Mechanical, physical and thermal properties of waste polypropylene/polystyrene/natural rubber (wPP/PS/NR) blends

Combining two or more polymers as a blend is necessary rather than synthesizing new ones for the balance of polymer properties for end-use applications. This work introduces a sustainable polymer blend (matrix) for high-impact applications, as the accessibility and cost of production of these high-impact polymers keep souring. This was achieved by designing an experiment using design expert v10.0 to account for the number of experimental runs and optimise the polymer blend. Mechanical, dynamic mechanical, and temperature effects were considered on the blended polymer. Sixteen (16) experimental runs were generated with blend ratio as the independent variable and Impact Strength (IS) and Tensile Strength (TS) as the responses. The optimal blend ratio was obtained for wPP, PP and NR as 23, 30 and 47% respectively. While, the optimum conditions for maximum impact and tensile strengths from the D.E was 241.62 J/m and 118.04 MPa respectively, with a desirability of 0.973. While the validated values obtained were 248.9 J/m; with errors of 2.93% and 120.14 MPa; with an error of 1.75% respectively. Thermogravimetry analysis revealed a single peak degradation for sp17, sp18, and sp19 (control samples) while multiple degradation peaks were observed for the blends. It was believed to be a result of different times for degradation of the individual components forming the polymer blend. Also, the T_d onset started around 300 °C and the T_d offset was around 500 °C for all tested samples. While, the Dynamic Mechanical Analysis (DMA) showed that there was an improvement in the T_g and damping factor for sp5 (109 °C, 0.171) as compared to sp17 and sp18 (81.1 °C, 0.089 and 104.3 °C, 0.061), but no improvement was recorded for storage and loss moduli. SEM micrographs showed a good surface morphology for the blend with optimal mechanical and thermal properties. The blend can be utilized for engineering applications, including matrices for body armour, helmets, car bumper, etc.