Enhanced Morphology-Dependent Tensile Property and Breakdown Strength of Impact Polypropylene Copolymer for Cable Insulation

Abstract

The decrease in electrical properties caused by the toughening of polypropylene (PP) is a difficult problem for the modification of PP used for cable insulation. In this research, an isotactic PP, a cross-linked polyethylene (XLPE) and two impact PP copolymers (IPCs) with an ethylene–propylene rubber phase content of 15 and 30% were prepared to assess the possibility of IPCs to be used as cable insulating material. The tensile properties and breakdown strength were evaluated, meanwhile, the rubber phase content dependence of the crystalline structure, morphology and trap distribution were also investigated. Results show that IPCs with a 15% rubber phase content (IPC15) can achieve the simultaneous improvement of elongation at break and breakdown strength compared with isotactic PP, which can be attributed to the special crystalline structure. According to the results of differential scanning calorimetry (DSC) and FTIR, it is proposed that the lamella thickness of IPC15 is maximal and some ethylene segments exist in PP crystals of IPC15 as crystalline structure defects, which is responsible for this enhanced breakdown strength. The morphology results reveal that rubber microspheres are found to coexist with spherulites, which can promote the relative sliding among lamellas under external force and further results in the increase in the elongation at break.

Simultaneous Promotion of the Mechanical Flexibility and Dielectric Strength of Impact Polypropylene Copolymers Containing Multifold H-Shape Long-Chain-Branching Structures for Recyclable Power Cable Insulation Application

“…However, increasing ethylene incorporation by merely increasing the EPC content is expected to be met with sheer deterioration of the electrical insulation properties. 7,8,10,11,14,15 3.2. Preparation of LCB-IPCs with Ethylene-Incorporated PP Copolymer Matrix.…”

Electrochromism of Viologen/Polymer Composite: From Gel to Insulating Bulk for High-Voltage Applications

“…However, under extreme high voltages, charges can be emitted from metal electrodes through Schottky thermionic emission [ 32 , 33 ]. Commonly, accumulated space charges can be of a density of 10 19 C/cm 3 , which is the minimum intensity required for electrochromism of viologen.…”

Eco‐friendly polypropylene power cable insulation: Present status and perspective

“…In this study, the manufacturers of PP with different ethylene content are not completely consistent, it is difficult to ensure the complete consistency of other parameters except ethylene content. To avoid the uncertainty of the synthetic process of commercial PP, we synthesised IPC with 15% and 30% elastomer content in the laboratory on the premise of ensuring the consistency of synthesis process and catalyst system, and studied its electrical and mechanical properties [23]. Results show that abundant elastomer microspheres embedded in spherulites, which can promote the relative sliding among the lamellas and introduce deep traps, thus resulting in higher elongation at break and breakdown strength than iPP.…”

“…ρ (Ω⋅m) ~10 15 [21] ~10 15 [21] ~10 16 [25] ~10 15 [3] E ba (kV/mm) 74 [20] / 143 [23] 109 [23] E bd (kV/mm) 345 [21] 450 [21] 400-600 [3] 349 [24] T m (°C) 110 [21] 130 [21] 168 [25] 112 [23] Y (MPa) 135 [22] 1000 [22] 586 [25] 102 [23] Abbreviations: LDPE, low-density polyethylene; PP; polypropylene; XLPE, cross-linked polyethylene.…”

“…At present, the development of eco-friendly cable insulating materials is mainly based on the modification of usual thermoplastic polymer, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) [12][13][14][15][16][17][18][19]. Table 1 compares some key properties of these thermoplastic materials and XLPE at room temperature [3,[20][21][22][23][24][25]. In terms of insulating properties, three kinds of thermoplastic materials are approaching or exceeding the levels of XLPE, which means that their insulating performances at room temperature can meet the needs of cable insulation.…”