Birefringence of Stressed Polystyrene Reinforced With Clay

Rohit Gupta, Harold Metcalf, John No, Laser Teaching Center, Department of Physics and Astronomy, and Miriam Rafailovich, Department of Materials Science and Engineering, State University of New York at Stony Brook

This study will test whether blending clay into polystyrene will reduce the material's response to stress, as observed by the intensity and form of birefringence patterns. This type of material modification is a relatively new field of study with important engineering implications.

Birefringence is the optical phenomenon that occurs when an object that has different indices of refraction in different directions is placed between two crossed polarizers; these different indices can be inherent in the object or induced by means of applied stress. Thus birefringence literally allows one to "see" the stress produced on an object because of the colored fringes induced.

The clay additive to be used will be cloisite 20A at a concentration of 5% clay. Polystyrene samples with clay and without clay will be molded into the same rectangular shapes (2x12 cm with a thickness of 2 mm) and subjected to the same stress.

Adjustable stresses will be applied to the samples in a Stress Opticon, and pictures of the stress fringes will be recorded with a camera. The shape and form of the fringes will be noted, and the intensities, if possible, will be measured.

This research was supported by the Simons Foundation.