MATERIALS | MEDICAL
Right: Polyplastics reports growing interest in TOPAS cyclic olefin copoly- mer for Covid-19 related medical vials and syringes
are inside the plastic parts means that the analytical tests are more complex and expensive. Finally, investing in a GMP quality system helps to develop robust products and shows a commitment to Quality by Design. The ISO13485 standard 2016 version is becoming the global standard. The US FDA was involved in a revision to make it accept- able in the USA, and it will be also accepted as the Japanese standard for GMP in the coming months. However, historically there has not been an adequate standard definition of a medical grade plastic. This lack of clarity leads to unjustified claims and misunderstandings. There is work underway to develop a standard definition. The German society of engineers (VDI) has published a definition of a medical grade plastic, while MedPharmPlast Europe is in the process of developing this further.”
Need for medical grades Duckworth continues: “The medical industry is attractive as a speciality market, but not one that drives volume or justifies development and supply of a plastic resin developed specifically for medical applications. The same is even more true for pigments and additives used. Resin consumption in healthcare is estimated at less than 5% of global demand and my estimate for pigments and additives is less than 0.05%. So, with a few excep- tions, medical grades are based on standard ingredients, but with additional controls and quality specifications.” But there has been progress in the polymer
industry, he says. “There is wider availability of medical grade plastics from a larger range of suppliers compared to ten years ago and several resin suppliers are creating specific medical grades. This is linked to investment in knowledgeable teams specifically dedicated to healthcare. This is not an industry that you can go into half-way and expect quick returns. There is a deep understanding required, and given the frequent changes in regulations, it is essential to be prepared to answer all questions that will come from medical device OEMs. This is why the membership of trade associa- tions, such as MPPE, is creating an information platform that benefits from multiple years of collective experiences. The more successful compa- nies are the ones that have had, and continue to have, a long-term commitment to the industry.” Further development of medical plastics will involve specific functionality. Duckworth says that this will probably arrive through compounding rather than development of specific plastic resins. The level of customisation needed tends to result in relatively small volumes. Examples include reducing
16 INJECTION WORLD | January/February 2021
friction in plastic-to-plastic contact, which helps to reduce actuation force in drug delivery devices. Higher drug viscosity usually presents a challenge of higher actuation forces and impact of friction. For pharmaceuticals contained in a device or container, plastics play a role in protection from UV, moisture and oxygen to provide a typical shelf-life of three years. There are existing solutions, but there is room for improvement. Newly launched functional additive solutions for oxygen protection in PET have been adapted from the food and beverage industries to give longer term protection in a monolayer/mono-materials with high transpar- ency. For polyolefin resins, which represent more than 60% of the plastic used in pharmaceutical containers, there is an issue. Current methods use multiple layers – usually at least five – with EVOH as the barrier and/or using sachets containing an oxygen absorber. Both these methods are relatively high cost and with multiple layer containers give potential recycling problems. Finally, changes in sterilisation methods from ethylene oxide (ETO) to e-beam and gamma can result in a degradation of properties and/or visual appearance (yellowing), for example in PP and COP. Radiation-resistant grades only partly solve this. However, functional additives can be intro- duced to protect the polymer and colouration tech- nology used to mask the yellowing. Future developments in medical plastics will see
regulation changes requiring more transparency on substances used. “Medical grade plastics will need to be supplied with a commitment to notify changes, and better information flow between the resin manufacturer, compounder, medical device provider and pharmaceutical company will be vital,” says Duckworth. “In addition, the sustainabil- ity challenge will require a change in thinking. Even though healthcare is only a small contributor to the problem, the industry will need to find ways of
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IMAGE: POLYPLASTICS
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