Synthesis and Properties of Polyamide 6 Random Copolymers Containing an Aromatic Imide Structure

In order to adjust the properties of polyamide 6 (PA6) and expand its application, a new strategy of introducing an aromatic imide structure into the PA6 chain through the random copolymerization method is reported. The diimide diacid monomer was first synthesized by the dehydration and cyclization of pyromellitic dianhydride and 6-aminocaproic acid before it reacted with 1,6-hexamethylene diamine to form poly(amide imide) (PAI) salt, and finally synthesized PA6/PAI random copolymers containing an aromatic imide structure by the random copolymerization of & epsilon;-caprolactam and PAI salt. The introduction of an aromatic imide structural unit into the PA6 chain could have a great influence on its properties. As the content of PAI increases, the crystallinity (X-c) and melting temperature (T-m) of the PA6/PAI random copolymer gradually decrease, but its glass transition temperature (T-g) increases obviously. When the PAI content is 20 wt%, the copolymer PA6/PAI-20 has the best comprehensive performance and not only has high thermal stabilities but also excellent mechanical properties (high strength, high modulus, and good toughness) and dielectric properties (low dielectric constant and dielectric loss). Moreover, these properties are significantly superior to those of PA6. Such high-performance PA6 random copolymers can provide great promise for the wider applications of PA6 materials.

Automated summary

A new strategy of introducing an aromatic imide structure into the polyamide 6 (PA6) chain has been reported to adjust its properties and broaden its applications. The PAI salt was synthesized by reacting the diimide diacid monomer with 1,6-hexamethylene diamine, and PA6/PAI random copolymers were obtained by random copolymerization of ε-caprolactam and PAI salt. The introduction of aromatic imide into the PA6 chain greatly affects its properties, and the copolymer PA6/PAI-20 with 20 wt% PAI content exhibits the best comprehensive performance with high thermal stabilities, excellent mechanical properties, and dielectric properties superior to PA6.