The chain extension behaviors of two diepoxides, epoxide TDE85 and 711, were studied to evaluate their coupling effects on polyamide 1010 (PA1010). The former cave better coupling effects and a faster reaction rate. The torque of PA1010 melt increased dramatically with reaction time. The effect of the diepoxy chain extender on the flowability, thermal properties, and mechanical properties of chain-extended PA1010 was investigated. The melt flow index (MFI) dramatically decreased as the diepoxide was added to PA1010, and the notched Izod impact strength of the chain-extended products also increased. Furthermore, study on the usage of chain extender showed that there exists an approximate platform on the curve of melt torque versus content of chain extender, beyond which crosslinking may occur. Theoretical analysis of the occurrence of crosslinking was carried out by Flory criterion, which demonstrated that the average amount of functional groups in the chain extension system played a significant role in avoiding crosslinking. (C) 2004 Wiley Periodicals, Inc.