In tabulating data on plastics for handbooks and manufacturers' bulletins, information on the effect of chemical reagents is generally included. The selection of compounds and concentrations for use in such tests was given early consideration by ASTM Committee D-20 on Plastics, and Tentative Method of Test D543-39 T for resistance of plastics to chemical reagents was included in the first group of methods adopted by that Committee.
This not only provided a uniform test procedure for use in purchase specifications, but insured comparable data on new and on the older varieties of plastics.
The Organic Plastics Section of the Bureau cooperated in the exploratory investigation undertaken while preparing the ASTM test method. The following plastics were examined: Molded, cast and paper-base laminated phenol-formaldehyde resin ; molded and paper-base laminated urea-formaldehyde resin; molded and cast polystyrene; cast methyl methacrylate resin ; vinyl chloride-acetate resin ; vinyl butyral resin ; coldmolded bituminous plastic ; cold-molded phenolic plastic ; cellulose nitrate ; cellulose acetate ; ethylcellulose ; and casein plastic. The resistance of these materials to all standard and supplementary reagents listed in the ASTM method was determined.
These included weak and strong acids, weak and strong alkalies, salt solutions, hydrogen peroxide, and organic solvents. Changes in the weight, dimensions, and appearance of the test specimens were recorded. These experimental data were reported in a paper by G. M. Kline, R. C. Rinker, and H. F. Meindl, presented at the annual meeting of the American Society for Testing Materials in Chicago on June 24.
The limitations of these results as well as those of other tests for determining the permanence of plastics should be recognized.
The choice of types and concentrations of reagents, duration of immersion (7 days), temperature of the test (25O C.), and properties to be reported upon, is necessarily