Preparation And Properties Of Inorganic Powder/polyimide Composite Adhesive

Polyimide(PI)adhesives,with the best high temperature resistance in organic adhesives,have exhibited some outstanding features such as high temperature difference resistance,water and chemical solvents resistance as well as strong mechanical strength.There are some shortages of polyimide with different chemical structures,such as high cost,weak toughness and bubble defects,so that the workability and application may be affected.Modification of polyimide becomes one of research hotspots.Sealing glass is mainly utilized for high temperature and gas-tight seal,has the attractiveness of properties like low sealing temperature,good high temperature resistance and chemical stability.Si02 has the advantages of low cost,extensive source,easy preparation and controllable properties.White carbon black is of good properties such as controllable particle size,porous structure,excellent dispersity and high temperature resistance.The latter two are commonly applied in composite materials as inorganic enhancing particles.In this paper,the preparation of inorganic powder/polyimide composite adhesive by direct dispersion method was in order to obtain excellent mechanical property,thermal stability,optical properties and weatherability.Composite adhesives with the three kinds of particles were prepared respectively to obtain both advantages of inorganic powders and polyimide.The main contents are as follows:1.The Si-Zn-B-Pb-based sealing glass was prepared according to a previous design,and the sealing glass powders were obtained by mechanical milling and sieving procedure.After a surface treatment on the powders with silane coupling agent,a direct dispersion method was adopted to prepare the sealing glass powder/polyimide composite adhesive and the properties were investigated.The results showed that the best mechanical property of the composite system came to be with the ratio of glass powder:KH550:Polyimide = 1:0.05:98.95(tensile shear strength of 18.26 MPa).The thermal stability was almost the same with PI,but the weight loss speed was slow.The composite adhesive had an excellent ultraviolet resistance as the ultraviolet transmittance was down to 0.1%.The glass powder/PI composite adhesive still had a better performance than PI after weatherability test.2.On the basis of the above research,Si02/PI and white carbon black/PI composite adhesives were prepared by the same method for investigating the effects of single oxide and the particle size on the properties.The results showed that the shear strengths of the two systems were increased to 20.08 Mpa and 22.40 MPa,respectively.During the initial period,Si02 and white carbon black played an effective role in slowing weight loss,but white carbon black/PI composite film had a worse weight loss in the decomposition phase.The ultraviolet transmittance of SiO2/PI was 2.1%,thus the ultraviolet resistance was lower than that of glass powder/PI.White carbon black/PI had an ultraviolet transmittance of 6.7%,with the worst ultraviolet resistance of composite adhesives but still better than PI.After weatherability test,compared with glass powder/PI,Si02/PI had better mechanical property and white carbon black/PI had the best.Si02/PI composite film had worse weight loss at extremely high temperature while white carbon black/PI had the least loss.The ultraviolet resistance of SiO2/PI or white carbon black/PI was lower than glass powder/PI.