Effect of Zinc Molybdate on the Fire-Resistant and Physicomechanical Properties of PVC Plastic

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—In this paper, we synthesized zinc molybdate in a quantitative yield and introduced it into polyvinyl chloride (PVC) plastic as a flame-retardant modifier. We determined the oxygen index, coke residue, and thermophysical and physicomechanical characteristics of PVC plastic/zinc molybdate composites during combustion. The introduction of zinc molybdate into PVC plastic compound was found to produce a flame-retardant material. Zinc molybdate was shown to promote the formation of coke residue of PVC plastic. Upon burning the plastic, the surface is covered with a denser coke crust that prevents combustible products of destruction of the plastic from coming into the flame zone. The rates of heat release and smoke emission during PVC plastic/zinc molybdate combustion, as well as its thermal stability, are determined. The introduction of zinc molybdate in PVC plastic was found to reduce smoke formation during combustion of the plastic and increase its thermal stability. This is due to the effect of zinc molybdate on combustion and dehydrochlorination of PVC plastic. Zinc molybdate alters the thermophysical parameters of combustion of PVC plastic and prevents the release of hydrogen chloride during its destruction. The amount of smoke and the heat of combustion of PVC plastic containing zinc molybdate are lower than those of the initial material. It is shown that zinc molybdate can partially or completely replace the toxic fire retardant Sb₂O₃ while maintaining a balance of smoke formation, fire resistance, and thermal stability. The introduction of zinc molybdate into PVC plastic is established to improve the basic physicomechanical and technological properties of the compound. In particular, an insignificant increase in the density of PVC plastic was found within the permissible limits; i.e., the upper limit does not exceed 1.50 g/cm³. At the same time, upon introducing zinc molybdate, the stress and relative deformation of PVC plastic also increase, which is due to reduction of the defectiveness of the structure of the compound upon the introduction of a flame retardant modifier.