Spontaneous Formation of Potassium Hydrofluoride during Aging of a Partially Dehydrofluorinated PVDF Film

IR spectroscopy, X-ray phase analysis and scanning electron microscopy were used to study the spontaneous formation and increase in the amount of potassium hydrofluoride in the inner region of a sample of a partially chemically dehydrofluorinated PVDF film during its long-term aging. The most probable mechanism for the synthesis of potassium hydrofluoride is the oxidative degradation of the sample with the formation of fluorocarbonyl groups and their subsequent hydrolysis under the action of atmospheric water. This results in the formation of hydrogen fluoride, which combines with potassium fluoride, a by-product of primary dehydrofluorination. The increase in the content of potassium hydrofluoride continues as the sample ages until potassium fluoride remains in it. The appearance and subsequent development of spectral features characteristic of libration out-of-plane vibrations of water tetramers indicates the formation of a system of nanometer-sized pores in the sample after 100 000 min of its aging.