The equipment provided in this grant is a special thermogravimetric system consisting of a Cahn Model C-1100 Pressure Balance plus associated pressurization, temperature control, and data acquisition equipment. Measurements will be possible at 700 degrees Celsius and 140 atmospheres, which represent conditions significantly beyond those capable with conventional thermogravimetric methods. With this unique capability, characteristic diffusion and gas solubility data will be possible for high temperature fluoropolymers and advanced thermoplastics. Currently, such data are nonexistent and these properties can be estimated only through extrapolation of low pressure data which is expected to produce significant errors. The ability to obtain such data, coupled with bubble nucleation and growth studies, should result in improved polymer foam processes and products with controlled open and closed cellular structures. In the case of costly foamed fluoropolymer insulation for data transmission cable, small improvements in void fraction would result in significant material cost savings and superior products. Also, studies of gas-polymer interactions arising with SF6, Freon 123, and Freon 134 gases with various polymers should provide a basis for evaluating these gases as substitutes for the chlorine-containing freons which are currently used in polymer foam processes. The latter gases have been shown to have deleterious effects on the upper atmosphere ozone layer, and it is important that satisfactory substitutes be identified.
