Adaptations of ASTM D746, ‘‘Brittleness Temperature ofPlastics and Elastomers by Impact’’, have also been used.Where low temperature service is involved, it may berequired that a certain percentage of parts must not bebroken by a standard blow at some selected temperature.Treatment with a solution of potassium acetate in water.This method requires a heated vessel with a cover and areflux condenser. By using the ratio of 125 parts by weightof potassium acetate to 100 parts by weight of water, amaximum of 2,8% of water (equivalent to 50% RH) isabsorbed by ZYTEL® 101. Unlike the previous method,additional time beyond that required will not put in moremoisture. Conditioning in potassium acetate solution iscarried out at or near the boiling point of this solution120°C for maximum acceleration of the process. The timerequired for any thickness may be read from Figure 6.19.The problems with this procedure are the cost of potassiumacetata and the need to maintain the solution at therequired concentration. This is an excellent method forpreparing test samples, since a true equilibrium conditionis established. It is not suitable where electrical or burningcharacteristics are to be studied because of absorption ofsmall amounts of potassium acetate on the surface.