Synthesis Of High Heat-resistant Polyimide

Polyimide is a kind of(PI)special engineering plastic with excellent performance.With its excellent performance,it is widely used by all walks of life.Materialism believes that there are two sides to things,and everything in the world is inevitable.In addition to the excellent performance of polyimide,its own materials have defects in processing and use.In recent years,polysiloxane has appeared in the world,and it has been introduced into the polyimide molecular chain for modification,which has received widespread attention from the society.Therefore,this article synthesized a series of amino polydimethyl diphenyl siloxane for the modification of polyimide,we further explored the synthesis process conditions of amino polysiloxane,and polyimide-The relationship between the structure and performance of siloxane copolymer,the specific work is as follows:1.In this experiment,octamethylcyclotetrasiloxane and octaphenylcyclotetrasiloxane were used as the polymerization monomer,1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyl Dimethicone is an end-capping agent.Under the joint action of catalyst tetramethylammonium hydroxide and accelerator dimethylsulfoxide,amino-terminated polydimethyldiphenylsiloxane was prepared by anionic ring-opening polymerization.The infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy were analyzed;the optimal reaction conditions for the polymerization reaction were determined by changing the polymerization temperature,the amount of catalyst and the amount of accelerator.(1)The polymerization temperature has a relatively obvious effect on the yield of aminopolysiloxane,and the best yield is at 125 ?.(2)With the increase in the amount of catalyst,the yield of polysiloxane shows a trend of increasing first and then decreasing.(3)When the dosage of accelerator is low,the yield gradually increases with the increase of the added amount;when the dosage is certain,the change of yield tends to be stable.2.The second part of this experiment uses aminopolysiloxane and 2,2-bis[4-(4-aminophenoxybenzene)] propane(BAPA)as the diamine monomer,4,4'-(hexafluoro Isopropylene)diphthalic anhydride is a dianhydride monomer,phenylethynyl phthalic anhydride is an end-capping agent,and a polyimide-siloxane copolymer is prepared by two-step method.Research data show that:(1)the introduction of flexible siloxane segments into the rigid links of polyimide has successfully improved the solubility of polyimide materials in polar aprotic solvents.(2)With the increase of the introduction amount of polysiloxane,the hydrophobic performance of the copolymer has been further improved,making pure polyimide change from hydrophilic to hydrophobic surface.(3)According to the analysis of thermal stability data,the introduction of polysiloxane leads to a decrease in the weight loss temperature of 5% mass,but it still maintains good thermal stability.The increase of the diphenyl content of the side groups of the siloxane segment in the copolymer,the thermal weight loss temperature of the 5% mass of the copolymer has increased,and the copolymer still maintains good thermal stability.(4)As the content of polysiloxane increases,the glass transition temperature tends to decrease,increasing the temperature difference from the curing temperature and increasing the processing temperature window.(5)It can be seen from the analysis of the rotary rheometer that the more polysiloxane flexible segments contained in the copolymer,the better the processing fluidity of the copolymer;By changing its composition,it can be found that the more the phenyl content in the side chain of the polysiloxane,the better the processability and fluidity of the copolymer.