Mechanical, Thermal, and Morphological Properties of PA/NBR TPVs: Influence of Processing Conditions and Recyclability

Abstract

Thermoplastic vulcanizates (TPVs) of polyamide 6 and nitrile butadiene rubber (PA/NBR) present excellent mechanical properties but traditionally suffer from performance loss during re-melt recycling. This study examines the impact of processing parameters and recyclability on the mechanical, thermal, and morphological properties of TPVs derived from polyamide (PA) and nitrile rubber (NBR). TPVs were dynamically vulcanized in a mixing chamber at different rotor speeds (65, 80, and 90 rpm), and their recyclability was assessed through multiple reprocessing cycles. Morphological analysis via scanning electron microscopy revealed that increasing rotor speed reduced the average rubber domain from ~8.6 to ~6.9 μm and yielded a more uniform dispersion, resulting in a 20% increase in tensile strength (from 8 to 10 MPa) and an increase in elongation at break. Differential scanning calorimetry showed a 4°C rise in crystallization temperature (from 147°C to 151°C) with crystallinity at ~20%. After two reprocessing cycles, the domain size and mechanical properties stabilized, indicating a preserved morphology, while the particle size distribution continuously narrowed, reflecting improved homogeneity. These findings demonstrate that high-shear dynamic vulcanization produces PA/NBR TPVs that retain performance through multiple recycling steps, offering a route to more sustainable reuse of rubber-thermoplastic blends in automotive and other industrial applications.