Increasing of rubber content in isotactic polypropylene/ethylene–propylene rubber (iPP/EPR) alloys can extend the applications of this kind of polyolefin. The EPR content and phase structure of isotactic polypropylene multicomponents have great effect on the viscoelasticity and mechanical properties. iPP/EPR in-reactor alloys with a high EPR content were obtained through the in situ crosslinking of EPR chains with α,ω-diene. The morphological observation results indicate that the crosslinked iPP/EPR in-reactor alloys have a good spherical shape with clean and rough external surfaces. The high EPR content is finely dispersed in the crosslinked iPP/EPR alloys in areas ranging in size from tens of nanometers to several micrometers, which implies that a sufficient crosslinking degree of EPR chains can effectively prevent their aggregation and restrict macro-phase separation. The rheological results show a clear plateau in the terminal region, which reveals an entangled polymer chain network in the crosslinked iPP/EPR alloys. The well-dispersed EPR and the bi-continuous phase structure have a great effect on the mechanical properties of the isotactic polypropylene multicomponent which were assessed.

The medium-deep coaxial borehole heat exchanger (CBHE) has been demonstrated to exhibit excellent heating performance. To further investigate the efficient heat transfer characteristics of novel inner-tube materials, a numerical simulation approach based on OpenGeoSys was employed. This approach was used to systematically examine and compare the thermal performance of novel and conventional pipes under various operational scenarios during both short- and long-term operation. The results show that the novel geothermal pipe was found to possess superior thermal insulation performance over the conventional pipe. During operation, an increase in thermal resistance of 0.5 m·K/W (approximately a 30.5% improvement) and a higher pressure drop of 0.4 MPa (approximately a 12.3% rise) were observed. This contributed to an outlet temperature approximately 1 °C higher (approximately a 2.5% improvement) and a temperature drop 2.5 °C lower (approximately a 19.2% reduction). Over a 20-year simulation, the novel pipe achieved a heat exchange capacity approximately 3.5 kW greater than that of the conventional pipe (approximately a 1.5% improvement).