Flexible/Rubber-Toughened UPR
Key Features
- 3-5× higher elongation at break versus standard UPR
- Significantly improved Charpy impact strength
- Suitable as toughening modifier blended into rigid UPR
- Reduces microcracking under dynamic fatigue loading
- Compatible with standard MEKP/cobalt cure systems
Flexible and Rubber-Toughened UPR is formulated with long-chain diol components (such as diethylene glycol or polyethylene glycol segments) and/or reactive liquid rubber modifiers incorporated into the polyester backbone to produce a resin with higher elongation at break and impact energy absorption versus standard rigid UPR grades.
This resin delivers an elongation at break of 2.5-5.0% (vs. 0.5-1.5% for standard ortho UPR) and significantly higher Charpy impact strength (8-15 kJ/m²). Flexural modulus is reduced to 2.5-3.2 GPa, reflecting the intentional softening of the network. This makes it ideal for applications subject to vibration, thermal cycling, point loading, or dynamic fatigue.
Viscosity at 25°C is 300-600 mPa·s, processable by hand lay-up and spray-up. Gel time with standard MEKP is 15-25 minutes. The resin is also used as a toughening modifier blended (10-30%) into brittle orthophthalic or isophthalic resins to improve impact performance without sacrificing processability. Applications include flexible automotive body panels, wind turbine blade root connections, sports equipment, and protective enclosures.
Specifications
| Parameter | Value |
|---|---|
| Appearance | Clear to pale yellow liquid |
| Density (25°C) | 1.10-1.13 g/cm³ |
| Viscosity (25°C) | 300-600 mPa·s |
| Charpy Impact (cured) | 8-15 kJ/m² |
| Flexural Modulus (cured) | 2.5-3.2 GPa |
| Elongation at Break (cured) | 2.5-5.0% |
| Gel Time (25°C, 1.5% MEKP) | 15-25 min |
Applications
FAQ
For moderate impact improvement, blend 15-20% flexible UPR into rigid orthophthalic or isophthalic grades. This raises elongation to ~1.5-2.0% and improves impact by 30-50% with minimal stiffness penalty. For aggressive impact or vibration applications, 25-30% blend ratios are used. Always characterize the specific blend for your application as properties are not strictly linear.
Direct Contact
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