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pps proceeding
Symposium: Recycling
Oral Presentation
 
 

THE INFLUENCE OF BIOPLASTICS ON THE PROPERTIES OF REPROCESSED LDPE

Lekube Blanca Maria (1)*, Burgstaller Christoph (1)

(1) Transfercenter für Kunststofftechnik GmbH - Upper Austria - Austria

Bioplastics are often designed for biodegradability; however they often end up in conventional plastic waste streams, a fact that adds a potential risk for the quality of recycled materials. Therefore, the aim of this work was to investigate to what extent two biodegradable blends based on starch and polylactid acid respectively could have an impact on the recycling process of low-density polyethylene (LDPE) as well as to evaluate the properties of the recycled material depending on the final application. With that purpose, the recycling of LDPE with different ratios of both blends was simulated by means of a co-rotating twin screw extruder and the yielded granules were, after a drying step, extruded to flat films and injection molded to universal test specimens. The changes on the mechanical, thermal, rheological and morphological properties of the final specimens were analysed. We found that mixing of the materials is possible, if sufficient shear is brought into the mixture during the compounding process. Morphological analysis shows intensively mixed materials with a fine disperse morphology even though they are not compatible. However rheological analysis shows a significant reduction of the viscosity with increasing amount of biodegradable material in the mixture. For the injection molded specimens the elastic modulus and impact properties are most influenced, while for the films the tear resistance reduces considerably. The main issue in the latter case is the lower melt stability for the film processing due to the reduction of viscosity. A slight change of colour was observed in both cases as well. In conclusion we found that the amount of biodegradable material content has some influences on the properties of LDPE, although these influences are not too high since acceptable mechanical properties are achieved for reuse depending on the applications. One of the main issues is the loss of melt stability as well as the change of color in the mixtures. Future investigations should improve the rheological properties as well as the compatibilization of the materials in order to minimize the influence on the mechanical properties of recycled materials.