Effect of Reactive Extrusion Process Parameters on Thermal, Mechanical, and Physical Properties of Recycled Polyamide-6: Comparison of Two Novel Chain Extenders

Two chain extenders having different molecular structures; an alternating copolymer of ethylene and maleic anhydride (EMA) and a novel chain extender, dimeric 2,4-toluene diisocyanate (DTDI), both at two different concentrations (0.5 and 1 wt%), were melt compounded with recycled polyamide 6 (rPA6) using a twin-screw extruder. In order to investigate the effect of temperature profile and residence time on the chain extension behaviors of these chain extenders three different temperature profiles and four different throughput rates were selected for the melt compounding. Effects of the parameters were observed through differential scanning calorimetry (DSC) measurements, relative viscosity measurements, and tensile and impact tests. Temperature and time dependent improvements of the chain extended products with EMA and DTDI showed different tendencies. While chain extension of rPA6 with EMA became more effective with the optimization of the barrel temperature profile, chain extension with DTDI was not affected by temperature changes. By adjusting the temperature profile 9.1% higher viscosity, 1.3 times higher elongation at break and 10.6% higher impact strength were obtained for the chain extension reaction of rPA6 with EMA. Longer residence time promoted the chain extension reaction of rPA6 with EMA. On the other hand, chain extension of rPA6 with DTDI was not significantly affected by residence time.