Carst & Walker (South Africa) has established itself as a significant agent and distributor of materials as well as offering technical support for these growing sectors, providing:
Aluminas are used for paint, ink, coating and filling paper, adhesives, rubber, pharmaceuticals, tiles, bricks, cooking utilities, table wares, electronic components, porcelain, pottery, dental restoration, and plastics.
They are available in several forms
Calcined aluminas are widely used in refractories and in the ceramic industry. Their specific properties include extreme hardness, refractoriness, high mechanical strength and resistance to wear abrasion, chemical attack, and corrosion.
Alumina hydrate, which is also termed as aluminium hydroxide and alumina trihydrate. These hydrates are available in both moist and dry forms. Coarse alumina hydrates are recommended in the manufacture of aluminium sulphate (alum), PAC (Poly Aluminium Chloride), zeolite, aluminium fluoride, glass, etc.
These are also available in fine white powders, with average particle size ranging from 5 to 15µm. They are used as fillers in paper and in SMC / DMCs; they also function as flame retardants in latex, rubbers, plastics, etc.
Antimony Trioxide is used as synergist for the flame retardant industry, as well as catalyst for the PET industry.
Blowing agents, as the name suggests, expand the structure of a polymer matrix and can be used in the following processes:
- Injection Moulding
- Extrusion & Blow Moulding
- Transfer/Compression Moulding
- PVC Plastisol
Carst & Walker sell mainly blowing agents which are azodicarbonamides, producing nitrogen through thermal decomposition. In addition to this, we also have access to “modified” azodicarbonamides as well as “special” blowing agents for particular polymers.
Carbon Black is produced through controlled, incomplete combustion of hydrocarbons. Carbon Black is used in almost every part of a car, from the engine compartment to the tyres and the exterior coatings. It is also used to reinforce rubber. Carbon Black’s biggest application is as a reinforcing filler in rubber products.
C&W offer an entire range of Furnace blacks.
In Addition C&W also offers the famous Thermax® Thermal Carbon Black range From Cancarb which is a leader in the development, manufacture and global marketing of thermal carbon black.
C&W have range of base fillers to include:
- Barium Suphate
- Calcium Carbonate
- Coated fillers (various)
- Other speciality fillers
Antimony Trioxide, Aluminium Trihydrate, Brominated Fire Retardant compounds and phosphate blends.
Carst & Walker represents Cray Valley Hydrocarbon Specialty Chemicals for their full range of C5, C9 and C5/C9 hybrid hydrocarbon resins. These include the Norsolene and Wingtack range, which are commonly added to rubber compounds for improved tack, physical and rheological characteristics, but are also prevalent in the adhesives, paint, bitumen and coatings industries (refer to our Adcoat Division for more information on these applications).
Magnesium Oxide is generally included in polychloroprene (Neoprene) where the metal oxide acts as an effective hydrogen chloride (or chlorine) scavenger. For compounders who still mill their chloroprene rubber during production, addition of MgO is especially important.
Carst & Walker offers high purity Magnesium Oxides in three particle sizes – 60 m²/g, 150 m²/g and 185 m²/g. The two finer grades are also available in 1 kg packs; ideal for the smaller user who doesn’t completely consume the 25 Kg pack in a batch.
DSP – Magnesium oxide – Metal oxide for crosslinking Polychloroprene Rubber.
Apart from powder, liquid and granular grades, Carst & Walker also provides masterbatch forms of rubber chemicals and other additives. We represent Omya UK, who supply both standard and custom masterbatches of a variety of chemicals and additives on a variety of polymer substrates. Omya’s product portfolio comprises the Multisperse, Garolite and Caloxol ranges, comprising active ingredients such as insoluble sulfur, MgO, ZnO, CTP, hexamine, CaO, blowing agents, lead-based flame retardants and rubber curatives on polymer binder systems such as NR, IR, NBR, EPDM, EPM, SBR and CPE, among others. The applications for Omya masterbatches include rubber compounding where dispersion is an issue, plastic and rubber recycling where desiccation is required and in areas where a dust-free environment is necessary to reduce the risks of health hazards, explosions and other safety concerns.
MC & PE Waxes
Carst & Walker represents Iberceras for their microcrystalline (MC) range of waxes, for example the Tiozone range. MC waxes are a type of wax produced during the petroleum refining process. In contrast to the more familiar paraffin wax, which contains mostly unbranched alkanes, MC wax contains a higher percentage of iso-paraffinic (branched) hydrocarbons and naphthenic hydrocarbons. It is characterized by the fineness of its crystals in contrast to the larger crystal of paraffin wax, and imparts greater flexibility and improved rheological properties, compared to paraffin waxes.
MC waxes are commonly used in the rubber industry (both in tyre and non-tyre applications), for protection against ozone degradation and premature ageing, and also for rheological reasons, e.g. to aid dispersion of additives and for ease of processing. In plastics applications, waxes are often included for the promotion of anti-blocking properties, i.e. to increase slip; as an internal lubricant, in assisting with mold release; and finally as a rheological additive, to tailor processing properties.
Waxes find use in many other applications, such as in paints, polishes, adhesives, inks, cosmetics, packaging and foodstuff, and more information can be found under the respective headings.
C&W stock the famous Imerys grades of mineral fillers. These include Polcarb, Polwhite, Polstar, Polarite.
We represent Akzo Nobel with their range of Trigonox® and Perkadox® organic peroxides which are a necessary and vital component in the manufacture of elastomeric products.
Automotive parts, golf ball cores, footwear soles, adhesive tapes, wire & cable and foamed products (rubber or thermoplastic) are examples of everyday products that use organic peroxides. Compared to sulfur vulcanization, organic peroxide cured elastomers exhibit superior physical properties such as low compression set, improved heat resistance, and rapid vulcanization without reversion.
Process aids are used to influence filler dispersion and homogeneity of rubber compounds. While extruding and calandering significant improvements in process ability can be achieved.
During injection molding they improve the processing behavior of rubber compounds and during extrusion they assist flow characteristics.
C&W offer both rubber and plastic grades.
We stock antioxidants, accelerators and retarders which we source from Rokem in China.
The antioxidants include the staining IPPD and 6PPD (which do have antiozonant properties), non-staining styrenated phenol and general purpose TMQ and BHT.
Delayed action, fast curing sulphenamide accelerators like TBBS / MBS / CBS, primary accelerators like MBT / MBTS, secondary thiuram accelerators like TMTD / TMTM plus D.P.G., D.T.D.M, HMT and others.
C.T.P (PVI) is our recognised scorch retarder.
All are available in oiled powder, granules or pellets. For open mill mixing a Rapiblend masterbatch version can be produced by Anchor Chemicals.
Silane is the silicon analogue of a hydrocarbon alkane (R-Si-X) and is most commonly used as a coupling agent for filler-polymer systems or a crosslinking agent for free radical crosslinking of thermoplastic systems (e.g. peroxide-cured polyethylene). In the tyre industry, silane is used to improve reinforcement and lower rolling resistance and energy (hence fuel) consumption in high-performance tyres and other tyre tread compounds which are highly silica-filled. Silanes are also used in the glass-fibre industry to improve adhesion between filler and resin, and in epoxy, urethane, acrylic and phenolic systems, among others. Carst & Walker offers the full range of silanes, including sulfide-, thiocyanate-, mercapto-, vinyl-, methacryloxy-, epoxy- and amino-based grades.
Precipitated silica (silicon dioxide) is gaining ground as the most environment-friendly and safety-conscious rubber reinforcing filler. Silica is now preferred by rubber manufacturers to enhance the strength and performance of truck and car tyres, rollers for printing, shoe soles and an increasing variety of other synthetic and natural rubber products.
High performance silica is mostly used in polymer reinforcement – in particular rubber and elastomers – or as carriers for powdered food stuffs.
Insoluble sulfur is the vulcanizing agent of choice for the tire industry. Crystex® is a polymeric form of sulfur that is a non-blooming vulcanizing agent for rubber. By being insoluble in rubber, Crystex® prevents sulfur migration and, in turn, bloom which interferes with the tire building process. The use of insoluble sulfur is critical for the manufacture of quality radial tires.
ZnO is used as an activator in rubber compounds containing organic accelerators. (except PCR).
C&W offers an extended range including std rubber grade and active grades.