Method 813 evaluates the degree of sinter (or densification) of polytetrafluoroethylene (PTFE) insulation on a wire specimen using a Differential Scanning Calorimeter (DSC) as described in ASTM D4591. A minimum 18-inch length specimen is required.
The PTFE specimen is prepared by removing just the PTFE portion of the insulation structure. The weight of the PTFE specimen should be between 7.0 mg to 12.0 mg, measured to the nearest 0.01 mg. The heating temperature scan is set to start at 270°C and stop at 380°C with a ramp rate of 10.00°C per minute.
After completion, the specimen is cooled to room temperature. A second heat scan is then performed. The degree of sinter is determined by analyzing the DSC thermal curves for melting point transitions and heat of fusion characteristics.