Optimization of the curing conditions of PVC plastisols plasticized with ethyl cinnamate

Abstract

The use of ethyl cinnamate, an ester of cinnamic acid present in many fruits and plants, as a bio-based plasticizer for polyvinyl chloride (PVC) plastisols has been investigated. Different temperatures (180, 190, and 200 °C) and curing times (8, 11.5, and 15 min) have been evaluated for PVC plasticized with 70 phr (parts by weight of plasticizer per one hundred weight parts of PVC resin) of ethyl cinnamate in order to optimize the curing conditions of the material, as these play a fundamental role in determining the final properties. Optimization of curing conditions has been carried out by analyzing the effect of temperature and curing time on the tensile mechanical properties, thermal stability, morphological, color changes, and migration tendency for the different plasticized materials. It has been observed that the optimal curing conditions for PVC plasticized with ethyl cinnamate are achieved at a curing temperature of 190 °C and a curing time of 11.5 min. Under these conditions, a material with high tensile strength, around 6.4 MPa, and a high elongation at break, close to 570 %, is obtained which is comparable or even superior to materials cured in the presence of other conventional plasticizers used in the PVC industry. Additionally, through field emission scanning electron microscopy (FESEM), it has been observed that for these conditions, the curing process is complete, resulting in the complete fusion of PVC microcrystals. A material with high cohesion and very low migration loss, around 2.4 %, is obtained. The effectiveness of these curing conditions has also been demonstrated using thermogravimetry. An increase in the PVC dehydrochlorination temperature has been observed due to optimum plasticizer absorption and gelation.