Influence of Heat-setting Temperature on the Microporous Structure and Properties of PP/HDPE Bilayer Microporous Membranes

• Published in: Chinese journal of polymer science Vol. 42; no. 8; pp. 1243 - 1252
• Main Authors: Xie, Jie, Wu, Yong-Shi, Xie, Jia-Yi, Xu, Rui-Jie, Lei, Cai-Hong, Song, Sai-Nan, Li, Guang-Quan, Huang, An-Ping
• Format: Journal Article
• Language: English
• Published: Singapore Springer Nature Singapore 01.08.2024; Springer Nature B.V
• Subjects: Bilayers; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Electrochemical analysis; Industrial Chemistry/Chemical Engineering; Lamellar structure; Lithium batteries; Melting points; Membranes; Permeability; Polymer Sciences; Porosity; Research Article; Stability; Wettability; PP/HDPE bilayer microporous membranes; Heat-setting temperature; SAXS
• ISSN: 0256-7679; 1439-6203
• DOI: 10.1007/s10118-024-3157-x

Due to the mechanical stability of PP layer, the PP/HDPE double-layer microporous membrane could be prepared at a higher heat-setting temperature than that of PE monolayer membrane. In this work, the effects of heat-setting temperature on the pore structure and properties of PP/HDPE double-layer membrane were studied. With the increase of heat-setting temperature from 120 °C to 130 °C, the length of connecting bridge crystal and crystallinity in the PE layer increase due to the melting of thin lamellae and the stability of connecting bridge structure during heat-setting. The corresponding air permeability, porosity, wettability of liquid electrolyte and mechanical property of the heat-set microporous membrane increase, exhibiting better electrochemical performance. However, when the heat-setting temperature is further increased to 140 °C, higher than the melting point of PE resin, some pores are closed since the lamellae and connecting bridges melt and shrink during heat-setting, resulting in a decrease of air permeability and porosity. In contrast, there is negligible change in the PP layer within the above heat-setting temperature region. This study successfully builds the relationship between the stable pore structure and property of microporous membrane during heat-setting, which is helpful to guide the production of high-performance PP/PE/PP lithium batteries separator.