Developing New Particulate Reinforced Composites

Polymer composites traditionally fall into two categories depending on the type of reinforcement, fibre or particulate. In particulate composites, mineral fillers (such as talc or mica) are often used to either extend the polymer (replace volume with cheaper component) or enhance its properties (reinforcement). Gypsum (calcium sulphate) is a naturally occurring mineral (also produced as a by-product in fossil fuel power stations) that has many uses including plaster and plasterboard. However, its effectiveness as a filler in particulate composites is less well understood. It is very likely able to extend a polymer such as polypropylene, but whether it can enhance useful properties such as strength or toughness is essentially unknown. The interface between the gypsum particles and the polymer is one of several important factors which affect the properties of the composite. Treatment of the gypsum with a suitable coupling agent is likely to improve this interface. The aim of this project is to assess how effective gypsum is in enhancing the properties of polypropylene. This will be done by making gypsum reinforced polypropylene with varying compositions using a twin-screw extruder which will be formed into a suitable sample geometry using an injection moulder. Mechanical properties (tensile modulus, strength and strain to failure) will be measured alongside thermal properties such as phase transitions. The results will be analysed in terms of the type of gypsum filler, the load level and the coupling agent.