Rubber vulcanization method and the characteristics

The main methods of rubber vulcanization are as follows:

A. Sulfur vulcanization

This is the oldest, most traditional, and most widely used method of vulcanization (invented by

Charles Goodyear).

Principle: Sulfur is used as a crosslinking agent to form sulfur bonds (single, double, or multiple

sulfur bonds) between rubber molecular chains at high temperatures.

Applicable rubber: Natural rubber (NR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), and

other general synthetic rubbers.

Characteristics: Low cost, mature technology, and excellent physical and mechanical properties (e.

g., high elasticity and strength). Disadvantages include relatively poor heat resistance (polysulfide

bonds tend to break at high temperatures) and potential sulfur frost phenomenon.

B. Peroxide vulcanization

This is a common vulcanization method used in silica gel and certain specialty rubbers, and it was

the primary method for silica gel vulcanization before platinum vulcanization. Principle: Organic

peroxides (such as 2,5-dimethyl-2,5-bis(tert-butylperoxycyclohexane)) are employed as vulcanizing

agents. When heated, the peroxides decompose to generate free radicals, which initiate cross

linking of rubber molecular chains, forming carbon-carbon bonds.

Applicable rubber types: silicone rubber (old process), ethylene propylene diene monomer

(EPDM), fluororubber (FKM), etc.

Characteristics: The formed carbon-carbon bonds have high bond energy, thus the heat resistance

of the product is superior to that of sulfur vulcanization. However, the drawbacks include the

generation of small molecular by-products with strong odors (such as phenyl ethyl ketone) during

the vulcanization process, and the mold is prone to contamination (scum accumulation).

Additionally, the transparency of the product is generally inferior to that of platinum vulcanized

silicone rubber.

C. Platinum Cured

Platinum vulcanization is a kind of addition vulcanization of silica gel. In this process, the

molecular chain of silica gel cross-link under the action of platinum catalyst, and change from

plastic linear structure to elastic three-dimensional network structure.

Key features of platinum-based silicone rubber:

Food-grade/medical-grade safety: This is its greatest advantage. No toxic by-products (such as

ketones or carboxylic acids generated during peroxide vulcanization) are produced during the

vulcanization process, making it particularly suitable for products that come into contact with food

and the human body (e.g., baby bottles and nipples, baking molds, medical devices).

Odorless and free of precipitates: The product is typically odorless, with extremely high

transparency and a smooth surface.

Excellent heat resistance, weather resistance and chemical stability.

Environmental compliance: Meets stringent food contact material standards, including FDA (U.S.

Food and Drug Administration) and LFGB (German Food and Consumer Goods Act).

D Metal Oxide Vulcanization

Principle: Use metal oxides (e.g., zinc oxide, magnesium oxide) as vulcanizing agents.

Applicable rubber: chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM),

chlorinated polyethylene (CPE), etc.

Characteristics: This type of rubber typically contains halogens, and metal oxides can react with

hydrogen halides to promote cross-linking.

E. Resin Vulcanization

Principle: using alkyl phenolic resin as vulcanizing agent.

Applicable rubber: butyl rubber (IIR), ethylene propylene diene monomer (EPDM).

Characteristics: Primarily used for butyl rubber, it exhibits excellent heat resistance in vulcanized

rubber and is commonly applied in thermally vulcanized capsules or tire air-tight layers.

Summary

If you’re seeking reliable sealing solutions for your equipment or have further questions about

vulcanization processes, feel free to contact us anytime. We’ll safeguard your equipment with our

professional expertise.

BOSS 密封解決方案

Henry, sales@bosssealing.com; WhatsApp：+86 13392768056