M. Pizzoli, G. Pezzin, G. Ceccorulli
1982
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Abstract
ABSTRACT The Methyl-, Ethyl-, n-Butyl-, n-Octyl- and n-Hexadecyl esters of Octadecanoic (Stearic) acid were synthetized from the corresponding alcohols and pure Stearic acid. Their physical properties were determined and their viscous flow parameters were calculated according to both the Eyring theory and the Batschinski-Hildebrand treatment of viscosity. The results are favourably compared with similar published data on hydrocarbons and with values for low molecular weight esters. Different amounts of each stearate were mixed with Polyvinylchloride at 90°C. The solubility of the esters in the polymer, determined by measuring the crystallizable undissolved ester by means of a Differential Scanning Calorimeter, decreases from 6.5% to 0.3% with increasing chain length of the stearates. The Flory-Huggins interaction parameter χ, obtained from the solubility results, increases from 1.6 (Methylstearate) to 4.2 (n-Hexadecylstearate). The lengthening of the aliphatic chain, which results in a dilution of the ester groups, apparently weakens the PVC-ester interactions. The glass transition temperature T g decreases with increasing diluent content down to a constant value closely related to the ester solubility. The decrease of T g brought about by the PVC-ester interactions is described by the free volume theory, using a single equation for all the systems examined.