MEDICAL | MATERIALS
costs and longer times involved. However, due to Covid-19, we have seen a spike in interest both in replacing current materials, such as silicone, with softer plastics in current applications, and in scaling current applications for the future. We see a larger proportion of consumers becoming more con- scious of infectious disease and manufacturers have the ability to prevent the spread of disease through the choice of appropriate materials. For us, this means that many applications that were previously not considered medical, for example a pen cup in a public waiting room, will in future need to withstand different sterilisation methods, such as autoclaving.” Huddleston adds that the company is observing
three major trends in injection moulding medical materials. These include standardisation of antimi- crobial additives in more application areas, as well as the need for sterilisation resistance – both heat and solvent sterilisation – in more traditional consumer goods. A further trend – seen across all industries – is more vigorous selection of the best material for the application where appropriate, whether this is TPE, silicone or TPU. New materials developments are now being driven by consumer demand and an awareness of materials that can be more easily sterilised or are resistant to microbes. “We already offer an antimicro- bial additive package to customers, which we use for medical and outdoor applications, but is typically not offered for consumer products because the custom- er does not want to pay for it,” says Huddleston. “We see this trend shifting in the future.” Nevertheless, new solutions are still needed in the development of medical materials. “Some part or assembly features are simply not possible to solve on a physical or practical level, given com- mercially available polymers and polymer feed- stocks,” Huddleston explains. “The most common request we must turn away is for combinations of ‘extreme’ parameters. For example, a 30 Shore A material with long-term temperature resistance at
150℃, resistance to acetone and no memory. We can fulfil two or three of these items at a time, but sometimes the combination of all the desired properties is simply not possible. This either leads to a discussion and modification of requirements, followed by more exhaustive testing, or to the manufacturer passing on the programme if it does not make business sense to pursue it.” Materials from United Soft Plastics have been in demand for face shields and ventilator parts in particular recently. “We had several companies come to us, both domestically and internationally, asking for materials to convert their non-medical
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manufacturing facilities to produce items to meet the demand from the pandemic,” says Huddleston. “We see this demand dropping towards the middle of this year, but there will still be significant longer-term support for these products than there was before the pandemic. Other medical applica- tions we are currently involved with include antimicrobial compounds, safety equipment such as gloves and masks, medical devices, tubing, films, pharmaceutical devices such as sealings and closures, and oxygen- and nitrogen-barrier materials for medical packaging. We see significant future growth in the antimicrobial and safety segments.”
Selection procedure While development and approval of materials for medical applications can take longer than normal, Huddleston outlines a typical development life cycle. Following contact from a new or existing customer, the company collects information and defines as many requirements as possible, before forming a plan of action. This typically might involve scenarios with three different materials. For example, material A has skin contact certification and costs $2.40/lb. While full USP Class VI may not be needed for this application, it is expected to pass. Material B has USP Class VI approval, but is $6.30/lb. Alternatively, material C has no medical approvals but is $1.85/lb and has passed other extraction testing, such as food or water contact. It is also easy to work with and has years of produc- tion data, meaning that any approvals can start almost immediately. The customer then decides the direction to go and orders samples. Trials are scheduled with a new programme or ramp-up coordinator at the moulder. Mould and material changes are discussed and made. Because every scenario is different, specific requirements from all parties are critical for medical programmes. For example, if a supplier changes one raw material for
January/February 2021 | INJECTION WORLD 23
Above: Low- permeability, no-kink tubing from United Soft Plastics. The part on the right is the fitting while the piece on the left is the tubing itself
IMAGE: UNITED SOFT PLASTICS
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