VISCOELASTIC EFFECTS IN CUTTING OF ELASTOMERS BY A SHARP OBJECT

The cutting behavior of elastomers by a sharp object was investigated using various elastomers such as acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), and natural rubber (NR). The effects of crosslinking density, cutting rate, and temperature on the cutting energy of elastomers were investigated. The cutting behavior of swolle n elastomers was also investigated. It was found that the cutting ener gy increased as the molecular weight between crosslinks increased. It was also found that the cutting energies of various elastomers did not yield a single line. Moreover, even in the threshold condition of cut ting process, the cutting energy was much higher than the threshold fr acture energy. These results suggest that the cutting behavior cannot be explained by only a C-C bond rupture process, but it includes other energy dissipation processes. The curves for cutting energies obtaine d at different cutting rates and temperatures were well superimposed o n a single master curve when they were shifted using the WLF (Williams , Landel, and Ferry) equation. Therefore, it is supposed that the cutt ing of elastomers by a sharp object includes viscoelastic energy dissi pation process and is the viscoelastic behavior. It was also found tha t the variation of cutting energy over a considerable range;of effecti ve rates was smaller than that of the tear energy. It is attributed to the fact that the change of the crack tip diameter, i.e., roughening or reduction, was restricted by the diameter of razor blade. (C) 1998 John Wiley & Sons, Inc.