Thermal dehydrochlorination of poly(vinyl chloride)—epoxidized butadiene/styrene triblock copolymer blends

Autor: Danuta Żuchowska, Wanda Meissner
Rok vydání: 1998
Předmět:
Zdroj: Polymer Degradation and Stability. 60:415-424
ISSN: 0141-3910
Popis: The effect of the type of epoxidized butadiene/styrene block copolymer [ESBS; linear (B/S) or radial (E(B/S)n), containing 0–27% of epoxy groups] on the thermal dehydrochlorination of poly (vinyl chloride) (PVC)-ESBS blends (ESBS content 10%) was investigated in the temperature range 170–180 °C, under a non-oxygen atmosphere. Thermal stability of the PVC-ESBS blends was estimated on the basis of induction time, t0, and maximum rate of hydrochloride emission, Vmax from the system. It was found that, for a similar degree of epoxidation of the SBS copolymer, the induction time i.e. the time after which emission of HCl begins, is longer in the series PVC < PVC-SBS < PVC-EB/S < PVC-E(B/S)n, and the same is true for thermal stability. However, the maximum rate of emission of HCl is lowest in the case of PVC-EB/S blends, in the range of molar ratios from 0.5 to 2.0 × 1O−2. On the basis of the dependence Vmax = f(EBVC), it was found that there is a certain content of epoxidized butadiene (EB) units in a mixture which causes the optimum stability of poly (vinyl chloride) during heating. During thermal destruction of the PVC-ESBS blends, the HC1 evolved undergoes addition both to epoxy fragments and to double bonds. The degree of conversion of EB units in time t0 is 20% at 170 °C and 30% at 180 °C. The glass transition temperature, Tg, of PVC in the PVC-ESBS blends shifts towards higher temperatures by about 6–8 °C, proving the existence of crosslinking processes during moulding of the blends. The epoxidized butadiene/styrene radial block copolymer, E(B/S)n, is a better thermal stabilizer of PVC than the linear EB/S copolymer.
Databáze: OpenAIRE
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