1985 Volume 13 Issue 3 Pages 114-124
The rheological properties in the melt state were investigated for several blends composed of butyrylated, caproylated or lauroylated wood and synthetic polymers, methyl methacrylate (MMA)-ethyl methacrylate (EA) copolymer and poly (methyl methacrylate) (PMMA). The results of viscoelastic measurements gave excellent time-temperature superposition for most of the blends. However, the superposition was not possible for blends with more than 90 % of the wood esters of higher aliphatic acids. Similar behavior is known for corresponding cellulose derivatives which are partially crystalline. The successful time-temperature superposition for the blends suggests the mutual plasticization among the derivatized wood components and also with the synthetic polymers in the blends. Also, it has been found that the better the compatibility of the chemically modified wood with synthetic polymer, the easier the occurrence of thermal flow, and the smaller the broadening of the second plateau, which is caused from the formation of higher ordered structures with longer relaxation times. In fact, the blend of butyrylated wood with MMA-EA copolymer, which shows the highest compatibility among samples used in this study, reveals the flow phenomenon within the range of the measurements, showing typical viscoelastic behavior starting from rubbery plateau to the flow. In the case of the blend of lauroylated wood with PMMA, which was confirmed to be a blend composed of two distinct phases, the viscoelastic properties of the blend sample became less temperature sensitive as the amount of lauroylated wood in the blend was increased. This trend can be understood by the reflection of the low temperature-dependent viscoelastic properties inherent in lauroylated wood. The compatibility of the chemically modified woods with synthetic polymer was measured on the corresponding films by the torsional-pendulum method, and evaluated in regard with the appearance of Tg, peaks in the logarithmic decrement-temperature curve. Furthermore, it was confirmed by the observation with a scanning electron microscope that the second plateau, which appears from the end parts of the rubbery plateau, broadens, when some fibrous residues of the chemically modified wood remain in the blend sample.
