| Poly(imide-amide)is a kind of polymer with amide groups and aromatic heterocyclic imide groups in the main chain.It was first known as modified polyimide and widely studied due to the excellent performance.So far,aromatic PAI has been commercialized and been applied in many field,such as enameled wire paint and film.Based on the design of molecular,the introduction of aliphatic segments into the main chain has been achieved,and two kinds of semi-aromatic PAI were synthesized.In this part,semi-aromatic binary co-poly(amide-imide)resin was synthesized by one step heating method with trimellitic anhydride(TMA)and 1,6-hexamethylene diisocyanate(HDI)as monomers,and N,N'-dimethlacetamide(DMAc)as the solvent.The optimum reaction conditions are as follows: the molar ratio of monomers was n(HDI)?n(TMA)=1.05?1,reaction temperature was 140 ?,reaction time was 4 h,and the amount of solvent was 80% of the mass of reaction system.IR spectrum showed there were both amide bonds and imide rings in the backbone of the polymer and semi-aromatic binary copolymerized PAI was obtained.The intrinsic viscosity of as-synthesized PAI was 35.49 mL/g.The results of the test of the mechanical properties indicated that the tensile strength of the polymer was 51.40 MPa,the elongation at break was 126.39%,the flexural strength was 45.29 MPa,and the impact strength was 58.45 J/m.As-synthesized PAI was a kind of amorphous polymer,its glass transition temperature was 133 ?.The temperature at 5% weight loss was 357.90 ?,and when the temperature rose to 509.46 ?,the char yield was 6%.Based on the optimum synthesis conditions,semi-aromatic binary copolymerized PAI films were prepared,and the structure of the polymer was not influenced by the heating.It was found that the surface morphology of semi-aromatic binary PAI film was better than that of the aromatic PAI film due to its good chain flexibility.In this part,the imide acid was obtained based on trimellitic anhydride and 11-aminoundecanoic acid.Then,the semi-aromatic ternary co-poly(amide-imide)resin was synthesized by the imide acid and 1,6-hexamethylene diamine.And the optimum conditions for the synthesis of imidic acid were as follows: the reaction temperature was 60 ?,the reaction time was 4 h,the dehydration temperature was 90 ?,the dehydration time was 3 h,the feed ratio was n(TMA): n(11-aminoundecanoic acid)= 1.2: 1,and they were obtained by studying the effect on yield of imide acid and the structure of ternary co-poly(amide-imide).Also,the preparation of the polymer was carried out at 180 ? for 3 h at a feed ratio of n(imide acid): n(1,6-hexamethylene diamine)= 1: 1.The structure of the semi-aromatic ternary co-poly(amide-imide)was characterized by the characteristic absorption peak of amide bond and the imine ring in the infrared.The intrinsic viscosity of as-synthesized PAI was 49.23 m L/g,with good solubility.And glass transition temperature and melting temperature of product was 127 ? and 259 ? respectively.The semi-aromatic ternary co-poly(amide-imide)has better processing performance than traditional polyamide imide,and better heat resistance than PA11.The ternary co-poly(amide-imide)s with the imide molar content of 20%,25%,33%,50%,100% were obtained by adding different amounts of 11-aminoundecanoic acid into the mixture of euqimolar imide acid and 1,6-hexanediamine.The effects of the molar content of imide groups on the mechanical properties of the polymers were systematically studied,the results showed that with the increase of the molar content of imide,the tensile strength of the ternary co-poly(amide-imide)gradually increased and the impact strength decreased.The material showed the best tensile strength of 123.14 MPa when the molar ratio of imide was 100% and showed the best tensile elongation at break and the impact strength of cantilever notch was 124.52% and 44.10 J/m when the molar ratio of imide was 20%. |
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