| Polyimide is one kind of polymers that contains imide ring. Since the advent of polyimide, it has been widely applied in the aerospace and microelectronic fields due to its excellent heat-resistant property, good optical property, solvent resistance, high strength and modulus of mechanical property. Recent years, as a high performance polymer material, polyimide has developed rapidly and found development with application in some special fields. BTDA-TDI/MDI ternary co-polyimide can be condensated from3,3’4,4’-benzophenone tetracarboxylic dianhydride(BTDA), toluene diisocyanate(TDI) and diphenyl methane diisocyanate(MDI). Now, the only commercialized product is P84(?) from the Lenzing Co.ltd. In this paper, we explore the preparation technology of this polyimide product and at the same time, consider about using a lower cost and better performance raw material to partly replace BTDA which named1,2,4,5-benzenetetracarboxylic anhydride(PMDA). Firstly, studies on the best polymerization process of quaternary copolymerization polyimide. Secondly, explores the viscosity and thermal properties, the steady and dynamic rheological properties of polymer within its spinnability and the performance of film products. These studies are all efforts which will contribute to the spinning process and provide the basis for future industrialization.This paper briefly introduces the current status of polyimide, including historical development, chemical structure, property applications and synthesis methods. Besides, the business prospects are also introduced. The polyimide is prepared by3,3’4,4’-benzophenone tetracarboxylic dianhydride(BTDA),1,2,4,5-benzenetetracarboxylic anhydride(PMDA), toluene diisocyanate(TDI) and diphenyl methane diisocyanate(MDI) with the method of solution polycondensation in the solvent of dimethylacetamide(DMAc). Among them, the mole ratios of BTDA:PMDA are100:0,95:5,90:10,85:15,80:20and the mole ratio of TDI:MDI is80:20. Then, we study on the viscosity of quaternary co-polyimide solution with influence of monomer mole ratio, reaction temperature and reaction time. The chemical structure of product is characterized by Fourier transform infrared spectrum(FT-IR), proton nuclear magnetic resonances(1H NMR). The thermal performance and viscosity are investigated by thermogravimetric analysis(TGA) and Ubbelohde viscometer. The performances of the film produced by method of tape casting include Tg, state of aggregation structure, surface and cross-section morphology, surface property, optical property, mechanical property and alkali resistant performance which are investigated by DSC, XRD, SEM, water contact angle, UV-Vis, material testing machine and so on. We also use rotary rheometer from the views of molecular mass, concentration and temperature to study on the steady state and dynamic rheological properties within different monomer mole ratio of samples.It is found that we get the exact structure and when the molar ratio of BTDA:PMDA is90:10, content is20%, reaction temperature is80℃and time is7h, in DMAc solvent and N2protecting, we can get a higher intrinsic viscosity with the value of1. The Tg is340℃; the thermal decomposition temperature of the weight loss5%and10%are440℃and510℃respectively while the maximum decomposition rate temperature stays around590℃. The char yield is60%in900℃N2atmosphere. The best tensile strength, modulus and elongation are53MPa,2GPa and4%when BTDA:PMDA is90:10. This kind of polyimide has strong resistance to acid but not for concentrate sulfuric acid and alkaline. Quaternary copolymer polyimide is a kind of amorphous polymer which has good surface property, optical property and strong absorption ability for UV light with cutoff wavelength at about400nm. The static and dynamic rheological properties of Quaternary copolymer polyimide show that the system mentioned above is typical pseudoplastic fluid. With the increase of concentration of solution and the relative molecular mass of polymer, the non-Newtonian viscous index, critical shear rate and tanδ decrease while the apparent viscosity, activation energy for viscous-fluid, complex viscosity, the loss modulus G" and storage modulus G’ all increase. With the increase of temperature, the apparent viscosity, activation energy for viscous-fluid, complex viscosity, the loss modulus G" and storage modulus G’ decrease while non-Newtonian viscous index, critical shear rate and tanδ increase. With the increase of shear rate(or frequency), the apparent viscosity, complex viscosity, activation energy for viscous-fluid and tanδ decrease while the loss modulus G" and storage modulus G’increase.For the ternary copolymerization polyimide product, we can use10%to15%of PMDA to replace BTDA while the system does not use phenol solvent which one-step polymerization commonly used but the DMAc solvent with lower toxicity. It shows that the products we get can keep excellent properties of polyimide itself while the thennal and mechanical performances have certain improvements within spinnability and processing formability. When considering the monomer cost saving advantages, this research has a certain application prospect in the future. |
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