New coupling agents as adhesion promoters at the poly(phenylene sulfide) glass interface-studies with micro and macro composites

Carboxy-functionalized poly(phenylene sulfide) having different molar masses and amount of the functional group were prepared in order to be used with gamma-aminopropyltriethoxysilane as surface treatment of E-glass fibers. These grafted polymer chains act as connecting chains in order to improve the interfacial shear strength of the PPS-glass interface. According to their chemical nature, which is the same as the PPS matrix, and their ability to crystallize in the same crystalline form as the pure PPS, a continuum of bonding from the fiber surface to the bulk matrix is achieved. A chemical linkage is established at the glass surface by means of hydrolyzed ethoxysilane groups of the gamma-APS and from the formation of amide units resulting from the reaction of amine functions of the silane and the carboxylic groups of the modified PPS. A "physical" linkage is expected between the grafted PPS and the PPS chains by means of entanglements and co-crystallization. A large improvement of the interfacial shear strength measured from the microdroplet test is observed when a modified-PPS having a medium molar mass and a low amount of functional groups is used in comparison with untreated or silane-treated glass fibers. This improvement is also observed for short glass fibers/PPS composite materials. In fact, a large improvement is obtained on mechanical properties such as the tensile, flexural, and impact strengths.