| With the progress of technology and the increasing concern in environment protection and energy saving, the requirements for nylon becomes higher and higher from various fields. In the electrical and electronic industry, the lead-free solder is widely used to reduce the pollution of the environment. However, the lead-free solder has a melting point up to 215℃, which requires a higher heat resistance for nylon. With the increasing demand for energy saving and emission reduction in the field of automotive and aviation, the combustion temperature of the engine is increased to fully burn the fuel. As a result, the surrounding temperature rises and materials with higher heat resistance are needed. Under this background, the requirement for high temperature nylon grows rapidly. Now the global market for high temperature nylon is about 1000kt/a and the annual increase is high up to 10%. In Chinese market, the demand is 300kt/a with annual increase of 15% and basically depends on import. Currently,there are four kinds of high temperature nylon, N46, N6 T, N9 T and N10 T in the market, each with its own characteristics.Polyoxamide is a kind of unique nylon with the unit of oxalic acid. The double hydrogen bonds of polyoxamide endow it with high melting point and low water absorption. In addition, it has excellent crystallization properties, size stability and mechanical properties. As to poly(hexamethylene oxamide)(N62), its melting point(Tm) is high up to 330℃ and the water absorption rate(H2O%) is as low as 2.5wt%. Comparing to N46(Tm=295; H2O%=15wt%), N62 has much better dimensional stability besides its higher Tm. The main problem for N62 is its melting point is too high to process.In this study, three series N62 copolymers: N62102,N62122,N62M2 copolymers are prepared with hexanediamine, diamine comonomer and butyl oxalate as raw material by solution polymerization and solid phase polycondensation. By solution polymerization, prepolymers with relative viscosity of about 1.1 can be obtained. In the following solid phase polycondensation, the relative viscosity increase to at least 2.7, 2.7 and 1.7 for N62102, N62122, N62M2 copolymers, respectively. The FTIR and NMR results prove the formation of the N62102, N62122, N62M2 copolymer. The calculated results reveal the composition of copolymer is very close to the feed ration, which indicates the copolymer are random copolymers. The XRD shows that copolymer N62102, N62122, N62M2 has good crystallization performance. For copolymer with rich N62,the crystallinity of the copolymer basically increase with the increase of 1,6-Diaminohexane content, suggesting the incorporation of the phenyl ring or long chain diamine hinders the crystallization. DSC test demonstrats that the higher the content of 1,6-diaminohexane unit, the higher the melting point of copolymer with rich N62. With the 1,6-diaminohexane unit content of about 70-80mol%, the copolymer possess a good performance balance with good heat resistance and good processing properties. TG test shows that the higher the content of N62, the higher the thermal decomposition temperature. Water absorption test results reveal that the Satwated water absorptions of all the copolymers are less than 3%, which is much low than that of N6(12.7wt%). This result confirms that polyoxamide has excellent low water absorption properties. All these results reveals that N62 copolymers possess excellent comprehensive property and have wide application prospect. |
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