Effects of PA6,6/PP ratio on the mechanical properties of short glass fiber reinforced and rubber-toughened polyamide 6,6/polypropylene blends

The tensile properties and notched Charpy impact energy of injection-molded rubber-toughened polyamide 6,6/polypropylene (PA6,6/PP) blends reinforced with short glass fibers (SGF) were studied. The glass fiber content was fixed at 40 wt%. The polymer blends containing various PA6,6/PP ratios, plus a mixture of 10 wt% styrene-ethylene-butylene-styrene (SEBS) and 10 wt% maleic anhydride (MA) grafted SEBS (SEBS-g-MA), were formulated. Two types (123D and 146B) of E-glass fibers were used to examine the influences of PA6,6/PP ratio on mean fiber length and critical fiber length (or fiber-matrix interfacial adhesion) and in turn on the mechanical properties. The PA6,6/PP ratio was found to have significant effects on both the mean fiber length and the critical fiber length in the final samples, and then on the mechanical properties. It was shown that the composite strength increased while the elastic modulus decreased with increasing PA6,6/PP ratio. This observation has been explained using the variance of interfacial adhesion and fiber length with the PA 6,6/PP ratio. The tensile failure strains were higher for the glass fiber-reinforced SEBS/SEBS-g-MA toughened blends than for glass fiber-reinforced toughened PA6,6 or PP composites. The notched Charpy impact energy of the reinforced blends at a medium (75/25) PA6,6/PP ratio was exhibited to be higher than for the reinforced rubber-toughened PA6,6 or PP composites. Consequently, it was concluded that control of the PA6,6/PP ratio would be an effective way to produce composites with optimal combination of superior overall mechanical properties.