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Molding the Market: The Future of Medical Resins

News Stories

Molding the Market: The Future of Medical Resins

by Brittany Willes, contributing writer, Plastics Business

Healthcare in all its various forms is a hot topic in today’s uncertain climate. While many are focusing on finished products, plastics manufacturers, molders and suppliers are on the front line making sure the highest quality materials are being used to meet ever-growing demand for medical supplies and parts. Plastics Business sat down with PolySource’s Director of Sales and Marketing Bob Findlen and Director of Applications Development Dr. Cliff Watkins to discuss the growing opportunities for medical resins as well as what challenges they present.

What are the emerging technologies for medical resins?

One area that we have been looking at, and that is quite pertinent to today, is that of high throughput screening – a process that allows automated testing of large numbers of chemical and/or biological compounds for a specific biological target and therefore of particular importance in the medical industry. With this process, micro chemical reactors evaluate different chemicals for different reactions. What’s unique about high throughput screening is that these very detailed surfaces are molded onto plastic parts that will have a lot of surface area and a lot of channels for the reactants to flow across. Picture a small microscope slide. Viewed under a microscope, it would appear almost like a corn maze where liquids are forced to flow back and forth across one another. The reactor plates might then be exposed to heat or UV light to induce energy for a chemical reaction.

When it comes to medical testing, it is vital that plastics used in various test equipment – such as those used in high throughput screening – do not contaminate whatever liquid the plastic container is holding. For example, there have been instances with plastics such as acrylic, polycarbonate or polystyrene, which are cost-efficient commodity type resins but have been shown to leave behind trace amounts of unreacted monomer. Those trace amounts can interfere with the reactions meant to take place.

Do medical resins present any unique challenges?   

A level of high quality is required for medical parts. The challenge is providing resin grades with low to no extractables or leachable chemicals, such as residual monomers.

A good example is the polymer ABS. It is a ubiquitous, high-volume, multifaceted polymer; however, it contains the monomer acrylonitrile. The national sanitation foundation (NSF) has been reducing the acceptable extraction levels for acrylonitrile down to fractions of a part per billion (ppb). As a result, resin manufacturers are striving to develop simpler, niche polymers made with benign monomers. One such resin, Topas COC, is an amorphous, highly certified medical plastic. Testing that has been done with Topas has shown essentially no extractables. This makes Topas and resins like it ideally suited for molding complex surfaces needed in high throughput screening devices.

Another challenge is sanitization using highly aggressive cleaners, solvents and chemicals. With these high-purity amorphous materials, and any amorphous materials for that matter, it is necessary to be careful about the kinds of sanitizing wipes, cleaners, solvents and chemicals the plastic is being exposed to. This is because amorphous polymers – while offering very good visual clarity, UV transparency and other advantages – by definition are not as chemically resistant as semi-crystalline resins. It is critical to be mindful of how the plastic is going to be used.

Are there any new issues facing medical resins/plastics?

A good example of this goes back to cleaning solutions and solvents that attack polycarbonate and now are being used in field hospitals and medical rooms. Materials that have been used for years without issue suddenly are cracking and breaking down. The materials of the past no longer will stand up to today’s more aggressive environment. This means molders have to look at other resins with improved chemical resistance.

How should molders select new resins to suit their parts?

We call it the triangle – the triangle between the OEM (in this case, the medical OEM), the processor and the material supplier. When OEMs are developing an application, they need to work closely with the resin supplier to make sure it follows all regulatory guidelines and also work with the processor to make sure the design of the part – the functionality that is built into the part – can be molded. In most cases, the molder will rely on the OEM to select the resin. Of course, there may be times where the material is not working or there may be physical performance issues or molding issues. At that point, it may become necessary to look at alternative materials. This is when it is important to have a good relationship between the molder, the OEM and the resin supplier in order to immediately address and eliminate any issues encountered at the start of processing or later on in the molding of the product.

From a resin supplier standpoint, it is critical to be part of those conversations to complete the triangle. Often, not just in the medical industry but in all industries, there is a prevailing desire when designing something new to say, “We’ve always used this plastic or that plastic, so we’ll just use it again for this new part.” There have been situations where, because of the requirements with sterilization, etc., what has been used in the past is no longer appropriate. If the process has gotten so far down the road where molders actually have made an injection mold, there is high potential for crisis as it can be quite a challenge to now fit – literally and figuratively – the best resin into that mold if it was designed for something quite different. Again, that triangle up front is so critical to head off what can be an incredibly costly decision to just do things the way they’ve always been done.

What questions should be asked to make sure the best material is utilized?

When working with the OEM or the processor, with the medical industry especially, it is crucial that the field team ask all the right questions regarding regulatory concerns and specifications the application must meet. Then there are more traditional concerns, regardless of the market: Are there chemical resistance requirements? Is there a heat source? What are the impact needs?

Ask all the plastic questions to make sure you know the answers. The material that resin suppliers provide for their customers is only as good as the questions they ask and the answers they get. In the case of medical resins, it’s possible to find something that meets all the regulatory requirements and looks good, but then the molded part is too brittle. Then the supplier realizes, “Well yeah, the material that we chose is brittle. We didn’t consider this application based on its design or realize it had to have more durability to it.” They should have known that up front.

As much as a customer may want to do things a certain way, it is the resin supplier’s job to be the referee and make sure all decisions are based on facts and data.

Bob Findlen is director of sales and marketing for PolySource with 39 years of experience in the plastics industry. PolySource Director of Applications Development Cliff Watkins has a Ph.D. in Chemistry and is the former owner of TP Composites with 39 years of industry experience. PolySource is a leader in engineered plastic resin solutions. Its technically trained professionals know the disciplines of plastic design, tooling design, troubleshooting and material selection.