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Fillers for Polyurethane
Thicken, lighten, strengthen, or create a metallic look : with our epoxy and polyurethane fillers, you can tailor every casting or laminating project to your exact requirements.
Choose from thixotropic agents , lightweight microballoons , aluminum trihydrate (ATH) , metal powders , and chopped fiberglass for professional results.
Product categories: Fumed silica (thixotropic), hollow glass beads / microballoons, aluminium trihydrate (ATH), metal powder (bronze/copper/aluminium/iron), chopped glass fibre 12 mm.
For whom: Professional users of epoxy, polyurethane and polyester resins who want to adapt their material for specific applications such as laminating, casting, spatula or cold casting.
Quick choice: which filler suits your purpose?
| Goal | Recommended filler | Result |
|---|---|---|
| Thicken / make thixotropic | Fumed Silica (Aerosil / Cab-O-Sil) | Non-sagging mix, transparent |
| Lighten / save material | Hollow Glass Beads (Microballoons) | Lower density, better sanding |
| Harder/stiffer & flame retardant | Aluminum trihydrate (ATH) | Higher stiffness, FR action |
| Metal look / cold casting | Aluminum, Copper, Iron powder | Real metal sheen, patina possible |
| Mechanical reinforcement | Cut Fiberglass 12 mm | Higher impact/tensile strength |
Key Benefits
- ✓ Versatile for epoxy, PU, polyester and silicone
- ✓ Adjustable to precisely adjust viscosity, weight and strength
- ✓ Cost-effectively reduce resin consumption or extend material
- ✓ Professional results for laminating, casting and spatulating
- ✓ Creative metal effects and special finishes possible
Areas of application
- → Composite construction lamination with fiberglass and reinforcement
- → Moldmaking thixotropic layers and fairing compounds
- Cold casting metal look sculptures and replicas
- → Industrial parts rigid, lightweight components
Thixotropic & thickening: Fumed Silica for Epoxy & PU
Filler Fumed Silica 150 gr.
Fumed silica (known as Aerosil or Cab-O-Sil ) is the standard thixotropic agent for thickening epoxy, polyurethane, polyester, or silicone . When mixed properly, the mixture remains colorless/transparent.
- Purpose: Pastes, spatulas, vertical laminates
- Properties: increases viscosity, anti-sagging
- Tip: process in small portions; avoid dust formation
Lightweight filling: Hollow glass beads / microballoons
Filler Hollow Glass Beads
Microscopic hollow glass beads for lightweight castings , syntactic foams, and fairing compounds . Reduces resin consumption and improves sandability.
- Goal: Lose weight, increase volume
- Compatible with: epoxy, PU, polyester
- Tip: Do not mix too aggressively to reduce breakage.
Hardness & FR: Aluminum Trihydrate (ATH) for Polyurethane
Filler Polyurethane (ATH-based)
Aluminum trihydrate increases hardness and stiffness and can contribute to flame-retardant properties (formulation and dosage dependent). It also reduces the cost per kg of final mixture.
- Purpose: stiffer parts, FR purposes
- Use: Dose according to TDS; viscosity increases
- Tip: degassing/lower casting thickness due to exotherm
Metal look & cold casting: Metal powders
Aluminum powder (100%)
Fine aluminum powder for metallic effects in paints, lacquers, casting resins, and plaster. After curing, polish to a shine or apply a finishing touch.
Copper powder (100%)
Copper powder creates a warm bronze/copper look . Suitable for cold casting ; patination is possible for an authentic effect.
Iron powder (100%)
Iron powder gives a robust steel/cast iron look . Create a rust patina for an industrial or antique finish.
- Goal: realistic metal look, weight/feel tuning
- Tip: first apply a thin "gel coat" with lots of powder, then fill it up
Reinforcement: Cut Fiberglass 12 mm
Cut Fiberglass 12 mm
Chopped strand for extra mechanical strength in acrylic resin, polyurethane, epoxy, polyester and even silicone.
- Objective: Increase impact resistance and stiffness
- Tip: Spread evenly; viscosity increases noticeably.
Processing tips for fillers
Mixing & Dosing
- → Add fillers slowly while mixing
- → Weigh accurately for consistent results
- → Test with small amounts first
Processing
- → Pot life shortens at higher filler percentages
- → Bleeding may become more difficult
- → Viscosity increases noticeably upon addition
Safety
- → Wear a dust mask when handling powder fillers
- → Work in a well-ventilated area
- → Follow TDS for maximum dosages
Product Overview – Fillers
Filler Polyurethane (ATH)
ATH-based filler for a harder end result , higher stiffness and lower cost per kg PU.
Fumed Silica 150 gr.
Make epoxy/PU thixotropic for troweling and vertical applications; stays clear when used correctly.
Aluminum powder (100%)
For metallic effect in resin and plaster; polishing/patina possible for a realistic finish.
Filler Hollow Glass Beads
Creates lightweight castings and fairing compounds; reduces resin consumption and improves sandability.
Iron powder (100%)
For cold cast and rust patina effect; industrial character.
Cut Fiberglass 12 mm
Reinforced epoxy/PU/polyester; improved impact and tensile strength.
Copper powder (100%)
Warm copper/bronze look with the possibility of patination; ideal for decoration and replicas.
Getting Started with Fillers
Order fillers for epoxy, polyurethane, and polyester. Compare products, download datasheets, and contact us for technical advice and fast delivery in Europe.
Frequently Asked Questions (FAQ)
How much fumed silica do I need to thicken epoxy?
Start with small percentages (1-3%) and gradually increase until the desired thixotropy is achieved. Too much fumed silica can hinder miscibility and deaeration.
What is the difference between hollow glass beads and microballoons?
In practice, the terms are used interchangeably. Both are hollow glass microspheres that reduce density and facilitate abrasion.
Can I use ATH for fire retardancy in PU?
Yes, aluminum trihydrate is often used for FR purposes. Its effectiveness depends on the dosage and the overall formulation of the system.
How do I create a metallic look with casting resin?
Mix metal powder into the resin (possibly first a thin "gel coat" rich in powder), then pour on the standard mix and finish with polishing or patination for the desired effect.
Technical advice & ordering
Not sure which filler your project needs? We're happy to help with dosage, compatibility, and application advice.
Contact us for personal advice and fast delivery in Europe.
Note: Always follow the Technical Data Sheet (TDS) and Safety Data Sheet (SDS). Add fillers gradually and test a small batch before scaling up to larger volumes.