Abstract ................................................................................................... 89 5.1 Introduction .................................................................................... 90 5.2 Materials and Methods ................................................................... 93 5.3 Results and Discussion .................................................................. 96 5.4 Conclusion ................................................................................... 104 Keywords .............................................................................................. 104 References ............................................................................................. 105

ABSTRACT

Different zinc borate species were tested for their use as thermal stabilizers for polyvinyl chloride plastigels. PVC thermomat tests, thermal gravimetric analysis (TGA) and color tests were made for measuring thermal stability. PVC thermomat tests indicated that the induction time was shorter and the stability time was longer for plastigel without any

zinc borate than the plastigels having different kinds of zinc borates. Zinc borates prevented dehydrochlorination of PVC at early times, but after accumulation of ZnCl2 to a critical level, the samples underwent accelerated dehydrochlorination due to strong Lewis acidity of ZnCl2. Zinc borates had a smoke suppressant effect leading to increase in the solid residue formed at 600°C as indicated by TGA. The discoloration of the samples with 2ZnO 3B2O3 7H2O, 7ZnO B2O3, and 4ZnO B2O3 H2O was prevented at early heating periods as indicated by their yellowness index values. Thus zinc borates can be recommended as thermal stabilizers for short heating periods at low temperatures.