Differential scanning calorimetry studies of various fluorinated plastics
Pederson, John Alvin
Margrave, John L.
Master of Arts
Partial fluorination of various hydrocarbon plastics have been done at different temperatures for different lengths of time. By visual inspection of the surface, polypropylene received the most effective surface fluorination while polyethylene received somewhat less effective fluorination. Thickness of the plastic and position in the cylinder were two parameters to be considered for optimum fluorination. The du Pont differential scanning calorimeter was used to measure the effectiveness of the Fluorokoting against thermal oxidation. Air was used for the atmosphere, and two heating rates were utilized: 5° and 1° per minute. Slopes of the curves were compared for all plastics. Areas(heat evolved) were considered for polypropylene only. Results show that polypropylene had the most effective fluorokoting while the polyethylenes were less effective. This observation confirmed the results of the visual inspection of the surface. The DSC was also utilized in the Department of Transportation project. The parameters of interest were the amount of heat released by the compound and the initial onset temperature. Other surface properties that can be examined are contact angles and "smoothness." The contact angle with water decreased initially with fluorination, but then increased with increasing time of fluorination. Also, the higher the temperature of fluorination, the larger the contact angle. A scanning electron microscope was used to visually examine the surface of one of the fluorinated samples of polypropylene as compared to the surface of unfluorinated polypropylene. Surface differences were easily detected in these samples by photographs of magnifications of 2,x.
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