Enhanced UV resistance of polypropylene via copper nanoparticle incorporation for outdoor applications

This study investigates the effect of copper nanoparticles (Cu NPs) on the ultraviolet (UV) resistance and long-term thermal and mechanical stability of polypropylene (PP) composites. Cu NPs were incorporated into PP at varying concentrations (0-10 wt%) to evaluate their influence on size distribution, melt flow index, density, tensile and flexural properties, Shore D hardness, and thermal behavior using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Accelerated aging tests over 1000 h were conducted to assess durability under simulated environmental exposure. Results show that Cu NPs, particularly at 1-2 wt%, considerably improve mechanical performance and thermal stability while mitigating photo-oxidative degradation. Reinforced composites exhibited enhanced yield strength, elongation, stiffness, and energy absorption compared to pure PP after aging. DSC and TGA analyses revealed better retention of crystallinity and delayed thermal degradation in Cu NP-filled PP. Although higher nanoparticle loadings (> 5 wt%) led to diminished benefits due to stress concentration and possible agglomeration, the 2 wt% formulation demonstrated the optimal balance between UV protection and mechanical integrity. These findings highlight the potential of Cu NP-reinforced PP for outdoor and engineering applications requiring enhanced weatherability and long-term performance.