Physico-mechanical characterization of recycled LDPE blended with EPS as a sustainable rigid alternative to polypropylene

Abstract

The accumulation of plastic waste, particularly low-density polyethylene (LDPE) and expanded polystyrene (EPS or Styrofoam), presents a growing environmental challenge due to their widespread use and limited biodegradability. In resource-constrained regions like Nigeria, uncompatibilized recycling of LDPE/EPS waste offers a low-cost path to valorize plastic pollution. Addressing this issue requires innovative recycling strategies that can transform waste into valuable materials. This study developed an uncompatibilized sustainable polymer blend from post-consumer waste and investigated the physical and mechanical properties of recycled LDPE blended with EPS under resource-constrained conditions as a sustainable rigid alternative to polypropylene (PP) for static applications, though trade-offs in impact resistance were observed. In achieving this, triplicate samples were statistically validated (ANOVA, p < 0.05), LDPE/EPS blends were prepared in varying weight ratios (80/20, 75/25, 70/30, 65/35, and 60/40) using a two-roll mill and compression molding. A series of tests; density, tensile strength, elongation at break, tensile modulus, flexural strength, hardness, and impact resistance; were conducted on triplicate samples, with results expressed as mean ± standard deviation. In the study, the 60/40 blend achieved a tensile modulus of 202 MPa (surpassing PP's 179 MPa) but exhibited 39 % lower impact strength than PP (0.20 vs. 0.33 J/mm²). However, increasing EPS content reduced elongation at break, indicating increased brittleness due to EPS's rigidity, though flexural strength (23.77 MPa) remains 56 % lower than PP (53.59 MPa), restricting load-bearing use. Findings validated suitability for rigid, static applications. Beyond performance, the blend contributes to plastic waste reduction and supports circular economy initiatives by transforming problematic waste materials into functional products.