Vulcanisation
Vulcanisation is a thermochemical process in which unlinked rubber molecules (natural latex or synthetic rubber such as NBR) are joined into an elastomeric network through sulphur bridges or other cross-linking reactions. The result is a material with high elasticity, tear resistance, and chemical stability.
Classical vulcanisation uses sulphur as the cross-linking agent, supplemented by accelerators:
- Thiurams (e.g. TMTD): most common accelerators in latex gloves, primary trigger for Type IV allergy
- Dithiocarbamates: similar allergen potential to thiurams
- Benzothiazoles (e.g. MBT): common in nitrile gloves
Accelerators are necessary because pure sulphur alone cross-links too slowly and incompletely. Without accelerators, the glove's mechanical properties would be insufficient.
Accelerator-free vulcanisation alternatives (e.g. UV cross-linking, sulphur-donor systems) are used for accelerator-free gloves. These reduce Type IV allergen potential but are technically more demanding to produce.
Vulcanisation directly affects mechanical properties (tensile strength, elongation) tested under EN 455-2.
Frequently asked questions
What is the connection between vulcanisation and Type IV latex allergy?
Type IV allergies (contact dermatitis) are triggered not by latex proteins but by vulcanisation accelerators – primarily thiurams and dithiocarbamates. Both latex and nitrile gloves may contain these accelerators.
What are accelerator-free vulcanisation processes?
Accelerator-free systems use UV cross-linking or sulphur-donor-based systems without classical accelerators (thiurams, carbamates, benzothiazoles). They are used for hypoallergenic gloves but are technically more demanding to produce.
How does vulcanisation affect EN 455-2 test values?
The degree of vulcanisation and accelerator concentration directly determine the glove's tensile strength and elongation. EN 455-2 sets minimum values: at least 6 N for latex and nitrile, 3.6 N for vinyl.