Medical Elastomers And Latex

Glove Manufacturing

Mr. Manan Shah, Rubber Technologist

The latex glove manufacturing process is a complex multi-stage process, during which the centrifuged latex undergoes many physical and chemical operations. Centrifuged Latex contains rubber content up to about 60%, also reduced protein content.

The different stages of glove manufacturing process :

1. Compounding
At this first stage, various compounding ingredients are added, including accelerators (which help control the later vulcanization process) and antioxidants (which prevent deterioration of the rubber molecules in the final product by heat, moisture and ozone). Accelerators (thiurams, mercaptobenzothiazole, carbamate, thioureas) are well known as Type IV allergens. Thiurams are well known as sensitising agents and many manufacturers now replace thiurams with dithio-carbamates as the accelerators of choice.

2. Dipping & Coagulation
The formers are coated with coagulant (e.g., calcium nitrate) and dipped into the latex to coat them with a thin film of latex. The coagulant converts the liquid latex film into a wet-gel on the former. Subsequent passage through a warm oven completes the coagulation process.

3. Leaching Before Vulcanization
In this process, the latex-coated formers are immersed into a bath or spray of water, to wash out excess additives from previous stages, such as coagulant. Chemical and protein content can be reduced at this stage.

4. Vulcanization
In this stage, the latex film is heated, and the combination of sulphur, accelerator and heat cause cross-linking of the rubber, giving strength and elasticity to the film.

5. Stripping
This is the removal of the gloves from the formers, where they are turned inside out.

6. Leaching After Vulcanization
This stage is similar to above-mentioned stage ‘Leaching Before Vulcanization”, except it is carried out on the dry/vulcanized latex film. It reduces water extractives.

7. Lubrication
Hydrolyzed corn starch is added as a lubricant, to enable easy donning of the glove by tumbling the gloves in a slurry of starch and biocide. OR
Chlorination
Instead of powdering, the gloves are dipped into a chlorinated solution (for example, sodium hypochlorite acidified with hydrochloric acid). This makes the glove surface slippery, and therefore addition of powdered lubricant is not required but excessive chlorination can also adversely affect the physical properties of the latex (tensile strength, elasticity).

8. Checking
The gloves undergo 100% testing by air inflation in few factories. In addition, some gloves will be removed and tested by the water method for pinholes as part of the routine quality assurance process. Other tests will also be performed, such as tensile strength tests etc as per respective standards as well as customer requirements.

9. Packaging
This is the last stage before the gloves are distributed to the user.
Note : More information about different stages of glove manufacturing and the effect of each process on substances which can cause allergic reactions are given at the following link.

Ref: http://www.smtl.co.uk/MDRC/Gloves/jowcpaper96/node1.html