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 starts from a resin master, then a room-temperature pour - 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* → ask us.

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 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.

Pot life minutes? - hours like epoxy -> Use epoxy page
Pot life minutes? - minutes -> Coupon OK?
Coupon OK? - no -> Change PU or RTV
Coupon OK? - yes -> Fill before gel?
Fill before gel? - no -> Bigger gate / vents / vacuum
Fill before gel? - yes -> Jacket for sag?
Jacket for sag? - yes -> Mother mold
Jacket for sag? - no -> Prototype real PU
Bigger gate / vents / vacuum -> Jacket for sag?
Mother mold -> Prototype real PU

Typical shop values

Reference values only. Confirm material-specific limits against the supplier’s technical data and agree project acceptance criteria before production.

Item	Typical shop value
MOQ	20 pcs/design after sample approval
Custom 3D modeling	USD $50 when that scope applies
Prototype	3-7 business days after CAD lock
Mix	Platinum 1:1 or 10:1; vacuum degas
Cavity Shore	10A-20A platinum; jacket for size
Platinum shrink	About 0.1-0.3% after full cure
Loaded-edge sag without a jacket	About 0.5-1.5 mm
Pot-life conversation	Minutes, not hours - name it

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.