The Synthesis Of Antimony Organic Sulfur-Containing Compounds And The Studies On Their Thermal Stability And Thermal Mechanism For Poly (Vinyl Chloride)

PVC is unstable and when subjected to heat they initiate a self-accelerating dehydrochlorination reaction. Stabilizers neutralize the HC1 produced and introduce nucleophilic substitution reactions that prevent further degradation. So stabilizers play a very important role in PVC formulation. Today people play more and more attentions on environmental protection, so many PVC stabilizers, such as lead, cadmium and barium stabilizers, will be limited strictly and some of them will be prohibited to use. Antimony mercaptides possess many advantages, such as good heat stability, long-term heat stability with little loss in color, low toxic effects on environments, good property for processing and offer unexcelled cost/performance as stabilizers for pigmented, rigid, extruded PVC. China is rich in antimony resources. We have advantages of using it to preparing PVC stabilizers.In this dissertation, a review has been made systematically in the field of heat stabilizer for PVC, especially in the current situation and the applied prospect of the research on antimony heat stabilizers. We have proposed antimony organic sulfur-containing compounds, which includes antimony reverse-esters and antimony pent (mercaptoacid esters) and their complex stabilizers. And, the stability and degradation kinetics of PVC which containing antimony stabilizers were studied. The PVC formulation design and the stability mechanism of PVC were studied also.At first, antimony tris (mercaptoethyl carboxylate), their general formula are Sb (SCH2CH2OOCR)3, (R: CnH2n+1 , n=7,ll,17), were synthesized from carboxylic acid, antimony trioxide and 2-mercapto ethanol in two steps. The reaction conditions of synthesis have been optimized through orthogonal test. The physicochemical properties of the products were tested too.The antimony pent (mercaptoacid esters), their general formula are Sb (SCH2COOCnRn-n)5, (R: CnH2n+i, n=8, 12, 16, 18), were synthesized by the methods of emulsion reaction and solid-liquid phase reaction. The reaction conditions were discussed in detail.AbstractThe thermal stability of PVC which incorporated with antimony thermal stabilizers was measured by Congo-red test paper, and the color was tested by heat-aging oven test combining with ultraviolet-visible spectrophotometer. In addition, the synergistic character of antimony compounds with calcium/zinc/barium stearate, rare earth compounds and organotin was discussed.The thermal stability data were obtained by orthogonal and simplex method, and fitted by least square method. Based on the concept of component contribution, "component-contribution parameter" and "synergistic parameter" were suggested. The optimization models of PVC formulation design were established by using quadratic programming. These models agree well with the experimental data.The weight loss behavior of PVC was measured by thermogravimetry (TG) and then using Arrhenius equation to fit the DTG data obtained from the TG measurement. The computer software has been developed with Matlab language, and the kinetic parameter can be obtained from DTG data directory by this software.In the end of this dissertation, we proposed that the degradation procedure of PVC can be divided into 3 steps according to the degradation kinetic character in the range of room temperature to 500 . Moreover, the thermal stability and synergistic mechanism of antimony thermal stabilizers were discussed by using the ultraviolet-visible spectrophotometer and infra-red absorption spectroscopy.