RESUMEN
A follow-up study evaluated the chemical and physical parameters of 10 disposable nitrile glove products in association with the observed variability in chemical permeation performance. The aim was to determine which polymer properties explained or were predictive of the observed wide variation in breakthrough time and steady state permeation rate. The physical and mechanical properties evaluated were thickness, area density, volume fraction and modulus 50-100%. The chemical composition properties evaluated were relative acrylonitrile content, relative carboxylation content, oily plasticizers, inorganic fillers and organic polymer content. A combination of correlation and multiple regression analyses were performed to evaluate the predictive nature of these parameters. For the regression analyses, stepwise, forward selection and backward elimination methods were used to determine an optimal regression fit. Both thickness and area density were strongly correlated with the breakthrough time. With the addition of volume fraction, these factors accounted for about 88-89% of the variation in breakthrough times. The correlation results for the steady-state permeation rate were largely inconclusive and only a moderate correlation with thickness was observed with one solvent. However, regression analyses revealed a moderate to strong association (R2 = 0.742; p < 0.001) between the permeation rate and thickness and volume fraction. With the inclusion of volume fraction in all regression models, the microstructure of the polymer played a critical role in chemical permeation, which requires further investigation. Based on these results, selection based on the availability of chemical permeation data for the product should always be preferred, especially when skin protection is critical. When chemical resistance ratings are based on general performance data, additional factors such as thickness and area density should be taken into consideration. In general, increases in thickness and area density are associated with increases in breakthrough time and decreases in the steady-state permeation rate. However, evidence in the literature and this study support the need for inclusion of additional factors associated with the microstructure of the polymer.