Low-temperature Preparation Of Polyimide Film By Microwave Assisted And Its Mechanical And Electrical Properties Research

At present,the preparation of polyimide(PI)films mostly uses the technical route of first polycondensation of dianhydride and diamine to form polyamic acid(PAA),and then dehydration and cyclization to generate PI at high temperature.This traditional high-temperature imidization method not only consumes too much energy,but also a curing temperature as high as 300?can easily cause depolymerization of PAA,which in turn affects the properties of PI film materials.Therefore,how to produce PI films at low temperature and through a simple and environmentally friendly route has become a research hotspot in recent years.Based on the principle that microwave irradiation can effectively increase the substrate temperature and the percentage of activated functional groups,induce the rotation and conformational changes of functional groups.This subject has carried out research on the relevant technology and material properties of PI films prepared at 70?by using microwave-assisted curing technology,and its influence mechanism has been discussed.The influence of microwave-assisted low-temperature curing method on the introduction of diphenylmethane diisocyanate(MDI-50)and graphene oxide to enhance the mechanical properties of PI films was further studied.The main research contents as follows:The influence of microwave power on the imidization degree,heat resistance,mechanical properties and electrical properties of PI film materials was systematically studied,and the optimal microwave power suitable for this technology path was screened out.The results show that the PI film(PI-2000W)prepared under the condition of 2000 W microwave power has the best overall performance.Compared with the PI film(PI-300?)prepared by the traditional high-temperature imidization method,it is not only has same degree of imidization,heat resistance,and the tensile strength reaches 122 MPa,an increase of 20.9%.In the range of 10^-1?10^-7 Hz,the dielectric constant is increased to 5.5?4.5,and the conductivity is increased by an order of magnitude.Further,the mechanism and law of the influence of microwave and its power on the properties of PI film materials was discussed.Based on the use of diphenylmethane diisocyanate(MDI-50)as a"grafting agent",the realization of anhydride group-terminated PAA inter-chain linkage,PI molecular chain growth,and finally improved performance of PI film.the effect of microwave-assisted low-temperature curing technology on the heat resistance,mechanical properties and electrical properties of PI film materials prepared under different dosages of MDI-50 has been systematically studied,and its change rules have been discussed.The results show that when the molar ratio of MDI-50 to diamine reaches 1:5,the prepared PI film(PI-2)exhibits the best mechanical properties and heat resistance,and its maximum tensile strength is 157 MPa,compared with PI-0 and PI-300?,it increased by 41.5%and 55.6%,respectively;the elastic modulus is 6.33 GPa,which was 36.1%higher than PI-0;T_g is 267?,which was 40?higher than PI-0.Based on the technical means of using amino-functionalized graphene oxide(ODA-GO)as a reinforcing agent to improve the mechanical,heat resistance and electrical properties of PI film materials,the effect of microwave-assisted low-temperature curing technology on the heat resistance,mechanical properties and electrical properties of PI film materials prepared under different ODA-GO dosage conditions has been systematically studied,and its change rules has been discussed.The results show that when the dosage of ODA-GO is 1.5 wt%,the prepared PI film(PI/ODA-GO-1.5)exhibits the best mechanical properties,and its maximum tensile strength is 196 MPa,compared with PI/ODA-GO-0.0 and PI-300?,it increased by 77.0%and94.6%,respectively;the elastic modulus is 10.40 GPa,which was 123.7%higher than PI/ODA-GO-0.0.When the amount of ODA-GO is 2.0 wt%,the prepared PI film(PI/ODA-GO-2.0)shows the best electrical properties and heat resistance,in the range of 10^-1?10^-7 Hz,the dielectric constant is increased to 5.5?4.5,and the conductivity is increased by two order of magnitude;T_g is 265?,which was 38?higher than PI/ODA-GO-0.0.