Synthesis and properties of star-branched nylon 6 with hexafunctional cyclotriphosphazene core

• Published in: RSC advances Vol. 5; no. 107; pp. 88382 - 88391
• Main Authors: Wang, Chunhua, Hu, Feng, Yang, Kejian, Hu, Tianhui, Wang, Wenzhi, Deng, Rusheng, Jiang, Qibin, Zhang, Hailiang
• Format: Journal Article
• Language: English
• Published: 01.01.2015
• Subjects: Crystallization; Mechanical properties; Molecular weight; Nylon 6; Polymerization; Rheology; Rheometers; Shear viscosity
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C5RA15598C

A novel star-branched nylon 6 with hexafunctional cyclotriphosphazene core was synthesized using hexa(4-carboxylphenoxy)cyclotriphosphazene (HCPCP) with six carboxyl groups as multifunctional agent in the hydrolytic ring-opening polymerization of ε-caprolactam, and then used for the investigation of mechanical properties, crystallization and rheology behaviors. Star-branching structure and molecular weight have great effects on its properties. Compared with linear nylon 6, star-branched nylon 6 has lower relative viscosity and higher melt flow rate while its mechanical properties can be almost retained by the use of star-branching and an appropriate molecular weight. Research on crystallization behavior indicates that the degree of crystallinity ( X c ) of star-branched nylon 6 decreases slightly, but its crystal structure still belongs to α form. The peak crystallization temperature ( T c ) and crystallization rate (1/ t 1/2 ) of star-branched nylon 6 are significantly higher than that of linear nylon 6 because of heterogeneous nucleation induced by HCPCP core, which is beneficial for the use of rapid molding process. As the molecular weight increases, the T c and 1/ t 1/2 of star-branched nylon 6 first increase and then decrease. Capillary rheometer measurement exhibits that the shear viscosity of star-branched nylon 6 decreases with decreasing molecular weight, and the shear viscosity of star-branched nylon 6 with an appropriate molecular weight shows a low value and little or no sensitivity to shear rate and temperature. Such rheology behavior allows for processing at low temperature and low pressure and reduces system cost.