Avaliação do desempenho de diferentes plastificantes em composições de poli (cloreto de vinila)

Abstract

The poly (vinyl chloride) (PVC) is one of the most widely used polymers in the world, mainly due to the versatility of properties. The incorporation of additives alter its final characteristics enabling a wide application, from pipes and fittings used for construction, to as packaging films. The addition of plasticizers in PVC compositions is commonly employed in order to reduce its rigidity, but the main representative of this additive class – dioctil phthalate (DOP) – has legal restrictions due to its carcinogenic potential, according to some studies. Two synthetic non-phthalic plasticizers with chemical structures near to DOP – (2-ethylhexyl) cyclohexanedicarboxylic (DHEH) and diisononyl cyclohexane-1,2-carboxylate (DINCH) – and two other renewable source plasticizers, non-phthalic – Olvex 51 FG and Unimoll – are characterized chemical, thermal, morphological, mechanical and physico-chemically and compared to DOP, as for their performance in PVC compositions injected in order to define criteria for the replacement of the same. PVC/DOP has characteristic peaks in the FTIR spectrum at 1580 and 745 cm-1 featuring phthalates in the sample. PVC/DOP has the largest deviation of the characteristic ester band (from 1680 to 1780 cm-1 ), suggesting greater compatibility between PVC and plasticizer, followed by PVC/DINCH and PVC/Unimoll. PVC/Unimoll, PVC/DINCH e PVC/Olvex presents the greatest potential for plasticization, measured by ratio between the absorbance of the regions in 1427 and 1435 cm-1 . Samples PVC/DINCH and PVC/Unimoll have the lower crystalline content (-58,9% and -46,3%, respectively), indicating an increase of the amorphous region of these samples. All compositions have a continuous phase, which indicates good homogeneity and plasticization. PVC/DINCH, PVC/Unimoll and PVC/Olvex have the lowest hardness values Shore A, elastic modulus and strain at break. With respect to thermal properties, all compositions exhibit two mass loss events and the same thermal stability. The compositions PVC/DINCH, PVC/Olvex and PVC/Unimoll have glass transition temperature (Tg) below 30 °C and lower storage modulus at 30 °C. In exudation tests, PVC/Unimoll e PVC/Olvex had low income, mainly in the extraction in hydrous ethanol solution. PVC/DINCH presents the best indices in performance analysis, with plasticization efficiency high, excellent compatibility and characteristics of permanency near to DOP, which makes him an effective substitute for DOP.