John Z. Lu

Maleated wood-fiber/high-density-polyethylene composites: Coupling mechanisms and interfacial characterization

Chemical coupling of maleated polyethylene (MAPE) copolymers at the interface in wood-fiber/high-density-polyethylene (HDPE) composites was investigated in this study. FTIR and ESCA analyses presented the evidence of a chemical bridge between the wood fiber and polymeric matrix through esterification. The feature peak of esterification occurred in the range between 1800 and 1650 cm−1 at FTIR spectra. Succinic and half succinic esters were the two primary covalent bonding products to cross-link the wood fiber and thermoplastic matrix. Maleated composites had a remarkable shift on most O1s and C1s spectra in respect to the wood, HDPE, and untreated composites. The binding energy of maleated composites at C1s and O1s spectra was around 282 eV and 530 eV, respectively. The mass concentration of chemical components at the interface was related to the coupling agent type, structure, and concentration. According to the FTIR and ESCA analyses, the coupling mechanisms of MAPEs were proposed. The interfacial morphology in wood-fiber/HDPE composites was illustrated with the pinwheel models based on SEM observations.

Chelating efficiency and thermal, mechanical and decay resistance performances of chitosan copper complex in wood–polymer composites

Wood-polymer composites (WPC) have been extensively used for building products, outdoor decking, automotive, packaging materials, and other applications. WPC is subject to fungal and termite attacks due to wood components enveloped in the thermoplastic matrix. Much effort has been made to improve decay resistance of WPC using zinc borate and other chemicals. In this study, chitosan copper complex (CCC) compounds were used as a potential preservative for wood-HDPE composites. CCC was formulated by reacting chitosan with copper salts under controlled conditions. Inductively coupled plasma (ICP) analytical results indicated that chitosan had high chelating efficiency with copper cations. CCC-treated wood-HDPE composites had a thermal behavior similar to untreated and zinc borate-treated wood-HDPE composites. Incorporation of CCC in wood-HDPE composites did not significantly influence board density of the resultant composites, but had a negative effect on tensile strength at high CCC concentration. In comparison with solid wood and the untreated wood-HDPE composites, 3% CCC-treated wood-HDPE composites significantly improved the decay resistance against white rot fungus Trametes versicolor and brown rot fungus Gloeophyllum trabeum. Especially, CCC-treated wood-HDPE composites were more effectively against the brown rot than the untreated and chitosan-treated wood-HDPE composites. Moreover, CCC-treated wood-HDPE composites performed well as zinc borate-treated wood-HDPE composites on fungal decay resistance. Accordingly, CCC can be effectively used as a preservative for WPC.