Internal Mold Release (Fatty Acid Ester)

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Key Features

  • Liquid form for easy, homogeneous mixing into resin systems
  • Self-releasing mechanism — migrates to resin-mold interface during cure
  • Compatible with MEKP, BPO, and cobalt/amine cure systems
  • Minimal effect on gel time, exotherm, and mechanical properties
  • Suitable for pultrusion, filament winding, RTM, and closed mold processes

This fatty acid ester internal mold release agent is formulated for addition to unsaturated polyester, vinyl ester, and epoxy resin systems to provide internal release activity during cure. Unlike zinc stearate powder, this product is supplied as a liquid for easier, more homogeneous dispersion in liquid resin systems without the need for pre-dispersion equipment. The fatty acid ester chemistry provides a self-releasing mechanism — the ester migrates to the resin-mold interface during the cure exotherm, forming a low surface energy boundary layer that prevents adhesion between cured resin and mold. Typical dosage is 0.5–1.5% by weight on total resin. Compatible with MEKP, BPO, and cobalt/MEKP cure systems for polyester. At recommended dosage, the product has minimal effect on cure exotherm, gelation time, and cured resin mechanical properties. Suitable for closed mold, RTM, pultrusion, and filament winding applications. Not recommended for structural bond-critical applications without surface preparation of the demolded part.

Specifications

ParameterValue
FormClear to pale yellow liquid
TypeFatty acid ester (liquid)
Dosage0.5–1.5% by weight on resin
Shelf Life18 months
Flash Point>100°C
Compatible Cure SystemsMEKP, BPO, cobalt/amine
Solubility in PolyesterGood

Applications

Pultrusion resin systems for continuous profile productionFilament winding of pressure vessels and pipesRTM and closed mold polyester/vinyl ester productionFiberglass chopped strand mat continuous laminationSMC and BMC compound formulation

FAQ

Add the liquid internal release to the polyester resin and mix using a mechanical stirrer for 5–10 minutes at low speed until fully homogeneous. The fatty acid ester is soluble in styrene-containing polyester resins at the recommended dosage — no heating or special equipment is required. Add before the promoter and catalyst. Do not add directly with the catalyst as the release agent can interact with the peroxide — always add to resin first, then add catalyst last.

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