The Self-Degradation Mechanism of Polyvinyl Chloride-Modified Slag/Fly Ash Binder for Geothermal Wells

Abstract

Polyvinyl chloride (PVC) releases hydrochloric acid (HCl) during its thermal degradation, and hydrochloric acid can react with hydration products of alkali-activated binders. According to this characteristic of PVC and the temperature change that occurs during the development of a geothermal well, the PVC was added into slag/fly ash binder to develop self-degradable materials. The thermal degradation properties of PVC, compressive strength, hydration products, and microstructure of binders at different stages were tested, in order to study the degradation mechanism of the material. It was found that 20% PVC reduced the compressive strength, decreasing the level of binder from 13.95% to 76.63%. The mechanism of PVC promoting the material degradation mainly includes the following: (1) the thermal degradation of PVC increases the number of multiple damage pores in the material, at a high temperature; (2) HCl generated by the PVC thermal degradation reacts with the binder gels, and breaks them into particles; and (3) HCl also reacts with other substances in the binder, including CaCO3 and NaOH in the pore solution.

Novel CaCO3-Based Material Formulation for Orange-Colored Spectrum Tracer Projectile

“…The intensity band at 3,443 cm −1 (-OH stretching) sharply increases after heating at 650 ℃ due to the interaction between calcium carbonate with hydrochloric acid which generates the amount of H2O, however the peak intensity reduced after the temperature reached at 850 ℃. In addition, there is also a shaper band at 1,625 cm −1 (O-H bending), which suggests that there was chemically bound water in the samples [53,55]. On the other hand, the heat treatment at 650 ℃ also leads the slightly shifting vibration peak at 2,512 cm −1 into 2,511 cm −1 , where this peak is represented as a hydrocarbon chain (C-H).…”

Synergistic effect of talc/calcined kaolin binary fillers on rigid PVC: Improved properties of PVC composites

“…On the other hand, PVC is a heat-sensitive polymer and its thermal decomposition releases toxic hydrogen chloride gas. [23] The thermal resistance of PVC can be improved by adding calcined kaolin. On the other hand, the risk of corrosion of processing machinery induced by the diffusion of chlorides and/or HCl by the presence of metakaolin in the PVC formulation can also be reduced.…”