 11477.5000000  STD DEV 2505.79995425 2160.63819937  STD ERROR  MINIMUM  885.93406997 763.90096123  10007.0000000 9916.0000000 PROB > F ' =  FOR HO: VARIANCES  ARE EQUAL, F ' -  1.35  WITH  7 AND 7 DF  V A R I A B L E : MOE WAFER EXT UNX  N 8 8  MEAN 19606.6250000 14449.1250000  FOR HO: VARIANCES  STD DEV 3089.76230882 3684.42185569  ARE EQUAL, F ' =  1.42  WITH  STD ERROR 1092.39594041 1302.63983946 7 AND 7 DF  MAXIMUM 18223.0000000 16277.0000000  VARIANCES UNEQUAL EQUAL  T 2.2242 2.2242  DF 13.7 14.0  PROB > | T | 0.0435 0.0431  0.7056  RESIN=6  MINIMUM 15620.0000000 10849.0000000 PROB > F ' =  MAXIMUM 23250.0000000 22802.0000000  0.6539  VARIANCES UNEQUAL EQUAL  T 3.0337 3.0337  DF 13.6 14.0  PROB > | T | 0.0092 0.0089  SAS  14:18  TUESDAY,  NOVEMBER  3.  1987  12  RESIN=3 TTEST  PROCEDURE  VARIABLE:  IB  WAFER  N  MEAN  EXT UNX  8 8  602.50000000 419.75000000  STD DEV 72.01587127 109.51418695  STD ERROR  MINIMUM  MAXIMUM  25.46145546 38.71911211  510.00000000 200.00000000  686.00000000 502.00000000  VARIANCES UNEQUAL EQUAL  T 3.9436 3 . 9 4 36  DF  PROB > | T |  12.1 14.0  0.0019 0.0015  PROB > F ' = 0 . 2 9 1 1 FOR H O : VARIANCES  VARIABLE: WAFER EXT UNX  ARE E Q U A L , F ' =  2.31  WITH  7 AND 7 DF  IB  RESIN=6  MINIMUM N 8 8  MEAN 624.75000000 435.75000000  FOR H O : VARIANCES  ARE E Q U A L , F ' =  STD DEV 79.42966340 80.24026421 1.02  STD ERROR 28.08262681 28.36921747  WITH 7 AND 7 DF  507.00000000 295.00000000 PROB > F ' =  MAXIMUM 750.00000000 553.00000000  VARIANCES UNEQUAL EQUAL  T 4.7347 4.7347  DF  PROB > | T |  14.0 14.0  0.0003 0.0003  0.9793  oo  SAS  14:18  TUESDAY,  NOVEMBER 3,  1987  13  WAFER=EXT TTEST  PROCEDURE  V A R I A B L E : MOR RESIN  N  MEAN  3 6  8 8  63.75000000 68.75000000  STD DEV 7.72287881 9.40744386  STD ERROR  MINIMUM  2.73044999 3.32603367  52.00000000 58.00000000 PROB  FOR H O : VARIANCES  ARE E Q U A L , F ' =  1.48  WITH 7 AND 7 DF  V A R I A B L E : MOR RESIN  N  MEAN  3 6  8 8  43.37500000 48.12500000  FOR HO: VARIANCES  ARE E Q U A L , F ' =  STD DEV 10.52802383 8.87110075 1.41  WITH  STD ERROR 3.72221852 3.13640775 7 AND 7 DF  > F'=  MAXIMUM 74.00000000 84.00000000  VARIANCES UNEQUAL EQUAL  T -1.1619 -1.1619  DF  PROB > | T |  13.5 14.0  0.2654 0.2647  0.6155  WAFER=UNX  MINIMUM 27.00000000 35.00000000 PROB > F ' =  MAXIMUM 59.00000000 60.00000000  VARIANCES UNEQUAL EQUAL  T -0.9759 -0.9759  DF  PROB  13.6 14.0  > |T| 0.3462 0.3457  0.6627  Or CD  SAS  14M8  TUESDAY.  NOVEMBER 3,  1987  14  WAFER=EXT TTEST  PROCEDURE  V A R I A B L E : MOE RESIN  N  MEAN  3 6  8 8  14079.3750000 19606.6250000  FOR H O : VARIANCES  STD DEV 2505.79995425 3089.76230882  ARE E Q U A L , F ' =  1.52  STD ERROR  MINIMUM  885.93406997 1092.39594041  10007.0000000 15620.0000000  WITH 7 AND 7 DF  PROB > F ' =  MAXIMUM 18223.0000000 23250.0000000  VARIANCES UNEQUAL EQUAL  T  DF  -3.9298 -3.9298  13.4 14.0  PROB > | T | 0.0016 0.0015  0.5940  WAFER=UNX  -  V A R I A B L E : MOE RESIN  MEAN  STD DEV  11477.5000000 14449.1250000  2160.63819937 3684.42185569  N  FOR HO: VARIANCES  ARE EQUAL, F ' =  2.91  WITH  STD  ERROR  MINIMUM  763.90096123 1302.63983946  9916.0000000 10849.0000000  7 AND 7 DF  PROB > F ' =  MAXIMUM 16277.0000000 22802.0000000  VARIANCES UNEQUAL EQUAL  T -1.9678 -1.9678  DF 11.3 14.0  PROB > | T | 0.0741 0.0692  0.1824  05  o  SAS  14:18  TUESDAY,  NOVEMBER 3,  1987  15  WAFER=EXT TTEST  PROCEDURE  VARIABLE:  IB  RESIN  N  MEAN  3 6  8 8  602.50000000 624.75000000  STD DEV 72.01587127 79.42966340  STD ERROR  MINIMUM  25.46145546 28.08262681  510.00000000 507.00000000 PROB > F ' =  FOR HO: VARIANCES  VARIABLE: RESIN 3 6  ARE EQUAL, F ' =  1.22  WITH  7 AND 7 DF  IB  MAXIMUM 686.00000000 750.00000000  MEAN 419.75000000 435.75000000  FOR H O : VARIANCES  STD DEV 109.51418695 80.24026421  ARE E Q U A L . F ' =  1.86  WITH  STD ERROR 38.71911211 28.36921747 7 AND 7 DF  WAFER=UNX  -0.5870 -0.5870  DF  PROB  13.9 14.0  > |T| 0.5667 0.5666  -  200.00000000 295.00000000 PROB > F ' =  UNEQUAL EQUAL  T  0.8026  MINIMUM N 8 8  VARIANCES  MAXIMUM 502.00000000 553.00000000  0.4306  -  VARIANCES UNEQUAL EQUAL  T -0.3333 -0.3333  DF 12.8 14.0  PROB  > |T| 0.7443 0.7438  SAS VARIABLE  18 TUESDAY, N  MEAN  NOVEMBER 3 ,  1987  STANDARD DEVIATION  RESIN=3 WAFER=EXT MOE MOR IB  8 8 8  14079.38 63.75 602.50  2505.80 7.72 72.02  RESIN=3 WAFER=UNX MOE MOR IB  8 8 8  11477.50 43.38 419.75  2160.64 10.53 109.51  RESIN=6 WAFER=EXT MOE MOR IB  8 8 8  19606.63 68.75 624.75  3089.76 9.41 79.43  RESIN=6 WAFER=UNX MOE MOR IB  8 8 8  14449.13 48.13 435.75  3684.42 8.87 80.24  05  SAS 14:18  OBS  RESIN  1 2 3 4  3 3 6 6  WAFER EXT UNX EXT UNX  TUESOAY,  NOVEMBER  3.  1987  STDEV 2505.80 2160.64 3089.76 3684.42  05 CO  17  APPENDICES / 64 .2. A P P E N D I X 2 : C O M P A R A T I V E D A T A F R O M A N O T H E R  SPECIES  App.nfllx 6.3: STRENGTH PROPERTIES Of ASPEN WAFERBOARD PANELS(JESSOME 1979: THICKNESS  1.27 CM (7/16 INCHES).  PROPERTY  NO. OF SAMPLES  MEAN VALUE  STANDARD DEVIATION  DENSITY (g p e r cu cm)  40  0.66  0.034  SWELLING!*)  39  e  2.B  35  MOR(MPA)  44  24  3.4  14  UOE(MPA) IB(KPA)  44 44  3776 586  414 117  1  COEFFICIENT VARIATION  THICKNESS  1  20  APPENDICES / 65 8.3. A P P E N D I X 3 WOOD  PHSICAL  AND CHEMICAL  PROPERTIES OF T H E  USED  pH 4.2: determined by mixing four of air-dried groundwood with 400cc of distilled water. After two hours the water and ground. wood was filtered and the filtrate used for pH determination using a standard Beckman pH meter. The pH was recorded after the meter had indicated a constant value. The pH average value of three samples was taken as the pH of the wood. Specific gravity of the wood .71 Specific gravity of the panels .83  

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