I. Standard Vulcanization Time (Main Process)
Rubber hot water bag (wall thickness 0.8–1.2mm, natural rubber NR/ styrene-butadiene rubber SBR):
Temperature: 140–150℃ (commonly 145℃)
Pressure: 2.0–3.0MPa
Time: 20–30 minutes (positive vulcanization T90, factory typical 25 minutes)
II. Reference for Different Types of Rubber (145℃/2.5MPa)
Natural rubber NR (high-end): 22–28 minutes (good elasticity, resistant to aging)
Styrene-butadiene rubber SBR (ordinary): 18–25 minutes (low cost, slightly prone to aging)
NR + SBR blend (general): 20–25 minutes (balanced performance and cost)
III. Temperature-Time Conversion (Q10 Law)
For every 10℃ increase in temperature, the time is approximately halved; for every 10℃ decrease in temperature, the time is approximately doubled. 140℃ → 30–35min
145℃ → 20–25 minutes (standard)
150℃ → 15–20 minutes (priority on efficiency, prevent over-sulfurization)
IV. Key Influencing Factors
Wall thickness: for every 0.2mm increase, the time extends by 3–5 minutes; hot water bags are usually 1.0mm, taking the average value.
Formula: more accelerator (M/DM) → shorter time; more sulfur → slightly longer time.
Sulfurization method:
Compression molding (flat/enclosed): 20–30 minutes (mainstream)
Continuous sulfurization (steam): 12–18 minutes (high temperature 155–160℃)
V. Quality Judgment (Insufficient Sulfurization/Proper Sulfurization/Excessive Sulfurization)
Insufficient sulfurization (<18 minutes): soft, prone to deformation, leakage, short lifespan
Proper sulfurization (20–25 minutes): good elasticity, non-sticky, temperature resistance, lifespan 2–3 years
Excessive sulfurization (>35 minutes): hard, brittle, prone to cracking, poor feel
VI. Key Practical Points in the Factory
New rubber materials should first undergo T90 test in the vulcanization machine (145℃), then determine the time.
Batch production: 145℃/25 minutes/2.5 MPa, the first piece must undergo inflation test for leakage and tensile test.
Old products: every 3 months review the sulfurization curve to prevent formula or equipment fluctuations.
