Whiskers, Microfibers, and Powdered Fillers

Fybex (du Pont Co.), which consists of single-crystal inorganic titanate microfibers with relatively high modulus and reasonably high strength, which 

Dawsonite (Aluminum Co. of America—Alcoa, U.S.), which is sodium aluminum hydroxycarbonate, NaAl(0H)2C03, and is synthetically manufactured in acicular form. It improves tensile and flexural strengths and moduli, increases the heat deflection temperature, and lowers the coefficient of thermal expansion of composites of PE, rigid PVC, and ABS resins. Dawsonite decomposes at 300-320°C giving off CO2 and H2O, so it functions also as a flame retardant. 

Franklin Fiber (Certain Feed Products Corp.), which is fibrous crystalline calcium sulfate in the beta anhydride form. It has a white, lustrous appearance and a soft, silky feel. It is recommended for polyamides, asphalts, mineral cement, paper, and paints. It improves the tensile strength and increases the modulus of elasticity of plastics. 

Powdered fillers, also called low-aspect ratio fillers, are mainly of inorganic origin. Patents mention many inorganic powdered fillers [52-54]. They function as inactive fillers and also as reinforcing agents for many plastics, such as polyolefins, polycarbonates, polyformaldehyde, polyamides, PVC, epoxies, and polyesters [55,56]. Most often recommended are feldspar, woUastonite, mullite, asbestos, silicon, silicates, cristobalite, a series of metals, Al, Zn, Pb, Mn, Ba, Ti, Fe, Co, Ni, etc., and their oxides, carbonates, and basic mineral compounds such as spodumene, montmorillonite, kaolin, bentonite, etc. Powdered fillers are added in large quantities, 40-90% by weight of composite. 

Examples of powdered fillers having low-aspect ratio follow [55,57,58]  

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