Polyamides: not just metal replacement

Consumption is up, driven by new applications and support for environmental sustainability. The future of polyamides is rosy pink, with a few drops of green

Replacing traditional materials with plastic polymers has now become the norm in many sectors. Automotive, aerospace, industrial and domestic machinery – for almost thirty years, these sectors have been benefiting from the advantages of lighter, better performing components, manufactured using efficient and economical processes. The polymers that have been most successful in this sense – particularly for replacing metal – are polyamides, especially by virtue of their elevated chemical, physical and mechanical properties, ease of processing with the addition of additives in the compounding stages and, not least, easy processing.

There are numerous families of polyamides available on the market today (PA 6, PA 6.6, PA with long-chain, semi-aromatic PA and so on) and ample choice, making the formulation of special materials certainly easier, capable of better meeting the technical specifications required for the end product.

A frequent question, the subject of debate within the manufacturing community, regards the trend towards using these materials in the future. Will the trend continue to be positive? Will new potential applications continue to be found? We will attempt to provide some answers below, taking into consideration some important aspects relating to the evolution of market demand. We will also illustrate some examples of projects that have used innovative polyamides that already respond to new important requirements.

Market demand

All industrial sectors share a need to source materials that are able to guarantee the operation of increasingly more sophisticated components that are subject to different types of stress. For example, an evolution is shaping the transportation sector, with a trend towards smaller and more powerful engines, greater active and passive safety systems, greater comfort and reliability, lower consumption, more captivating interiors, among other things. But this is not all, the advent of electrical engines is further changing the scenario, making the need to reduce the weight of components increasingly important. In the electrical and electronic sectors, on the other hand, there has been a general trend towards miniaturizing the applications we use in the home and in industry, increasing the thermal and mechanical stress that the components can withstand, greater demand for safety regulated by increasingly more stringent regulations, lower emissions of toxic fumes and substances in the event of a fire, respect for environmental regulations for products that have terminated their life cycle, and the list goes on. Even other industrial sectors today are looking for alternatives to metals. Such as, for example, the plumbing, heating and sanitary elements sector, where replacing copper parts requires plastic materials with excellent mechanical properties, that will last for fifty years, and are safe in contact with drinking water.

Another emerging trend in many sectors of application is attention for the environment, which is driving the choice of materials to becoming more environmentally friendly, from renewable sources, but also towards design methods that consider dismantling, so products can be more easily reclaimed and recycled at the end of life cycle. The importance of environmental impact on human activity cannot be ignored. Laws and regulations establish increasingly stringent limits on harmful emissions and consumption of fuels. Aspects that closely affect polymer producers.

Trends in the transportation sector

The transportation sector is also the engine of innovation that leads to the design of increasingly high performance polymers. In order to reduce the weight of components, materials must be found that are capable of performing functions that have previously been performed by metal components. In this context, polyamide based polymers have played a very important role, especially when high temperature and stress are concerned. New nylon solutions have been introduced following, for example the evolution of engines, which have become smaller, more powerful, and which have to last longer.

Today some applications at continuous ambient temperatures of 230 °C are already using nylon components for high temperatures, suitably reinforced to stand up to mechanical stresses. Some important manufacturers are already asking for materials capable of withstanding temperatures of up to 250 °C for engines that will become available over the next 5-10 years. This means that, to avoid going back to using metal, new, higher performing materials need to be developed at a competitive price.

As far as replacing metal is concerned (particularly aluminium alloys), many applications are currently mature, the replacement rate is nearing 80-90 percent. For example, radiator tanks, air manifolds, valve caps, accelerator and clutch pedals, and so on. Other components continue to still be made primarily from metal, but there is potential for them to be replaced: engine supports, pipes for turbo engine hot pipes, engine oil tanks, transmission covers and so on. Other applications are already attracting interest to replace metal with hybrid solutions: plastic with suitably positioned metal inserts or plastic with continuous fibre. The latter include brake pedals, suspension elements, front-end parts, car seat parts, dashboard supports.

Replacing aluminium

In general, in the auto sector, replacement of aluminium parts leads to a reduction in weight estimated to be between 20 and 30 per cent. This is the typical case for engine supports, engine brackets, and belt tightener brackets. From a mechanical point of view, it is often apparent that though polyamide components show excellent properties, they do not share the same features as aluminium. There are advantages and disadvantages to this. For example, PA components show less resistance to fatigue and corrosion, improved acoustic performance, and, at the same time they experience a reduction in properties, such as modulus of elasticity and resistance to break as the temperature increases. This has implications for the use of design criteria for the polyamides and engineering polymers in general that are very different from metals, while they still ensure good operation, as we have learned from decades of successful replacement with positive results.

As an example, we cite the engine support bracket and an air pipe on a turbo engine made using blow-molding techniques (figure 1). The bracket was developed using a 6.6 polyamide filled with 50 per cent glass fibre, to guarantee sufficient rigidity and resistance to vibrations and greater mechanical resistance at weld points. For air flow, on the other hand, a special, high-temperature polyamide was chosen, which can be transformed using blow-moulding techniques, with the addition of 15 per cent glass fibre. These examples reflect the great versatility of polyamide solutions with the introduction of formulas to ensure the reliability of applications, including the processing stage as one of the important functions.

As far as environmental impact is concerned, figure 2 shows values for six categories of environmental impact for the product Radilon® A RV500RW 339 BK (special PA66-GF50) and die cast aluminium. The data refers only to the production of materials (from first development to leaving the facility). The relative values for the various indexes were obtained by Radici using EPD certified data for polyamides, while data published by the Aluminium European Association for GER and GWP were used for die cast aluminium; for other parameters, data from Simapro8/Ecoinvent3 was used.

More ecological solutions with bio polyamides

Sticking with the transportation sector, we will illustrate an example of replacing a component in the fuel transportation system using a PA 6.10 base polymer instead of a fossil origin PA 12. The 6.10 polyamide in question is made up of approximately 64 per cent polymer of biological origin. This polymer comes from castor oil. When the plant that produces the seeds grows, it consumes carbon dioxide, a solid advantage for the environment.

Figure 3 shows the values of bursting pressure measured according to standard ISO 7628 for Radilon® D 40EP25ZW, a flexible grade used for the production of blown pipes. The mechanical characteristics of this product meet class 1 and 2 specifications.

Figure 4 illustrates a blow pipe produced by the extrusion process for this special PA 6.10 grade in blue. The most important characteristics include the excellent aptitude for extrusion processing, with excellent resistance to all types of fuel, and excellent chemical resistance.

Applications in contact with water

In the heating and plumbing sector, and in numerous other applications that come into contact with drinking water and foodstuffs, there is ample room for the introduction of polyamides.

In the heating and plumbing sector, metal applications (brass, aluminium and copper) still represent the state of the art. However, the steady introduction of polymers is under way, thanks to some immediately perceptible advantages, such as: better resistance to corrosion, greater ease of design and productivity, anti-limescale features, competitive costs. In addition, in this case also, environmental impact has been an additional advantage, that perhaps today is not always appropriately quantifiable. In this segment, polyamides are used only if they can meet typical requirements for the applications. Contact with water, hot water and steam, requires good resistance to hydrolysis, especially at high temperatures. The mechanical characteristics must guarantee long life in elements under pressure for long periods of time. Let’s not forget that certain equipment is guaranteed for a period that might range from a minimum of five up to a maximum of 50 years. If, then, we consider that it will come into contact with drinking water and food, we have to think of products that can ensure the good health of users and also maintaining their sensorial characteristics. For this reason, special formulas are proposed, with low rate of extracted substances after coming into contact with food and water, to meet regulations in place in almost all countries.

As an example, figure 5 shows a water container in 6.6 polyamide filled with 30 per cent glass fibre, stabilised by hydrolysis, ACS and KTW certified. Figure 6, on the other hand, shows some kitchen utensils in polyamide 6.6 filled with 30 per cent glass fibre, approved for applications in contact with food.

Inverter casing for photovoltaic units

Another example of virtuous use of polyamides is inverter casings for photovoltaic units (figure 7). A special polyamide 6.6 base compound was developed to guarantee function and safety, filled with 25 per cent glass fibre. The main features of the polymer are: UL-VO class flame resistance, absence of halogens and red phosphorous, resistance to external exposure to ultraviolet rays, excellent surface appearance and very low release of substances after exposure to high humidity cycles (85 per cent) at high temperature (85 °C). This property is essential for guaranteeing the integrity of electronic circuits and therefore component functioning.

A growing trend

Polyamides for engineering applications is, today, an important point of reference considering the numerous successes achieved in various industrial sectors. The previous examples demonstrate some possible success stories only because of notable flexibility in defining custom formulas. We can say that in these cases, the innovation is, primarily, in the competence and creativity of the people working together: namely producers of parts responsible for accurate engineering, plastic experts able to identify the practical needs of application and evaluate feasibility, even of innovative products, formula developers (R&D) who can translate the input they receive into competitive, reliable products and, potentially, products that are easy to process.

Polyamides, in polymers for engineering uses, still play an important role in the most advanced applications, being able to provide a combination of properties that are difficult to achieve with other polymers. The possibility of having different types is an additional favourable factor: high fluidity PA, for high temperatures, with long molecular chains, with low hygroscopicity, of biological origin. If hybrid solutions find use alongside single material solutions with metal inserts as reinforcement, or with the addition of continuous fibre reinforcements locally, additional horizons can be broadened for applications where metal exclusively has, to date, been used. This latter approach appears to represent the new frontier for development using solutions with polymers for engineering use over the next 10-15 years.

Many market research projects are confirming interesting in solutions with polyamide base technical polymers, estimating nylon consumption to grow over the next decade at a rate of approximately 4 per cent increasing to 7 per cent for higher performing products.

 

 

 

Figura 1 – mettere in apertura

1 Air pipe for turbo engine. In this type of component, special polyamides are steadily replacing metals

 

Figura 2 – mettere vicino al paragrafo Replacing aluminium

2 Comparison of some categories of environmental impact relative to polyamides and die cast aluminium. For all the groups considered, polyamide demonstrates a lesser environmental impact

 

Figura 3 – mettere vicino al paragrafo More ecological solutions with bio polyamides

3 Radilon D 40EP25ZW, flexible polyamide 6.10 grade, meets the provisions of standard ISO 7628

 

Figure 4 – mettere vicino al paragrafo More ecological solutions with bio polyamides

4 Highly flexible blown tube of polyamide 6.10. The item can replace similar polyamide 12 applications with benefits in terms of environmental impact

 

Figure 5 – mettere vicino al paragrafo Applications in contact with water

5 Water distribution tank in Radilon A RV300RKC (polyamide 6.6 filled with 30 per cent glass fibre with improved resistance to hydrolysis)

 

Figure 6 – mettere vicino al paragrafo Applications in contact with water

6 Kitchen utensils in Radilon A RV300FC (polyamide 6.6 filled with 30 per cent glass fibre, suitable for contact with food substances)

 

Figure 7 – mettere vicino al paragrafo Inverter casing for photovoltaic units

7 Inverter casing for photovoltaic systems in Radiflam ARV250 HF (polyamide 6.6 filled with 25 per cent glass fibre; certified UL-V0)

 

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