Influence of Interface Properties on Mechanical Strength of GFPP

Glass-fiber (GF) reinforced polypropylene (PP) is a very important industrial material. However, as PP is a non-polar polymer, the interfacial adhesion strength between PP and GF is very weak. In order to resolve this problem, maleic acid grafted PP (MA-PP) is generally used. In this way the tensile strength of GFPP can be improved remarkably. Moreover long glass-fiber reinforced PP pellets for injection molding have been recently developed. In spite of these improvements, the strength of GFPP still lags those of other GF reinforced engineering plastics. In order to improve the strength of GFPP, it is necessary to reinforce the weakest of the many interfaces and interphases in the GFPP system. It was found that the interface between the malefic acid grafted PP and the neat matrix PP is the weakest layer. Thus, to reinforce this interface, it is important to increase the entanglement between the MA-PP and PP molecules. It was found that the strength of GFPP could be improved by using high molecular weight MA-PP.