Toughening Effect of Aluminium Particles in Conductive Polyester Composites

Abstract

Particulate composites have been known for a long time and are convenient for making complex plastic shapes by injection moulding, at lower costs, or with added functionality. However, it is well known that including a rigid filler in a rigid polymer matrix usually leads to a moderate increase in tensile modulus (~2×), but with a decrease in elongation-to-break, and most often with a reduction in tensile strength and impact resistance. This trend is observed with a wide range of plastics with mineral fillers and whiskers, metal particles, and also the newer nanofillers like clay, carbon nanotubes and graphene. It is a challenge to increase simultaneously modulus, strength and toughness. The industrially practised method to toughen a high T g polymer is to add particles of rubber, but this involves a trade-off with a decreased modulus. During our work on conductive plastics, we studied aluminium (Al) powder of different shapes in amorphous poly(ethylene terephthalate) (PET). The Al particle–PET composite showed an unusual mechanical property portfolio: the tensile modulus increased (as in other systems with rigid particles), and the elongation-to-break dropped even more drastically than other filled plastic systems, but without a drastic drop in tensile strength and impact resistance.