THE ART AND SCIENCE OF ELASTOMERS
Built on real industrial experience, this masterclass bridges theory and production reality, offering insights that go beyond textbooks and into the core of rubber manufacturing.
Chapter 23
The Production Cycle
Raw rubber is soft.
It creeps, deforms and flows under stress.
To become useful, it must be cured.
That transformation is called vulcanization, the moment rubber gains structure, resilience and memory.
At the molecular level, long polymer chains are chemically bonded together, forming a three-dimensional network that holds its shape under load. Stretch it, it resists. Release it, and it returns. That’s what gives rubber both flexibility and strength.
Four key curing systems define modern rubber.
Sulfur curing is the classic method, used in natural rubber, SBR, NBR and EPDM. With accelerators, it delivers fast cycles and crosslinks that balance elasticity with excellent fatigue resistance.
Polyhydroxy, or bisphenol curing, is standard for many FKMs, producing strong, chemically stable networks with outstanding resistance to solvents.
Peroxide curing is used in EPDM, silicone and in FKMs exposed to steam or amines. It creates thermally stable networks, often with slightly lower elasticity but superior heat performance.
Metal oxide curing is reserved for halogenated rubbers such as chloroprene, forming durable, weather-resistant bonds with strong long-term aging behavior.
In every case, heat and pressure inside the mold trigger the reaction.
But timing is critical.
Undercuring leaves a weak, unstable part.
Overcuring makes it brittle and short-lived.
To control this window, engineers rely on cure-monitoring instruments that track how stiffness evolves during vulcanization. From the resulting curve come vital reference points: t₂ known as the scorch time, a warning that curing has begun, and t₉₀, the time required to reach effective cure.
Once cured, rubber is no longer a soft, shapeless polymer.
It’s stable.
Elastic.
High-performance.
Ready to seal, to absorb, to endure.
And sometimes, especially in medical, aerospace or precision components, even this isn’t the end.
A final step remains: post-curing.
