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Polyamide 6 (PA6) and stabilized PA6 with two different thermal stabilizers, (ie, metal salts CuI/KI and hindered amine KYN818 [l,3-benzendicarboxamide,N, N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)]) were separately prepared by melt blending and then aged for different time. The effects of aging temperature and aging time on crystallization behaviors of PA6 and stabilized PA6 were systematically investigated by differential scanning calorimetry and X-ray diffraction. The variations of melting temperature, crystallinity and 2[theta] values suggest that aging under high temperature will accelerate the formation of crystals initially and then the degradation of molecular chains. The yellowness index and maximum decomposition temperature of stabilized PA6 are higher than that of PA6, which is dominated by different aging mechanisms and properties of stabilizers. In addition, the viscosity of all systems is increased at the preliminary stage, which is caused by the crosslinking network and the post-polycondensation. The results of dynamic mechanical analysis showed that the glass transition temperature ([T.sub.g]) decreases because the degradation of molecular chains during the aging process. Moreover, the carbonyl index for stabilized PA6 is lower than PA6, indicating the degradation is hindered by stabilizers. A comparison of the stabilization performance between CuI/KI and KYN818 was investigated to differentiate the long-term stabilizing efficiency. KEYWORDS hindered amine, metal salts, physical properties, polyamide 6, thermal-oxidative aging, 1 | INTRODUCTION Polycaprolactam (polyamide 6, PA6) is an important engineering thermoplastic which is widely used in the automotive, aerospace, and other industrial fields due to its excellent mechanical properties, [...]

To improve the heat resistance of polyester-based thermoplastic polyurethane (TPU), in the present work, polyamide 1212 (PA1212) was chosen as a modifier and a series of TPU/PA1212 blends with different compositions were prepared using a twin screw extruder. The solubility parameters, characteristic of chemical structures, hydrogen-bonding interaction, as well as interfacial tension of the single component and blends were taken into account to describe the good compatibility of TPU/PA1212 blends. The effect of PA1212 content on the rheological behaviors, morphology, mechanical, and thermal properties of TPU/PA1212 blends were systematically investigated with scanning electron microscope, tensile strength measurement, thermal gravimetry analysis, differential scanning calorimetry, and Vicat softening temperature (VST). The results showed that PA1212 formed submicron dispersion domains in the TPU matrix, indicating good compatibility between TPU and PA1212. A slight increase of the tensile strength was achieved as PA1212 content is relatively low. Because of the strong hydrogen-bonding interaction between TPU and PA1212, the thermal stability of the blends is improved, and VST values rise up from about 80 (pure TPU) to 100°C, showing attractive potential application. POLYM. ENG. SCI., 48:249-256, 2008. © 2007 Society of Plastics Engineers, INTRODUCTION Thermoplastic polyurethanes (TPUs) are linear block copolymers, composed of multiple hard segments and soft segments. The hard segments are based on diisocyanates and short diol or diamine, and the [...]