Dynamic mechanical properties of toughening polyamide composites

The effect of incorporating thermoplastic rubber on the dynamic mechanical
properties, storage and loss moduli, of virgin and recycled glass-fiber-reinforced
polyamide 66 has been investigated in this study. Styrene-Ethylene–Butylene-Styrene and Ethylene–Propylene grafted with maleic anhydride were used as elastomers for
toughening. Dynamic mechanical properties of the composites were examined by
the rotational rheometry. Shear storage and loss moduli of recycled and virgin materials were measured against frequency. Also the variation of storage modulus of the virgin composites was measured against temperature by conducting a series of torsion tests.
Both dynamic storage and loss moduli of the composites were found to increase with increasing glass fiber and rubber contents. Recycled composites had lower values of dynamic modulus compared to that of virgin composites; however by proper
combining of fiber and rubber into the recycled material, its modulus fairly matches
that of the virgin material. Addition of rubber to virgin composites causes a reduction in G′ as temperature increases. Rubber, which acts as a stress concentrator, had a major effect on minimizing the overall modulus of the composites. The drop in G′ versus temperature has been observed for all composites; however the temperature at which the transition in G′ occurs decreases with increasing rubber content.