The experiment Polymers and Plastics introduces students to the nature of the crystalline and amorphous regions inherent to polymers and to the microscopic nature of the glass and melting transition temperatures. Viscoelastic mechanical properties of polymers are related to these concepts. Likewise related are the possible roles of plasticizer molecules in plastics. Students prepare cast biopolymer films and test several of their mechanical properties as a function of plasticizer content.