Photoelastic Properties of Polystyrene in the Glassy State. II. Effect of Temperature

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Abstract
The effect of temperature on the stress‐optical coefficient of polystyrene was measured at twelve different temperatures from −195° to +24°C using samples of unoriented polystyrene sheet. The stress‐optical coefficient appears to decrease with temperature from a value of about +17 brewsters at −195°C to a value of about +10 brewsters at room temperature. The elastic (Young's) modulus of polystyrene was also measured as a function of temperature using a flexural technique and was found to decrease linearly with temperature from 6.36×105 psi at −198° to 4.65×105 psi at +24°C. A curve of strain‐optical coefficient vs temperature was obtained by multiplying stress‐optical and modulus values; this curve increases with decreasing temperature from about +0.03 at +24° to +0.073 at −195°C.