density structure to investigate this possibility a series of thermogravimetric analysis tga experiments were done using a 1 1 mixture of carbon fibers and borazine fig1 is a representative tga showing that the majority of the hydrogen and other by products evolved from the borazine below 150 u00b0 c this indicated that applying pressure would be most effective below this temperature for two reasons 1 after attaining 150 u00b0 c the viscosity would become too high and the sample less compressible 2 this is the region where most of the hydrogen by product is being produced a high pressure at this temperature could help prevent the introduction of pores into the matrix structure in general the system should be maintained under pressure at a temperature of at most 150 u00b0 c until about 80 of the weight loss due to borazine polymerization has occurred however pressure during the higher temperature processing 150 u00b0 c to about 350 u00b0 c is still essential in order to keep the evolving hydrogen from creating porosity in the structure borazine monomer was oligomerized in an inert atmosphere at 70 u00b0 c for 36 hours until an oligomer of viscosity of 500 to 2500 cp was attained in a dry box chopped carbon fibers were placed into a two inch diameter mold and a measured amount of the borazine oligomer was added graphite foil was then placed on top of the sample as a releasing agent followed by a tightly fitting disk of teflon.