Nature calls: The potentials of bioplastics within medical plastics
Nigel Flowers, Sumitomo (SHI) Demag, examines the use and potential of bioplastics in the medical plastics sector.
For more than 50 years, global production and consumption of plastics have continued to rise. In 2016, we produced around 335 million metric tons[i]. However, continued support for the introduction of bio-based products continues to gain momentum, suggesting that wider market penetration is around the corner. Market data shared at the 12th European Bioplastics Conference last November indicated: “Global production capacities of bioplastics are expected to grow by 20 percent in the next five years.”
Bio-based plastics have been used in medicine for years. This includes the use of gelatin-based capsules made of animal or vegetable matter, for example, which naturally dissolve in the digestive tract. These are common in many over the counter and prescription medicines. Other products include, biodegradable stitches, which do not require manual removal after healing, and biodegradable bandages designed to promote clotting and proactive skin regeneration. For applications like this poly-lactones or polyhydroxyalkanoates offer comparable properties to petroleum-based plastics. However, these applications are not typically injection moulded.
According to ProBI, 85% of plastics could technically be substituted with bio-based plastics, although this is predominantly in the packaging arena. However, for medical products, the use of bioplastics remains quite a niche area, particularly in the injection moulding arena as for applications like orthopaedics, implants etc., the material would be highly regulated, and would not be able to withstand the injection moulding process from a stability perspective.
Single use is common place in moulded medical applications. For example, disposable devices are proven to significantly reduce the risk of cross infection among patients due to the sterile nature of the items and to prevent cross contamination. Sterile plastic packaging and plastic medical disposables in particular contribute to keeping the rates of Staphylococcal infections low. Realistically, only a small number of polymers are available as medical grade for medical application, and an even smaller number is used for implants. The choice of polymer depends on the extent of contact with body fluids, internal and external tissue as prescribed by the regulatory framework.
Currently, prosthetics and medical packaging are possibly the only sectors where bioplastics can be viably injection moulded, and even here the material must be classified depending on the application type.
The bio-based PET market is one area undergoing significant growth and is expected to reach $8,682.6 million by 2023[ii]. Bottles are expected to be the fastest-growing application in the market, registering a CAGR of 13.7% during the forecast period. However, the material is also widely used in blister packs and cosmetic containers.
If the application is suitable, in theory, you can run bioplastics through an injection moulding machine just as you would any other polymer, although it can be more difficult to process as a result of heat sensitivity and moisture absorption. The main issue lies in how that plastic performs as an end product, which will dictate what applications it can be considered for. Typically, it would be medicine caps and closures, or items that have no contact with the human bodily fluids.
Likewise, if the bioplastic material properties differ from the material it’s intended to replace, it can have an impact on the production costs of the article in question.
Stability of the material and certification would be the biggest factors to consider.
[i] https://www.statista.com/statistics/282732/global-production-of-plastics-since-1950/
[ii] https://globenewswire.com/news-release/2018/03/22/1444217/0/en/Bio-Based-PET-Market-to-Reach-8-682-6-Million-by-2023-P-S-Market-Research.html