engleski

Investigation of PVC/PLLA blends

Poly(vinyl chloride) (PVC) is one of the most important and the most used polymer. Among other things, it is very often used for packaging. It is commonly known that today mostly biologically non-degradable polymers, such as PVC, are used for various packaging. This results in tremendous amount of plastic waste that is considered to be one of the greatest ecological problems of modern society. By blending these commodity polymers with biodegradable ones, usually with polyesters, ecologically and technologically acceptable polymeric materials can be obtained. In this work biodegradable polyester, poly(L-lactide) (PLLA), which can be produced from renewable resources (corn or sugar) and which can successfully substitute some commodity non-degradable polymers, is used. The main drawback of this polymer is its high price compared to commodity polymers. So, blending of PLLA with commodity polymers could be commercially advantageous in order to obtain biodegradable materials with wide variety of properties. In this investigation PVC/PLLA blends of different mass fraction of polymers were prepared by solution blending method and precipitating in non-solvent. Differential scanning calorimetry was used to study the thermal properties of the blends. The glass transition temperatures, melting temperatures, enthalpies of fusion and enthalpies of crystallisation were determined. DSC curves of the blends show neither a shift of the PVC glass transition temperature nor a shift of PLLA glass transition and melting temperature, which means that these blends are heterogeneous. Therefore, we should find a suitable biodegradable compatibilizer, which would also act as a plasticizer, since both PVC and PLLA are stiff and brittle polymers. Thermal degradation of the blends was carried out thermogravimetrically in the temperature range 30· ; · ; · ; 750º ; C. The nitrogen flow was 30 cm-3 min-1 and the heating rates were 2.5, 5, 10 and 20º ; C min-1. It can be noticed that thermal stability of each polymer in the blend is not significantly changed, so there is no interaction of these polymers or their degradable products in the blends.

PVC/PLLA blends; miscibility; DSC curves; dynamic TG analysis; thermal stability

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