Preparation And Properties Of Polyarylene Ether Nitrile Foam

High-performance polymer foaming structural parts have urgent needs in aerospace and military fields.As a new type of thermoplastic special engineering plastics,polyarylene ether nitrile（PEN）has high strength,high modulus,high temperature resistance,electrical insulation,self-flammability,and functional processing modification,which is a promising candidate for the preparation of high-performance foam materials.However,the high melting viscosity of special engineering plastics generally requires extremely high processing temperatures,which limits the choice of blowing agent and the control of foaming projects,and it is almost impossible to use traditional foaming processes.At present,the research of PEN is mostly focused on molecular structure design,synthesis and performance of functional materials such as photoelectromagnetic,and there are few studies on PEN foaming materials.In order to obtain the high-performance PEN foam,our work use green and environmentally friendly supercritical CO₂ foaming technology to foam poly aryl ether nitrile,in order to improve the dissolution and diffusion properties of the supercritical fluid in the polymer matrix and thus enhance its expandability.In this paper,from the perspective of molecular design,bisphenol A polyarylene ether nitrile（BPA-PEN）was used as the model compound,and bisphenol AF polyarylene ether nitrile（BPAF-PEN）resin with high carbon dioxide affinity was synthesized and studied.The foaming process,the method of regulating the cell structure and the influence of the molecular structure on the foaming behavior have resulted in high-performance polyarylene ether nitrile foams with nano-scale micropores.The specific research work is as follows:1.From the perspective of molecular design,BPAF-PEN with high carbon dioxide affinity was successfully synthesized,and its structure was characterized by infrared spectroscopy（FTIR）and nuclear magnetic resonance hydrogen spectroscopy（1H NMR）.The thermal decomposition kinetics of BPAF-PEN was studied by non-isothermal thermal decomposition process,and the thermal decomposition data was synchronously fitted by consecutive reactions based on the model based simulation method.For the nucleation growth reaction,the activation energy of the reaction is236.09 k J/mol.The second step is the N-th order reaction,and the activation energy of the reaction is 232.43 k J/mol.2.Secondly,it was verified that the introduction of fluorine-containing groups significantly increased the amount of CO₂ dissolved in the polymer and increased the diffusion coefficient to shorten the saturation time.The diffusion coefficient of BPA-PEN at 15 MPa,40℃is 1.02×10^-7 cm²/sec,the saturation adsorption equilibrium time is 600 min,and the diffusion coefficient of BPAF-PEN with fluorine-containing groups is 4.27×10^-7 cm²/sec,saturated The adsorption time is 120 min,which is 4times higher than the former diffusion coefficient,and the saturation adsorption time is shortened by 5 times.Among them,at 40℃and 30 MPa,the amount of CO₂ dissolved in the BPAF-PEN polymer is as high as 17.0277 g/100g polymer,and the diffusion coefficient is 9.86×10^-7 cm²/sec.3.Finally,the intermittent foaming method was used to prepare BPA-PEN and BPAF-PEN microcellular foams.The effects of foaming conditions on the cell structure and morphology of the two foams were compared and the relationship between molecular structure and foaming behavior was discussed.Furthermore,BPAF-PEN nanoporous foam was obtained by adjusting the thickness,pressure and temperature of BPAF-PEN film.The pore size was 10 nm-160 nm,and the cell density was 4.40×10¹⁶ cells/cm³-2.137×10¹³ cells/cm³.Moreover,the tensile strength of the microcellular foam under the condition of 15 MPa is 33.6 MPa,while the tensile strength of the nanocellular foam under the condition of 20 MPa is 50.8 MPa,which is an increase of 51.19%.Compared with microcellular foam,the mechanical properties of nanocellular foam are significantly improved.