Thermal, mechanical and physical properties of chain extended recycled polyamide 6 via reactive extrusion: Effect of chain extender types

Chain extenders having different structures such as: alternating copolymer of ethylene and maleic anhydride (EMA), multi-functional epoxy-based oligomeric chain extender (EPO), polyester wax with reactive caprolactam groups (CW) and dimeric 2,4-toluene diisocyanate (DTDI), were melt compounded with recycled polyamide6 (rPA6) in various amounts via a twin screw extruder. DTDI, which is generally used for polyurethane applications, was used as a chain extender for rPA6 for the first time. In order to evaluate the effects of chain extender's structural differences on the chain extension behavior of the resulting materials, differential scanning calorimetry (DSC) measurements, heat deflection temperature (HDT) measurements, vicat softening temperature (VST) measurements, relative viscosity measurements and mechanical tests including tensile and impact tests were performed. The results showed that mechanical properties were improved by all chain extenders, however the highest improvement was achieved with EMA. The addition of EMA increased relative viscosity by 41%, HDT 12.4%, elongation at break by 6.3 times and impact strength by 26%. DTDI showed 22% increase in relative viscosity, 10% increase in HDT, 23% increase in impact strength and it also increased elongation at break by 6.1 times, making it a very good chain extender candidate for rPA6.