抄録
The rate of decrease of mean molecular weight and the change in molecular weight distribution of PVP by ball-milling in an atmosphere of nitrogen, air or oxygen were investigated. The influence of an atmosphere on the probability of the degradation of a PVP molecule in a unit time and molecular size distribution of the polymers formed by the degradation was then discussed.
If the function representing the probability a PVP molecule to be cut off in a unit time, S(M), was proportional to (M-M∞)α, α was considered to be between 1.0 and 1.5, and to be 1.0 for the case of ball-milling in nitrogen or air and to be larger than 1.0 for the case of ball-milling in oxygen.
It is considered to be probable that a PVP molecule with molecular weight of 1.6×106 is broken both at the center and at the molecular weight between 6.0×103 and 1.1×104 from the end of a main chain by ball-milling in nitrogen, and at the molecular weight of 3.6×104 from the end by ball-milling in air or oxygen. It seems to be possible that the PVP molecule is broken at the molecular weight between 5.0×104 and 3.7×105 from the end by ball-milling in oxygen.
