Thermoaminolysis Products of Polyethylene Terephthalate as Modifiers of Highly Filled PVC Plastic Compounds

The effect of replacing the plasticizer dioctyl terephthalate (DOP) with the plasticizer dioisononyl phthalate (DINP) in PVC plastics filled with calcium carbonate and modified with thermoaminolysis products of recycled polyethylene terephthalate was studied. Research was carried out on the thermal stability of the studied PVC plastic compounds using the Congo red method. It has been shown that the thermal stability of all experimental samples is within standard values (no more than 40% weight loss). It has been established that aminolysis products have a positive effect on increasing the thermal stability of PVC plastics. It was found that the most effective aminolysis products are those synthesized at a temperature of 170 °C at the ratio (mol) PET:MEA = 1:2 (IIIa), 1:4 (IIIb)). Replacing the plasticizer DOP with DINP does not significantly affect the induction period before the start of PVC dehydrochlorination. The Hansen method was used to calculate the compatibility of PVC with plasticizers DOP, DINP and a modifier obtained by aminolysis of recycled polyethylene terephthalate. Calculated data indicate high compatibility of plasticizers DOP and DINP with PVC. At the same time, the compatibility of DOP and DINP with PVC is at a fairly high level. It was found that the aminolysis product of PET is also well compatible with PVC. Physical and mechanical tests of PVC plastic samples were carried out. It has been established that aminolysis products contribute to an increase in the elastic modulus and tensile stress. It was revealed that the use of the plasticizer DINP does not have a significant effect on the change in the strength parameters of the experimental samples. When studying the swelling of PVC composite samples in water and gasoline, high resistance to the test media was revealed. It has been established that the degree of swelling in water is up to 0.1% wt., and in gasoline - from 1.5 to 1.9% wt. These values are within the permissible limits according to GOST 6960-72. The effectiveness of the influence of aminolysis products on the heat resistance of PVC samples with the additions of DOP and DINP was examined using thermogravimetric analysis. As a result, the increase of thermal resistance was revealed, with the best results shown by samples with plasticizer DINP.