Fracture of polycarbonate/ABS blends

Toughness of a polymer is described as the ability to resist fracture by absorbing energy and is therefore a very important material property. Much research in the polymer field aims at improving the toughness of a material and investigates the mechanisms by which such an improvement is obtained. A polymer that is well known for its toughness is polycarbonate (PC). However, this material has several drawbacks, which sometimes limits its field of application. The material has a high melt viscosity, and this can be a problem in injection moulding of thin-walled products. In thick-walled applications, PC loses its tough character and shows brittle fracture. One of the main problems, however, is that the material also turns brittle when a small flaw or small scratch is present in the material. Such sharp hairline cracks can form when the material is exposed to the environment. This effect is known as ageing. To reduce the sensitivity to these conditions, PC is often blended with acrylonitrile-butadienestyrene (ABS). PC/ABS is a ternary blend and is therefore more complex than the binary blends. Though the components of PC/ABS were studied separately in the past, the fracture behaviour of the ternary system has been rarely studied. This study therefore aims at gaining insight in the fracture behaviour of PC/ABS blends. The influence of several material and test parameters is investigated: ABS-structure, ABS-content, rubber content in ABS, strain rate, temperature and specimen geometry.