Vulcanization — the formation of crosslinks between polymer chains — is the most critical processing step in rubber manufacturing. The crosslink density, distribution, and chemistry determine the final mechanical properties, compression set resistance, and regulatory compliance of every rubber component. Blue Diamond engineers select and verify cure systems for every new compound.
Sulfur Cure System
Sulfur vulcanization (with accelerators such as CBS, TBBS, MBT) is the most common system for natural rubber, SBR, EPDM, and NBR. Advantages: low cost, wide temperature processing window. Disadvantages: forms N-nitrosamines from certain accelerators (regulatory concern for food/medical contact); polysulfide crosslinks are less thermally stable than carbon-carbon bonds; sulfur residue may affect metal compatibility.
Peroxide Cure System
Peroxide curing (DCP, DBPH) forms C–C crosslinks via radical mechanism. Results in: better heat resistance and compression set than sulfur; no N-nitrosamine concern; required for EPDM/silicone grades that cannot be sulfur-cured. Disadvantages: higher cost; produces volatile by-products (acetone, methanol) that must be removed by post-curing; sensitive to oxygen inhibition near mold surface.
Platinum (Addition) Cure
Platinum-catalyzed addition cure is used exclusively for silicone (VMQ/LSR/FVMQ). No by-products, no post-cure required. Achieves the lowest compression set, tightest dimensional tolerances, and full FDA/USP Class VI biocompatibility. Platinum cure silicone is the material of choice for medical, food, and aerospace components.
Cure System Selection Guide
Natural rubber for structural applications: sulfur CBS system. EPDM for automotive seals: sulfur TMTD-CBS blend. NBR for oil seals: peroxide-cured NBR for heat resistance. Silicone for medical contact: platinum LSR, no exceptions. Silicone for general industrial: peroxide VMQ. FKM (Viton): bisphenol or peroxide cure depending on temperature and chemical environment.
