94 / 2022-03-12 21:49:39

Comparison of thermal degradation for aPP and sPP as potential cable insulating materials

insulation,polypropylene,temperature,ageing,mechanical properties

    As a typical insulating material for power cable, crosslinked polyethylene (XLPE) exhibits superior electrical endurance and mechanical performance under a higher temperature owing to crosslinking. Crosslinking process changes the material from thermoplastic to thermoset, which also becomes an obstacle in recycling the insulation after cable retires. Recent years, polypropylene-based materials have aroused wide attention and show a great potential as insulation for power cables. Researches show that in short-term properties, polypropylene-based materials can meet the demands of power cable and even be better than XLPE. However, as an important aspect, aging performance of polypropylene (PP) for power cable has not been intensively investigated. This paper compares the thermal degradation of atactic polypropylene (aPP) and syndiotatic polypropylene (sPP), promoting the application of polypropylene in cable insulation.


    Pellets of aPP and sPP were purchased from the same supplier. Plate specimens with a dimension of 10mm×10mm×1mm were made by hot-pressing at 190^oC and 15MPa. Samples were put in the oven at a series of temperatures including 130^oC, 135 ^oC, 140 ^oC, 145 ^oC, and 150 ^oC for 168 hours. Before and after aging test, structural characterizations such as infrared spectroscopy (IR), differential scanning calorimetry (DSC), and X-ray diffraction analysis were conducted. Besides, tensile tests and volume resistivity measurements were also performed.


    With the increase of aging temperature, aPP an sPP show a similar behavior. Tensile strength and volume resistivity of both decrease. At the same temperature, sPP shows a better performance in tensile tests and volume resistivity measurements than that aPP does. These phenomena are attributed to their differences in structure.


    This paper compares aging performance of sPP and aPP at different temperatures. The increase of crystallinity for PP sacrifices the mechanical flexibility but increase its anti-aging properties.