Interaction between organic solvents and their mixtures with elastomers

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Interaction between organic solvents and their mixtures with elastomers. While these materials are widely used in the manufacture of protective gloves against chemical hazards, aspects surrounding their interactions with solvents are however complex and remain somewhat misunderstood.

The first problem analyzed involved the effects of solvents on neoprene. This elastomer is widely used in the manufacture of protective gloves against chemical hazards, particularly hydrocarbons and lubricants. It was observed that solvent absorption in neoprene behaves in a Fickian manner. In the case of "bad solvents", the effects of mechanical tensile strength properties seem to correlate with the amount of solvent absorbed, whereas for "good solvents", there is a great reduction in mechanical resistance at the onset of swelling. Finally, the molar volume of solvents seems to produce a more significant effect than the solubility parameters. The second part of the work concerned butyl rubber, which among other things, is used in great quantities in personal protective equipment against CBRN terrorist agents. It provides good resistance to a large number of liquid, gas and particulate chemical species. However, significant swelling can be observed in non-polar solvents, and it has been shown that among the factors controlling the swelling rate, the nature of the solvent's chemical family and saturation vapour pressure play a major role.

Moreover, the permanent effects of swelling on the mechanical properties of butyl were measured. They appear to be linked to the weight loss after deswelling, which is due in part to the extraction of additives, and not to the swelling ratio. The tests performed also showed that degradation continues even after the swelling has reached its maximum value. As for the behaviour at swelling and at permeation of solvent mixtures, a predictive model was developed using partial Hansen solubility parameters. It seems to properly apply for cases where there is a strong attraction between solvents, whereas for cases where the attraction is weak or where there is a strong repulsion, the solvent/butyl interaction becomes predominant. Finally, tests also showed that permanent damages resulting from swelling by solvents do not add up. This raises some issues in the case of repeated contact. These projects were covered in an article published in an international scientific journal and in two conference proceedings articles. They are included in Cédrick Nohilé's Doctorate thesis entitled « Étude de l’effet du gonflement par les solvants sur les propriétés du caoutchouc butyle » - Study of the effect of swelling by solvents on the properties of butyl rubber. This work was carried out jointly with researchers from the Université de Montréal and from the IRSST's Protective Equipment division, and in partnership with La Ganterie Best.