This is the second blog in a series of three outlining the background, properties and use of the plastic materials we at Merriott Group use to provide our customers with diverse products here in the UK, Europe and worldwide. You can find part one of this series here: A guide to thermoplastic materials.

Engineering Plastics

This range of materials is used for the majority of industrial products, as a result of their mechanical and environmental use. As such they have a higher cost than the commodity plastics but come into their own in specified applications where the end use is more demanding.

Acrylonitrile Butadiene Styrene (ABS)

ABS is one of the most common thermoplastic materials that you are likely to encounter, as it is widely used for appearance parts, and is the number one choice for designers. Its smooth feel, appearance and cleanliness of colours makes it very appealing, along with its great properties for easier assembly. ABS can be assembled with adhesive, screws, clips, welded, inserted, painted, printed onto and chrome plated.

The letter B is for Polybutadiene, a synthetic rubber which improves the impact resistance of this vital thermoplastic material, along with allowing flex with strength for clip designs. All of these options improve the product design and ensure improved assembly times and reduction of other fixings.

Using ABS with its excellent impact properties, toughness and rigidity, can be further improved for temperature requirements by adding glass fibre, or creating an alloy with PC (Polycarbonate), known as PC/ABS.

ABS has a relatively short history, having been developed in the late 1940s and came to market in 1954. The first company to do so was Borg Warner, the market leader for many years. Their most notable grade was Cycolac T, and this was used extensively for telephones of the non-digital type of the 60s, 70s and 80s. With the wide colour range of both homes and offices at the time, thousands of tons of ABS material were converted into telephone housings.

Of course, the most widely known product created using ABS is Lego.

Parts made in ABS have the recycle triangle and the letters ABS. The material is not recycled at the kerbside collection however, but at recycling centres or through industrial waste reclamation facilities.

We use ABS thermoplastic for many products, such as covers for air movement assemblies, agricultural incubator parts, drainage parts for care home/domestic/NHS shower/wet rooms, to name but a few.

Nylon (PA)

Developed by DuPont in America at the tail end of the Great Depression and launched to market just prior to the start of WW2, this thermoplastic material is viewed as a major engineering material.

At that time, ‘Nylons’ was in great demand as a lady’s garment, and very highly sought and fought over, due to the feel/appeal and demand. Thanks to its importance and output, Nylon was used to support the war effort with parachutes and many items for aircrafts being built rapidly.

Nylon material today is used extensively in many ‘under bonnet’ applications in automotive and many commercial vehicles, engine and electrical components. This is due to its strength, chemical and impact resistance, and temperature range, but also its impact/flexibility properties. It is these properties and weight savings that are key to reducing emissions of the vehicles of today and the future.

It is also used widely in the electrical industry for its insulation, heat resistance and strength properties, which enable the designer to build in complex forms and keep costs down.

Known in the trade as PA6, PA66, there are now more options being created by linking other materials. The same is also true of the addition of glass fibres, beads, minerals and other additives which improve both fire resistance and smoke emissions, making this material a key choice.

Producing products in Nylon requires much soul searching as the material shrinks after different rates according to the direction of flow within the thermoplastic injection moulding tool. The choice and position of feed points is a critical decision by the tool designer, and requires detailed discussions with the tool designer, customer and tool maker at the outset.

Processing Nylon is also key to quality products, with the most important consideration being ensuring that the material is thoroughly dry at the outset, since Nylon absorbs moisture. The presence of moisture leads to poor quality parts that are brittle and of poor appearance. Process temperatures are closely monitored during production, as well as having hot tools to ensure a quick mould fill. After thermoplastic injection moulding parts need to normalize by the absorption of moisture which improves the product impact. This can be achieved over a few days from the atmosphere or in some circumstances, by placing the parts in very hot water for a period of time (the exact time is determined by the part section).

Parts made by Merriott Group are for electrical products in lighting and electric panels, under bonnet engine management plus many more. A recent development is the replacement for a steel spinning, which is then welded, that has been replaced with a complex design in glass filled and bead Nylon. This is a drum that is used in a macerator unit in hospitals and care homes. This is moulded on our 1,100t press due to the tool complexity and part height of 450mm. The material was selected for its weight reduction, impact, design requirements and ability to incorporate complex features to aid final assembly.

Polycarbonate (PC)

Yet another material that was developed following the Second World War in Germany in 1953 and then registered by the worldwide company Bayer, under the trade name of Makrolon. This was closely followed by General Electric with their trade name of Lexan. GE only commenced commercial selling of their material in 1960, following a trade agreement with Bayer. Both of these trade names are widely known and are even stronger in today’s market, as a result of further material developments for many applications.

Known for its natural fire retardancy that can be further enhanced to V0, being glass-clear, strong impact, polycarbonate is used widely both as a thermoplastic moulding material and as a forming material from sheet.

Critical to the processing of Polycarbonate is oven dried material and very hot mould tools, typically 60-80°C, to ensure good fill of the mould using least pressure. Moulded parts not made under these conditions do suffer with internal stress which can lead to cracking of vulnerable features.

Typical applications are lighting, both commercial lights/diffusers thus replacing glass. Automotive light clusters, which can be enhanced with coatings to protect against road debris and scratches. Its biggest single use is CDs, where cycle times are extremely fast (as low as 3 seconds on multi-cavity tools). Your mobile phone is mainly built around polycarbonate covers, where the material is moulded to very thin sections, but offering the designer features to improve assembly along with a pleasing appearance.

PC is additionally widely used in the construction market as sheet materials, for roofs, conservatories and large roof lights where weight is a concern.

One of Polycarbonate downfalls is its link to Bisphenol A and use in food applications. Polycarbonate was previously the most used material for baby feeding bottles, and other food applications. However, when the container reached a certain temperature, the Bisphenol A leached out of the Polycarbonate and contaminated the food stuff within. Many studies were carried out at the time and as a result, more suitable food compliant Polycarbonates are used for modern food applications today.

The linking of Polycarbonate and ABS above (known as PC/ABS in the trade), is a widely used material in automotive, electrical and other applications where the properties of the two materials enable designs to incorporate clips features, along with strength, impact and flex all at the same time.

At the Merriott Group, all of the above materials are processed daily, providing our diverse customer base with thermoplastic mouldings for many industries here in the UK, in Europe and further afield. Our knowledge of the tooling requirements for these materials has been built up over many years, along with the processing and design expertise necessary to bring applications to market.

If you need any further information about thermoplastic materials, get in touch.