Determining Resin Content
Chemical & Engineering News · 1956
THE National Bureau of Standards has developed a fast and accurate method for determining resin in glass fiber-polyester laminates where calcium carbonate is a filler. S. D. Toner of the Bureau's plastics laboratory has demonstrated that high, resin-decomposing temperatures used in the usual test cause calcium carbonate to decompose, producing errors in the results. The new method, developed for the Air Force, restores the decomposed calcium carbonate to the residue so that resin content can be more precisely calculated. Normally, the resin content of a glass fiber-polyester laminate is determined by igniting the specimen at 565° ±27.5° C., until the resin is vaporized and driven off. The difference in weight between the original specimen and the ignition residue is equal to the resin content. In the Bureau's method the laminate specimen is ignited until no weight changes occur. The ignition residue is then treated with excess saturated ammonium carbonate solution, which reacts with calcium oxide ...