Dynamical mechanical behaviors of rubber-filled wood fiber composites with urea formaldehyde resin

Wood composites glued with thermosetting synthetic resins tend to show inadequate damping performance caused by the cured resinous matrix.Waste rubber maintains prominent elasticity and is feasible to be an optional modifier.To that end,composite panels of granulated tire rub-ber(GTR)powders and thermal-mechanically pulped wood fibers were fabricated in this study.Urea formaldehyde(UF)resin was applied as the bonding agent(10%based on wood/rubber total weight).Dynamical mechanical analysis(DMA)was conducted to disclose the thermo-mechanical behaviors of the rubber-filled wood fiber composites.Influence of two technical pa-rameters,i.e.,GTR powder size(0.55-1.09 mm)and addition content(10%,20%and 30%based on wood/rubber total weight),was specifically discussed.The results showed that storage modu-lus(E’)of the rubber-filled composite decreased while loss factor(tan𝛿)increased monotonously along with elevated temperature.A steady“plateau”region among 110-170°C was found where both E’and tan𝛿keep constant.Accordingly,tan𝛿showed two peak values at 103-108 and 231-233°C due to glass transition of lignin and thermal degradation of hemicellulose,respectively.Addition of rubber fillers resulted in lower bending and internal bonding strengths as well as stor-age modulus values.When the temperature was above 183°C,all the rubber-filled composites showed higher tan𝛿values than the control.The findings above fully demonstrate the improved damping performance of the UF-bonded wood fiber composites on account of rubber component.Further work is still needed to optimize the rubber/fiber interfacial bonding strength.

Dynamical mechanical properties of wood-high density polyethylene composites filled with recycled rubber

Application of out-of-service rubber from a variety of sources is of both environment-protecting and resource-saving importance.To that end,recycled tire rubber was utilized as a filler to fabricate wood-high density polyethylene(HDPE)composite with enhanced toughening performance using the injection procedure in this work.Dosages of rubber powders were 0,5,10,and 15wt%based on the overall weight of poplar wood flour and HDPE(HDPE:wood flour=70꞉30).The injection-fabricated composites were subjected to a four-cycle repetitive compressing loadings(0-3 kN)and dynamical mechanical analysis(DMA,room temperature to 150℃,in the dual cantilever mode).It was found that the rubber-filled materials exhibit advantageous energy absorption performance compared to wood-HDPE composites under repetitive compressions.The rubber-filled wood-HDPE composites are thermomechanically labile in an environment with raised temperature.The HDPE matrix substance occupies the predominant role in thermally yielding of the overall composite,typically in the temperature range of 50-75℃ resulting in a loss modulus peak.Up to 130-150℃,all the composites fully loses their moduli with loss factor(Tan δ)reaching its peak values of 0.30-0.38.To conclude,rubber-filled wood-HDPE is a qualified material applicable in proper temperature range.