Plastics & Composites

Plastics & Composites

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:

ABS

ABS, Acrylonitrile-Butadiene-Styrene

ABS is a “polymerised alloy” of the three materials acrylonitrile, butadiene and styrene. The material is located under the group styrene plastic. Styrene plastics are in volume one of the most used plastics.

Properties

The mechanical properties for ABS are good for impact resistance even in low temperatures. The material is stiff, and the properties are kept over a wide temperature range. The hardness and stiffness for ABS is lower than for PS and PVC.

Weather and chemical resistance

The weather resistance for ABS is restricted, but can be drastically improved by additives as black pigments.

The chemical resistance for ABS is relatively good and it is not affected by water, non organic salts, acids and basic. The material will dissolve in aldehyde, ketone, ester and some chlorinated hydrocarbons.

Processing

ABS can be processed by standard mechanical tools as used for machining of metals and wood. The cutting speed need to be high and the cutting tools has to be sharp. Cooling is recommended to avoid melting of the material.
If the surface finish is of importance for the product, the ABS can be treated with varnish, chromium plated or doubled by a layer of acrylic or polyester.

ABS can be glued using a glue containing dissolvent. Polyurethane based or epoxy based glue can be used for gluing to other materials.

Generally

By the introduction of additives the properties and the look of the material may change.

Application

ABS is used for auto body parts, suitcases, toys etc. Extruded profiles, tubes and bolts can be made from ABS when the requirements are high impact resistance and a nice surface.

Acetal Co-Polymer

Acetal is a high-performance engineering plastic and is also known as polyacetal, polyoxymethylene (POM), acetal resin, polytrioxane, polyformaldehyde or paraformaldehyde. Because of its high strength, modulus, rigidity and resistance to impact and fatigue, it is used as a weight-saving replacement to metal in certain applications. POM is often used for gears, bushings and other mechanical parts (cf. nylon, teflon, UHMWPE).

Apart from exceptional physical and mechanical properties, acetals have excellent resistance to heat, moisture and most solvents, and have excellent inherent lubricity. Applications include automotive fuel system and seat belt components, steering columns, window support brackets, gears, cams, bushings, clips, lugs, cranks and handles.

Typical plumbing applications that have replaced brass or zinc components are shower heads, ball cocks, valves, faucets, impellers and various other fittings, where the lubricity, corrosion and hot-water resistance of POM is utilized.

In consumer and industrial applications, POM is used where dimensional stability is required, e.g. conveyor links, watch gears, sprockets and various other mechanical parts. Glass-fibre-reinforced grades are often used for parts that require exceptional load-bearing stability at elevated temperatures, e.g. cams, gears, tuner arms and under-the-hood automotive parts. FDA-approved grades are also available.

Additives

Specialty additives:

Animal repellents – included in formulations to protect plastic, wood and wood-plastic composite materials against animal attack. Common examples are in rodent protection of telecommunication, power cables and electrical wires, and termite protection in construction materials. Our brand is the only one in the world which is 100% non-toxic, but 100% effective in its repellent and aversive efficacy. It is also used to prevent accidental ingestion of toxic materials, such as anti-freeze and glycols (ethanol denaturation).   Rodrepel, Termirepel, Combirepel, Aversion (denatonium benzoate) are available from Carst & Walker, and are produced by C-Tech Europe.

Anti-microbials (Ionpure) – included in formulations to protect plastic surfaces against bacterial, fungal and other microcidal growth/attack. Common examples are in work surfaces and surgical auxiliaries in hospitals, buttons and touch-surfaces, and counter-tops in bathrooms and kitchens.

Optical brighteners – added to formulations where a “whiter-than-white” effect is needed, or where simple whitening or brightening of articles is required.

Composites

Carst & Walker offers a range of resins, reinforcing fillers, coupling agents, specialty additives and mold release lubricants for the composites industry. More information can be found under the respective headings.

CSM

CSM (Chloro sulfonated Polyethylene) has outstanding resistance to most chemicals, heat and oil are among the most important characteristics. Further, it is flame resistant, offers excellent color stability, weather and abrasion resistance. Low moisture absorption, good dielectric qualities, and high abrasion resistance are among its other features.

Like most synthetics, it is superior to NATURAL RUBBER in temperature, oil and resistance to the effect of ozone.

It is highly used in the inflatable boat industry.

EVA

Ethylene Vinyl Acetate (also known as EVA) is the copolymer of ethylene and vinyl acetate.  The weight percent of the vinyl acetate normally varies from 10% to 40%, with the remainder being ethylene.

It is a polymer that approaches elastomeric materials in softness and flexibility, yet can be processed like other thermoplastics.

The material has good clarity and gloss, barrier properties, low temperature toughness, stress crack resistance and is resistant to UV radiation.

EVA has multiples uses, including hot melt adhesives, a clinginess-enhancing additive in plastic wraps, in biomedical engineering applications and even in mouthguards (that soften in boiling water for a user specific fit).

EVA, with the incorporation of a blowing agent is popularly known as expanded rubber or foam rubber, an example being the use in EVA sandals and babies crawling mats.

HIPS/GPPS
Nylon

A polyamide is a polymer containing monomers of amides joined by peptide bonds.  They can occur both naturally (silk) and artificially (nylon).  Polyamides can be homopolymers, viz. PA6 and PA66 or copolymers, viz. PA6/66 and PA66/610.

The high molecular polyamides are especially suitable as compounds used in the injection moulding and extrusion of engineering components.

Polyamides naturally exhibit the following properties:

  • high impact resistance
  • high abrasion resistance
  • low friction
  • high damping
  • high thermal dimensional stability
  • good chemical resistance to petrol, oil and grease, making it highly suited for use in the automobile industry
  • good resistance to esters, alcohols, ketones, ethers, chlorinated hydrocarbons, alkalis and dilute organic acids

The properties of polyamides can be further improved by the incorporation of, for example, glass fibre (increases tensile strength and thermal dimensional stability), glass beads (increases rigidity and lessens warping) and elastomer (improved impact strength).

In order to reach their optimum properties, nylons need to be dried prior to processing and conditioned (immersed in warm water until the required water absorption has taken place) subsequent to processing.

Examples of areas in which polyamides may be used are amongst others, bushes, gears, castors, bearings, housings, oil filters, hinges and weedeater line.

Polycarbonate

Polycarbonates are long-chain linear polyesters with many versatile characteristics and useful properties in the modern plastics industry. PC has good thermal resistance but relatively high viscosity (i.e. low melt flow index) during processing.

PC has an inherently low crystallinity, due to its relative rigid molecular structure, and is therefore has very high light transparency.

It exhibits excellent toughness and strength, exceptional impact resistance, high heat resistance and excellent dimensional and colour stability. A shortfall in properties is in its fair-to-low chemical resistance, allowing attack by many organic solvents.

Typical applications include lenses and lighting fixtures, exterior automotive components, equipment housing, appliance parts and containers.

PVC Emulsion, Suspension Resins
sPVC and ePVC:

PVC is produced industrially by emulsion (ePVC) and suspension (sPVC) methods, and the products thereof exhibit different physical and rheological properties based on their different particle size and molecular mass characteristics.

Additives:

PVC can be plasticized or used in its unplasticized form (uPVC), depending on the application and in-service requirements.
Heat stabilizers are almost always added to PVC compounds, as harmful HCl is produced during the thermal degradation of PVC in the absence of such stabilizers. Heat stabilizers (CaZn, BaZn, etc.) can be obtained from Carst & Walker, and fall under our Additives section.

In addition to heat stabilizers, flame retardants are often included in PVC formulations, for example antimony trioxide, aluminium hydroxide and zinc borate, all of which are available from Carst & Walker.

If impact strength is required in PVC articles, various impact modifiers can be added to the formulation. Examples are acrylic-based, MBS and chlorinated polyethylene (CPE), all of which are available from Carst & Walker.

CPVC:

Chlorinated PVC (CPVC) is a specialty PVC grade with elevated chlorine content and is also available from Carst & Walker. CPVC is used in niche applications, for example in hot-water plumbing fittings.

Applications:

PVC is commonly used in the production of tarpaulins, coatings, water-proofing, flooring, conveyor belting, synthetic leather, pipe, plumbing fittings, conduit, window frames and seals, cable, hose, bottle and packaging.

Thermoplastic Elastomers
TPV, TPE, TPR (thermoplastic vulcanizates, elastomers, rubbers):

Thermoplastic rubber (TPR), thermoplastic elastomers (TPE) and thermoplastic vulcanizates (TPV) are materials which have characteristic properties of both thermoplastic and elastomer, in that they process like a thermoplastic, but exhibit end-use properties of an elastomer.

They are therefore recyclable, reduce cycle time and cost, and are replacing conventional thermoset rubbers in a variety of applications. Although they can be poorer in compression set (vs. EPDM, CR, etc), TPVs offer superior resistance to flex fatigue and their recyclability offers a more favourable cost-to-performance ratio in many applications. Carst & Walker offers both the block-copolymer type (styrenic) and the physical blend type (e.g. unvulcanized TPE and fully vulcanized TPV, based on PP/EPDM), and can supply standard, specialty, medical, FDA and custom grades.

These materials are used in diverse applications, e.g. automotive exterior and under-the-hood, medical, general rubber goods, footwear, adhesives, bitumen modification, impact medication, household and industrial articles, wire and cable, hoses and tubing, seals, grommets, gaskets, bellows and boots, plugs, soft-touch grips, white rubber goods and castors, window seals and glass run channel.

TPU

Thermoplastic polyurethane (TPU) is a fully thermoplastic elastomer.  It is made up of linear segmented block copolymers with hard and soft segments.  The hard segment can be aromatic or aliphatic and soft segment can be a polyether or polyester type, depending on the application.  They can be processed on extrusion and injection, blow and compression moulding equipment.

TPU can be vacuum-formed or solution–coated and works well with a variety of fabrication techniques.  They exhibit a wide range of physical property combinations, which makes them extremely flexible and suitable to a broad range of applications, e.g. cell phone housing, soft touch/high grip parts, synthetic leather handbags, breathable roof membranes, wire and cable jackets, shoe soles, automotive adhesives and medical catheters.

Attributes of TPU are outstanding abrasion/scratch resistance, toughness and durability, excellent low temperature flexibility, ease of processing and manufacturing flexibility, resistance to most fuels, oils and greases, paintability with no primer and UV resistance.

Other Engineering Polymers

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