Preparation And Properties Of PEEK Foam By Thermally Induced Phase Separation

With the rapid development of science and technology,the traditional polymer foams based on general plastics can’t meet the needs of high temperature resistance,solvent resistance and high strength.Foam thermoplastic specialty engineering plastics is a good way to further enhance the performance of polymer foams in harsh environments.Polyetheretherketone(PEEK)is a kind of special engineering plastics with excellent comprehensive properties,high strength,good stability and high heat resistance.So,the light weighting of PEEK into foams is of great importance for the development of polymer foam materials.Here,polyetheretherketone(PEEK)foams were prepared by thermally induced phase separation(TIPS).To further enhance the heat resistance and mechanical properties of PEEK foams,molecular design of polymer backbone and carbon fiber(CF)reinforcement were used.The effect of molecular structure change and CF introduction on foam properties were also discussed.The specific research work is as follows:Firstly,we have introduced diphenyl structures into the molecular structure of PEEK to obtain diphenyl polyetheretherketone(PEDEK).The diphenyl structure further increases the rigidity of the molecular chain and thus the high temperature resistance of the PEEK.At the same time,a series of polyetheretherketone(PEEK)and diphenyl polyetheretherketone(PEDEK)microporous foams(0.13-0.25 g/cm~3)were prepared by thermally induced phase separation(TIPS)using diphenyl sulfone as solvent.The prepared foams have an open-cell structure with relatively uniform pore size and are close to the normal distribution.Meanwhile,the introduction of diphenyl structure can effectively improve the thermal properties of PEEK.The Tg and Tm of PEDEK increase around 30℃ and 80℃ in comparison with PEEK,while those of PEDEK are 175℃ and 414℃.The introduction of diphenyl structure can effectively also improve the performance of PEEK foams at high temperatures.It is found that PEDEK foam has a higher operating temperature than PEEK,and the compressive strength of 0.24 g/cm~3foam is still nearly 1 MPa at 200℃.Furthermore,PEEK and PEDEK foams have excellent thermal deformation and corrosion resistance.The pore structure of PEDEK foam remains unchanged after treated at 400℃ for 2 h,proving its feasibility for application in certain extreme environments.Secondly,to further improve the mechanical property of the peek foam,CF was introduced into the PEEK matrix as the reinforcement filler.CF/PEEK composite foams with a density of approximately 0.20 g/cm~3 were prepared by the TIPS to explore the feasibility of high-strength PEEK based composite foam.By adjusting the addition amount and length of CF,it was found that the highest mechanical property could be obtained when the length of CF was 1 mm and the addition amount was 1%.And,its compressive strength at 20℃,150℃ and 200℃ were 3.28 MPa,2.18 MPa and 1.23MPa,respectively,which were much higher than those of PEEK foam with similar density.That is due to the introduction of carbon fiber,which enhanced the support of the PEEK foam,and improved its heat resistance temperature and mechanical strength.