Study On Preparation And Performance Of The Fluorinated Imide Resin

Polyimide was a kind of macromolecular polymer whose main chain contains imides groups, possessing excellent properties of thermal stabilities,mechanical and electric.It was widely used in many fields,such as aerospace,machinery,micro-electronics etc.However,it also had drawbacks such as higher melting point,poor solubilities,difficulty processing,weaker adhesion, higher hygroscopy,higher water absorption and higher cost etc.The design,synthesis,development of the new polyimide materials were based on the synthesis of the new monomers. The characteristics of the polyimide materials were largely laid on the characteristics of the monomers.The focal research of polyimide materials were still by the polymerization way of the synthetical monomers which have some special characteristics,the fluorinated polyimides were now one of the synthesis and modification ways.This article mainly contained four parts:(1) the synthesis and characterization of new fluorinated diamine monomers,(2) the synthesis and characterization of fluorinated bismaleimide, (3) the synthesis and characterization of fluorinated polyimide films,(4) molecular structure and properties.Firstly,eight kinds of fluorinated dinitrides were synthesized by the nucleophilic substitution of 2-chloro-5-nitrobenzotrifluoride with diphenol in the presence of N,N-dimethylformamide,then fluorinated dinitrides were reduced into fluorinated diamines in the reduction system of Pd/C and hydrazine hydrate.The fluorinated diamines involved BAPP-2TF,BAPFP-2TF,BAPB-2TF,DARes-2TF,DATHQ-2TF,DATBHQ-2TF,DABP-2TF,DATMBP-2TF.The properties of the fluorinated diamines were characterized by FTIR,DSC.Secondly,eight kinds of fluorinated bismaleimide acids were synthesized by the synthetical monomers and maleic anhydride.Then the corresponding bismaleimide were prepared by thermal imidization of the bismaleimide acid.The properties of the fluorinated bismaleimide were characterized by FTIR,DSC.Finally,The polyamic acid solutions were prepared by polycondesation reaction between diamine and aromatic dianhydride including pyromelitic dianhydride(PMDA),4,4'-oxydiphthalic anhydride(ODPA),3,3',4,4'-tetracarboxylicbenzo phenone dianyhydride(BTDA),3,3',4,4'- tetracarboxylic biphenyl dianhydride(BPDA),2,2-[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride(BPADA),and the corresponding forties kinds of polyimide films were prepared by thermal imidization of the polyamic acids in the solvent(DMAc).The characteristic absorptions of carbonyl group at about 1780 and 1720 cm^-1(C=O asymmetric and symmetric stretching) and C-N stretching bands at about 1380 cm^-1 indicate the correctness of the prepared polymer films. The test of UV-Vis Spectrometer showed the transmittances under the visible light are above 80%, which indicated these films have better optical properties.The water absorptions of all these polyimide films were mostly less than 1%,which indicated these films have low water absorption. The surface energy of each film was lower than 43mJ/m² which was far lower than the corresponding data of water:72mJ/m² showing the good hydrophobic property.The test of DSC showed the lowest glass temperature of the synthisized polyimide films was 185.2℃,while the highest was 305.7℃.The test of TG showed the onset decomposition temperature of the polyimide films in nitrogen condition was mostly above 450℃,which indicated these films had excellent thermal stability.The test of Material Testing Machine showed all polyimide films had higher tensile strengths,and some films' tensile strengths are above 100MPa,which indicated these films had better mechanical properties.