The influence of various resin parameters on the physical properties of oak flakeboard

Graduation date: 1979The substantial increase in resin costs due to the recent energy\ud crisis, increased public awareness to the problem of free formaldehyde\ud from boards bonded with urea-formaldehyde resins, and a projected\ud increase in the production of exterior board have emphasized the need\ud for new and substitute adhesive systems. One new development is the\ud use of lignosulfonates in combination with conventional phenol-formaldehyde\ud resins for the production of particleboard.\ud An experiment was carried out to test the applicability of such a\ud substituted adhesive system. A commercial phenol-formaldehyde resin\ud and six ammoniated-lignosulfonate-phenol-formaldehyde resins of varying\ud viscosity were used in the fabrication of randomly oriented oak flakeboards.\ud Resin application rates of 3, 4 1/2, and 6 percent were\ud employed in combination with nominal board densities of 40 and 45\ud lbs/cu.ft.\ud Test results indicated similar properties (internal bond, modulus\ud of rupture, modulus of elasticity, linear expansion, thickness swell,\ud and weight gain) between the commercial phenolic resin and the\ud substituted resins. Internal bond strength increased with increasing resin viscosity in the range studied, while modulus of rupture, modulus\ud of elasticity, thickness swel1, and weight gain properties generally\ud decreased. Increasing resin application rate and board density\ud resulted in an increase in board strength properties.\ud In a second study, resin wetting and resin molecular weight\ud properties were related to internal bond and modulus of rupture\ud strength values. Contact angle measurements were used as indicators of\ud resin wetting properties. Measurements were taken at 5, 30, 60, 300,\ud and 600 second intervals. Resin molecular weight distributions were\ud broken into low, medium, and high fractional molecular weight areas.\ud No significant relationships were found between wetting properties\ud and bond strength (IB, NOR). Wetting alone was not sufficient for the\ud formation of a strong adhesive bond. Significant relationships were\ud found, however, between fractional areas under the molecular weight\ud distribution curve and internal bond strength. IB values were\ud negatively related to low and medium molecular weight resin molecules,\ud while high molecular weight resin molecules were positively related to\ud IB values. Medium molecular weight area exhibited the highest degree\ud of correlation. No correlation was found between resin molecular\ud weight distribution and modulus of rupture values. In addition, no\ud significant relation was found between IB and NOR properties and resin\ud pH