Effect of β nucleating agent and rotational shear on morphology and mechanical properties of polypropylene pipes

Herein, we report a new method of introducing circumferential shear to polypropylene (PP) pipes via a self-designed rotational shear system (RSS) with the addition of a β-nucleating agent (TMB-5). The prepared PP pipes exhibited remarkable enhancement in toughening and tensile strength over conventional PP pipes incorporating 0.025 wt% of the nucleating agent into the sheared sample increased the elongation at break to 243.30%. At 0.05 wt% nucleating agent content, an optimal tensile strength of 40.98 MPa was attained compared to 33.62 MPa for unsheared PP, and the elongation at break also reached 108.09%. In creep tests, the PP pipes prepared with nucleating agents and shear rotation exhibited a minimum displacement of 2.1 mm and the lowest creep rate of 3.23 × 10⁻⁵ mm/s. In addition, the samples also showed a high resistance to crack growth compared to conventional PP pipes with a crack initiation time of 24 h and a crack growth rate of 0.08 mm/s. Highlights: Reinforced and toughened PP pipes were prepared using a rotational shear system. The shish-kebab structure and β-crystals exhibited a synergistic effect. Both short-term and long-term mechanical properties were studied.