The Influence of Maleation on Polymer Adsorption and Fixation, Wood Surface Wettability, and Interfacial Bonding Strength in Wood-PVC Composites<sup>1</sup>
Keywords:Bonding strength, contact angle, coupling agent, dipping time, extractives, graft rate, laminates, maleation, maleated polypropylene (MAPP), <i>monolayer</i>, PVC, retention, sessile droplet, wettability, yellow-poplar veneer
AbstractThe influence of maleation on polymer adsorption and fixation, surface wettability of maleated wood specimens, and interfacial bonding strength of wood-PVC composites was investigated in this study. Two maleated polypropylenes (MAPPs), Epolene E-43 and Epolene G-3015, were used to treat yellow-poplar veneer samples. Retention of coupling agent, graft rate, graft efficiency, static contact angle on treated samples, and shear strength of resultant wood-PVC laminates manufactured under hot-pressing were measured. It was shown that the relationship among graft rate, coupling agent retention, and treating solution concentration for MAPP-treated wood specimens followed a three-dimensional paraboloid model. Graft efficiency decreased with the increase of concentration and retention. The relationship between retention and concentration was linear for G-3015 and polynomial for E-43. Maleation treatment greatly improved the compatibility and interfacial adhesion. The veneer samples treated with these two MAPPs presented different wetting behaviors. For G-3015-treated samples, measured contact angles varied from 115° to 130° independent of retention, graft rate, and wetting time. For E-43-treated samples, retention, graft rate, and wetting time had a significant influence on the contact angle. Compared with controls made of untreated wood and PVC, shear strength of the maleated wood-PVC laminates increased over 20% on average. There was no direct correlation between measured contact angle and shear strength. Extractives had negative effects on retention. However, they did not significantly influence contact angles and interfacial bonding strength. Monolayer models were proposed to illustrate the bonding structure at the interface.
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