Investigation of the creep property of fast-growing poplar wood modified with low molecular weight resins

Fast-growing poplar wood was modified with low molecular weight urea-formaldehyde resin (UF) at 41.5% concentration or phenol-formaldehyde (PF) at concentrations of 15, 25, and 40%. The physical and mechanical properties were measured, and creep behavior tests were carried out under ambient indoor conditions. The specimens were subjected to 30 and 50% of their maximum bending load. The density, modulus of elasticity, and modulus of rupture of UF-wood increased by 37.16, 45.86, and 28.36%, respectively, and the corresponding increases in 15% PF-specimen were 39.41, 31.80, and 27.74%, respectively. The wood modified with resins exhibited less creep deflection. The relative creep deflections of modified wood were about 0.22, 0.53, 1.22, and 0.32 times those of the untreated specimen at 30% of stress level after 15% PF, 25% PF, 40% PF, and UF were added, respectively. At the lower loading level, the relative creep deflection of the 15% PF specimen was 63.94% that of the 41.5% UF-specimen. Specimens treated with UF at 30 and 50% loading were broken within 120 d and 80 d respectively, whereas the untreated specimen was broken within one month at 50% loading.