Improving thermal stability and mechanical performance of polypropylene/polyurethane blend prepared by radiation-based techniques

Abstract

Polymer blending techniques can address the disadvantages of polyolefin-based polymers by creating a mixture of polymers with different characteristics. One of the polyolefin-based polymers is polypropylene (PP), which has good mechanical strength and machinability, but its weakness is impact resistance at low-temperature. In contrast, polyurethane (PU) has excellent mechanical and thermal properties. However, blending PP and PU has been limited because PP is a hydrophobic polymer, and PU is a hydrophilic polymer. In this study, we used gamma-irradiation (doses of 25 and 50kGy) to graft styrene onto PU to change its hydrophilicity into hydrophobicity, and we developed PP blends with styrene grafted PU (PP/SPU) blends. With increasing styrene content and radiation dose, the surface morphologies (determined by using a field emission scanning electron microscope (FE-SEM) were smoother than PP blended unmodified PU owing to the styrene that was successfully grafted onto the PU and blended with PP. The mechanical properties of the PP/SPU blends were confirmed using a universal testing machine (UTM). Whereas the elongation at break of the PP was 518%, the low-temperature resistance (−20°C) of the PP was decreased to 304%. However, the elongation at the break of the PP/SPU blends was almost unchanged in terms of both the mechanical property (594%) and low-temperature resistance (607%). After holding in oven at 150°C for 1 h, the thermal stability of PP/SPU increased by more than quadrupled, compared to PP. In addition, the permittivity of PP/SPU increased with radiation dose compared to PP. Energy dispersive X-ray spectroscopy (EDS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and differential scanning calorimetry (DSC) were also used to evaluate the blended polymers. Therefore, this study confirmed the possibility of developing highly functional polymers using radiation-based techniques.