The emulsion used with rubber sealing rings (mostly silicone‑based emulsion for mold release, lubrication or protection, the most suitable type for this application) must NOT be applied directly as undiluted stock solution.

1. General Preparations: Emulsion Dilution (Critical Step)

• Dilution medium

  Use deionized water first (to avoid demulsification and film defects caused by calcium, magnesium ions and impurities in tap water). If deionized water is unavailable, soft water may be used. Hard water or polluted water is strictly prohibited.
• Dilution ratio

  The conventional ratio is stock solution : water = 1:5 to 1:20, adjustable according to actual needs:
  • For mold release / lubrication: 1:5 to 1:10 (higher concentration, stronger lubricity, suitable for demolding and assembly sliding of sealing rings).
  • For surface protection / light lubrication: 1:10 to 1:20 (lower concentration, thin and uniform film, minimal residue, suitable for high‑demand sealing surfaces).
• Preparation requirements

  Pour water into a mixing container, then slowly add the emulsion stock solution. Stir at low speed for 3–5 minutes (≤ 300 rpm) until the emulsion is fully dispersed, without layering or flocculation. Let stand for 5 minutes before use (to avoid excessive bubbles, which cause pinholes after application).

2. Core Application Methods (3 Common Ways for Different Production Scales)

Dipping Method (Recommended, for small batches / small rings; most uniform film)

Spraying Method (For mass production lines; high efficiency)

Wiping Method (For special‑shaped / large sealing rings, e.g., square rings, large‑diameter O‑rings)

3. Mandatory Step: Drying & Film Formation (Determines Final Performance)

• Natural drying (preferred, no equipment needed)

  Lay the coated sealing rings flat on dust‑free trays with spacing (to prevent sticking). Dry at room temperature (20–35 ℃) for 10–30 minutes.
• Low‑temperature baking (for faster production; high temperature forbidden)

  To accelerate drying, bake at 40–60 ℃ for 5–10 minutes.

  Temperature ≥ 80 ℃ is strictly prohibited (high temperature causes emulsion demulsification, film cracking, and accelerated aging of rubber sealing rings, impairing material properties).

4. Key Notes (Core Requirements for Rubber Sealing Rings)

• Compatibility test

  Before first use, apply and dry a small sample of sealing rings following the process. Inspect after 24 hours: the sealing rings show no swelling, discoloration or tackiness, and the emulsion film does not peel off – this indicates compatibility.

  Separate tests are required for different rubber materials: silicone rubber, nitrile rubber (NBR), fluororubber (FKM), ethylene propylene diene monomer (EPDM), to avoid chemical reactions between emulsion and rubber.
• Residue control

  The film shall be thin and fully covered. Excessive residue results in poor sealing surface fit, especially for sealing rings in hydraulic / pneumatic systems, where residue may contaminate the medium.
• Food / medical grade requirements

  If the sealing rings are for food contact (e.g., water cups, food equipment) or medical use, food‑grade or medical‑grade silicone emulsion must be used. Dilution shall be performed under aseptic conditions. After drying, the product shall comply with GB 4806.10, USP Class VI, etc.
• Storage and usage

  Diluted emulsion is recommended for same‑day use only.

  Unused stock solution shall be stored sealed at 5–30 ℃, away from freezing and direct sunlight to prevent demulsification and failure.

5. Simplified Process Flow (Ready for On‑Site Implementation)

For non‑silicone emulsions (e.g., polyurethane, paraffin‑based), the core process remains the same. Only the dilution ratio and drying temperature need adjustment according to the emulsion manufacturer’s technical manual.