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

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1030 L. Harrabi et al. / Safety Science 46 (2008) 1025–1036 Force (N) 25 20 15 10 2.3. The psychophysical evaluation test 5 0 0 Fig. 6. Configuration 0: palm and back sides in contact. Fig. 7. Configuration 1: 10-mm deformation of the glove. Ansell Neox 9-022 Best UltraFlex 22-R 10 mm 0 2 4 6 8 10 12 14 Displacement (mm) Fig. 8. Examples of the initial part of the force displacement curve for two models of protective gloves illustrating the calculation of the initial work. A psychophysical evaluation of the glove stiffness was performed by thirty healthy human subjects, naive relative to this kind of evaluation, aged between 20 and 55 and selected on a voluntary basis. Each subject had 1
to classify the gloves using a scale from 1 to 10 (1 being the most flexible and 10 the stiffest). The test was adapted from the CR-10 Borg scale (Borg, 1998), with excluding the score 0 which corresponds to the absence of constraint, i.e. the bare hand condition, and forcing the subject to select at least once the scores 1 and 10, which ensures an optimal discrimination between the gloves. In fact, the rating of perceived exertion using the CR-10 Borg scale would have likely produced values lower than 5 because numbers are anchored by verbal expression, with a 10 meaning ‘‘very, very strong” exertion (almost max) and a 5 meaning ‘‘strong” exertion. The procedure included two steps. First, the subject had to try on all the gloves one by one in order to rank them according to their stiffness. It allowed identifying the two anchoring points of the distribution, i.e. the most flexible glove (level 1) and the stiffest glove (level 10). Clear instructions were provided that the gloves had to be evaluated according to their stiffness and not based on comfort, size or any other property. However, apart from moving the fingers, no particular task was requested or suggested for the evaluation of the glove stiffness. Then, the subject had to attribute to each of the remaining gloves a number between 1 and 10 inclusively according to its level of stiffness. In other words, no verbal expressions were used to anchor the values from 1 to 10. In order to allow for an iterative evaluation procedure, the gloves were placed by the subject in baskets numbered 1 to 10 corresponding to their level of stiffness. It was specified that the subject could put two or more gloves in one basket if evaluated of the same stiffness and that some baskets may contain no glove. The time and the number of trials for each glove were not restricted. In general, an average of 20–30 min was necessary for the subjects to sort the gloves. One model of the list of 28 gloves displayed in Table 1 could not be included in the psychophysical evaluation test because the insufficient number of gloves available prevented providing each subject with a new specimen. 3. Results and discussion 3.1. The KESF uniaxial bending approach The 28 protective gloves have been characterized with the KESF bending technique. The results are displayed in the form of a histogram in Fig. 9. For two glove models, it was not possible to carry out the Bending rigidity (μN.m) 14 12 10 8 6 4 2 0 L. Harrabi et al. / Safety Science 46 (2008) 1025–1036 1031 Longitudinal direction Transversal direction Ansell Hyflex 11-900 Ansell Canners & Handlers #392 Ansell Hyd Tur 52-547 Best Nitri-Pro® 7000P Ansell GoldKnit Kevlar 70-225 Ansell Seams-Rite 20-115 Best Nitri-Solve® 747 Best The Original Nitri-Flex® 4000P Ansell Hycron 27-607 Ansell PowerFlex 80-100 Best KPG® 960 Ansell Grab It Safe 28-362 Best Skinny Dip Aramid® 4811 Best Ultraflex Nitrile® 22-R Ansell Golden Grab It 16-300 Ansell Scorpio 8-352 Best Cannonball®803 Best Natural Rubber Latex HD®55 Best Neo Hyde® 361 Ansell Grab It 6-620 Ansell Winter Monkey Grip 23-193 Best Cannonball® 812M Ansell Crusader 42-325 Ansell Snorkel 4-412 Best Neo Grab® 6780-R Ansell Neox 9-022 Fig. 9. Measured bending rigidity along the longitudinal and transversal directions with the KESF technique.
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