Non-isothermal melt crystallization kinetics for ethylene–acrylic acid copolymer in diluents via thermally induced phase separation

Abstract

Non-isothermal crystallization kinetics of the ethylene–acrylic acid copolymer (EAA) in diluents during thermally induced phase separation (TIPS) process was investigated via differential scanning calorimetry (DSC). Dioctyl phthalate (DOP), diphenyl ester (DPE), and peanut oil were used as diluents. Kinetic models, such as Jeziorny theory, Ozawa theory, and Mo’s approach, were utilized for description. The effective activation energy of EAA component in mixture was calculated by Friedman’s method. In the results, the Jeziorny theory and Mo’s approach could obtain good linear fitting relationship with the primary crystallization behavior of EAA, but the Ozawa theory failed to get a suitable result. The homogeneous nucleation of EAA proceeded at the end of liquid–liquid phase separation, while the non-isothermal crystallization developed within a solid–liquid phase separation environment. In the mixtures, the molecular weight, polar groups, and conformation of the diluent molecules would affect the nucleation of EAA, and its growth rate. Comparing with the non-isothermal crystallization of neat EAA, EAA in diluents obtained a higher Avrami index n, and comparatively lower crystallization rate. Peanut oil facilitated the homogeneous nucleation of EAA, leading to a higher melting peak temperature of EAA in the subsequent melting endotherms. The largest EAA’s Avrami index obtained in peanut oil also indicated a higher crystal growth dimensional geometry. The crystallization rate and crystallinity of EAA during the non-isothermal process decreased in the sequence: EAA/DPE > EAA/DOP > EAA/peanut oil.