Effects of alkali metal catalysts on the melt fluidity of polycarbonates with different degrees of polymerization. Issue 10 (10th January 2023)

• Record Type: Journal Article
• Authors: Zheng, Mingfu; Chen, Mengdi; Zhang, Lu; Peng, Wenjun; Zhang, Xian‐Ming; Chen, Wenxing
• Is Part Of: Journal of applied polymer science. Volume 140:Issue 10(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-10
• Subjects: alkali metal catalysts -- empirical fitting -- melt fluidity -- polycarbonate; Polymers -- Periodicals; Polymerization -- Periodicals; 668.9
• DOI: 10.1002/app.53587
• Languages: English
• ISSNs: 0021-8995

Abstract

Abstract: The melt fluidity of polycarbonate (PC) significantly influences the processing, while the melt viscosity depends on the molecular structure. Specifically, the melt viscosity increases sharply with the increase of polymerization degree. However, the influence mechanism of alkali metal catalysts on the fluidity by affecting the molecular structure remains unclear. Herein, high and low concentrations of NaOH catalysts were used to synthesize PC with different polycondensation degrees. The effect of NaOH catalyst content on the molecular structure and thus melt fluidity of PC were systematically characterized and discussed employing NMR spectroscopy, absolute and relative molecular weight, intrinsic viscosity, melt flow index, and thermal analysis. The results show that a random branched structure of the PC molecular chain caused by excess NaOH improves the melt flowability. However, the residual NaOH promotes the degradation of carbonate bonds during thermal processing, resulting in poor PC stability. Based on the above discussion, empirical fitting equations are proposed to describe the relationship between molecular structure and flow properties, which provides a new way to judge PC performance. Abstract :