Outdoor Walkway Flooring from Natural Rubber and Reclaimed Rubber Blends with Superior Environmental Resistance

Abstract

This study systematically investigated the effects of reclaimed rubber (RR) content on the mechanical properties and accelerated aging resistance of natural rubber (NR) vulcanizates for outdoor walkway flooring applications. Six formulations were prepared with NR/RR ratios ranging from 100/0 to 50/100 parts per hundred rubber (phr), maintaining a total rubber content of 100 phr after accounting for the 48-50% actual rubber content in reclaimed rubber (confirmed by thermogravimetric analysis showing 55% mass loss at 350-400°C). Results demonstrated that increasing RR content from 0 to 100 phr progressively decreased tensile strength and elongation at break, while hardness and 300% modulus exhibited slight increases due to residual cross-links and higher filler concentrations in reclaimed rubber. Notably, accelerated aging tests (ASTM D573: 100°C for 22 hours; ASTM G154: UV-A 0.89 W/m² at 340 nm, 60°C for 8 hours, followed by condensation at 50°C for 4 hours, total 168 hours) revealed substantial improvements in aging resistance with increasing RR content. The percentage decrease in tensile strength after aging diminished progressively as RR content increased. The optimized formulation containing 100 phr reclaimed rubber was selected for commercial production. Despite having a relatively lower tensile strength compared to virgin NR formulations, this composition provided adequate mechanical performance while demonstrating superior resistance to environmental degradation. Compression molding at 170°C for 8 minutes produced 1 m² × 0.06 m rubber tiles with anti-slip lozenge patterns. Implementation at a commercial café yielded positive user feedback and achieved an approximately 30% cost reduction compared to virgin rubber formulations, supporting the sustainable utilization of rubber waste.