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Unsaturated polyester resins

Unsaturated polyester resins are produced by the condensation polymerization of two or multi-value alcohols with dicarboxylic acids and then dissolved in polymerizable monomers, usually 30-40 percent styrene.
The cross-linking reaction, hardening, is achieved through a graft copolymerization. The main fields of application for UP resins are glass-fiber reinforced plastic articles such as: tanks, containers, pipes, boats, yachts and ships and non-reinforced articles such as buttons, artificial marble, fillers and adhesives.
AEROSIL® fumed silica is added to UP resins for viscosity control and to achieve the desired thickening/thixotropic effect. Typical applications, for example, are (hand) lamination resins, gel coats and bonding paste. For more detailed information, we recommend reading "Technical Bulletin Fine Particles TB 54" from our library of literature".
In gel coats, applied by airless spray guns, SIPERNAT® precipitated silica is used in combination with AEROSIL® fumed silica to control and reduce porosity, caused by air entrappment of the spray process. For further information regarding SIPERNAT® 22LS in Gelcoats, please attend to our Flyer "Eliminate Gel Coat Porosity with SIPERNAT® 22LS.
SIPERNAT® FPS-5 is a high purity precipitated silica that can be utilized in dark colour gel coats to provide porosity reduction and improved leveling with no negative effects on blush resistance.
The following table shows the typical applications and effects for the use of AEROSIL® and SIPERNAT® products in UP resins and gives recommendations for grades and dosage.
 
AEROSIL® and SIPERNAT® precipitated silica in UP resins
Application
Effect
Product
Dosage
[wt.%]
Remark
Gel Coat
Clear
Rheology
AEROSIL® 200 
1.0‑2.0
 
Filled/ colored
w/talc, TiO2 etc.
Rheology


Porosity
AEROSIL® 200

SIPERNAT® 22 LS 
2.5‑4.5
Ratio: 40 percent (AEROSIL® 200) with 60 percent (SIPERNAT® 22 LS) to start. Similar usage in putties and pastes.
Dark colored
non-white
Rheology


Blush Resistance

AEROSIL®
200

SIPERNAT®
FPS‑5
2.5‑4.5
For marine gel coat


High purity ppt. silica
Laminating Resin
General
Rheology Control
AEROSIL® 200 
0.8‑1.3
 
Low Styrene
Rheology Control
AEROSIL® 200

SIPERNAT® 22 LS 
0.8‑2.5
For environmental resins
Rising viscosity with less solvent
SIPERNAT® specialty silica for UP resins
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