Plastics Engineering is a practice which encompasses the design, development, processing and manufacture of products. A plastic is a polymeric material that is a semi-liquid state which has the property of plasticity and exhibits flow. The shear nature of plastic materials poses constant challenges to an engineer. The mechanical properties of plastics are difficult to quantify and the plastics engineer has to design a product that meets certain specifications while at the same time keeping costs low. Other issues which the plastics engineer has to address are outdoor weatherability, thermal properties such as temperature, electrical properties, barrier properties and its resistance to chemical attack. In plastics engineering the economics of the product plays an important role. Price with respect to processability is important as some materials need to be processed at very high temperatures which increase the cost particularly during long cooling down processes. Some plastics are made from recycled materials but their use is limited in engineering because the consistency of materials are less reliable.