Heard it several times, but still you don't know what to do with it: vulcanization in protective gloves. In this article, the safety professionals explain what vulcanization means in protective gloves, how it works and what effects it can have.
Protective gloves: the choice of material
For liquid-tight protective gloves, raw materials are used that are either made of natural raw materials (such as natural latex) or synthetic materials (such as butadiene/acrylonitrile). Such raw materials can initially be either low-molecularly solid or liquid to gaseous. In order to achieve a usable material condition, synthetic glove materials are often polymerized first.
Protective gloves: Vulcanizing latex
Natural rubber (also called rubber or latex), on the other hand, receives another special pre-treatment, namely vulcanization. At the end of vulcanization, molecular chains are present, whereby a plastic state is reached. However, a plastically deformable raw material is not yet suitable as a glove material, as it is usually too sticky, at least at higher temperatures. By means of cross-linking via molecular bridges between the molecular chains, the material must therefore be converted to the elastomeric state. This is done by so-called vulcanization.
Protective gloves: vulcanization accelerator as a catalyst
Vulcanization is carried out by adding sulfur or other cross-linking substances. Since vulcanization is usually too slow for an industrial process, auxiliary materials are added as catalysts, so-called vulcanization accelerators. Due to the addition of vulcanization accelerators, small amounts of sulfur, lower temperatures and shorter vulcanization times are required in the manufacturing process. A few common substance classes of these vulcanization accelerators are, for example: dithiocarbamates, thiurams, thioureas, mercaptobenzothiazoles and many of their derivatives.
Protective gloves: vulcanization accelerators and allergies
These vulcanization accelerators are primarily auxiliary materials for production, i.e. process chemicals, but they also have some significance for the function of the finished glove. In the finished glove, however, they have the unpleasant property of being able to trigger type 4 allergies. (Type IV allergies are contact allergic reactions that are mainly triggered by additives). Of course, this is completely contrary to the purpose of using these liquid-tight protective gloves, namely to protect the glove wearer. Every glove manufacturer therefore tries to minimise the residual quantities of vulcanisation accelerators in gloves or to use processes that do not require the use of vulcanisation accelerators.
Protective gloves: without vulcanization accelerator
When using certain starting materials, crosslinking can be carried out, e.g. by means of ultraviolet light, e.g. in the case of isoprenes. No vulcanization accelerators are used here and therefore no allergic reactions can occur. Overall, however, the procedure with ultraviolet light is significantly more expensive and is therefore mainly used in sensitive areas, such as surgical gloves in the medical field.
The Semperguard Nitrile Green safety glove without vulcanization accelerator
There are now more and more protective gloves on the market that contain as few allergy-causing materials or additives as possible. An example of such a glove is the Semperguard Nitrile Green Glove. The Semperguard Green Glove is made of nitrile and without the use of accelerators and chlorine.
"That's why we use nitrile as a raw material, which, unlike natural latex, does not contain any allergenic proteins," says Tan. "And we use a different method to make the nitrile latex film, as well as a different crosslinking process. This allows us to dispense with accelerators and reduce heating and cooling steps. This, in turn, saves both energy and water." - Lean Seey Tan, Head of R&D Sempermed Asia (Source: Partner magazine from 1_2018)