Mechanical Properties of Alkyl Isocyanate Modified Scots Pine Wood Surfaces

Thin longitudinal sections (100 μm thick) were reacted with butyl isocyanate and octadecyl isocyanate under dry conditions. Weight gain and nitrogen analysis demonstrated reaction to degree of substitution about 0.9 (based on published wood cell wall analytical data). Infrared spectra data gave good evidence for the formation of carbamate ester (urethane bonds). Up to weight gain of about 30% no practically significant loss of tensile strength or toughness was observed. Above this level, strength and toughness was observed to fall as a function of weight increase, similarly with both reagents. Over the range examined the precise degree of substitution (loss of hydroxyl functionality) appeared to have no direct effect on mechanical properties. The strength losses seem to be related to cell wall rupture resulting from excessive swelling occurring at the higher levels of reaction.