Ordinary polydimethylsiloxane emulsions, conventional amino silicone emulsions, and simple textile-grade hydroxyl silicone emulsions cannot independently form elastic rubber molds. After drying, they only produce an oily film or soft resinous film with poor resilience, low mechanical strength, and tend to turn tacky and break easily.
Silicone elastic films that can dry and cure on their own without extra crosslinkers, featuring peelability and rebound properties, fall into two main categories:
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Pre-crosslinked silicone elastomer emulsionRecommended for thin elastic films; no chemical crosslinking reaction required.Internally, pre-crosslinked silicone rubber microparticles are dispersed in water. Only water evaporation is needed; latex particles fuse together to directly form a continuous elastic film without crosslinking chemical reactions. The one-part stock solution can be coated or cast directly.✅ Features: Simple operation, ready-to-use once opened; formed film is soft, low-modulus with good elasticity. Suitable for thin elastic films ranging from tens of micrometers to 0.5 mm. Films thicker than this tend to develop micropores and have limited mechanical strength.
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Waterborne one-component self-crosslinking condensation-type silicone emulsion (suitable for thick standalone elastic molds that can be demolded)Water emulsion of alkoxy-terminated polydimethylsiloxane, with latent catalyst built into the system. After water evaporates, silane alkoxy groups undergo condensation reactions under ambient moisture, constructing a 3D Si-O-Si crosslinked network in situ to form genuine silicone rubber elastomer.⚠️ Key distinction: Simple textile-grade hydroxyl silicone emulsion (cationic hydroxyl emulsion) does not belong to this category. Dried pure linear hydroxyl silicone oil only forms tacky soft gel. It must be compounded additionally with MQ silicone resin, fumed silica and catalysts and cannot form molds independently.✅ Features: Can be cast into films ≥1 mm thick with higher tensile and tear strength. Fully peelable after curing, ideal for standalone elastic molds. Curing relies on humidity; thick films require a long full curing cycle, which can be accelerated by heating.Mature domestic commercial product available: one-component room-temperature-curable waterborne silicone elastic emulsion (specially for waterproof elastic coatings / soft molds).
Brief reference for other systems (rarely used for independent mold formation)
Waterborne addition-type (hydrosilylation) silicone emulsion: Crosslinking yields high-performance elastomers, but most are two-part systems (Part A + Part B separated) with poor storage stability. Few are formulated as ready-to-use one-component emulsions.
MQ resin-modified hydroxyl silicone emulsion: It is a blended formulation rather than a neat silicone emulsion. Formula compounding is required; the raw liquid cannot be used alone.
Selection Recommendation
If only thin, soft elastic films (coatings, thin skins) are needed, prioritize pre-crosslinked silicone elastomer emulsion IE-2610 / PF2520. Simply pour it into a mold and dry off moisture to obtain elastic films.
If you need standalone elastic molds with thickness ≥1 mm, full demold capability and certain tear strength, choose waterborne one-component alkoxy self-crosslinking silicone emulsion.
Supplementary Notes
All waterborne silicone emulsions undergo volumetric shrinkage during curing due to water evaporation. Reserve shrinkage allowance in mold design.
Film-forming environment requirements:
- Pre-crosslinked elastic emulsion: Ensure sufficient ventilation for water removal.
- Self-crosslinking condensation type: Ambient humidity cannot be too low; otherwise incomplete internal crosslinking occurs and the film remains tacky.
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