Influence of magnesium sulfate whiskers on the structure and properties of melt-stretching polypropylene microporous membranes

• Published in: Journal of applied polymer science Vol. 133; no. 35; pp. np - n/a
• Main Authors: Lei, Caihong, Cai, Qi, Xu, Ruijie, Chen, Xiande, Xie, Jiayi
• Format: Journal Article
• Language: English
• Published: Hoboken Blackwell Publishing Ltd 15.09.2016; Wiley Subscription Services, Inc
• Subjects: Absorption; composites; crystallization; differential scanning calorimetry (DSC); Electrolytes; Magnesium sulfates; Materials science; Membranes; Nucleation; Polymers; Polypropylenes; Rechargeable batteries; Strength
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.43884

ABSTRACT The influence of magnesium sulfate (MgSO4) whiskers on the structure and properties of polypropylene cast films and stretched microporous membranes was investigated. We found that for the cast films, MgSO4 showed some nucleation effects, and the introduction of MgSO4 led to the decrease of the orientation degree along the machine direction (MD), whereas that along the transverse direction (TD) was improved; this indicated that MgSO4 whiskers were mainly arranged along the TD. The introduction of MgSO4 up to 10 wt % did not induce apparent changes in the pore structure and air permeability properties of the stretched microporous membranes but improved the electrolyte absorption ability. The most pronounced change for the stretched microporous membranes was the strength along the TD. It was increased by 110% when the MgSO4 content was 2 wt %. During the fabrication of microporous membranes, only stretching along the MD was carried out to initiate pore formation; this resulted in a lower strength along the TD. This study gave us a method for improving the mechanical properties of stretched microporous membranes along the TD. The obtained microporous membranes with better electrolyte absorption and higher mechanical strength along the TD could be used in lithium‐ion batteries as separators. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43884.