Surface Modification And Application Of Alkaline Clay PVC Thermal Stabilizer

Polyvinyl chloride resin (PVC) is polymerized from vinyl chloride monomer, because of its unique flame resistance, abrasion resistance and weather resistance and other characteristics, has become general-purpose plastics. It is a significant material in people's life. But there is unstable structure in PVC, it will lead to the degradation of HCl and affect on material properties. So it is necessary to add the thermal stabilizer in fabrication of PVC. The most commonly used heat stabilizers is lead salt stabilizers, metal soaps stabilizers, organotin stabilizers, hydrotalcite stabilizers. Due to the efficient and non-toxic stabilizers are expensive, so cheaper but toxic lead salt stabilizer still occupy a certain market, when it is limited to use. In order to provide an efficient, non-toxic and inexpensive heat stabilizer, this paper explores the possibility of alkaline clay PVC heat stabilizer. Study the surface modification of the alkaline clay and its evaluation of application performance.This article was based on the preparation of high-capacity alkaline clay and it was modified by stearic acid in the surface as the PVC thermal stabilizer. Activate the index and sedimentation volume in paraffin as evaluation index, the amount of stearic acid, modified temperature and modification time were studied in the process of alkaline clay surface modification. Analyze the mechanism of the surface modification by X-ray, FT-IR. SEM and particle size determination were used to study the surface morphology and particle size of alkaline clay. The influence of alkaline clay or mixed with zinc stearate as thermal stabilizers to the PVC paste was studied by Congo red experiment, heat oven method and TG. The influence of alkaline clay on mechanical properties and insulation were studied by measuring the stretch, elongation at break and volume resistivity. Mechanism for stabilizing alkaline clay heat stabilizer was discussed and compared with other thermal stabilizers in performance and cost.Single factor experiment results showed that the optimum conditions for the surface modification were as follow:The amount of stearic acid is 3%, modified temperature is 70? and modified time is about 2-3 h. Character-ization results showed that stearic acid did not enter the interlayer of betonies powder and would produce calcium stearate in the process of modification. Alkaline clay maintained the layered structure in the plastic processing tempe-rature range, and it was more stable after the surface modification. The average particle diameter was 24.1 ?m. Production cost estimated for 2708 Yuan per ton, the price was set at 4500 Yuan per ton.The experiments of PVC paste adding alkaline clay stabilizer results showed that the alkaline clay significantly improved the thermal stability of PVC; HCl was absorbed by hydroxide that was loaded in inter-layer, so it could be used as a long-term thermal stabilizer. Adding less than 5 phr, the tensile properties of the material has little effect. Volume resistivity of the material could be improved. Alkaline clay had a synergistic effect with zinc stearate, improved initial coloring, when alkaline clay added 3 phr and the optimum amount of zinc stearate was 0.2 phr. Compared with the common heat stabilizers, the performance is slightly worse than that of the hydrotalcite stabilizers, lead salt heat stabilizer, but alkaline clay was better than the calcium zinc stabilizer. And alkaline clay had obvious advantages in the price, was expected to promote and replaced some toxic lead salt thermal stabilizer and high price thermal stabilizer.Filling polyethylene experiment showed that alkaline clay modified by stearic acid could be as filler. When the adding amount less than 15 phr, the tensile strength of alkaline clay was better than calcium carbonate, and its elongation at break less than the addition of calcium carbonate. The alkaline clay had obvious smoke suppression function to polyethylene. It is possible to complex alkaline clay with the halogen flame retardants to reduce smoke emission and acid gas release.