Studies on the thermal stabilization for Polyvinyl chloride by some metal stearates

Abstract

In this study, preparation of some metal stearates derived from stearic acid with metals ;
Iron , Cobalt, Nickel, Copper and Zinc . They were used as thermal stabilizers for Polyvinyl
chloride. These metal stearates were identified by elemental analysis and infrared
spectroscopy.I.R, spectroscopy within the rang 1500-1900 cm-1 was used to study the thermal
stability for PVC containing prepared metal stearates , and that depending on thin films
technique . The variations in the absorption bands intensity of the groups C = O , C = C ,
COO - at 195oC were studied at different times (15 ,30 ,45 , 60 min) from thermal stress.
These variations resulted from the rule of the metal stearates in the stabilizing of polymer .
U.V-V.S spectroscopy was used to study the thermal degradation of unstabilized PVC and
the reprecipitated PVC from the stabilizers .This study was carried out by the investigation of
the polymer resulted from the evolving of HCl from the polymer chain at 275nm and 385 nm
corresponding to three and seven conjugated double bonds respectively .The results were
indicated that metal stearates and their synergistic mixtures have the ability to stabilize PVC
by decreasing the conjugated double bonds in the polymer .
The thermal stability of the unstabilized PVC and PVC containing different metal
stearates was investigation by thermogravimetric analysis (TGA). Many functions were
calculated such as the decomposition temperature , rate of decomposition ,activation energy
,char content ,and percentage of HCl evolving from the polymer chain . The results indicated
that metal stearates was increasing the thermal stability for PVC.