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by Mark Buckingham
A key question repeatedly encountered in product design is ‘what materials will work in this application?’ A good starting point is to consider the purpose. How is function created by the interplay between the shape and composition of the product? Is it important what it looks like? Should it let the light in or keep it out? What about electrical properties? Does it need to insulate to protect the user from mains voltage inside, or conduct electricity to prevent build-up of charge? Should it be very strong, or break in a controlled way in extreme conditions to fail safely? If it gets very hot or wet, do we expect it to continue to function in the same way, or should it undergo a recognisable change to indicate that it is no longer safe to use?
In many markets, first impressions of a new product design are very important and different materials can convey distinct messages. Does it feel cold or warm, grippy or slippery, rigid or flexible? Does the surface texture give an impression of a quality product that will last? Should it be a particular colour to stand out or blend in?
We want our products to be safe, but choice of appropriate materials will depend on the application. Medical devices and products used by children or in contact with food need to be tested to the appropriate standards to check that no harmful ingredients might leach out during use. But inside a nuclear power station, the ability to continue to operate unaffected by radiation will be crucial.
For many materials, properties will change with time, and this may affect the period of usability of a product. Predicting lifetime will depend on the temperature range over which articles are used. Accelerated ageing at a range of elevated temperatures can be carried out to model the expected life of products at room temperature. If use at low temperatures is envisaged, it is also important to check that materials which are flexible at room temperature do not become brittle when very cold.
For repeated or extended use, materials need to be chosen which retain their properties over time. Ease and comfort of handling may be very important, for example fit and grip, or the ability to stay clean and free of microbes. Items subject to repeated deformation may tend to change shape. For high voltage applications, the ability to retain safe insulating properties is important.
We often focus on the opportunity for cost reduction by material substitution, but in many applications the cost of the materials is only a small fraction of the end price of a product. There may also be some scope to include small amounts of expensive materials in the formulation to provide additional functions. For example, ‘smart’ materials may be included to modify optical, magnetic, thermal or electrical properties.
Material substitution can often reduce overall costs by providing a route to reduction in process time or temperature. Choosing a more expensive material that can be handled in a simpler type of fabrication process is another option. Manufacturing methods are continually evolving; hence the choice of process needs to be regularly reviewed. When rapid delivery of prototypes is crucial, additive manufacturing may offer a route to fulfil this need. However, when moving to a different process for larger volume production, it is important to verify that the material will perform in the same way.
In the area of composite materials, thermoset systems have proved difficult to recycle, but the recent increased use of high temperature engineering thermoplastics in composites provides more possibilities.
Many material problems can be solved by understanding the interface between different items e.g. how implants interact with the human skeleton in the long term or careful process control of co-moulded plastic and rubber parts to ensure good adhesion between them. Often the simplest solution is to store newly manufactured parts under controlled conditions for a set time before exposing them to customer use.
The availability, price and customer acceptability of many materials continues to change, and consumers and manufacturers are increasingly looking to choose more sustainable alternatives. Be this through materials that facilitate recycling or repair, use of sustainable raw materials such as a move from oil based to plant based raw materials, or through a reduction in the energy embodied in the material manufacture, processing and recycling at the end of life.
New information about the safety of existing materials may also emerge. For example animal fur and asbestos insulation are no longer available and plastics are now often called resins. Which materials will become unpopular or unavailable next?
The CDP team has very broad knowledge in a variety of areas of consumer, industrial and medical applications from materials for printed electronics through adhesives and hydrogels to pesticides for rodent control. We have not just a materials expertise but an expert interface with engineering and manufacturing disciplines to offer a range of product design solutions.
We have specialist experience in materials for energy generation and storage, from batteries to supercapacitors and fuel cells, enabling us to identify opportunities to generate intellectual property in both materials and applications.
In particular, the CDP skillset includes a detailed understanding of materials in healthcare applications. This is of particular importance for drug delivery devices, where this capability provides a vital insight into the possible chemical interactions between a medical device and the drug being delivered. Manufacturing processes such as sterilisation methods, coupled with formulation characteristics including viscosity, surface tension or particle size will all have an impact on the selection of materials.
When we consider materials, product form and manufacturing process separately, we can go a long way towards achieving a good design. But it is only when we look at the choice of appropriate materials as part of the overall design and manufacturing process that we can achieve so much more.
We use so many different products in our everyday lives and they all need to be made from the most appropriate materials so that they will continue to perform well for many years.
Senior Consultant Chemist
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