Studies On Effect Of Additives On Photo Aging And Smoke Suppression Property

With the development of west of China, Poly(vinyl chloride) has large and broad uses in many industrial applications. Because of atrocious weather of the West, especially under ultraviolet light, polymeric material is accelerated aging, and lost the service performance. Therefore, it is important to study the mechanism of accelerated photo aging behavior for PVC.In this paper, the law and mechanism of accelerated aging of poly (vinyl chloride) systems was studied via simulating the typical environment of strong ultraviolet radiation in West of China. The effect of UV irradiation on performances of pure PVC, PVC/stabilizer systems and PVC/ impact modifier systems were studies. With the increase of ultraviolet radiation time, the changes of mechanical properties, appearance colour, surface resistance and weight loss before and after aging were observed. In addition, gel content, SEM, UV—Vis, FTIR, GPC, DSC, TG, XPS were taken to characterize the microstructure of PVC/additives system during the process of aging. The purpose of this study is to gain the law and mechanism of accelerate aging of PVC in the only influence of ultraviolet radiation and accumulate data for the research of the law and mechanism of accelerate aging of PVC in the synergic influences of the typical environment in West of China.1. With the increase of ultraviolet irradiation time, the colour of PVC darked, the mass loss increased, the surface resistance decreased slowly. The model of SG-3 has better colour stability, lower rate of elimination of HCI and crosslinking, The rate of formation of conjugate double bond and crosslinking reaction has same tendency, that is increase rapidly in the earlier period, and increase slowly in the later period. The tendency of oxidation degradation reaction is increased gradually. Furthermore, photo aging lead to lower molecular weight, wider Molecular-weight distrbution, worse stability.2. The sequence of retained percentage of impact strength of PVC/stabilizer systems: Pb＞Ca-Zn＞Sn. The tensile strength is constant almostly during UV-irradiation. The elongation at break decreased rapidly in the beginning of UV-irradiation. The order of retained percentage of elongation at break is: Pb＞Ca-Zn＞Sn. The stability of appearance colour: Sn＞Pb＞Ca-Zn. The decrease extent of surface resistance: Ca-Zn＞Sn＞Pb. The rate of conjugate double bond and crosslinking has same order, that is Ca-Zn＞Pb＞Sn. The rate of photooxidation and photodegradation: Ca-Zn＞Sn＞Pb3. The sequence of retained percentage of impact strength of PVC/ impact modifier systems: CPE＞ACR＞ABS. The tensile strength is constant almostly during UV-irradiation. The order of retained percentage of elongation at break is: ABS＞ACR＞CPE. The stability of appearance colour: ACR＞CPE＞ABS. The rate of mass loss: ABS＞CPE＞ACR. It was found that ACR and CPE decelerates PVC photodehydrochlorination and photocrosslinking. The sequence of rate of conjugate double bond and crosslinking is ABS＞CPE＞ACR. The rate of photooxidation and photodegradation: ABS＞ACR＞CPE.4. The stabilizers have positive effect on smoke suppression of PVC. It can reduce the total output of aromatic compounds during decomposition of PVC, increase the gel of condensed phase and char residue, especially Ca—Zn stabilizers. The activity of Ca—Zn stabilizers change the decomposition process of PVC via ZnCl₂ formed during decomposition: On one hand, ZnCl₂ can restrain the intramolecular cyclization reactions, and reduce the total output of aromatic compounds during decomposition of PVC. On the other hand, it can promote the crosslinking reactions during decomposition and increase the char residue.