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2.4 Results and discussion 13
2.4.1 Analysis of the mechanical properties of PI film 13
2.4.2 PI film Thermal Performance Analysis 14
2.4.3 PI film UV - visible spectroscopy 15
2.4.4 PI film adhesion performance analysis 16
3 Preparation and Properties 9FDA-TFODA-PMDS- PI film 17
3.1 Experimental materials and equipment 17
3.1.1 Experimental materials 17
3.1.2 Experimental equipment 17
3.2 Experimental content 18
3.2.1 Drying of materials and equipment 18
3.2.2 Synthesis of PAA 18
3.2.3 Preparation of PI film by thermal imidization 19
3.3 Performance Testing 19
3.3.1 PI film mechanical property 19
3.3.2 PI film thermal performance test 19
3.3.3 PI film optical performance test 19
3.3.4 PI film adhesion test 19
3.4 Results and discussion 20
3.4.1 Analysis of the mechanical properties of PI film 20
3.4.2 PI film Thermal Performance Analysis 21
3.4.3 PI film UV - visible spectroscopy 22
3.4.4 PI film adhesion performance analysis 23
Conclusion 24
Express thanks 26
References 28
1 Introduction
1.1 Foreword
Polyimide is a kind of polymer containing imide ring, because of its outstanding performance in heat resistance, mechanical properties, dielectric properties and other excellent properties, and it was widely used in aerospace, microelectronics industry and other fields[1], but the widely used PI materials, because the backbone contains rigid benzene and imide ring structure, the molecular chain has strong interaction, PI is difficult to dissolve in organic solvents, which makes it difficult to be machined, the preparation of PI,mainly through the first synthesis of PAA, and then through the thermal imidization or chemical imidization , but PAA is not stable and is hard to be reserved for a long time, which greatly limits the application of PI. The flexible solar battery plate, a liquid crystal display orientation film, communication connection of optical waveguide material require a good transparency and high heat resistance , the traditional polymer ,such as PMMA and PC, have a good transparency in the visible light range, but its heat resistance limits its application in this area. PI, as traditional heat-resistant high-temperature materials, due to inter-molecular and intra-molecular charge transfer complexation, making PI films generally show a pale yellow to dark brown. Therefore, we prepared colorless transparent PI on the basis of molecular structure design of PI, in order to reduce the intra-molecular and inter-molecular effect to decrease the charge transfer complexes (CTC) formation.
In order to obtain colorless and transparent polyimide, the molecular structure design is essential of decreasing effect of inter- and intra- molecular charge to reduce inter- and intra- molecular CTC formation[2]. To get colorless and transparent polyimide, the main design method is:(1) The introduction of trifluoromethyl in the molecular structure of PI. Trifluoromethyl can cut off the conjugated electron cloud, reducing the formation probability of CTC, weakening the interaction between the molecular chains; (2) Introducing the alicyclic structure into the main chain of PI, It can reduce the content of aromatic structure in PI;(3) The introduction of flexible structural units (, ether bond or thioether bond ) in the main chain of PI, it can increase flexibility and reduce the interaction of polymer molecular chain; (4) The introduction of bulky side groups, the existence of side groups can reduce the bulk density of polymer without affecting The rigidity of the polymers. (5) The introduction of non-planar structure or asymmetric structure, It can change the molecular chain, reduce regularity, increase the free volume of molecular weight; (6)The synthesis of copolymerization, using the difference of molecular structure, the symmetry of PI is destroyed; (7)The introduction of strong electron-withdrawing group( sulfone) and other design methods.