Optimization of laminated rubber foam composites incorporating ground tire rubber: A response surface approach after accelerated weathering

The valorization of ground tire rubber (GTR) into functional composites is an important strategy for advancing sustainable materials within a circular economy framework. However, exploration focusing on the development of laminated rubber foam flooring materials that balance elastic recovery, flame resistance, and impact energy dissipation remains insufficient. This study addresses the gap in knowledge by optimizing laminated rubber foam composites incorporating GTR for force-absorbing flooring applications. A Central Composite Design and the Response Surface Methodology were implemented to systematically evaluate the effects of GTR content (20–60 phr), blowing agent loading (4–12 phr), and forming temperature (130–150 °C) on compression set, burning rate, and energy absorption. Quadratic regression models were developed and statistically validated through analysis of variance, showing high coefficients of determination ( R ² = 98.17–98.84%). Morphological analysis revealed that increasing GTR content enhanced cell density, whereas higher blowing agent loading and forming temperature promoted larger, more interconnected cells. Rebound resilience varied between 45.9% and 62.5%, while tensile and compressive strengths ranged from 0.95 to 2.51 MPa and 0.92–3.34 MPa, respectively, under unweathered conditions. Multi-objective optimization identified an optimal formulation comprising 60 phr GTR, 4 phr blowing agent, and a forming temperature of 150 °C, yielding a compression set of 16.0%, a burning rate of 16.3 mm/min, and an energy absorption of 4.9 J, with an overall desirability of 0.676. These results demonstrate that GTR can be effectively transformed into high-performance laminated foam composites suitable for flooring applications, offering a scalable route for upcycling discarded tires into value-added materials that support industrial circularity.