POLYPROPYLENE CELLULOSIC FIBER COMPOSITES - CHEMICAL TREATMENT OF THECELLULOSE ASSUMING COMPATIBILIZATION BETWEEN THE 2 MATERIALS/

The present work deals with the realization of composites with a polyp ropylene (PP) matrix and cellulosic fibers as reinforcement. In order to achieve a good adhesion with the PP matrix, the modification of dif ferent cellulosic fibers has been performed with various chemical func tions: carboxylic anhydrides, isocyanates, vinylsulfone, and chlorotri azine systems. All these compatibilizing agents carry an alkyl chain o r a PP chain. Grafting is evidenced by infrared and ESCA spectroscopie s, and the grafting rates for the different chemicals are determined b y microweighing measurements. Modification of the surface characterist ics is followed by wettability tests and inverse gas chromatography. D etermination of the water sorption isotherm for the treated fibers sho ws an important decrease in water regain in the case of isocyanate tre atments in swelling medium. Enhancement of adhesion between fibers and the matrix is demonstrated by mechanical tests: the interfacial shear stress obtained by the microbond test increases by 70% for cellulosic fibers treated with maleated PP. This may be the result of entangleme nts between PP chains, but for macrocomposites the effect is much more limited due to the predominance of external factors during developmen t of the composite.