Avaliação da utilização de agente antioxidante na reciclagem de resíduos de etileno-acetato de vinila (EVA) reticulado

Abstract

EVA foam is a class of materials that combine mechanical properties with reduced density and the ability to absorb energy and impact, which is why they are widely applied in the footwear industry. However, during its manufacture and use, many shavings scraps end up becoming waste. In this sense, the present study aims to develop a recycling process, in order to be able to incorporate the EVA waste in the manufacture of new foams. Initially, the foam waste was processed in a twin screw extruder, with the alteration of different processing parameters, such as the number of reprocessing, temperature, rotation speed and the use of antioxidants. In this first stage, the characteristics of the recycled were evaluated through the gel content tests, scanning electron microscopy (SEM), thermogravimetry (TG) and parallel and torque plate rheometry. From the sixteen samples extruded, four samples with the highest probability of forming homogeneous foams were chosen. Then, EVA foams were made with and without the incorporation of recycled material, and the following parameters of the new foams were evaluated: scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and physical density, abrasion tests and permanent compression deformation (PCD). The results demonstrated a decrease in the content of crosslinked gel by up to 13 percentage points for the sample processed with antioxidant. As well as the lower viscosities for these same samples. However, there was a possible residual crosslinking, as the viscosity of all samples is greater than the reference (foam). The greatest homogeneity, observed in the SEM, occurred in the samples processed for five repetitions without antioxidant. These parameters allowed to choose the recycled material for making new foams. Some of them presented very similar aspects to EVA foam made without recycled content. From the SEM you can see the foam with recycled extruded once, at 180 °C, 450 rpm, without antioxidant (sample G1), as the most uniform and spherical cells. This foam also showed the best responses for the physical tests of DCP and abrasion, even compared to foam without recycled content.