Keramicalia

Tel: +27 (0)11 412 3261 or +27 074 587 2728 Fax: +27 (0)11 692 1232
We manufacture specialised refractories and ceramics.

Binders

 

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 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 aluminate cement 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.

Lightweight binders are a Keramicalia speciality. Vermiculite binder is popular, and is being outperformed now by Rapolite Binder binder.

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 Binder

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. Kerawet is our super powerful wetting agent.

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.

Keracoal Binder

A cold setting resin, developed for binding coal fines. It is totally organic, yet it does not burn out before the coal. Other organic binders decompose thermally and the coal briquette disintegrates back into dust before it burns. Mineral binders are pure ash, and tend to encapsulate the coal particles and hamper combustion. Keracoal binder BEHAVES LIKE COAL in a combustion or other chemical process.

Keracoal binder is totally water resistant, and stable immersed in water for years. It is used with an accelerator, so it hardens rapidly by itself WITHOUT A DRYING process. Often water is added to enable the binder content to be reduced. Activator is added after mixing in the binder, 20% 0f binder weight, more if the water content is high.

 

 

 

 

 

Applications

  1. Briquetting waste coal fines to make a combustable product.
  2. Briquetting waste coal fines to use in coke ovens or char furnaces
  3. Briquetting coal and hematite fines for direct reduction feed.
  4. Briquetting metal fines.

Setting speed: can be varied from 5 minutes to 4 hours by using different activators and percentages..

Keracoal can be fired to 900°C in a reducing atmosphere, and can be quenched in water

 

2017 Price guide

Binder

Activator

5kg bottles

R40.00/kg

R75.00/kg

25kg Polycans

R36.00/kg

R74.00/kg

230kg Drums

R34.00/kg

R71.00/kg

1200kg Flobins

R33.00/kg

R69.00/kg

20 tons plus in road tankers

R29.00/kg

R67.00/kg

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. We will also undertake to build, commission and operate your plant for you.

Storage; The activator may attack fiberglass and some plastics. Store in metal or high density polypropylene containers.

Development no. 119812

 

Rapolite Binder

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.

Silica Fume

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:

(Sedigraph 5000)

      CHEMICAL ANALYSIS:  
E.S.D.   Cumulative % passing      Si02     92%
40µm 99     C     5-6%
20µm 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%
0,4µm                  73        
O,3µm                  54        

          

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.

APPLICATIONS:

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.

                         

                                                                   

 

 

 

Super Binder M

Source;      Dow Chemical Company.

Trade Name;    METHOCEL J75MS

Chemical type;    Cellulose Ether

Viscosity;  75 000 cps @2% concentration 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.

Application;

Binder for high green strength.

Suspention agent

Plasticiser.

Thickener,

Cost in product @ 0,2%; ±12  cents/kg

Aluminium Orthophosphate

Formula: Al (H2 PO4 )3 Also known as "Mono aluminium phosphate".

Specific gravity: 1,3 to 1,4g/cm³

Solids content as Al (H2 PO4 )3 38%

dried 110°C : 45% ( Undergoes various dehydration reactions up to 460°C.

pH: 1

Impurities:

Na2 O Not detected
MgO Not detected
Fe2 O3 16ppm
ZnO 1ppm

 

Colour: Clear light straw to greenish.

Contains no additives. Will not settle out or crystallise on storage.

Application: Binder for refractories. AOP gives high dry strength, very high strength at 200°C and full strength at 460°C. The bond is still effective long after a good ceramic bond has formed.

Packaging: 25 litre polycans of 36Kg each.

Shelf life: Indefinite.

Keracast Binder for Rigidising Ceramic Fibre

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

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.

 

Vermiculite Binder

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.

With ciment fondu (also 85%), vibratable at +70% water you get a wet density of 1,20g.cm³, dry density 0,79g.cm³.

Vermiculite binder gives a wet density of 1,16g/cm³, dry density 0,68/cm³.

Costs; 2017

Ciment fondu costs R 25/kg ex vat
Vermiculite binder costs R 17/kg ex vat
Vermiculite is R 23/kg ex vat

Ciment fondu bonded insulation therefore 0.85 x R25 + 0.15 x R23 = R24.88/kg, therefore R19659/m².
Vermiculite binder 0.85 x R17 + 0.15 x R23 = R17.74/kg = R12067/m³.

Chemical analysis of product with:

  Ciment fondu Vermiculite binder  
Al2 O3 39.0 48.0  
Fe2 O3 12.0 1.6  
SiO2 4.5 26.0  
TiO2 2.5 2.0  
CaO 38.5 15.5  
MgO 0.6 1.5  
Na2 O 0.1 0.3  
K2 O 0.15 0.2  

Hardcast

Hardcast is a range of silicate bonded materials.

It is used in place of concrete where very low permeability is necessary, for acid resistance.

It is also very quick setting, and can be used in thin applications where concrete would be sucked dry before it can set, for example repairs of factory floors.

It can be used to repair acid damaged floors:  Hardcast Acid Resistant Floor Screed.

Hardcast light is acid resistant insulation.

Chloresist is the high temperature version, used in incinerators where chloride attack is the main problem.

Hardcast Fine Acid Resistant Mortar is used as a glue where air setting is not possible, for example when bonding impervious sintered ceramic tubes.

The data sheets are all very similar, just read one and you know all the tricks. Once you have started using Hardcast, you will seldom use concrete again for small jobs.

Keraset

Keraset is a range of very hard castable materials based on magnesium oxychloride cements.

They come in two components; powder and liquid. They mix easily and pour freely. After an hour or two they set, generating intense heat. This exothermic reaction is volume sensitive. The larger the casting, the more the heat builds up. For very large castings, special grades are required to prevent the temperature exceeding boiling point, which can cause either foaming or steam explosion.

Keraset is easily coloured. Normally the colours range from pink through red to grey. Black is very attractive. The surface is very opaque, and takes up the exact texture of the mould. A glossy mould gives a glossy casting. Buffing will enhance the gloss.

Keraset 22727 is used for abrasive wheels such as glass bevelling wheels, steel polishing wheels and polishing blocks used by stonemasons. It contains 80 grit fused alumina.

Keraset 22728 is similar but finer, containing 180 grit silicon carbide.

Multimould is a useful moulding material for Keraset, especially for cloning.

Keraset is very hard and abrasion resistant.It will decompose if left standing in water for long periods.

Cold crushing strength after 3 days is 30 MPa, after 6 months 45 MPa.

Mix 68% powder with 32% liquid Keraset Binder.

Rigidiser

Rigidiser A liquid containing colloidal silica particles. It is used to consolidate ceramic fibre blanket which is exposed to burner blast or high velocity gases. Conventional rigidisers are difficult to apply evenly, as they are transparent and you cannot see where you have painted or how much. We therefore add a blue dye which burns out later. If you need more protection, use our electric paint. If you need extreme protection, use our Fibre Plaster. Rigidiser is also used to strengthen ceramic fibre boards, e.g. when elements are pinned onto it.

Shelf life ± 5years. Do not allow to freeze.

Packaging: 6kg in 5litre bottles 30kg in 25 litre polycans

Development no. 11418

Calcium aluminate cement

Description:   A pure white hydraulic cement, strong and quick setting.   “Kerabond White” is a highly fluid variation which sets in about an hour.   Used mostly in high temperature refractories.   We also stock dark brown “Ciment Fondu”.

Chemical Analysis:    70% Al₂ O₃,    27% CaO,    0,35% SiO₂,    0,25% Fe₂ O₃.

Mineral composition:   Calcium aluminate CA, with some CA2.

Bulk density:   About 900kg/m³

Specific gravity:   3,0

Surface area, Blaine:   About 3600cm2 /g =  360m² /kg

Addition:    Typically 22% by weight of mix.

Water addition:   Preferably half of cement weight.

Setting time:   About 3 hours.

                          Kerabond white:   About 1 hour.

                          Both have a very strong exothermic reaction.

Strength development:   Half strength in 6 hours, full strength in 7 days.

Shelf life:   About 2 years.

Packaging:   25kg bags

Price, 2017:   Kerabond white R68/kg        114403

                       Ciment Fondu: R44/kg            

Sodium Silicates

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 CO₂ 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, 6 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.

Price 2017;  R 25/kg all grades.

Kerawet

 

A wetting agent developed specifically for coal.

0,3% concentration in water will wet the coal and enable chemicals to bind to it.

As soon as the water evaporates the dust particles are released.    Antivap prevents the water from evaporating.

Sand Hardener

liquid solution of binders.  The solution is designed for very rapid drying and is flammable.

APPLICATIONS:

Hardening of moulds, especially foundry sand moulds in areas where there is high turbulence.  It also allows sodium silicate bonded moulds to be stored for up to a year before use.

Mould hardener can be brushed on or sprayed on.  Use between half a litre and two litres per square metre.  This will give a penetration of between 1mm and 4mm.

Hardening will occur as soon as the solvents have evaporated.  To speed up the drying, ignite the surface with a match.

Clean the spraying equipment or paint brushes thoroughly with solvent after use.  Application by a "swab" or rag is convenient, if the equipment can be burned after use.  This stuff is seriously sticky, and it usually pays to wear gloves when working with it.  If you struggle to get it all off your hands, just dry your hands well, as with a hot air blower, and once dry the stickiness almost disappears.

Read the safety data sheet.

Development no.  102600