Preparation of dipentaerythritol-combined layered double hydroxide particle and its thermostabilizing effect for polyvinyl chloride

Abstract

In recent years, layered double hydroxide (LDH) well-known as hydrotalcite-like compound has received considerable attention due to its potential technological applications such as antacid, anion-exchangers, stabilizers and reinforcing fillers for synthetic or natural organic polymers. On the other hand, one of polyhydric alcohols, dipentaerythritol (Dpe), is known as a typical component of polyvinyl chloride (PVC) stabilizer. In this study, we attempted the intercalation of Dpe into a carbonated Mg–Al LDH (the Mg–Al/CO3/LDH) interlayer by the thermal reaction using molten guest substance to develop a new effective thermostabilizer for PVC resin. During the thermal reaction at 200–235 °C, the decarboxylation and dehydration of the Mg–Al LDH proceeded and the solid product at 235 °C after 3 h was found to be the most disordered structure, not the Dpe-intercalated LDH. The results of FT-IR, TG-DTA, and chemical analysis exhibited that the solid product was the aggregate of the disordered LDH particles covering with Dpe molecule (Mg–Al LDH-Dpe composite) and a small amount of the Mg–Al/OH/LDH. Next, we prepared the PVC sheet by loading the solid product or various kinds of additives into PVC paste resin with dioctyl phthalate and etc. by molding and subsequently by heating. In the heat-resistance test of the resulted PVC sheets at 180 °C for 2 h, the PVC sheet loaded with the solid product showed the longest heat-resistance in all the cases. It also exhibited the best results in each the hardness and elongation tests of the PVC sheet recovered after the heat-resistance test. Although we could not prepare the Dpe-intercalated LDH, the Mg–Al LDH-Dpe composite exhibiting the expectable ability as thermostabilizer for PVC resin was obtained in this study.