Natural rubber latex is harvested from the Hevea brasiliensis tree. The drc in NR latex is increased to 60% or more to improve the economics of transportation by subjecting the field latex to centrifugation. NR latex concentrates need to be preserved with suitable preservatives to inhibit bacterial growth which would destabilized the latex and ultimately resulted in spontaneous coagulation.

The types of natural rubber latex that are commonly used for the manufacturing of examination gloves are HA (High Ammonia) or LA (Low Ammonia) centrifuged latex concentrate.

The raw latex concentrates are highly specified materials where the most commonly used specification is outlined in ISO 2004 : 1979.

Concentrate latex is delivered in road tankers.

Basic principle of compounding is the process of mixing of latex concentrate with various curative dispersion and chemical stabilizers to achieved the desired processing behavior and product properties. Latex compound for examination gloves have four main components : Latex, stabilizer, vulcanizing agent and protection system. Other than that, ingredients that need to be included are pigments such as titanium dioxide, processing aids e.g., deformers, de Webbers, mould release agent etc.

Compounding mixing tank is specially made from stainless steel. The bottom of the mixing tank is an inverted cone with 2 discharge valves positioned at the apex and midway along the incline. It is designed in this way so that compounded latex of homogeneous mix can be discharged to lines by gravity feed. A stirrer is provided for continuous stirring.

After latex is compounded, the latex will be allowed to mature for a period of time. This has to be strictly observed prior releasing latex to the dipping tank. The purpose of maturation is to allow initial vulcanization and also to release air bubbles entrapped during compounding.

The matured latex is then supplied to the production line through a rubber hose. The release of latex into the dipping tank in each line is automatically controlled by a electro-pneumatic level sensor.

Laboratory approval are obtained prior to release for use, the degree of maturation is check by means of chloroform number or swelling diameter test.

The production line is a 100 meters chain conveyor type. The chain conveyor travels through 6 loops. Lowest loop progressing through the former cleaning and dipping processes. The upper loops traveling through the beading station vulcanizing, drying, post leaching and powdering.

Heat is transferred to the whole production system through closed loop boiler system. For a better and even temperature distribution in the vulcanizing oven, forced circulation is used. Ducting along the length of vulcanizing oven also assists in the even distribution of temperature.

Porcelain formers are attached on both sides on the chain conveyor and with approximately of 13,000 – 15,000 pieces former per line.

The movement of the formers is achieved by different contour steel plates along the line. The whole chain is driven by a variable speed controller.

Gloves coming out from the vulcanization oven are peeled at the front end of the line. After the gloves are peeled, the surface of the formers will be left with process residues. Before the formers are again dipped in the latex compound, the residues need to be removed. This is achieved by dipping the former into Nitric Acid solution.

The acid left over on the formers are then rinse by running water with sprinkle system then dip into an alkaline former cleaner to remove the yellow stain on the former at the same time to neutralize the reside acid on the former.

The formers are then rinsed by dipping the formers into rinse tank at an elevated temperature.

The formers are then dipped into coagulant surface solution, it is essential to avoid entrapping of air bubbles in the coagulant solution to avoid excessive pinhole in the final product.  

The former with a layer of coagulant solution are then channeled to a short oven to achieve a just dry stage (neither too dry nor too wet)

The formers are then dipped into the latex dipping tank, then through a short oven again before 2 units of leaching tanks to remove all soluble chemicals and non-rubber particles.

Then the formers shall go into another curing oven before beading is done with a set of beading brushes.

Next, the formers will go into a long vulcanizing oven to complete full vulcanizing drying before gloves are post leach to leach out all soluble protein. Then formers will be dipped into a modified cornstarch solution and go through another short oven to complete the full vulcanizing drying before gloves are brush and air stripped from the former.