Binders are chemicals for sticking particles together into a solid mass, as opposed to adhesives, which are normally used to stick surfaces together. Most chemical solutions will give some binding effect after drying. The chemical solutions used as binders are typically those that give good bonding strength when used in small percentages.
Organic binders are mostly polymers. There are cellulose derivatives which are familiar as wallpaper glue, “office paste” and thickeners. Super binder M is the top of the range of cellulose derivatives. Many organic binders are emulsions of polymers, such as acrylic, PVC, PVA, latex etc. We supply a good acrylic emulsion called Plasticast resin. Lignin sulphonate is a by-product of the paper industry, reasonably cheap. Our stock is a bit hard. Wood gum resin or rosin (stocked) is a natural binder that has been used for millennia. Other natural gums are gum Guar, gum Acacia, gum Arabic etc. Sugars are also used; molasses, Dextrin or Dextrose is common, and sucrose is used as a binder for cupels. Starches are also used.
Then we get tar, asphalt and pitch, working largely on the basis of viscosity. They are mixed hot, and harden on cooling.
Proteins are another group of binders, also important as foam stabilisers
Phosphates are a large and complex group of binders. We stock sodium tripolyphosphate (STPP) and sodium hexametaphosphate (Calgon) and the liquid aluminium orthophosphate.
Silicate binders include colloidal silica, which we call “Super binder L” (from which we make Rigidiser), sodium silicates and ethyl silicate. We stock the two end members of the sodium silicate range and a “gassing “ grade. Hardcast binder is based on modified sodium silicate. We also stock a potassium silicate.
Calcium sulphates and their hydrates are most familiar as Plaster of Paris. We stock several grades and manufacture several moulding materials based on calcium sulphates.
Calcium aluminates are used in very many refractories. We stock these and calcium sulphoaluminates, and some modified ones for specific purposes.
Sorel cements or magnesium oxychloride cements are extremely hard. We stock the components and make several tailor made products under the name “Keraset”. We have done about 17 development projects in this field, and are increasingly active in it. Our Keraforce fiberglass is a winner and a range of insulating building materials. Polystyrene coated with Keraforce is cheaper, lighter and more rigid than steel.
Resin binders include epoxy, polyester, polyurethane, phenolic resins, furanes, urea formaldehyde and lots of others. Of this group we only stock a specially developed one for coal bonding, called “Keracoal“.
One of the cheapest binders is OPC, ordinary Portland cement, with a few varieties such as white Portland cement. Blast furnace cement or slagment is a pozzolan, a glassy material which has slow developing cement properties. Certain fly ashes are pozzolanic, but not South African fly ashes. “Lime” or calcium hydroxide is used in pozzolanic formulations, dating back millennia. We can supply a range of cement additives to change the rheology, enhance the strength and modify virtually any property desired. We have a new development which are provisionally calling "Ettringite cement" which sets fast, very hard and has a very large water tolerance.
Binders are often used in combination. In refractories you may use a chemically setting binder to hold the shape together while still wet, another binder to greatly increase the strength once air dried, a third to take over from an organic binder when it burns off, and a fourth to assist in sintering.
Most binders need a carrier, which may be water or a solvent. Different particles react more favourably with one or the other, depending on the surface tension. The particles should be wetted by the carrier. If not wetted, surface active agents can be added to render the particles wet. Soap is a familiar example. We have a wetting agent called Kerawet, which is effective in very small additions.
Some superfine mineral particles are used with binders to hugely increase the surface area for bonding onto. One is a montmorillonite clay mineral called bentonite and the other is silica fume, with a median particle diameter of 0.2 micron. When using these materials, it is critically important to get them properly dispersed, usually by intensive mixing.
If binding proves to be difficult, it may be necessary to adjust the particle size distribution by adding a readily available cheap mineral of the “missing” size. This technology has been studied intensively from an academic point of view. We can refer you to literature or give some advice from experience.
Sometimes porous materials need strengthening, by our Sand Hardener.
Keramicalia probably stocks the widest range of binders under one roof in Africa, and conceivably in the world. We use them all for our own products and therefore have experience of them and are not prejudiced towards a particular group of binders. We have technical relationships with the manufacturers in nearly all of the binder groups.
We can solve most binder problems. We have a close relationship with the PSS mineral binding laboratory and undertake R&D projects for binding minerals.
These are a range of viscous liquids with very good bonding properties. They are water soluble and highly alkaline. Their chemistry and reactions are complex. We supply 2:1 silica to soda ratio with a density of 1,54kg/litre, solids content of 44%. Used in refractory mortars with long shelf life.
We also supply a 3, 3:1 silica to soda ratio with a density of 1,4kg/litre. It is more reactive and less soluble.
We sometimes stock a “gassing grade” which is made to set instantly on contact with CO? gas used in porous bodies like foundry sand.
We manufacture our own variant, called Hardcast Binder, which is designed for use in chemically setting insoluble formulations. Use with 10% Hardcast hardener on binder weight. Typically they set in one hour. We also make Rapolite binder for a 20minutes setting time.
Packaging: 1kg plastic bottles, 7 kg plastic bottles, 33,5kg polycans, 210litre drums.
We also supply various silicate fillers which work well with sodium silicate and composite fillers for a variety of applications.
A cold setting alkaline phenolic resin, designed for binding coal fines.
Use 8% Keracoal resin plus 2% Keracoal activator to bond coal fines before briquetting.
Setting speed: can be varied from 5 minutes to 4 hours by using different activators.
Keracoal can be fired to 900°C in a reducing atmosphere, and can be quenched in water.
Appearance: pale straw to dark red liquid.
Viscosity @25°C: 70 to 160cP
Specific gravity: 1,25
Research & Development: We will undertake to develop a product for you. You define the goals, we quote to achieve them, you only pay if we achieve the goals.
Storage: The activator may attack the fibreglass and some plastics. Store in metal or high density polypropylene containers.
Development no. 119812
A new binder system for producing pourable, quick setting insulation materials. It can be used with vermiculite, perlite or other lightweight materials.
Rapolite sets in 20 minutes and can be stripped from ideal types of mould immediately. Consult us about mould design and materials.
We have a vermiculite composition with a dry density of 0,45kg/litre.
The water content is high, and castings can take a week to air dry.
The microstructure is extremely fine, giving a particularly high insulation value.
DESCRIPTION: Fumed silica. (Volatilised silica / silica fume) Consists of 0,1 micron to0,5 micron diameter spheres of amorphous silica. It is a by product of silicon metal manufacture.
PARTICLE SIZE DISTRIBUTION: CHEMICAL ANALYSIS:
E.S.D. Cumulative % passing Si02 92%
40µm 99 C 5-6%
2Dµm 95 Al2 03 0,3%
10µm 92 Fe2 02 0,1% ,-
5µm 90 Ca0 0,1%
1µm 88 MgO 1,3%
O,6µm 86 Ti02 0,01%
O,5µm 80 P2 05 0,05%
SPECIFIC SURFACE AREA: Approximately 20m³
SPECFIC GRAVITY: 2,3g/cm³ = 2300Kg m-³
BULK DENSTTY: 250Kg m-³ loose packed to 400Kg m-³ compressed.
COLOUR: Off-white to light grey.
Silica fume has an enormous surface area per gram, and when used in formulations this increases the bonding surface by orders of magnitude. All the super high strength castables, puttys etc. use large doses of silica fume.
It is a filler for the plastics rubber and paint industries, and an excellent suspension agent,
which performs well in an acidic environment where bentonite and many organic suspension agents break down. It is a strong sintering agent in the metallurgical and ceramic industries.
The above data are typical, but given only for illustration purposes. We can supply silica fume from a variety of sources, chosen for your particular application. There will be appreciable differences from batch to batch. We suggest you buy enough to last you for 6 months, so your batch change adjustments are infrequent.
Source; Dow Chemical Company.
Trade Name; METHOCEL J75MS
Chemical type; Cellulose Ether
Viscosity; 75 000 cps @2% conctretion in water.
Addition; 0,2 will change pourable slurry into putty.
Mix powder into, powders, and it will disperse when water is added, without making lumps. Immediately after mixing, the slurry can be poured into mastic tubes, where it can react into paste.
Binder for high green strenght.
Cost in product @ 0,2%; ±12 cents/kg
Formula; Al (H2 PO4 )3 Also known as "Mono aluminium phosphate".
Colour; Clear light straw to greenish.
It is often necessary to harden the surface of ceramic fibre, particularly in areas of high gas flow velocities.
There are two different materials used. The one is sodium silicate, and can only be used at low temperatures. The other is colloidal silica, which is far superior but expensive. Keracast binder is colloidal silica based.
The greatest problem with using rigidisers is that the extent of application cannot be seen. Keracast binder contains an organic dye which makes the area and extent of application easily visible. It can therefore be applied more economically and no areas will be missed.
Ferrochrome binder, also known as "Versimould Binder", is an aluminium phosphate solution with excellent binding and refractory properties. Its bond is strongest with metals and alumina. Its properties are similar to sodium silicates, but the main difference is that it has high strength at high temperatures, whereas sodium silicates are molten glasses at high temperatures.
Ferrochrome binder may be used to bind ferrochrome fines to form ingot moulds. Ferrochrome fines are often used to form loose beddings for ferrochrome ingots. The reason for this is purely to prevent contamination. When ferrochrome binder is used, the function of the ferrochrome fines is to provide HIGH STRENGTH AND HIGH THERMAL CONDUCTIVITY, and has nothing to do with chemical compatibility. Such ingot moulds are equally suitable for any metal. Ferrochrome fines make the best agregate for such ingot moulds because of their high thermal conductivity and stability against volume changes due to oxidation. The surface of the ingot mould must be isolated from the molten metal. Graphite paint is usually the best coating because it allows excellent release of the ingot.
Ferrochrome binder develops increasing strength with increasing temperature. It undergoes a series of dehydration reactions, the last of which occurs at just below 400°C.
Preparation; Normal crusher fines have a distribution of particle sizes suitable for consolidation to a high density. Minus 3mm would be suitable. Mix the ferrochrome fines with sufficient ferrochrome binder to coat all the particles but not saturate the pores between the particles. This condition is achieved between roughly 3% and 20% binder by weight. 8 to 10 % is probably best in most gradings. Low additions give low strength and oversaturation will lead to blistering as the vapour will not be able to escape.
Compact the fines into the rough shape desired for the mould. Tramping it into shape with gumboots is fairly effective. The ideal means of compaction will depend on the grading of the fines. Scrape off the excess to get the final shape of the mould. Sharp corners are undesirable and a good taper is preferred. If the ingot is to be removed with a grab, gaps must be left and filled later with loose fines.
Drying; The mould must be dried to at least 400°C. A gas flame is ideal. Keep the burner on until the surface of the mould starts to glow.
Coating; Spray with graphite paint until the surface is smooth. The graphite paint may be applied while the mould is still hot. Re-spray the mould as soon as the aggregate can be seen or if a piece breaks off.
Tapping; Ideally the metal should flow slowly into the mould from a low angle runner or tundish. If the metal is squirting in from a height or under pressure, the angle of incidence should be kept low, or some metal scrap should be placed over the area of impact. In difficult applications, a striker block of Keraplas may be built in. If the graphite paint is consistently washed away, a coating of green refractory paint may be required.
Maintenance; The mould will inevitably crack, from various causes, and should be repaired with Keraplas. Cracks must be repaired before graphite paint is sprayed. If chunks break off, Keraplas repair may be too expensive, and repair may be done with ferrochrome fines, a few % Versimould hardener and perhaps a little clay or alumina. This forms a very rapid hardening highly exothermic compound which should be handled cautiously with rubber gloves. If the moulds give unsatisfactory lives, various steps may be taken, eg. use of supplementary binders, thickening of the walls, reinforcing, modification of the agregate grading, modifaction of the shape of the mould, improvement of ingot handling etc.
Description: A binder for making efficient vermiculite insulation. Add 15% vermiculite medium to 85% binder and add +70% water. It is vibratable, cohesive not spongy, and the water will not separate from it. It stiffens sooner than a ciment fondu bonded mix, and has a lower density. The lower density further reduces the cost per cubic meter.
We now also supply a strong binder for precast vermiculite articles.
Claimer; The above data had better be correct because Dave Onderstall stakes his reputation on it.