Origin of impact strength in polycarbonate. III. Effect of liquids and orientation
- 1 October 1974
- journal article
- research article
- Published by Taylor & Francis in Journal of Macromolecular Science, Part B
- Vol. 10 (3) , 441-476
- https://doi.org/10.1080/00222347408215164
Abstract
The effects of Arochlor 5442 (a chlorinated terphenyl) dibutyl phthalate, butyl stearate, a high molecular weight polyester plasticizer, acetone, methyl ethyl ketone, isopropyl alcohol, carbon tetrachloride, and water on the dynamic mechanical properties of polycarbonate have been studied. Results show that all liquids except water and carbon tetrachloride suppress the low-temperature β-transition loss peak and shift the temperature of maximum loss to lower temperatures. Water causes the β loss peak to broaden and be more asymmetrical. Nonpolar carbon tetrachloride causes a splitting of the β loss peak which may indicate a selective suppression of local segmental motions in nonpolar regions of the polymer. Polycarbonate liquid blends may also exhibit additional loss peaks at temperatures above or below the β loss peak. Volume losses are observed for all blends whose specific volume has been measured. Electron microscopy of etched polycarbonate blends indicates 600 to 1100 Å structures exist in brittle polycarbonate blends with Arochlor 5442 whereas a 300-Å structure exists in ductile blends with dibutyl phthalate or unmodified polycarbonate. Tensile property measurements demonstrate that absorbed liquids do not embrittle glassy polycarbonate though largely reducing yield strain. Orientation decreases specific volume and produces only slight changes in shape and intensity of the low temperature β-transition loss peak. The major effect of orientation is to enhance “intermediate” loss processes at 80 and 120°C in glassy polycarbonate. The β-transition appears isotropic; however, the intermediate loss process at 80°C is anisotropic. These results tend to question previously suggested correlations between high-impact strength and the low-temperatureβ-transition or free volume. It is suggested that the impact strength of polycarbonate at 23°C may be associated with loss processes at higher temperatures. This association is supported by a comparison of activation energies for yielding with activation energies for transitions due to molecular motion.Keywords
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