Frequently Asked Questions
Insights for supply chain professionals and manufacturing engineers.
1. What is the difference between thermoset rubber and thermoplastic elastomers (TPE)?
Thermoset rubber undergoes vulcanization, a chemical process creating permanent cross-links. It cannot be melted down and re-molded. TPEs behave like rubber at room temperature but can be melted and reprocessed like plastic, making them highly recyclable but unsuitable for high-heat environments.
2. Why is sulfur used in vulcanization?
Sulfur acts as a bridging agent, forming strong but flexible bonds between polymer chains. This turns a sticky, easily deformed material into a highly elastic and durable product. Charles Goodyear pioneered this technique in 1839.
3. Is natural rubber still relevant in modern industry?
Absolutely. Natural rubber possesses unparalleled tensile strength, tear resistance, and low heat build-up under dynamic stress. It is mandatory in heavy-duty applications like airplane tires and large anti-vibration mounts where synthetic alternatives fail.
4. Which synthetic rubber is best for oil resistance?
Nitrile Butadiene Rubber (NBR) is the industry standard for environments exposed to petroleum, oils, and fuels. For extreme high-temperature oil resistance, Fluorocarbon (FKM/Viton) is preferred.
5. How is rubber hardness measured?
Hardness is measured using the Shore Durometer scale. For solid rubbers, the Shore A scale is used (0-100). A rubber band is around 30 Shore A, a tire tread is about 70 Shore A, and a rigid caster wheel can be 90 Shore A or measured on the Shore D scale.
6. What causes rubber to crack over time?
Ozone degradation and UV exposure break the double bonds in the polymer chains. To combat this, manufacturers add anti-ozonants and waxes to the formulation which migrate to the surface to form a protective barrier.
7. What is flash in molding, and how is it removed?
Flash is the excess rubber that squeezes out of a mold cavity where the metal plates meet. It is removed post-cure manually, or through cryogenic deflashing, where parts are frozen with liquid nitrogen and tumbled to break off the brittle flash.
8. How long does a rubber mold take to manufacture?
Steel tooling for injection or compression molding can take anywhere from 4 to 12 weeks to cut, polish, and validate, depending on the complexity of the part and the number of cavities required.