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About fillers (CaCO3, Al2O3)

Fillers are additives to resins, usually in powder form. They may be added up to 50% by weight (for dense fillers) or 35% by volume. Fillers add bulk to the resin and can reduce cost. They can improve composites properties by increasing compressive strength, reducing shrinkage during cure or reducing exotherm (heat build up) during cure. Too much filler should not be added as it can reduce the flexural and tensile strength of the composite, increase its water absorption and reduce its chemical resistance.

Typical fillers used in the composites industry are: calcium carbonate (CaCO3), talc (Mg3(OH)2Si4O10), aluminium oxide (Al2O3), lime also known as calcium oxide (CaO), hollow glass beads (e.g Q-cells) and recycled materials.

Other materials that are added to resins are sometimes also called fillers. These include thixotropes such as fumed silica and treated clays. These powders help the resin hold onto vertical surfaces during manufacture. Pigments and dyes can be added to the resin, to give colour and protect the composite from degradation in sunlight. UV absorbers improve the resistance to weathering in sunlight. Fire retardants improve a resin’s resistance to fire. Typical additives to improve fire performance are aluminium trihydrate (ATH) (Al2O3.3H2O) and compounds containing chlorine or bromine.

Since many fillers are fine powders, they have a large surface area, and can accumulate relatively large electrical charges. Because of this they can catch fire or explode. These fine powders can also easily be blown into eyes, onto the skin and inhaled. Many fillers are not toxic but some can cause severe health problems such as lung damage or eye irritation.

Special Protection Information

Respiratory Protection: Adequate ventilation should be provided. If above NOHSC exposure standard level, use SA approved respiratory protective equipment.
Eye Protection: Use SA approved safety goggles.
Protective Clothing: Wear chemical resistant gloves. Wear full length trousers, long sleeved shirts and safety boots.

Effects of Exposure

Eyes: Can cause irritation.
Inhalation: Can cause respiratory tract irritation. Some fillers such as TALC and MICA are known to cause lung damage on repeated exposure to high concentrations.
Skin: Can cause drying of the skin.
Swallowing: Not expected to be toxic.

First Aid Procedures 

Eyes: Flush with water for at least 15 minutes.
Inhalation: Remove to fresh air.
Skin: Wash with soap and water.
Swallowing: Consult a doctor.

Spill or Leak Procedures 

Sweep or shovel solids into container. Dispose of waste in accordance with local, state and federal regulations. Seek advice from supplier.

Fire Extinguishing Procedures 

Use extinguishing media appropriate for surround fire condition. Firefighters should wear protective equipment including self-contained breathing apparatus.

Storage and Handling Procedures

Store in dry place. Dry powdered materials can build static electrical charges when subjected to friction.

KEY to abbreviations – CNS: Central Nervous System EPA: Environmental Protection Authority NOHSC: National Occupational Health & Safety Commission (Worksafe Australia) PVC: Polyvinyl chloride SA: Standards Australia

Disclaimer: Facts and information reported on this page are believed by Composites Australia to be accurate at the date of printing. No responsibility is accepted by Composites Australia for the use or misuse of information on this page. Composites Australia accepts no responsibility for damage or injury caused by information or omissions contained on this page.