Modulation of Dielectric Properties of Furfuryl Isopropyl Sulfide Grafted Polypropylene and Applicability to High-Voltage Cable Insulations

Facing the demand of energy transition for high voltage insulating materials with “high temperature tolerance, low dielectric loss, and recyclability”, we adopt Furfuryl Isopropyl Sulfide (FIPS) graft modification to address the shortcomings in the performance of polypropylene (PP) as a substitute for crosslinked polyethylene (XLPE), and set up <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.1 \%, 0.2 \%$</tex>, and 0.5 % grafting gradients to investigate the regulation of PP crystallization, mechanics, and dielectric properties (breakdown field strength, energy storage density). A grafting gradient of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.1 \%, 0.2 \%$</tex> and 0.5 % was set to investigate the regulation of crystallization, mechanical and dielectric properties (breakdown field strength and energy storage density) of PP. The results showed that the grafting amount showed a “moderate-optimal” effect: 0.2 % grafted PP had the best crystalline regularity, tensile strength and long-chain entanglement, with a breakdown field strength of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$30.116 \text{kV} / \text{mm}$</tex> at ambient temperature, and the highest energy storage density in the wide temperature range of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{2 5 - 1 3 0}{ }^{\circ} \mathbf{C}$</tex> and excellent thermal stability; <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0. 5 \%}$</tex> grafting was the best for the polar groups, and 0.5 % grafting was the best for the dielectric properties of PP. Excessive grafting induces phase separation due to aggregation of polar groups, and modification effect is limited by insufficient grafting of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0. 1 \%}$</tex>. Compared with XLPE, this graft-modified polypropylene has better high-temperature dielectric properties and recyclability, which verifies its feasibility as a high-voltage cable insulation material and provides support for the upgrading of polyolefin insulation and the independent development of the industrial chain.