Preparation And Properties Of High Heat-resistent Polyether Polyoxamide Copolymers

With the progress of industrial technology,high heat-resistant polyamides are playing an increasingly important role in various fields,widely used in electronic appliances,automobile and aviation.At present,the global market for high heat-resistant polyamides is 100,000 tons and its annual growth rate is as high as 10%.In China,the annual demand for high-heat-resistant polyamides is more than 30,000 tons and the annual growth rate is expected to reach 15%or more.However,almost all the high-heat-resistant polyamides in domestic market rely on imports.Polyoxamide is a kind of special polyamide containing oxalic acid units in the main chain,the unique adjacent hydrogen bonds among the polymer chains give it very strong intermolecular interaction,high melting point,excellent crystallization performance,low water absorption and excellent mechanical properties.As a representive of polyoxamides,PA62 has good comprehensive performance with saturated water absorption less than 2%.Howerver,the melting point of PA62 is high up to 329°C,which leads to problems in melt processing.In this study,polyether polyoxamide copolymers(PA62/PG2 and PA62/PEG2)were synthetized through amine-ester condensation polymerization with polyoxypropylenediamine(PG)and polyoxyethylenediamine(PEG)as comonmers.PA62/PG2 prepolymer with a relative viscosity of about 1.3 was firstly prepared by a solution prepolymerization in toulene with1,6-hexanediamine,polyoxypropylene diamine(PG)and dibutyl oxalate as raw materials.Then postpolymerization(solid state polymerization or melt polymerization)was carried out and the polymer with a relative viscosity of more than 2.5 can be obtained.The formation of the copolymer was confirmed through infrared spectroscopy and nuclear magnetic resonance spectroscopy.GPC measurements showed that the number average molecular weight(M_n)of PA62/PG2 was up to 5.6×10⁴ g.mol^-1.DSC tests revealed that the melting point of PA62/PG2copolymer decreased to 293?when the content of polyether diamine unit was 20mol%,which could improve the melt processability.The TGA results suggested that the thermal stability of the copolymer decreased with the content of PG while it was still good.WAXD results showed that the crystallinity of the copolymers decreased with the content of PG units but still kept at a higher level(>30%)for PA62/PG2 copolymer with PG content less than 20mol%.Furthermore,the saturated water absorption for these copolymers was lower than 3%,suggesting good properties of low water absorption.PA62/PEG2 copolymer was sucesseessfully synthesized by similar procedues with polyoxyethylenediamine(PEG)as comonomer and had similar properties as PA62/PG2.The results above demonstrated that the introduction of polyether diamine units effectively modified the properties of PA62.Copolymers with polyether diamine content of 20mol%?30mol%had a good comprehensive performance and great potential as high heat-resistant polyamides.