Effect of isothermal heat treatment and thermal stretching on the properties of crystalline poly (arylene ether nitrile)

As a special polymer material, poly (arylene ether nitrile) (PEN) has been widely used in commercial areas. By enhancing the crystalline properties of PEN, it is more conducive to improving its heat resistance, mechanical strength and corrosion resistance. In this paper, a crystalline PEN copolymer was synthesized with the monomers of bisphenol A, hydroquinone and dichlorobenzonitrile by random copolymerization, and the film was cast by a simple casting method. Then the crystalline PEN film was modified by isothermal heat treatment and thermal stretching method. During the heat treatment, the crystallization of the PEN film was researched, and suitable temperature conditions were found for the thermal stretching experiment. During the thermal stretching process, the bisphenol A segment increased the plasticity of the copolymer, promoted crystallization, and improved the overall performance of the copolymer film. The final sample with a stretching rate of 200% had the best overall performance with the thermal decomposition temperature of 5% mass (Td5%) of higher than 500 °C, the mechanical tensile strength of 197.6 MPa, the dielectric constant of 3.4, the dielectric loss of less than 0.02, and the crystallinity of 34.49%. Besides, the closely arranged spherulites were observed by scanning electron microscope. Therefore, this article provides a new effective way to improve the crystalline properties of the crystalline PEN, and the modified PEN copolymers have potential application value in the fields of high temperature resistance and electronics.