MINERAL FILLERS Presented by JUNIYA ELSA THARIYAN 2ND MSC BPS CBPST

CALCIUM CARBONATE• Calcium carbonate is a soft, inexpensive filler, that is readily available

world-wide.• High purity calcium carbonate is colorless but appears white in

powder form due to light scattering. • For many applications, it is the obvious choice, particularly in the less

expensive polymers like PE, PP and PVC where it can improve stiffness, retain strength and improve impact resistance while lowering materials costs.

• Ground calcium carbonate is used predominantly but finer, submicron precipitated grades are available. If reinforcement of the polymer is not required, then calcium carbonate is often the first choice.

• Precipitated calcium carbonate is produced using the most economic process existing today. Limestone is converted into calcium oxide and carbon dioxide by means of calcination at temperatures in excess of 900°C.

• To ensure a high level of purity, the calcination process is carried out using natural gas. After the calcined lime has been slaked with water, the resulting milk of lime is purified and carbonated with the carbon dioxide obtained from the calcination process

• Following total carbonation, a suspension of CaCO3 results. A cake comprising 40 per cent – 60 per cent solid matter (depending on particle diameter) is then obtained by filtration. This filter cake is then dried and subsequently deagglomerated in grinders. Ultrafine precipitated calcium carbonate grades are reacted with fatty acids prior to filtration (ie) when still in the suspension stage.

• The fineness of the grain, as well as the crystal form (aragonite, calcite), is controlled by temperature, concentration of reactants and time. Depending on the chemical composition of the milk of lime used and on the purifying stages during production, both technical as well as foodstuff and pharmaceutical grades can be produced. © SpecialChem

• Burning of limestone CaCO3 --> CaO+CO2

• Slacking of quicklime CaO + H2O --> Ca(OH)2

• Precipitaion Ca(OH)2 + CO2 --> CaCO3 + H20 (precipitated calcium carbonate)

• Calcium carbonate is the most widely used white filler in paints because of its low cost, high brightness for TiO2 extension, high purity, low abrasivity, and resistance to weathering.• Calcium carbonate is also the most widely used filler in

adhesives and sealants. The coarsest grades are used at high loadings in drywall joint cements and in ready-mix adhesives for heavy wall tile. • Two grades of calcium carbonate is available• GCC and PCC

GCC• Ground calcium carbonate is most often available with

rhombohedral or prismatic particles.• Needle-like calcium carbonate is collected as aragonite sands in the

Caribbean, but this is not generally used as filler other than in cement

• Dry-ground calcium carbonates are among the least expensive white fillers available. Wet-ground products are produced in finer particle size ranges. Wet-ground fine and ultrafine products are also sold in 75% solids slurry form for high volume paint and paper applications

• Fine-ground grades are used as general purpose fillers in most types of adhesives, sealants, and gap fillers because they allow economically high loadings without adversely affecting flow

• Ground calcium carbonate is the most common filler in plastics due to its low cost, low abrasion, low oil absorption, low moisture, high brightness, and easy dispersion.

• These attributes account for its widespread use in rubber as well, where it can be used at very high loadings with little loss of compound softness, elongation, or resilience.

• Precipated calcium carbonate(PCC) is produced for applications requiring any combination of higher brightness, smaller particle size, greater surface area, lower abrasivity, and higher purity than is generally available from ground natural products.

• Fine PCC has typically a 0.7 micrometer median, while ultrafine PCC has typically a 0.07 micrometer median. The shape of PCC crystals can be manipulated according to end use requirements.

• PCC is used in plastics to improve impact resistance, surface gloss, weatherability, shrinkage control, low and high temperature properties and dielectric properties, and to reduce plasticizer migration and crazing of molded parts.

• PCC and ultrafine wet-ground grades contribute to rheology and stability and provide good dry hide and gloss retention

PCC

• In rubber, stearate coated ultrafine PCC is used for its low moisture absorption, good dispersion and good elastomer-filler contact, imparting good tensile strength, tear resistance, resilience, abrasion resistance and flex crack resistance.• High performance polymer-based adhesives and sealants use

stearate-coated PCC and ultrafine natural products to control flow and slump on application, and to provide low modulus with good tear and tensile properties in the cured state.• Precipitated calcium carbonate (PCC) is produced for

applications requiring higher brightness, better TiO2 extension, smaller particle size, greater surface area, lower abrasivity or higher purity.• Calcium carbonate, particularly PCC, is the predominant paper

filler and coating in alkaline papermaking, where it provides opacity, high brightness, and good ink receptivity

KAOLIN• Kaolinite – Al2Si2O5(OH)4

• Kaolinite clay is a member of the Kaolin family of aluminosilicates.• It is a soft white where the particles are platy in shape. Similar to

talc in that it can reinforce when the aspect ratio is high enough.• Kaolinite is widely available, inert and inexpensive.• It is commonly referred to as "China Clay“ because it was first

discovered at Kao-Lin, in China. • The term kaolin is used to describe a group of relatively common

clay minerals dominated by kaolinite and derived primarily from the alteration of alkali feldspar and micas Kaolin is an industrial mineral used primarily as an inert filler and customers combine it with other raw materials in a wide variety of applications.

• Kaolin is a white, soft, plastic clay mainly composed of fine-grained plate-like particles.

• Kaolin is formed when the anhydrous aluminium silicates which are found in feldspar rich rocks, like granite, are altered by weathering or hydrothermal processes. The process which converted the hard granite into the soft matrix found in kaolin pits is known as "kaolinisation".

• The quartz and mica of the granite remain relatively unchanged whilst the feldspar is transformed into kaolinite. Smectite may also form in small quantities in some deposits.

• The refining and processing of the fine fraction of the kaolinised granite yields predominantly kaolinite with minor amounts of mica, feldspar, traces of quartz and, depending on the origin, organic substances and/or heavy minerals.

• Kaolin clay is available in a number of grades.• Air float clay is dry ground kaolin that has been air separated to

remove impurities and control particle size distribution.• Water-washed clay, usually soft clay, has been slurried in water and

centrifuged to remove impurities and produce specific particle size fractions. Water-washed clays are often treated to improve brightness. This includes chemical bleaching and/or high-intensity magnetic separation to remove iron and titanium impurities.

• Delaminated clay is made by attrition milling the coarse clay fraction from water washing. This breaks down the kaolin stacks into thin, wide individual plates for improved brightness and opacity.

• Calcined clay is usually water-washed soft clay that is roasted to either partially or totally remove surface hydroxyl groups. Calcining increases brightness, opacity, oil absorption, and hardness (i.e., abrasivity).

• Kaolin clay is also available in surface coated grades (e.g., with stearates or silanes)

• Delaminated clays improve thermoplastic physical properties, including enhanced impact resistance when surface-treated. Kaolin for rubber is principally air float hard clay.

• Water washed and delaminated clays are used for better color, properties, and abrasion resistance.

• Calcined and surface-treated clays are used for improved electrical properties and ease of extrusion.

• High brightness, low abrasion water-washed kaolin are used as paper fillers.

• Kaolin is the preferred filler in acid Ph papers. Partially calcined and delaminated grades act as TiO2 extenders.

• Kaolin's add brightness, gloss, smoothness, and ink receptivity to paper coatings. Fine particle size air float kaolins are used as pitch control agents.

• In adhesives and sealants, kaolin is used to control flow, penetration, and adhesion on application, as well as adhesive strength, tear strength, tensile strength and elongation after cure.

• The principal use of kaolin in coatings is as a TiO2 extender. Partially calcined grades generally provide the best extension, durability, and dry hide.

• Water-washed and delaminated clays are used in water-based coatings to control gloss, film integrity, durability, scrub resistance, covering power, suspension ability, flow, and leveling.

• The largest single use of kaolin in plastics is as calcined kaolin in PVC wire insulation to improve electrical resistivity.

• Calcined kaolin is also used in agricultural polyethylene films to improve IR absorption characteristics, and in engineering resins, both untreated and silane-treated, for improved physical properties and heat deflection.

• Air float and water-washed kaolins are used in thermosets to provide a smooth surface finish, reduced cracking, warping and crazing, and to obscure fiber reinforcement patterns.

TALC Talc is a mineral composed of hydrated magnesium silicate. Its chemical formula is Mg3Si4O10(OH)2. It is very soft and can be cut with a knife. Talc is insoluble in water, but

it is slightly soluble in dilute acids. • Talc is a very soft mineral that is colorless when pure and appears white

in powder form.• The particles are generally platy so talc does reinforce when the aspect

ratio is high enough.• It is used extensively for applications needing good mechanicals with

low cost and low weight. • Talc is also a good nucleating agent, helping polymers like PP and

nylon to crystallize faster which speeds part production.

Talc is a metamorphic mineral resulting from the metamorphism of magnesium minerals such as Serpentine, Pyroxene, Olivine, in the

presence of Carbon Dioxide and Water. This is known as Talc Carbonation.

a)Talc is formed through hydration and carbonation of serpentine. Serpentine + carbon dioxide → talc + magnesite + water

b) Most talc is formed from the alteration of Dolomite in the presence of excess dissolved Silica

Dolomite + silica + water → talc + calcite + carbon dioxide c)Talc can be formed from magnesium chlorite and quartz through the

following metamorphic reaction: chlorite + quartz → kyanite + talc + water

• Talc products are processed using various combinations of dry grinding, air separation and flotation depending upon the quality of the crude ore and the properties required for intended applications.

• The talc most often used as filler is commonly called platy talc. It is distinctly lamellar characteristically soft talc. Purity is typically >90% and filler grades are 325 mesh and finer.

• 1. Stiffness (E-Modulus)• The main reason for incorporating talc in plastics is to increase the

stiffness (E-modulus).The degree of rigidity depends on the filling level, aspect ratio and fineness of the talc

• 2. Thermal Conductivity talc has significantly higher thermal conductivity (compared to the

polymer), Incorporating talc in a compound increases the thermal conductivity, resulting in faster production rates. Experience with filled polymers is that conductivity depends only on the filler content, within reasonable tolerances

3 Impact Strength• Addition of mineral fillers will not generally improve impact

strength. There are exceptions, for example the use of fine talc in PP compounds for car bumpers. In the latter case, 5 to 10 % of fine talc is added. Impact strength decreases at higher loadings.

• 4. Deflection Temperature• In many applications such as in plastic parts for cars or packaging,

rigidity is required at elevated temperatures. The heat distortion temperature (HDT) can be used to demonstrate how a mineral influences the stiffness of a plastic compound at elevated temperatures. Lamellar talc with high aspect ratio improves the deflection temperature of polyolefins to a greater extent than talc with a lower aspect ratio .

5. Creep Resistance• Substantial reduction of creep is achieved with filled polymers

in comparison to unfilled ones. Best results in our creep tests were obtained with fine platy talc. Various fillers and filler combinations reduced creep as follows: High aspect ratio talc >medium aspect ratio talc >blend of talc and carbonate >calcium carbonate >unfilled polypropylene

WOLLASTONITE• Wollastonite – CaSiO3

• Wollastonite appears as a white powder with high hardness compared to other common fillers. • The hardness makes it good for scratch resistance particularly in

PP for automotive use. • It is the most common fibrous mineral reinforcement and has

replaced asbestos since its demise. It is not as effective as the best reinforcements because aspect ratio tends to be lower than for HAR talc or mica. • Unlike other silicates, wollastonite does not have good resistance

to acids and bases.

• Wollastonite usually occurs as a common constituent of a thermally metamorphosed impure limestone, it also could occur when the silicon is due to metamorphism in contact altered calcareous sediments, or to contamination in the invading igneous rock. In most of these occurrences it is the result of the following reaction between calcite and silica with the loss of carbon dioxide.

• CaCO3 + SiO2 → CaSiO3 + CO2

• Wollastonite is ideal filler for plastic compounding in many ways. • The physical properties, such as acicular shape of the particles, very

fine particle size, Surface treated or coated wollastnite renders unique technical properties for thermoplastic compounds, thermosets and elastomers such as:

• Increased Stiffness• Excellent Impact Resistance• Increased HDT• Dimensional Stability• Increased Scratch Resistance• Excellent Surface Appearance• Increased Tensile Strength & Modulus• Lower Costs compared to fiber glass

• Acicular grades are produced from ore containing a suitably high percentage of long needles. The ore is milled in such a way that very fine, needle-like particles are preserved and recovered. Acicular grades typically have aspect ratios of 15:1 to 20:1.

• Both powder and acicular forms of wollastonite are available with surface coatings usually silane.

• Wollastonite is used in coatings as an extender pigment, and to provide resistance to flash and early rust. Its acicular nature imparts film durability and superior scrub resistance. • Fine ground and micronized grades provide smooth flow,

water resistance, improved wet adhesion, and good gloss in epoxy powder coatings.• Acicular grades impart mud-crack resistance to texture paints.• Wollastonite is used as a reinforcing filler in plastics because

of its low oil and moisture absorption, high brightness and acicularity, and availability with a variety of surface treatments.

• High aspect ratio wollastonite is a lower cost alternative or complement to short-milled glass fibers for both thermoplastics and thermosets, and is used together with organic and metallic fibers in asbestos-free formulations for friction products such as clutches, brake linings and brake pistons

• It is also used as an asbestos substitute in phenolic molding compounds and as a reinforcing filler in nylons, particularly high-impact and platable compounds.• Wollastonite is a white reinforcing filler in adhesives and

sealants, where it can be used at high loadings. Powder and fine particle sized high aspect ratio grades are used as semi reinforcing fillers in rubber.

MICA• Mica ,any group of hydrous ,potassium ,aluminium silicates

minerals.• It is a type of phyllosilicates ,exhibiting a two –dimensional sheet or

layer structure. Among the principal rock- forming minerals ,mica s are found in all three major rock varieties-igneous, sedimentary and metamorphic.

• The general formula for minerals of the mica group isXY2-3Z4O10(OH,F)2 with X=K, Na, Ba, Ca, Cs, (H3O) ,(NH4).Y=Al,Mg,Fe2+, Li, Cr, Mn, V ,Zn and Z =Si ,Al,Fe3+, Be, Ti..

• Mica have sheet structures whose basic unit consists of two polymerized sheet of silica (SiO4) tetrahedrons. The two such sheets are juxtaposed with the varieties of tetrahedrons pointing towards each other: the sheets are cross linked with cations.

• Most filler grade mica is first collected as flakes by flotation from ore that contains several minerals. Dry-ground products are air milled from flotation concentrate that has been partially of completely dried.

• Wet-ground products are ground in water using mills designed to delaminate the mica into flakes having a higher aspect ratio, sheen, and slip compared to dry-ground mica.

• Micronized mica is dry-ground to <20 or <10 micrometers in fluid energy mills using superheated steam.

• Fine-ground and micronized mica is used in paint to improve suspension stability, to control film checking, chalking, shrinkage and blistering, to improve resistance to weathering, chemicals and water penetration, and to improve adhesion to most surfaces.

• Mica is considered the most effective mineral for reducing warpage and increasing stiffness and heat deflection temperature in plastics.

• Fine-ground and micronized grades are also used to improve electrical, thermal and insulating properties.

• Its largest single use is in polyolefins.• Mica is used as an asbestos substitute in brake linings and gaskets,

and as a mold lubricant and release agent in the manufacture of tires and other molded rubber goods.

SILICA• Silica is the name given to a group of minerals composed of silicon

and oxygen.• Silica is found commonly in the crystalline state and rarely in an

amorphous state .It is compose of one atom of silicon and two atoms of oxygen resulting in the chemical formula SiO2.

• The dominant component of sand is the mineral quartz, which is composed of silica

• Silica is hard ,chemically inert and has a high melting point ,attributable to the strength of the bonds between the atoms.

• Ground silica, also known as ground quartz or silica flour, is produced by grinding high-purity quartz to finer than 200 mesh. Air separation is used as required to remove mineral impurities.

• Ground silica for filler uses offers high brightness, low moisture, chemical inertness, relatively low surface area, and the low liquid absorption that allows high loading levels.

• Quartz is the most common and has a specific gravity of 2.6. refractive index of 1.54-1.55.

• Novaculite is microcrystalline quartz that is milled to low-moisture, high purity, platy particles. Brightness is generally lower than for other forms of ground silica, but novaculite offers higher aspect ratio, lower binder demand, lower abrasivity, and availability in a range of particle size distributions (to as small as 2 micrometers average.)

• Polymers uses are based on the high hardness ,chemical inertness, heat resistance ,low coefficient of thermal expansion and good electrical insulation properties.

• Crystalline silica's also respond well to silane coupling agents.• The main uses are in thermosets such as epoxies, unsaturated

polyesters and PMMA .Some forms can also be used as semi –reinforcing fillers in silicone elastomers.

• There are toxicity concerns surrounding crystalline silicas and this tend to limit their usefulness.

• Precipitated silica is produced by the controlled neutralization of sodium silicate solution by either concentrated sulfuric, hydrochloric or carbonic acids.

• Reaction conditions are manipulated according to the particle size required. Dilute solutions and controlled acid addition rate are used to minimize the formation of silica gel.

• The reinforcing properties of precipitated silica can usually be related to particle size; 10-30 nm particles are reinforcing, while 30+ nm particles are semi-reinforcing.

• Because of the difficulty in measuring the size of particles this small, surface area , rather than particle size, is usually used for classifying various grades. For example, silica in the range of 125-250 m2/g is generally reinforcing, while products in the range of 35-100 m2/g are semi-reinforcing.

• In rubber compounds, which are the primary application for precipitated silica. the silica particles exist mostly as small clustered agglomerates rather than discrete particles.

• Precipitated silica is usually sold with about 6% adsorbed free water and a surface essentially saturated with silanol groups, the latter making it very receptive to in situ reaction with organosilane, most often mercaptosilane.

• Coatings ,flame retardant materials ,optical devices, electronics and optical packaging materials ,photoresist materials etc..

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