Influência do polietileno reciclado nas propriedades de peças obtidas pelo processo de rotomoldagem.

Abstract

This work is concerned the effect of recycled material content on the properties of rotomolded polyethylene pieces. Linear low density polyethylene (LLDPE) formulations with 0 to 100% recycled material were tested. Virgin LLDPE was mixed with 0.5% pthalo-blue pigment in a Henschel type high intensity mixer to simulate an industrial product. The recycled material was obtained from the extrusion of rejects from the rotomolding process itself. Samples were micronized, manually compounded with different proportion of virgin to recycled material, and rotomolded. Dry flow properties and particle size distribution were controlled to insure good behavior during the rotomolding. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to characterize the material. Melt flow index, impact strength, and mechanical properties under traction were measured on the rotomolded samples. Yield stress and tensile strength, initially lower, increased afterwards in samples with large content of recycled material. Impact strength increased uniformly with the content of recycled material, probably due to changes in crystallization caused by cross-linking and/or because of the better homogenization during extrusion. The presence of recycled material also improved pigment incorporation. Resistance to environmental stress cracking (ESCR) was found to be 50% lower in the internal areas as compared to the external ones, and this may compromise the performance of the rotomolded pieces in the long term. A preliminary study of accelerated aging revealed a significant loss of properties when samples were exposed on the internal side. This effect may be explained by antioxidant and UV additive degradation on this side, exposed to the air and reaching higher temperatures during rotomolding process.