Hydrophilic Modification of PP-PE Composite Films via Electron Beam Radiation-Induced Grafting

BI Shengsheng; WU Xilai; CHANG Kunpeng; YANG Xujing; ZHANG Ronghui; SHU Xingjuan

doi:10.16490/j.cnki.issn.1001-3660.2026.18.015

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Surface Technology ›› 2026, Vol. 55 ›› Issue (18) : 191-196. DOI: 10.16490/j.cnki.issn.1001-3660.2026.18.015

Functional Surfaces and Technology

Hydrophilic Modification of PP-PE Composite Films via Electron Beam Radiation-Induced Grafting

BI Shengsheng, WU Xilai, CHANG Kunpeng, YANG Xujing, ZHANG Ronghui, SHU Xingjuan^*

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Abstract

This study aims to develop a high-performance and safe battery separator by modifying polypropylene/ polyethylene (PP/PE) composite wet-laid nonwoven fabric via electron beam pre-irradiation grafting technology, to enhance the separator's electrolyte wettability and ionic conductivity in alkaline batteries while rigorously maintaining its inherent mechanical properties—a critical parameter often compromised in conventional hydrophilic modifications.
Firstly, the PP/PE composite fabric was subjected to pre-irradiation with an electron accelerator to generate active sites. Subsequently, a grafting reaction was carried out in a mixed aqueous solution containing acrylic acid (AA) and α-olefin sulfonate (AOS) monomers. The synergistic action of these monomers was designed to impart durable hydrophilicity and potential sulfonic acid groups for improved ion transport. The effects of key processing parameters, including irradiation dose (kGy) and reaction time (h), on the grafting ratio and the resulting separator performance were systematically investigated. A comprehensive characterization of the modified membranes was performed, including evaluations of liquid absorption capacity and kinetics, mechanical strength (tensile testing), electrochemical performance (electrochemical impedance spectroscopy for area-specific resistance), and surface properties (contact angle measurements).
Under the optimized process conditions (irradiation dose: 100 kGy, monomer concentration: 5wt.%, reaction temperature: 60 ℃, reaction time: 6-8 h), a grafting ratio of 44% to 52% was achieved. This significant grafting level led to a remarkable enhancement in the separator's overall performance. The liquid absorption ratio increased dramatically from an initial 115% to a maximum of 420%, indicating a vastly improved porosity and affinity for the electrolyte. Concurrently, the electrolyte absorption time was drastically reduced from over 180 seconds to just 24 seconds, confirming superior wettability and capillary action. Most notably, the area-specific resistance (ASR) in the wet state, a direct indicator of ionic conductivity, decreased substantially from 1.85 Ω·cm² to 0.15 Ω·cm². This order-of-magnitude reduction was pivotal for minimizing internal resistance in battery applications. Importantly, these enhancements were achieved without sacrificing mechanical integrity. The longitudinal maximum tensile strength was maintained above 65 N, ensuring the separator's dimensional stability and mechanical robustness during cell assembly and operation.
The electron beam pre-irradiation grafting method has been successfully demonstrated as a highly effective technique for significantly improving the hydrophilicity (or more precisely, hydrophilicity towards electrolytes) and ionic conductivity of PP/PE composite wet-laid nonwoven fabric. The modified separator exhibits an excellent balance of properties: exceptional electrolyte uptake and wicking speed, dramatically reduced ionic resistance, and preserved mechanical/dimensional stability. This unique combination of performance metrics, achieved through a controllable radical grafting process, underscores the material's strong potential for industrial application as a next-generation separator in high-power alkaline batteries, where both safety and performance are paramount. Future work may focus on long-term stability tests in full cell configurations and further optimization of the monomer blend for targeted applications.

Key words

radiation grafting / electron accelerator / hydrophilic modification / battery separator / liquid absorption performance

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BI Shengsheng, WU Xilai, CHANG Kunpeng, YANG Xujing, ZHANG Ronghui, SHU Xingjuan. Hydrophilic Modification of PP-PE Composite Films via Electron Beam Radiation-Induced Grafting[J]. Surface Technology. 2026, 55(18): 191-196

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Funding

Henan Province Electron Beam Radiation Engineering Technology Research Center Operating Funds (20251015002) and the Henan Provincial Key Laboratory of Radiation Chemical New Materials Operating Funds (20251015001）