Physical aging of blends of cellulose acetate polymers with dyes and plasticizers

A systematic study of physical aging in polymers that have been plasticized by the addition of dyes and polymeric plasticizers is undertaken using the heat capacity as the structural probe. The dyes are actually dye sets and are mixtures of various dyes with slight structural differences, each with a different glass transition temperature (Tg). The polymeric plasticizers are low molecular weight polyesters that have low values of Tg. From experimental results and their analysis, it is shown that aging occurs under ambient temperature conditions most rapidly for the polymer–dye samples that have their Tg value at 20°C above ambient temperature. The results for these thermorheologically complex blends also indicate that, although the incorporation of the polymeric plasticizers substantially reduces the Tg of the blend, the distribution of relaxation times is broadened. cs of aging for the blends are determined using the Tool–Narayanaswamy model for structural relaxation. The fictive temperatures were calculated as a function of annealing temperatures and annealing times in order to assess the effects of storage upon the practical performance of these blends.