Talc-plastic composite

The size of the crushed ore can be further reduced using roller mills or cone crushers. The requirements of the talc-plastic composite determine the fineness of the talc. A standard grinder roller produces 50 pm particles, finer grades are between 10 and 40pm, and the finest grades are between 3 and 10 pm [2]. Roller-milled products are used in low impact strength polymer-filled parts, such as fans in automotive under-the-hood applications. Fine micronization (1-12 pm) is carried... 

U.S. Pat. No. 6,337,138 [101] (by Crane Plastics Company, TimberTech) discloses a cellulosic, inorganic-filled plastic composite, comprising 25-40% of polyethylene, 30-70% of cellulosic material, such as wood fiber, seed husks, rice hulls, newspaper, kenaf, coconut shells, and 1-20% (by weight) of talc. 

U.S. Pat. No. 6,632,863 [115] (by Crane Plastics Company, Timber-Tech) discloses a wood-plastic composition manufactured as feedstock pellets comprising 55-90% cellulosic material such as wood flour and wood fiber, 10-40% of polyolefin such as HDPE, LDPE, and polypropylene, and 0-35% total of additive(s), such as lubricants and inorganic fillers, such as talc and mica. 

O. Noel and R. Clark. The use of talc in wood-plastic composites. In Progress in Woodfibre-Plastic Composites, Canadian Natural Composites Council University of Toronto, Canada, Toronto, 2004. 

O. Noel and R. Clark. Recent advances in talc-reinforced wood-plastic composites. In Intertech s 4th Conference of Natural Fiber Wood Composites, Intertech, Portland, ME, Orlando, FL, 2005. 

Wood plastic composites (WPCs), which are produced from wood flour and TP, are used widely as industrial material in the fleld of biocomposites. WPC is included under the category of the filler for filling plastic material, which includes inorganic materials, such as sihca, talc, and calcium carbonate. Therefore, its method of production is also based on the method used for fillers for filling plastic, divided into the compounding process that makes molten mixture of wood flour as filler and... 

Hybrids combine plastics or composites with other materials such as metal, wood, etc. Plastics filled with talc or other powders are not taken into account in this chapter. 

Westlane Plastics (USA) [45] uses an extrusion method to produce rods of up to 31.75 mm diameter, stri K, pipes with 9.52-12.7 mm wall thickness and other profile artides from compositions based on phenol, melamine, carbamide, and alkyd resins. Fillers used incluse wood crush, cellulose, chalk, talc, clay, mica, silica, coke, graphite, and carbon fibers. 

U.S. Pat. No. 6,255,368 [114] describes plastic cellulosic composite pellets comprising 20-60% by weight of polyethylene, polypropylene or polystyrene, 40-80% of cellulosic fiber (jute, kenaf, sisal, bamboo, rice hulls, corn husks, wood fiber, and wood flour) with an aspect ratio of between 2 and 20 and a trace of mineral coating (talc) dispersed on the surface of the pellet. 

Thermal expansion-contraction of inorganic fillers is much lower compared with that of plastics. Therefore, the higher the filler content, the lower the coefficient of expansion-contraction of the composite material (see Chapter 10). Many inorganic nonmetallic fillers decrease thermal conductivity of the composite material. For example, compared with thermal conductivity of aluminum (204 W/deg Km) to that of talc is of 0.02, titanium dioxide of 0.065, glass fiber of 1, and calcium carbonate of 2-3. Therefore, nonmetallic mineral fillers are rather thermal insulators than thermal conductors. This property of the fillers effects flowability of filled plastics and plastic-based composite materials in the extruder. 

Data in Table 4.6 show that both calcium carbonate and talc increase flexural modulus by about 40-60%, decrease impact resistance and energy to break by about 30-40%, and slightly increase moisture absorption. All these effects are generally known in the composite research and development, and slightly vary quantitatively by changing the particle size of minerals, a type of plastic, a type of cellulose (wood) fiber, density (specific gravity) of the matrix, and so on. 

Talc is hydrated magnesium silicate, a nonmetallic mineral, white-colored, chemically inert. Unlike many other minerals, its particles have a distinct platy shape. It has a natural affinity to oil and, therefore, serves as a good filler for hydrophobic plastics, such as polyethylenes and polypropylene. Platy particles of talc are structurally not uniform they have a layered composition, in which a brucite (magnesium-based, tetrahedron-cell atomic structure) sheet is sandwiched between two silica (octahedron-cell atomic structure) sheets. The elementary sheet is of ik (0.7 nm) thick. 

Water absorption showed a rather complex quantitative pattern for composites of HDPE, wood flour, and talc. Evidently, the higher the plastic content and the talc content, the lower the water absorption. However, in the triple system when talc also replaced plastic, and wood fiber content increased, the relationship with water absorption was not that simple, particularly when weight and volume percents of the ingredients were considered. For example, after 4000 h of water immersion, the composition of 44% HDPE, 27% wood flour, and 27% talc (the balance was a lubricant) absorbed 6% water (w/w). A slight increase of HDPE content to 47%, with a concurrent increase of wood flour to 40% and decrease of talc content to 10% gave 11% of water absorption. A sharp decrease of HDPE content to 25%, with both a concurrent decrease of wood flour (36%) and increase in talc (36%) resulted in 13% of water absorption. Finally, a composition with 28% of HDPE, 54% of wood flour, and 14% of talc absorbed 20% of water [6-8]. 

T. Dombrowski. Phyllosilixates in WPC applications Talc and MinFlexT. In WPCs 2006, The Changing Technology in WPCs. The First World Congress on Woodfiber/ Plastics and Related Composites, San Francisco, CA, April 2-4, 2006. 

Talcum (talc, 14807-96-6) is a natural hydrous magnesium silicate that can be associated with deposits of crude asbestos. Industrial talc, used extensively as a filler in plastics, cosmetics, coatings, lubricating compositions, and polishes may contain or be strengthened with up to 2 particles per 100 of asbestos fibre. 

Fillers may be divided into particulate and fibrous types. Particulates include calcium carbonate, china clay, talc and barium sulphate. Fillers affect shrinkage on moulding and the dimensional stability of the finished plastic, increase tensile strength and hardness, enhance electrical insulation properties and reduce tackiness. They also impart opacity and colour (Figure 3.16). Carbon black is now the most widely used filler for polymers usually in the form of furnace carbon black, which has a particle diameter of 0.08 mm. Fibrous fillers reinforce polymers and greatly increase their tensile strengths. They include fibres of glass, textile and carbon. Plastics filled with fibrous fillers are known as composites. 

Talc is an imusually soft mineral that occurs naturally in many parts of the world, but the composition varies considerably from one place to another. Commercial grades have plate-like particles that impart reinforcement to polypropylene at low cost. They have a high surface area and a high aspect ratio that improves the rigidity of plastics. Unlike wollastonite (see later), it is acid-resistant. It is also relatively cheap. 

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