Journal of Applied Polymer Science · 1963 · 51 citations · 15 references
Natural SciencesChemistryMaterials SciencePolymer ChemistryPolymer EngineeringSpectroscopyOxygen EffectPolymer DegradationRadiation ChemistryRadiation Damage In MaterialsRadical ReactionsThermosetsHeating RegimesPolymer Degradation Under RadiationPolymer PyrolysisPolymer Radiation DamagePyrolysisRadiation Chemistry Of PolymersRadiation DegradationRadiation-induced Degradation
Abstract Powders and compacted preforms of virgin unmelted polytetrafluoroethylene were subjected to ionizing radiation in high vacuum. The specific gravities, melt Visccmities, and mechanical strengths of the irradiated samples after a standard heating cycle in air or at reduced pressures indicate that degradation is more pronounced in the presence of oxygen than in vacuum. The presence of oxygen in the excessively degraded sample was shown by electron spin resonance and pyrolysis experiments. It is suggested that some branched molecules are also formed on heating the irradiated samples resulting in a broadening of the molecular weight distribution. Primary fluorocarbon radicals of the type . disappear rapidly when heated at 75°C. in vacuum while secondary radicals are stable thermally at 200°C. and disappear only slowly at 400°C. Both typea of radicals react rapidly with oxygen and tetrafluoroethylene at 0°C. The reactions which occur in irradiated polytetrafluoroethylene in various atmospheres and at several temperatures are reviewed in light of the information developed during this research.
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