Characterization of protective gloves stiffness: Development of a ...

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1034 L. Harrabi et al. / Safety Science 46 (2008) 1025–1036 Stiffness ranking by the KESF method along the longitudianl direction 25 20 15 10 5 0 r = 0.79 0 1 2 3 4 5 6 7 8 9 10 Psychophysical evaluation rating Fig. 12. Association between the psychophysical evaluation test results and the stiffness ranking provided by the KESF measurements along the longitudinal direction. Stiffness ranking by the KESF method along the transversal direction 25 20 15 10 5 r = 0.76 0 0 1 2 3 4 5 6 7 8 9 10 Psychophysical evaluation rating Fig. 13. Association between the psychophysical evaluation test results and the stiffness ranking provided by the KESF measurements along the transversal direction. dinal direction and r = 0.76 for those along the transversal direction). This shows that the free-deforming multidirectional method describes much more closely the stiffness of protective gloves as wearers perceive it. The differences observed between the results of the psychophysical evaluation test and the measurements provided by the KESF technique do not appear to be related either to the differences measured between the KESF uniaxial rigidity results along the longitudinal and transversal directions of the glove, the type of material used in the composition of the glove, or the presence of a different material for the back side of
the glove than for the palm side. The better correlation between the psychophysical evaluation and the freedeforming method is thus attributed to the type of deformations subjected to the glove during the measurement, uniaxial for the KESF system test method and multidirectional for the free-deforming technique. 4. Conclusions Stiffness ranking by free-deforming multidirectional method 25 20 15 10 5 0 L. Harrabi et al. / Safety Science 46 (2008) 1025–1036 1035 r = 0.93 0 1 2 3 4 5 6 7 8 9 10 Psychophysical evaluation rating Fig. 14. Association between the psychophysical evaluation test results and the stiffness ranking provided by the free-deforming multidirectional method. A new test method applying multidirectional deformations and using a conical spherical probe head which better simulates the type of mechanical deformations sustained by glove in use has been developed and evaluated. The stiffness of 28 models of protective gloves was measured by this new multidirectional test method and by the KESF method for fabrics that measures the uniaxial bending rigidity in both directions (longitudinal and transversal) of the gloves. It was also characterized using a psychophysical evaluation test performed with thirty subjects. Large differences in the bending rigidity measured by the KESF technique were found between the measurements along the longitudinal and transversal directions for some protective gloves, causing large differences in the stiffness rankings along the longitudinal and transversal directions. These differences can not be related to the anisotropic nature of the material since they exist even for some models of elastomer gloves. In addition, two models of gloves could not be characterized due to thickness limitations. For the free-deforming multidirectional technique, the analysis of the force–displacement curves in terms of the initial work corresponding to the first 10 mm of deformation of the glove has allowed characterizing all 28 models of protective gloves according to their stiffness. The analysis of the correlations between the glove stiffness measurements produced by the two mechanical test methods and the results of a psychophysical evaluation test shows a much better agreement with the free-deforming multidirectional method, which indicates that this method describes much more closely the stiffness of protective gloves as wearers perceive it. This can be attributed to the multidirectional deformations applied to the glove during the test, which better simulate the deformations subjected to gloves in service. Using the initial work values, the tested gloves have been divided into six classes corresponding to six levels of stiffness, which can be used for a selection of gloves as a function of the tasks. Two additional practical advantages of the free-deforming multidirectional technique should be mentioned: first, it is very easy to implement, the simple set-up of probe and drilled plate being inserted in a mechanical
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