Abstract: In order to improve the mechanical properties of PTFE based composites, glass fiber must be added to the dielectric layer as the reinforcing material. In this paper, ultra-fine glass fiber cotton was taken as the research object. A kind of low-speed grinding equipment is adopted. By adjusting the speed and grinding time of the equipment, the length of glass fiber was controlled. The length information of the fiber was characterized by Bauer-Mcnett fiber classifier. Then the fibers were mixed with PTFE and ceramic powders to prepare PTFE based composite as randomly filling reinforcing material. The composite ultra-thin layers were made. The experimental results showed that the length distribution of the short glass fiber prepared under the grinding speed of 70 rpm and grinding time of 10 s was moderate, which met the requirement of PTFE matrix composite material preparation. The mass fraction of trapped glass fibers in 50 mesh, 100 mesh, 200 mesh and 400 mesh screens was 15.3wt%, 20.8wt%, 19.5wt% and 14.6wt%, respectively. The fiber slurry was evenly dispersed without aggregation, and the tensile strength, tensile module and compression module of the prepared PTFE based composite were increased to 15.4 MPa, 762 MPa, and 1232 MPa, respectively.

Key words: glass fiber, fiber length, PTFE composite material, mechanical property