Polymeric Thickener for UPR Systems
Key Features
- Transparent viscosity building — no haze in clear UPR casting and coating systems
- Pseudoplastic flow — thins under processing shear, recovers viscosity at rest
- Compatible with low-styrene and styrene-free formulations where reactive diluent content is reduced
- No activation required — simple addition and mixing at ambient temperature
- Does not affect fiber wet-out or reinforcement impregnation at typical loading levels
Polymeric Thickener for UPR Systems is a reactive or non-reactive polymeric viscosity modifier used to increase the viscosity and paste consistency of unsaturated polyester resin (UPR) formulations without the use of inorganic fillers or particulate thixotropes. These thickeners are typically based on polyurethane associative thickeners, acrylate copolymers, or reactive polyester polyol chains that entangle with or chemically bond into the UPR network during cure.
In SMC (Sheet Moulding Compound) and BMC (Bulk Moulding Compound) production, a specialized class of polymeric thickener — magnesium oxide (MgO) and magnesium hydroxide reactive thickeners — is used to mature (thicken) the UPR paste from a low-viscosity liquid to a handleable non-tacky sheet or dough over 24–72 hours. This chemical maturation is based on carboxyl-metal oxide reaction that forms ionic crosslinks between polyester carboxyl end groups and Mg²⁺ ions. However, this product covers the organic polymeric type used in non-SMC applications.
Organic polymeric thickeners based on polyurethane or high-molecular-weight polyester provide viscosity building in clear casting resins, decorative resins, and low-styrene or styrene-free systems where inorganic fillers are not desired. They provide pseudoplastic viscosity (thinning under shear) compatible with RTM, infusion, and casting processes. The advantage over fumed silica and organoclay is that polymeric thickeners contribute minimal haze to clear systems and do not affect the optical clarity of transparent or translucent UPR castings.
Specifications
| Parameter | Value |
|---|---|
| Appearance | Viscous liquid or semi-solid, colorless to pale yellow |
| CAS Number | N/A (polymeric, variable composition) |
| Chemical type | Polyurethane associative or high-MW polyester thickener |
| Compatibility | UPR in styrene, low-styrene, or styrene-free formulations |
| Typical addition level | 1–10% by weight of total resin |
| Viscosity (neat, 25°C) | 5,000–50,000 mPa·s (grade dependent) |
Applications
FAQ
MgO and magnesium hydroxide SMC thickening systems work by chemical reaction: the magnesium ions react with carboxyl end groups of the unsaturated polyester chains to form ionic crosslinks, rapidly and irreversibly building viscosity from ~5,000 mPa·s (liquid paste) to >10,000,000 mPa·s (non-tacky SMC sheet) over 24–72 hours at elevated temperature. This chemical maturation is specific to carboxyl-functional UPR and is not reversible — the matured SMC cannot be re-dissolved. Organic polymeric thickeners, by contrast, are physical thickeners that work through chain entanglement and do not chemically react with the resin. Their thickening effect is reversible (shear thinning), compatible with all UPR formulations including those without carboxyl end groups, and the viscosity increase is much more moderate (typically 2–10x starting viscosity) compared to MgO maturation.
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