| Glass fiber reinforced polytetrafluoroethylene wave-transparent composites have been widely used in various fields such as antenna windows,radome,printed circuit board,because of its light weight,good molding process,good electrical insulation performance,good environment resistance.The domestic high-end wave-transparent composites are basically monopolized by German and American companies,which is very expensive.In this paper,the three kinds of domestic E glass fiber plain clothes which have different linear density,fabric count and tightness are used as the reinforcing material.The domestic polytetrafluoroethylene dispersions are used as the resin matrix to prepare the wave-transparent composites which can meet the requirements of certain performance.For materials which need higher tensile strength,coupling agent and epoxy are used to modify and bond the single layer composites.By testing the tensile strength of the materials and testing the weathering resistance such as water boiling,thermal cycling,ultraviolet radiation and rain test,it was found that the optimum preparation process of the composites are as follows: the emulsion concentration of PTFE is 50wt%;the gel content of PTFE is 55wt%;the molding pressure is 35MPa;the heating rate is 60?/h;the sintering temperature is 380?,and the sintering time is 1.5h;The coupling agent B with a concentration of 0.8wt% is used to modify three kinds of cloths.Besides,the curing process of epoxy resin is curing at 130°C for 1 hour,and then at 150°C for 1 hour,and finally curing at 180°C for 1 hour.The electromagnetic properties of the materials are tested by means of resonant cavity method,flange coaxial method and bow frame method.The wave-transmitting properties of composites are obtained from the absorption,reflection and wave penetration,and the free space test system is set up to test the dielectric energy of the sample.According to the free space method,the maximum dielectric constant of the epoxy-bonded double-layer modified wave-transparent composite is 3.86 which is made by “a” whose linear density is the maximum and tightness is the minimum,and the dielectric loss is 0.0066.On the contrary,the dielectric constant of epoxy-bonded double-layer modified wave-transparent composite made by “c” whose yarn number is the minimum and the tightness is the maximum is 3.06,and the dielectric loss is 0.0051.Moreover,the dielectric constant of composites made by “b” is 3.76,and the dielectric loss is 0.0056,which is fully satisfied with the property of the high performance wave-transparent composites whose ?<4,and the order of tan? is in the range of 10-1 10-3.The maximum tensile tenacity of composites made by “a” whose specific strength is the minimum are 271 MPa,and the minimum tensile tenacity of composites made by “c” is 189 MPa which completely meet the requirements of mechanical property of the wave-transparent materials.The overall anti-aging performance is good,and it might be used in the later period. |
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