Molecular-topological structure of γ-irradiated polytetrafluoroethylene
The molecular-topological structure of polytetrafluoroethylene (PTFE) has been studied in the range of −100 to +450°C by thermomechanical spectrometry. Revealed in this temperature range is a fourblock topological structure composed of one amorphous (T
 g = 16°C) and three crystalline (low-melting (T
 m = 315°C), intermediate (T
 m
 1
 = 355°C), and high-melting (T
 m
 2
 = 388°C)) polymorphs. At a dose of 1 kGy, the long-range orientation of chains in the intermediate and high-melting crystalline blocks of PTFE is replaced by short-range orientation of the cluster association structure. At doses of 100–500 kGy, the latter structure transitions to the amorphous state and the irradiated samples acquire a semicrystalline structure of the two-block type. The molecular-mass distribution function of interjunction chains of the pseudo-network of the amorphous block is bimodal in character and its maxima are noticeable shifted toward lower masses with an increase in the radiation dose. As the dose increases, the crystallinity decreases and the molecular mobility of amorphized chains is enhanced. As a result, both the glass transition and the molecular flow onset temperatures of the polymer are reduced.