Silicone molds for polyurethane resin: short pot life and vents

Polyurethane resin is not a synonym for epoxy. PU often has a short pot life, a real exotherm in thick sections, and moisture sensitivity epoxy buyers don't budget for. The RTV mold still uses master, box, A/B platinum, vacuum degas, keys, jacket - but the pour/vent plan has to fill the cavity before gel. A 3-minute pot life with no high-point vents leaves air in the face. RUUIPON builds PU-casting RTV tools in Bao'an since 2018. Prototype in 3-7 business days after CAD lock. MOQ 20 pcs/design. The longer PU explainer is polyurethane resin molds. Slow epoxy: epoxy. Hub: resin molds. LSR *parts* → wydsilicone.com.

Gate and vents for *this* minutes-long window

Send PU family, pot life in minutes, filled grams, thickest section, and whether you pressure-pot the casting. If pot life drops to 90 seconds, you need a bigger gate or a shorter fill path. Don't keep a 4-minute vent plan. See split lines.

Some PU systems fight some tin RTVs. Coupon on a leftover skin. Don't assume platinum is immune.

Jacket for belly, not Shore for heat

A 180 mm figure still sags 0.5-1.5 mm without a mother mold. Don't jump to 40A to "resist heat." Fast demold (green pull) tears 10A skins if there is no split.

When this PU-slug advice does not apply

Slow epoxy belongs on the epoxy page. Food trays are food pages. A one-off figurine can take a block pour. Geometry can override quantity: locked arm pockets still need a plug at 20 molds.

If you only have photos, custom 3D modeling is USD $50 when that scope applies.

PU RFQ to copy

• Process: platinum RTV (craft)
• PU family; pot life; filled grams
• Coupon compatibility
• Split / plug / jacket
• Pressure pot / vacuum on the casting: yes/no
• Custom 3D modeling: USD $50 when that scope applies
• Prototype with real PU, then MOQ 20 pcs/design

Send pot life, grams, and the master to contact ([email protected] / +86 135 3006 2969). Licheng Technology Industry Park, Xinhe Blvd, Shajing, Baoan.

Matched CTA: Send PU pot life, filled grams, and a coupon request - not an epoxy vent plan, and not a generic free quote.

We would not recommend quoting a slow epoxy vent plan for a 3-minute PU

We would not recommend skipping the coupon. We would not raise Shore A first to hide a missing jacket. We would not hang 177.2600 on a PU skin. We would not yank a one-piece glove around a locked arm.

RUUIPON Mold Structure Decision: open-back if you can peel slowly. Racing a 5-minute gel with undercuts? keyed two-part plus plug. Wet/hot mass? mother mold.

flowchart TD
  A[PU pour] --> B{Pot life minutes?}
  B -->|hours like epoxy| C[Use epoxy page]
  B -->|minutes| D{Coupon OK?}
  D -->|no| E[Change PU or RTV]
  D -->|yes| F{Fill before gel?}
  F -->|no| G[Bigger gate / vents / vacuum]
  F -->|yes| H{Jacket for sag?}
  H -->|yes| I[Mother mold]
  H -->|no| J[Prototype real PU]
  G --> H
  I --> J

Typical shop values

Caption: Typical shop values (not a named lot).

FAQ

Is PU the same as epoxy for the mold? No. Pot life, exotherm, and moisture change vents and jacket.

Will platinum always cure against PU? Coupon. Don't assume.

Do I need a split if I demold green? Often yes. A fast yank tears undercuts.

Is this food-grade? Not by default.

How fast is a prototype? 3-7 business days after CAD lock. Pour the real PU.