INTERFACES IN POLYOLEFIN CELLULOSIC FIBER COMPOSITES - CHEMICAL COUPLING, MORPHOLOGY, CORRELATION WITH ADHESION AND AGING IN MOISTURE/

This paper details the characteristics of pure cellulose and wood fibe rs when associated with thermoplastic matrices for composite applicati ons. Chemical modification of the cellulose is performed to allow a go od compatibilization, and the most efficient compatibilizing agents mu st possess: i) a function highly reactive with the OH groups of the ce llulose and ii) a non-polar chain with preferably a polymeric structur e. Polypropylenes grafted with maleic anhydride are thus efficient age nts. Smaller compatibilizing agents, especially if reacted with cellul ose in swelling media, react with the bulk of the fiber and lead to di mensional stability. All treatments, even when performed with low degr ees of grafting or small alkyl chains, significantly modify the hydrop hilicity of the cellulose surface and play a role in a better wettabil ity of the fiber by the matrix leading to improved adherence. The glob al mechanical properties are then improved, but the effect is preferab ly studied at the scale of a single filament composite. The morphology of the matrix in the vicinity of the non-treated fiber shows that, in some cases, the fiber acts as a nucleating agent involving the format ion of a transcrystalline phase. Aging in moisture is generally detrim ental to the mechanical properties. This phenomenon is limited by the chemical treatment performed on the fibers.