Demonstrating the Effects of Processing on the Structure and Physical Properties of Plastic Using Disposable PETE Cups

An educational activity is described in which the structure and physical properties of disposable plastic cups were directly related to the method of processing. The mechanical properties of specimens cut from the walls of poly­(ethylene terephthalate) (PETE) cups, oriented parallel and perpendicular to the thermoforming direction, were measured in tension. The parallel sample displayed greater elastic moduli, yield stress, and predominantly ductile deformation behavior compared to the relatively weaker and more brittle perpendicular sample. This observed mechanical anisotropy was related to the processing-induced orientation of polymer molecules within the cup. This activity, which is suitable as a classroom demonstration, short laboratory task, or an outreach activity, effectively demonstrates the relationship between polymer processing, structure, and properties without the use of large-scale melt processing equipment.