Study On The Preparation And The Properties Of Polyimide Films Modified By Inorganic Nano Materials

Polyimide(PI)film is a kind of film with great research value in the field of engineering plastics.It is an aromatic heterocyclic polymer compound with imide chain in the molecular structure.It was developed in the United States in the early 1960s,and has excellent performance in all aspects.It has been widely used in aerospace,optics and microelectronics.Nowadays,with the rapid development of electronic display technology and new materials,a variety of display technologies are emerging.Among them,flexible display has become one of the most concerned fields because of its unique convenience.Among them,the flexible substrate is the support and protection component of the whole flexible display,which must have good heat resistance,high temperature dimensional stability,good flexibility,water resistance and oxygen permeability.At present,there are three kinds of materials that can be used as the substrate of flexible display devices:ultra-thin glass,metal foil and polymer film.Compared with the other two kinds of materials,the polymer film is superior to the other two kinds of materials in optical system performance,mechanical equipment performance and chemical product performance except for the slightly poor water vapor and oxygen permeability.Among polymer films,polyimide films have attracted much attention due to their excellent high temperature resistance,mechanical properties and chemical stability.As an important material of flexible display substrate,PI must have good barrier performance,mechanical system performance and thermal stability.However,the traditional polyimide films still have some problems,such as low tensile strength and insufficient thermal stability.Therefore,the purpose of this thesis is to improve the performance of polyimide film by adding nano barium sulfate and titanium nitride,prepare twophase and three-phase composite film,and study the performance changes of polyimide composite film under different external conditions.Firstly,through the single factor and design expert response surface optimization analysis of the reaction conditions of polyamic acid,a precursor of polyimide film,the optimum experimental conditions of intrinsic viscosity of polyamic acid were obtained as follows:the solid content of reactant 10.38%,the reaction time 1.87h,the molar ratio of reactant dianhydride:diamine=1.02:1,its intrinsic viscosity is 0.9325;the polyimide film,the nano barium sulfate/polyimide composite film and the nano titanium nitride/polyimide composite film were prepared by adding nano barium sulfate and nano titanium nitride under the optimized experimental conditions.The mechanical properties,thermal properties and barrier properties of the composite films were tested.The results show that at the content of BaSO4 is 8%,the properties of the nano barium sulfate/polyimide composite films are the best.At the content of TiN is 4%,the mechanical properties of the tin/polyimide composite film can reach the best;at the content of TiN is 8%,the other properties of the nano titanium nitride/polyimide composite film can reach the best.Next,the barium sulfate/titanium nitride/polyimide three-phase composite films were prepared by adding composite nano barium sulfate and titanium nitride in a certain proportion.The mechanical properties,the thermal properties and the barrier properties of the three-phase composite film were tested.The results showed that when the two kinds of nanoparticles were compounded into polyamic acid solution with 4%content respectively,the properties of the three-phase composite film reached the best.The molecular modeling and micro dynamic analysis of polyimide were carried out by the software Materials Studio.The results show that the mechanical properties and the thermal properties of the three-phase composite film are better than the corresponding two-phase composite films.Finally,several kinds of polyimide composite films were treated in neutral salt spray environment,humid and hot environment,ozone corrosion environment and alternating high and low temperature environment.The mechanical properties,thermal properties and barrier properties of the treated films were analyzed.The experimental results show that the performance of several kinds of films will decline to a certain extent after being eroded by different external environment,but compared with the decline speed of the two-phase composite films,the decline speed of three-phase composite films is more moderate,which proves that three-phase composite films have better anti-aging environmental erosion performance.