ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The hydrolytic stability of a new commercial polycarbonate (Calibre 300, Dow Chemical USA) was investigated and compared with that of other commercial polycarbonates. The tests were conducted between 56% and 95% relative humidity (R. H.) at 100°C. Also performed were water immersion tests at 80 and 100°C. The water diffusivity was found to be 8.7 × 10-7 cm2/s at 100°C with an activation energy of 7.9 kcal/mole. These values are similar to other glassy polymers. The equilibrium water sorption, C∞, was found to increase with temperature and R.H. The isotherm at 100°C was determined to be: C∞ = 0.005945 [R.H.]. When samples immersed in a water bath at 100°C were transferred into room-temperature water, visible aqueous microcavities were formed due to the condition of super-saturation, and under stress may become crack initiation sites. For the polycarbonate investigated here, it was found that the decrease in weight-average molecular weight (M̄)w was a first-order process under a constant R.H. and temperature, and that hydrolytic embrittlement, i. e., (M̄)w 〈34,000, was reached after ca. 188, 143, 99, and 66 days under 56%, 73%, 87%, and 95% R.H., respectively, at 100°C. A comparison with reported hydrolytic stability data for other polycarbonates showed large differences in their stability which are believed to be due to the extent of end-group capping (over 95% in Calibre 300) and resin purity: both phenolic end-groups and some additives (i.e., fire retardants, thermal stabilizers) are known to accelerate hydrolytic degradation.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760292402
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