INFLUENCE OF INTERFACIAL INTERACTIONS ON THE PROPERTIES OF PVC CELLULOSIC FIBER COMPOSITES

The surface properties at the interface between thermoplastic and cell ulosic fibers strongly influence the mechanical properties of plastic/ cellulosic fiber composites. This paper examines the role of surface a cid-base properties of plasticized WC and cellulosic fibers on the mec hanical properties of the composites. The acid-base surface characteri stics of cellulosic fibers were modified by treating the fibers with g amma-aminopropyltriethoxysilane (A-1100), dichlorodiethylsilane. phtha lic anhydride, and maleated polypropylene. The empirical acid (K-A) an d base (K-D) characteristics (i.e., electron donor/acceptor abilities) of untreated and treated fibers, as well as plasticized PVC, were det ermined using inverse gas chromatography (IGC) technique, These parame ters were used to yield information on the acid-base pair interactions that were correlated with the tensile and notched Izod impact propert ies of the composites. Acid-base pair interactions have been found to be a valuable parameter in the design of surface modification strategi es intended to optimize the tensile strength of the composites. By tai loring the acid-base characteristics of cellulosic fibers and plastici zed WC, a composite with equal tensile strength and greater modulus th an unfilled WC was developed. However, the acid-base factors did not c orrelate with tensile modulus, the elongation at break, and the notche d Izod impact property of PVC/newsprint fiber composites. Aminosilane has been observed to be a suitable adhesion promoter for PVC/wood comp osites improving significantly the tensile strength of the composites. Other treatments (dichlorodiethylsilane, phtalic anhydride, and malea ted polypropylene) were found to be ineffective, giving similar streng ths compared to the composites with untreated cellulosic fibers. FTIR spectroscopy results suggested that aminosilane was effective because treated cellulosic fibers can react with PVC to form chemical bonds. T he resulting bond between PVC and cellulosic fibers accounts for the e ffectiveness of aminosilane, when compared with other coupling agents.