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

The objectives of this study is to develop high functional polymer through the enhancement of interfacial bonding between polypropylene (PP) and polyurethane (PU) by using radiation grafting technique. The results was that the thermal stability of PP/PU blend increased by more than quadrupled after holding in an oven at 150°C for 1h and the low-temperature resistance increased by more than doubled after holding in a freezer at −20°C for 2h, compared to neat PP. The permittivity of the blend increased by more than 20%. In addition, the blends were characterized by FE-SEM, EDS, ATR-FTIR, DSC, UTM, limiting oxygen index (LOI) and water contact angle. [Display omitted] •We developed PP with styrene grafted PU blends having significantly improved thermal stability.•The thermal stability of PP/PU blend increased by more than quadruple, compared to neat PP.•The low-temperature resistance increased by more than doubled, compared to neat PP. 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 permittivit