Carbon flour fillers

In other parts of the world, plywood adhesive fillers are obtained from local sources and may be quite different than those used in North America. In Southeast Asia, banana flour is quite important. In Europe, calcium carbonate (chalk) is often used. Nearly any fibrous material or fine particulate material capable of forming a functionally stable suspension can be made to work if the formulator is sufficiently skillful. However, the mix formulator will be very specific about the type and grade of filler to be used in a particular mix. Substitutions may lead to serious gluing problems. 

Fillers (calcium carbonate, calcium sulfate, aluminum oxide, bentonites, wood flour) increase the solid content of the dispersion. They are added up to 50%, based on PVAc. The purpose of the addition is the reduction of the penetration depth, provision of thixotropic behavior of the adhesive, gap filling properties and the reduction of the costs. Disadvantage can be the increase of the white point and a possible higher tool wear. 

As discussed in Chapter 10, a wide variety of additives is used in the polymer industry. Stabilizers, waxes, and processing aids reduce degradation of the polymer during processing and use. Dyes and pigments provide the many hues that we observe in synthetic fabrics and molded articles, such as household containers and toys. Functional additives, such as glass fibers, carbon black, and metakaolins can improve dimensional stability, modulus, conductivity, or electrical resistivity of the polymer. Fillers can reduce the cost of the final part by replacing expensive resins with inexpensive materials such as wood flour and calcium carbonate. The additives chosen will depend on the properties desired. 

One outlet for polypropylene, polyethylene, and polyvinyl chloride waste is plastic lumber. These materials, often containing more than one polymer and a wide variety of additives, provide superior weather resistance in humid environments when compared to natural wood. To manufacture these materials, the compound incorporates compatibilizers, which allow dissimilar polymers to mix evenly, Additionally, they assist in the incorporation of fillers and additives, such as wood flour, calcium carbonate, and pigments. 

Other spherical fillers include carbon black. This has several roles particularly in combination with elastomers, e.g., black pigment, anti-oxidant and UV stabiliser, reinforcing filler, and an electrical conductor when used at 60% concentration. Wood flour is particularly effective in phenol/formaldehyde and melamine or urea/formaldehyde thermoset resins because the phenolic lignin component in the wood reacts with the methylol groups (-CH2OH) in the growing polymer. 

Very often particles are blended into polymers, in thermoplasts as well as in thermosets and in synthetic rubbers. This is done for various reasons the aim may be stiffness, strength, hardness, softening temperature, a reduction of shrinkage in processing, reduction of thermal expansion or electric resistance, or, simply, to reduce the price of the material. The fillers used are wood flour, carbon black, glass powder, chalk, quartz powder, mica, molybdene sulphide, various metal oxides, etc. etc. 

Commonly used fillers for epoxy systems are calcium carbonate, micas, silica, clays, powered metals, talc, wood flour, aluminium silicate etc. The properties imparted by fillers to an epoxy system are given in Table 2.4 (Dow Chemical Company, undated d). 

Fillers. Fillers mentioned for epoxy systems (subsection 2.2.6.4) are used in polyurethanes too. Ground calcium carbonate (coated as well as uncoated) is commonly used. Barium sulphate, silica fumes, wood flour and milled glass fibres are also used. 

Typical fillers wood flour, glass fiber, carbon fiber, mica, wollastonite, mineral wool, talc, magnesium hydroxide, graphite, molybdenum sulfide, carbon black, cashew shell particles, alumina, chromium oxide, brass and copper powder, iron particles, steel fiber, ceramic powder, rubber particles, aramid, wollastonite, cellulosic fiber, lignin... 

Typical fillers barium sulfate, calcium carbonate, carbon black, calcium sulfate whiskers, diatomaceous earth, glass fiber, glass spheres, hollow silicates, kaolin, mica, talc, wollastonite, silica, magnesium hydroxide, hydrotalcite, red mud, ground tire rubber, ferromagnetic powder, nickel fibers, wood flour, zirconium silicate, starch, soot, marble, aluminum, lignin, sand... 

Typical fillers calcium carbonate, talc, glass fiber, glass beads, glass flakes, silica flour, wollastonite, mica, sepiolite, magnesium hydroxide, carbon black, clay, metal powders (aluminum, iron, nickel), steel fiber, si-licium carbide, phenolic microspheres, wood fiber and flour, antimony trioxide, hydrotalcite, zinc borate, bismuth carbonate, red phosphorus, potassium-magnesium aluminosilicate, fly ash, hydromagnesite-huntite... 

The use of inert materials in vinyls is widely practiced. The filler can be used to lower cost and increase hardness. The most common types of fillers in use today include the calcium carbonates and silicate types. Also available are various silica gels, barytes, gypsum, alums, wood flour, and antimony oxide. Depending upon the oil absorption value of the inert material, a filler will (1) lower tensile properties, (2) increase hardness, (3) lower flexibility, and (A) increase processing temperatures. 

U.S. Pat. No. 3,546,158 [20] describes a flooring composition involving a terpolymer, a nonflbrous filler (calcium carbonate, silica, clay, kaolin, and carbon black) and a fibrous filler, such as wood flour, cellulose fibers, and asbestos. Compositions may include 25-53% by weight of nonfibrous filler and 17-40% by weight of fibrous filler, with the fillers accounting for 50-80% of the total composite weight. 

U.S. Pat. No. 4,165,302 [32] describes filled thermoplastic resin compositions comprising LDPE, polypropylene and other resins (in amonnts ranging from 95 to 50% by weight), organic fillers (snch as wood flour), and inorganic fillers (snch as fly ash or calcinm carbonate). This patent is concerned primarily with increasing the melt flow index of filled thermoplastic resin compositions rather than their mechanical properties. 

Low moisture content of fillers are typically observed in calcium carbonate and wollastonite (0.01-0.5%), talc and aluminum trihydrate, mica (0.1-0.6%). Medium moisture content can be observed in titanium hydroxide (to 1.5%), clay (to 3%), kaolin (1-2%), and Biodac (2-3%). High moisture content is often seen in cellulose fiber (5-10%), wood flour (to 12%), and fly ash (to 20%). Biodac absorbs 120% of water under direct contact with an excess of water. 

This property can be beneficial for hydrophobic plastics, such as polyolefins, as hydrophobic fillers can show a good interaction with the matrix. Also, hydrophobic fillers can very significantly influence the viscosity of the matrix, hence, its rheology and flowability. Fillers typically absorb oil in much higher quantities compared to water. Calcium carbonate absorbs 13-21% of oil, aluminum trihydrate absorbs 12-41% of oil, titanium dioxide 10-45%, wollastonite 19-47%, kaolin 27-48%, talc 22-57%, mica 65-72%, and wood flour 55-60%. Biodac absorbs 150% of oil by weight. 

As one can see, all the fillers decrease the mold shrinkage, with wood flour showing better results compared with calcium carbonate and talc, but a higher shrinkage compared to glass fiber. 

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