Preparation And Characterization Of Polyimide Based On Multicomponent Reaction

Polyimide?PI?is a kind of high performance engineering plastic with excellent comprehensive performance dominated by high heat resistance.It is widely used in solar panels,satellite antennas,nuclear industry and fire protection.In order to meet the needs of the rapid development of society,people focus on developing new structure and improving performance of PI.In this thesis,the multi-component reaction is used for of PI synthesis.Multiple components is introduced into the structure of PI,and the molecular chain of PI forms a long-chain linear structure or crosslinking structure.By introducing multi-component reactions into the synthesis of PI,a series of PI materials were prepared and their structures and properties were studied.The main studies as follows:1. A series of different low molecular weight diamine-terminated polyamic acid?PAA?that we designed and synthesized,terephthalaldehyde and thioglycolic acid as raw materials for reaction,a series of high molecular weight linear polyimide?MPI?was synthesized.Chemical structure was characterized by nuclear magnetic resonance hydrogen spectroscopy?¹H NMR?,infrared spectroscopy?FTIR?,and intrinsic viscosity tests.Thermogravimetric analysis?TGA?,integrated thermal analysis?TG-DSC?,ultraviolet-visible absorption spectroscopy?UV-Vis?,hot stage polarizing microscope?POM?,adhesion test,one-dimensional X-ray diffraction?1D WAXD?,were harnessed to characterize the performance of a series of MPI.Water absorption test,and the effect of imidization temperature on the performance of MPI were also explored.The results show that the initial thermal decomposition temperature?T_i?of a series of MPI materials is between 462?540°C,the 5%thermal decomposition temperature(T_d5%)is between592?608°C,and the glass transition temperature?T_g?is between 275?279°C adhesion level is between 0?1.There is no phenolmenon of dissolution swelling and destruction in most chemical reagents and acid-base environment.Water absorption rate is between1.77%?2.09%.As explained above,the prepared series of MPI materials have excellent thermodynamic properties,strong chemical resistance and low water absorption.The investigatied results of the influence of the imidization temperature on the performance of MPI show that:with the increase of the imidization temperature,the degree of imidization of MPI increases,thermal performance,the lower the light transmittance,the adhesion of the coating was obviously decrease,the solvent resistance will be stronger and the water absorption rate decrease.2. A series of different low-molecular-weight diamine-terminated polyamic acid?PAA?molecular chains with amino groups and carboxylic acids,benzaldehyde and methyl isocyanoacetate as the raw materials of-two components reaction,a series of high molecular weight polyimide?UPI?was synthesized by Ugi reaction.The chemical structure of the polymer was tested by nuclear magnetic resonance hydrogen spectroscopy?¹H NMR?,infrared spectroscopy?FTIR?,and intrinsic viscosity mothed.Characterization:Thermogravimetric analysis?TGA?,differential thermal analysis?DTA?,ultraviolet-visible absorption spectroscopy?UV-Vis?,hot stage polarizing microscope?POM?,adhesion test,one-dimensional X-ray diffraction?1D WAXD?,chemical resistance The performance test and water absorption test characterize the performance of a series of UPI,and explore the effect of imidization temperature on the performance of UPI.Characterization results show that a series of UPI materials have an initial thermal decomposition temperature?T_i?between 486?506°C,a 5%thermal decomposition temperature(T_d5%)between 586?604°C,a glass transition temperature?T_g?between303?320°C,and adhesion The level is between 0?1,there is no dissolution and swelling and destruction in most chemical reagents and acid-base environments,and the water absorption rate is between 3.56%?3.99%.It shows that the prepared series of UPI materials have excellent thermodynamic properties,good chemical resistance and low water absorption.The investigation results of the impact of the imidization temperature on the performance of UPI show that:with the increase of the imidization temperature,the degree of imidization of UPI increased,thermal performance improved,the light transmittance decreased.Furthemore,with the increase of the imidization temperature,adhesion strength of the coating decreased,the solvent resistance were be stronger,and the water absorption rate decreased.