The variation of the fiber length during beating is slight in considering its beating time and freeness. This is due to the fact that the bamboo fibers are easier peeled, split and fibrilated than cut during beating, as a result of their peculiar layered structure. At the early period of beating, the outer-most layer peels off and the next layer begins to be separated. And at the freeness 50°SR, these layers are loosened in the peculiar "accordion" shape. Finally, the loosened part is split and broken down, and from here the film is peeled off. The peeled film is fibrilated. The diameter of fibril is about 500mμ. It is considered from the observation of the microstructure of the beaten fiber, that the outer-most layer consists of the fibril arranged vertically against the fiber axis and that this layer resists beating. The number of the distinct layers is from 3 to 4, and this is equal to that of the concentrical layers in the cross section of bamboo fiber as shows in Part 1.
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