Synthesis And Characterization Of Imide Oligomers Containing Pendent And Terminal Phenylethynyl Groups

Aromatic polyimides are well known as polymers with outstanding mechanical properties and high temperature capabilities. They can be utilized for a wide range of applications: as matrices for high-performance advanced composite materials, as thin films in electronic applications, as structural adhesives and sealants, as high temperature insulators for aircraft wire coatings, and as membranes for gas separation. In this dissertation, phenethynyl terminated imide oligomers are disscussed to be used as resins in the aerospace field.Matrices for high-performance advanced composite materials (ACM) comprise two types: thermoplastics resins and thermoset resins. Each has many advantages and disadvantages. The thermal-plastic resin has good toughness, however, a poor processability limited their widespread adoption as matrix resins for structural composites. To improve the processability, more and more attention has been focused on the study of various kinds of thermoset resins,such as BMI, PMR-15, epoxy, and so on. These material has the fatals of low toughness and low CAI values. The aim of the dissertation is to find a newly material to meet the demands.Herein, imide oligomers containing pendent and terminal phenylethynyl groups were synthesized from the reaction of or 3,3′,4,4′-biphenylenetetracarboxylic dianhydride (s-BPDA), 2,5-bis(4-aminophenoxy)-biphenyl (p-TPEQ), 3,5-diamino-4′-phenylethynylbenzophenone(DPEB) , 4-phenylethynylphthalicanhydride (PEPA). It was expected that, for the corresponding cured resins, the incorporation of this unsymmetrical and hindered moiety would disturb the coplannarity of the aromatic unit to reduce packing efficiency and crystalline-ability, and introduction of pendent phenylethynyl groups would enhance thermal properties of cured resins. In all, five oligomers were prepared and compared the properties. The obtained imide oligomers were molded, and varies method such as DSC,DMA,TGA and melt viscosity test were used.All the results proved that the PETIs (phenylethynyl terminated polyimide oligomers) has retained good properties. The incorporation of p-TPEQ increased processablity of the oligomers compared with the other reported PETI oligomers. The oligomers have low Tgs and low minimum melt viscosities at low temperature, which was contributed to the pedant phenyl groups. As the content of pendent phenylethynyl groups increased, the films of cured imide oligomers have higher T_gs, and maintained higher modules above Tg due to higher crosslink densities.The results proved that the oligomers have reached the high level of the world. One of them named oligo-1.0 is the best of all. Compared with PETI-5(which was exploited by NASA, 5000 g/mol ), they have the alike mechanical properties, however, our oligomers has far lower melt viscosity and higher Tg(above 300℃). Compared with TriA-PI, (another oligomers which was discovered by JAXA), our oligomers not only have the alike all properties, but also avoid to use the costly monomer (a-BPDA), it has good competition.In future, it is necessory to study a long term thermal-stablity of the oligomer resins and CFRC(Carbon Fibre Reinforced Composites) based on them.