Preparation and characterization of heterocyclic polyamide 6 (PA 6) with high transparencies and low hygroscopicities

A heterocyclic polyamide 6 (i.e. caprolactam (CPL; 90 mol%)/sebacic acid (SBA; 5 mol%)/1,3-cyclohexanebis (methylamine)(CHM; 5 mol%) copolyamide) with superior transparency, haze, hygroscopicity and crystallinity to an ordinary polyamide 6 (PA 6) based on CPL (100 mol%) have prepared by the design of appropriate prescriptions. The transparency, haze, hygroscopicity, and crystallinity of lab-made heterocyclic PA 6 are 86.5%, 13.2%, 1.36% (24hr)/1.89% (48hr), and 11.5%, respectively, while those of PA 6 are 26.0%, 94.2%, 1.80% (24hr)/2.45% (48hr), and 24.0%, respectively. Experimental results demonstrate that physical properties of lab-made heterocyclic PA 6 deeply depend on its heterocyclic structure and introduction of SBA and CHM into PA 6 can effectively improves optical, hygroscopic, thermal decomposition, and crystalline characteristics of PA 6, revealing that it is a highly potential polymeric material for optical films, electrical encapsulation, and food packages.