Thermal dehydrochlorination of pure PVC polymer: Part I—thermal degradation kinetics by thermogravimetric analysis

Abstract

Thermal degradation of PVC occurs in two stages, with each stage subdivided into two substages. The first refers to the dehydrochlorination, where hydrochloric acid is formed, and giving polyene structures. Hitherto, the degradation mechanism and action of hydrochloric acid as a catalyst during the dehydrochlorination stage are poorly known. Recently, the importance of the tacticity has gained attention for its influence on the dehydrochlorination mechanism. The present work focused on the dehydrochlorination stage, studying the molecular structure by FTIR analysis and the kinetic parameters by TGA analysis in Nitrogen atmosphere, based on three mathematical methods: Friedman, Kissinger, and Flynn-Wall-Ozawa. The sample was a pure homopolymer obtained by suspension polymerization. The dehydrochlorination kinetics follows a first order reaction model and occurs by nucleation and growth. The dehydrochlorination begins with the loss of very labile chlorine atoms present in defective and isotactic molecular segments. The formed HCl acts as a catalyst in the degradation. Following 40% conversion, a drop in Ea is observed. After that, chlorine atoms present in syndiotactic and atactic sequences, are released and, added to the large number of polyene chain sequences, and an increase in Ea is observed up to 60% conversion, where the dehydrochlorination stage is concluded.

Effects of Organic Based Heat Stabilizer on Properties of Polyvinyl Chloride for Pipe Applications: A Comparative Study with Pb and CaZn Systems

“…Moreover, in Figure 8 , the activation energy for the first substage of the dehydrochlorination of PVC/Pb and PVC/CaZn tended to decrease from 10% conversion until approximately 40% conversion and increasing thereafter as similarly reported in Ref. [ 25 ]. These characteristics confirmed that the energy required to break the C-Cl bond in the first substage of dehydrochlorination is high.…”

“…The first stage is mainly attributed to dehydrochlorination by the removal of hydrogen chloride from the PVC main chain, thus forming a conjugated polyene structure. The second stage is mainly attributed to the fracture of conjugated polyene structures to form small molecular weight linear or cyclic hydrocarbons, and finally tar formation [ 25 , 26 ]. In addition, it was observed that there is a substage in the first stage of the PVC, indicating the existence of different events in this stage, suggesting a complex dehydrochlorination mechanism.…”

Synthesis, Characterization, and 3D Printing of Silver Nanoparticles/Photopolymer Resin Composites

“…It is demonstrated by the viscosimetric analysis and its response to the temperature and heat flow using thermogravimetric analysis (TGA). Polymeric solutions are generally non-Newtonian fluids, but they possess intrinsic properties and thereby possess the ability to increase the viscosity of the composites [20]. Due to its easy processability, PMMA is a good viscosifier and provides good polymer-additive interaction [21].…”

An AuCl3‐CuCl2 catalyst on a Melamine‐modified Carbon Support with High Coke‐resistance for Acetylene Hydrochlorination

“…Due to our country's rich coal resources, acetylene hydrochlorination based on the coal route is the main process for the synthesis of vinyl chloride monomer (VCM) in China, which provides raw materials for the polyvinyl chloride (PVC) industry. [1] However, the HgCl 2 catalyst used in this process is volatile and toxic, which seriously endangers the environment and lives. In recent years, it has gradually been restricted by the scarcity of mercury resources and environmental protection policies.…”