A low-cost tensile testing machine was built for testing polymeric films. This apparatus also allows for tear-strength and flexural tests. The experimental results, obtained from common-use materials, selected by the students, such as plastic bags, illustrate important aspects of the mechanical behavior of polymeric materials. Some of the tests performed in class are illustrated in the paper, involving tensile and tear-strength testing of HDPE films and flexural testing of polystyrene bars.