Thermoplastics and Mica

Mica is considered as the third most important white filler for thermoplastics but has some unique characteristics that sometimes give filled materials exceptional properties not obtained with any other mineral. Mica is a transparent, flexible and elastic phyllosilicate that can be ground to very fine particles with a high-aspect ratio and high mechanical properties, e.g., tensile modulus = 175 MPa, flexural modulus 220-270 MPa, compressive 

Compounded mica filled polypropylenes are available from a number of manufacturers, with however a large offer from India (where are the largest deposits of mica). Grades up to 40% are marketed and Table 6.11 is a compilation of typical average properties, based on manufacturers data sheets. 

The incorporation of mica generally reduces thermal expansion and helps eliminating the nonuniform thermal shrinkage in injection molding both effects are obviously associated with the natural flake-like form of ground mica. Like talc, mica has also excellent barrier properties, all the more if the particles are properly oriented with respect to the trajectory of the permeant. 

Mica provides similar benefits in a wide range of thermoplastic and thermoset composites including polyolefins, polyamides and styrenics. It is also reported that surface coated mica further increases tensile strength, flexural strength and modulus, and heat deflection temperature. The automobile industry is the main user of mica-filled composites, either with polypropylene or nylon as polymer matrix. Up to 40% mica loadings are used, sometimes in association with calcium carbonate, to produce various injection 

Theoretical densities were calculated with respect to the given weight percentage of (uncoated) mica the following densities were used PP, 0.90 mica, 2.82. 

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