On the weathering of modified PVC based compounds during the polymerization process

Abstract

The variations of molecular spectra, colours and characteristic viscosity of modified and unmodified PVC compounds during the polymerization process in various periods of time of natural ageing have been investigated. The PVC types modified during synthesis by 0,25 % vol. plasticizers or plasticizers' mixture are characterized by 10 -12°C lower glass transition temperature, higher thermal stability, long-term behaviour and better physical and mechanical properties. The Charpy-impact resistance is increased by 50 to 8 5 %. The rate of the relative UV-sorption variation during outdoor exposure was lower for compounds based o n the modified PVC types. The polyene parts amount of chain length n=13, evaluated by means of Raman spectra, was increased during the first and seconc month, * By means of IR-spectroacopy the variations of the hydroxyl-and carbonyl groups were .valuated and the diffemncee in the oxidation kinetica were establiehed. IIPTRODUCTION The problem related to the low photooxidation etability of the PVCone of the main induetrial polymers, is a subject of numarour inveetigatione1*2. It is well that polyvinylchloride compounds weathering is a procees influenced by a lot of factore and is accompanied by photolyee, photooxidation and dehydrochloration. The sensibility, the transfer of energy and the einglet oxygen processes are aleo of coneiderable importance5. The defective structures and mixture8 in the PVC decreeee the photooxidation stability of the polymer and the PVC baaed compounds photooxidation etability. In order to enhance this property additive8 for internal a t a b i l i~a t i o n~*~, W-stabilization8 and colouring agents' are uaed. The photooxidation deetruction ie extremely complex proceee, which mechaniem is not well explained5*''. The inveetigatore mainly examine the photooxidation kinetics procees created by the influence of the monochromatic light of wave length 254 m~~~" . Theee investigations may hardly be compared to the natural ageing resulta due to the differences in the intensity of the acting factors complexee. The subject of our work ie to evaluate some properties variations during the outdoor expoeure of eheeta baaed on various types of PVC which are modified during the synthesis procese with amall amounts of plaaticizere or plaeticizerel mhtures and unmodified typee of PVC to compare the reeulte.I08