Effect of dissolution-based recycling on the degradation and the mechanical properties of acrylonitrile-butadiene-styrene copolymer

A dissolution-based recycling technique for acrylonitrile-butadiene-styrene copolymer (ABS) is proposed, and the effects of repeated recycling cycles are studied measuring changes in chemical structure, melt viscosity, and tensile and impact properties. Acetone as solvent, 0.25 g/ml concentration, room temperature and 40 min for dissolution have been found to be the most reliable recycling parameters. FTIR, DSC and MFI results have shown that the dissolution-based recycling itself does not degrade the ABS. However, TGA analysis suggests that during the dissolution some stabilizers are probably eliminated, and consequently degradation takes place in the following injection moulding step. Darkening of recycled ABS is attributed to the butadiene degradation, pointed out by FTIR results. Otherwise, the chemical structure of the SAN matrix has not been modified, but its molecular weight has been reduced. The modulus of elasticity is not affected even after four recycling cycles. However, yield stress and impact strength decrease after the first recycling cycle, and remain constant in the following steps.