مقاله ها
نویسنده : TAGHI ZADEH M.T. ،FAKHIMI F.
بازدید : 209

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 Organic stabilizers have been investigated as thermal stabilizers for rigid polyvinyl chloride (PVC) at 180°C in inert atmosphere by measuring the rate of dehydrochlorination and changes in intrinsic viscosity، UV absorption spectra، FT-IR spectra and levels of unsaturation in the degraded polymer samples have been used to assess the effects of the materials on the degraded polymer. Theirs stabilizing efficiencies are based on measuring the length of the induction period (TS)، the period during which no detectable amounts of HCl gas could be observed، and also from the rate of the dehydrochlorination as measured by bromometry titration on the one hand، and the extent of discoloration of the degraded polymer samples on the other. The results revealed the greater stabilizing efficiencies of the investigated materials as shown by their longer induction periods (TS) and by the lower dehydrochlorination rate in relation to blank PVC. The stabilizer efficiency attributed to the replacement of the labile chlorine on the PVC chains by a relatively more thermally stable aromatic and aliphatic moiety. A radical mechanism for the stabilizing action of the investigated stabilizers is offered. A synergistic effect achieved when the material under investigation were blended in 1:1 weight ratio with either. The results reveal that mixing of the stabilizers improves the TS values، the rate of dehydrochlorination and the extent of discoloration.  
 


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