Summary

The number of workplace accidents in Quebec has declined over the last 30 years. Nevertheless, a worker is still injured or maimed every six minutes. Hand injuries accounted for 14.9% of all injuries compensated by Quebec’s Commission des normes, de l’équité, de la santé et de la sécurité du travail (CNESST, Labour Standards, Equity, Health and Safety Board) in 2012. The proportion was as high as 30% in some sectors, including metal machining and food preparation. Wearing protective gloves suitable for the work environment is one of the ways to reduce the risk of hand injuries. There are standardized methods for determining the level of protection that gloves afford, especially against cuts and punctures. Still, these levels of protection are generally valid for new gloves only, and little research has focused on how the degree of protection changes over time and according to the stresses to which the gloves are exposed in the workplace. In many areas of activity, like metal machining, there are often many different hazards, and exposure to cutting fluids can alter the mechanical resistance properties of gloves. In addition, gloves can sometimes be cleaned to extend their useful life and reduce costs, but what impact this treatment may have on protection has not been determined.

The objective of this study was to characterize the effect of cutting fluids on the mechanical resistance of protective gloves, under controlled laboratory conditions and in the workplace. To this end, gloves and contaminants already used in three sectors of two companies that were partners in the study were chosen. The effects of contamination of these gloves in the lab and of cleaning treatments on the residual cutting and puncture resistance of the gloves were assessed with different glove/contaminant pairs. Then, inflation tests were conducted in the lab on different polymers to determine which glove coating polymers were the most resistant to the cutting fluids used in metal machining. Inflation tests on two of these polymers exposed to cutting fluids at different temperatures were also carried out to assess the effect of temperature on chemical resistance. Additional characterization testing of the cutting fluids was done, along with multiple linear regression analysis of the inflation test results. Through this analysis, the parameters characterizing the fluids that have a significant impact on inflation were determined. Last, on the basis of these results and considering the sectors targeted in the two partner companies in the study, gloves that could meet workers’ needs in terms of protection and functionality were selected from among those available on the market. These “new” gloves were tested in the workplace as part of a glove wear-and-tear program. The program involved measuring the cutting and puncture resistance of the gloves after use and comparing these properties with those of new gloves, as well as asking workers, by means of a questionnaire, whether the selected gloves did indeed meet their needs.

Based on the results of the inflation tests on the polymers, the potential coating polymers for the gloves were classified by decreasing order of their cutting fluid resistance: PVC, nitrile, polyurethane > neoprene > butyl, latex. The multiple linear regression analysis showed that the density (or viscosity-gravity constant) of the fluid and the solubility parameters of the polymers have a significant impact on inflation; on this basis, models were proposed that explained up to 74% of the total variation in inflation.

The results of the laboratory tests of glove contamination on different glove/contaminant pairs showed that glove condition had a significant effect on a glove’s mechanical resistance, especially its puncture resistance. Generally speaking, cutting, and especially puncture resistance, decline when the gloves are in contact with a cutting fluid. However, with several of the glove/contaminant pairs tested, the effect of the cutting fluids on mechanical resistance was not statistically significant. These results make sense insofar as the gloves initially used by the partner companies were made primarily of nitrile or polyurethane polymers, which showed better resistance to cutting fluids in the laboratory inflation tests. The results of the glove-cleaning treatments highlighted changes in morphology and mechanical properties, especially discoloration and a slight increase in puncture resistance.

The results of the workplace glove wear-and-tear program showed that the effect of normal use when contaminants are present is highly complex and not the same as with laboratory contamination. In the workplaces, the gloves were exposed not only to the effects of cutting fluids, but also to mechanical wear and tear associated with the specific characteristics of workplace operations (which sometimes differed from one worker to another). The puncture resistance tests showed that used gloves provided less protection than new ones. Changes in glove material morphology were also noted, including holes, traces of erosion and tears of varying depth. These signs of wear and tear may be due to chemical deterioration of the material and/or to mechanical wear and tear that occurs during work activities. The results of the user satisfaction survey and worker acceptance of the tested gloves show that there are no universal models valid for all professional tasks and appropriate for all types of work environments. A large proportion of workers will agree to wear some models, while refusing to wear others, and workers’ opinions about some gloves are extremely divided.

Generally speaking, the data from the cutting tests revealed wide variability, making it difficult to detect specific effects, whether for the gloves contaminated in the lab, cleaned or subjected to wear and tear in the workplace. To use this property in future studies, the specific cutting method needs to be clarified and better control over the different sources of variability should be considered.

This study enabled us to make recommendations regarding the best coating polymers for gloves used in metal machining and to determine which gloves could potentially replace those currently being used in the partner companies involved in the study. The research results also led to a better understanding of the effects of cutting fluids on the behaviour of the gloves under different conditions of use.