In this work, a novel synthetic path for preparing semi-armotic components modified polyamide 6 was developed by caprolactam as solvent of purified terephthalic acid and 1,6-hexanediamine. First, the ring opening reaction and poly-addition of caprolactam were initiated by 1,6-hexanediamine to generate a prepolymer containing amino groups in both ends, then followed by the poly-condensation reaction with purified terephthalic acid, a long chain copolymer was produced, which the reaction time was reduced by 4 h compared with conventional hydrolytic ring-opening polymerization of pure caprolactam. By varying the ratio of terephthalic acid and 1,6-hexanediamine, a series of copolymers with different number average molecular weight and physical properties were prepared. Analytical results showed that the conversion percentage of caprolactam is significantly increased by the proposed method. Furthermore, this new copolymers exhibited excellent transparence and high decomposition temperature. Besides, the copolymers with average molecular weight !15,000 present good mechanical properties, making it a potentially useful application in plastics, textile yarn, and membranes. V C 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 959-967

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The characteristics of pure α- and β-form of the cyclic dimer (1,8-diazacyclotetradecane-2,9-dione) were systematically and integrally investigated during this study. The results showed that the α-form could dissolve and rapidly transform into the β-form in methanol, and in caprolactam solution at a lower temperature, an interesting transition occurred and formed co-precipitates, which refract colourful light under PLM. However, these dimers can aggregate in water, and they are then transformed into multi-slice layers and compact structures. The detailed transition behaviours between the two forms were further measured by FT-IR, XRD and DSC by varying the temperature from 25°C to 360°C, respectively, which showed that there are two endothermic transitions over the course of the heating programme. At a temperature of approximately 242°C, the β crystals were initially converted into α crystals, and then they melted when the temperature reached over 345°C. A video recorded under a light microscope also showed that the sublimation of the β cyclic dimer occurred after the transition. However, the α-form might sublimate at temperatures lower than 150°C when mixed with volatile matter.

In this study, series of blends were prepared by blending unextracted polyamide-6 (PA6) and thermoplastic ester elastomer (TPEE) in certain ratios. The morphologies, thermal behaviors, and mechanical properties of blends have been investigated. Scanning electron microscope results revealed that the morphology of blends was improved significantly when the content of TPEE is less than 50 wt%. Tensile fracture surface images confirmed reactive compatibilization and stress-induced crystallization in blends. The effect of unextracted PA6 content on the elasticity and tensile strength of blends was also studied, and higher elongation rate at break and breaking strength could be achieved when the content of TPEE is !50 wt%. The most interesting finding in this study is that the glass transition temperature for rubber phase of blends shifts to lower temperature and decreases with the increase of unextracted PA6 content at certain ratios range.

The mechanical properties of blends of poly (vinyl chloride) (PVC) and poly (styrene-block-(ethylene-co-butadiene)-block-styrene) (SEBS) were investigated using maleic anhydride grafted SEBS (SEBS-g-MAH) as a compatibiliser. The results indicated that addition of a small amount of SEBS-g-MAH during melt blending significantly improved the mechanical properties of PVC/ SEBS blends. The impact strength of the compatibilised PVC/SEBS blends was found to reach a maximum of 53 . 5¡2 . 78 KJ m 22 at room temperature and a maximum of 32 . 8¡1 . 66 KJ m 22 at 220uC at an SEBS-g-MAH loading level of 6 phr. The two glass transition temperatures of the components in the blends converged to some degree upon addition of SEBS-g-MAH for compatibilisation. At room temperature the dynamic storage modulus of the compatibilised blends was higher than that of the blends without compatibilisation. The size of the dispersed phase domains in the blends was appreciably reduced on addition of SEBS-g-MAH during melt blending according to scanning electron microscopy. All the above observations revealed that SEBS-g-MAH enhanced the compatibility between PVC and SEBS in the PVC/SEBS blends.