Nonisothermal crystallization and morphology of crystallites of polyamide 66 and copolyamide 66 containing 2‐carboxyethyl phenyl phosphinic acid

Abstract

Flame-retardant polyamide 66 with a 10% mass fraction of 2-carboxyethyl phenyl phosphinic acid (CEPPA) hexamethylene diamine salt (PA66-10) was fabricated in our previous study. In this study, the nonisothermal crystallization kinetics of pure polyamide 66 (PA66-0) and PA66-10 were measured by differential scanning calorimetry, and the data obtained were analyzed, and we calculated the average Avrami exponent (n) and used the Jeziorny, Mo, and Kissinger methods. The results from all of these methods show that the crystallization mechanism of PA66-0 mainly consisted of three stages, whereas PA66-10 mainly consisted of two stages. At the prime stage, both PA66-0 and PA66-10 may have had the same crystallization mechanism. When the cooling rates were 15 and 20 C/min, the approximate n suggested that the growth form of the spherulite mode in PA66-0 may have been complicated, whereas PA66-10 may have had a one-dimensional, two-dimensional space-extension, circular, diffusion controlled growth. The crystallization activation energies were determined to be 183.2 and 301 kJ/mol for PA66-0 and PA66-10, respectively, by the Kissinger method. To further study the influence of the addition of CEPPA on the crystallization behaviors of PA66-0, the spherulitic morphologies were examined by polarized light microscopy.