In a parenteral packaging world often dominated by discussion of vials, stoppers, and pre-filled syringes, flip caps rarely take centre stage. While these components never come into contact with drug products themselves, their role is anything but secondary – flip caps are mission-critical in maintaining sterility and safeguarding product integrity.
But as critical as they may be, their traditional reliance on single-use virgin plastic is of increasing concern. Could the next generation of injectables benefit from a less carbon-intensive flip cap? Following the recent launch of Datwyler’s latest sustainable design, the answer is yes.
How do flip caps work?
Flip caps are a special type of two-part vial closure that sit on top of the rubber stopper, with crimping around the vial neck to ensure a seal. When the medical professional prepares the drug for injection via a needle, the uppermost part of the flip cap, a colourful plastic disc, is ‘flipped off’, revealing an aluminium shell crimped below the vial neck. This shell has a hole in the middle, providing access to the piercing area.
The role of the flip cap is multi-fold. The crimped aluminium provides a hermetic seal for the stopper, while the unopened plastic cap protects the piercing area and gives the healthcare professional a visible indication as to whether the vial has been tampered with. Available in a range of colours, flip caps also offer opportunities for customisation and differentiation between products.
“It’s very important what types of caps you use, how they are made, and how they are crimped, because that’s really what allows you to seal your vial,” states Camille Ermine, Product Manager for vial closure systems at Datwyler.
Rethinking flip cap plastic
At Datwyler, sustainability is a key driver of innovation. In 2024, the company received the Platinum award from Ecovadis, placing it within the top 1% of more than 150,000 rated companies. Sustainability is not a trend at Datwyler but a responsibility and a strategic goal. The company has a clear roadmap with eco-design high on the agenda, and rethinking the materials used in its flip caps soon became a priority.
In 2025, Datwyler unveiled a new flip cap option featuring a bio-based polypropylene disc made from used cooking oil, instead of petroleum. The feedstock qualifies as waste or residues and the end material is fully recyclable, supporting circular economy practices.
“What is important with this new material is that we are using waste, a second-generation feedstock, rather than harvesting something which also creates environmental impacts,” says Ermine.
The feedstock is mixed with chemicals and certified by the International Sustainability & Carbon Certification (ISCC) as ‘bio’ using the mass balance method. ISCC operates a voluntary certification scheme, ISCC Plus, which is designed to validate sustainability characteristics of alternative feedstocks. When materials like Datwyler’s combine plant-based feedstocks with fossil fuel-derived feedstocks, ISCC uses the mass balance approach to validate the share of certified materials incorporated in the end product.
In a world where ‘green’ claims are often misleading or unsubstantiated, the mass balance recognition from ISCC Plus is noteworthy, enabling customers to understand the origins of new materials. Beyond this, of course, lifecycle assessments are critical in measuring the true environmental benefits.
Quantifying the carbon savings
During eco-design, lifecycle assessments or ‘cradle to grave’ analyses help designers evaluate the full environmental impact of a new product across its complete lifespan. However, as a packaging supplier with no control over how components are used and disposed of, full lifecycle assessments are near impossible and ‘cradle to gate’ analyses must act as a substitute.
Cradle to gate studies take into account raw material extraction, inbound transportation, manufacturing, and packaging – essentially, everything that happens to the component up until the moment it leaves the manufacturing facility. As part of its wider sustainability roadmap, Datwyler is currently conducting this type of study for each of its products.
“We made this assessment for the bio-based flip caps, taking into consideration the different raw materials, how they come into our facilities, how they’re transformed into a plastic disc, et cetera,” says Ermine.
In a cradle to gate analysis, materials made from bio-based feedstocks can theoretically have a negative carbon footprint, since the carbon absorbed by the plant across its life is stored in the material. However, during end-of-life treatment, this stored carbon is eventually released back into the atmosphere, resulting in a net positive carbon footprint. This makes it crucial to consider emissions across the entire lifecycle – including end-of-life – rather than focusing solely on cradle-to-gate emissions, which encompass only raw material extraction, inbound transport, and processing.
Applying a cradle to gate analysis without including the biogenic content, the product carbon footprint of the bio-based plastic disc is ~65% lower than the fossil-based analog.
What about aluminium?
The aluminium component of Datwyler’s flip caps was also analysed during the eco-design process and was found to be environmentally friendly due to its infinite recyclability. While there are currently no opportunities to use recycled aluminium within “pharma-grade” packaging components like flip caps, the silver lining is that the aluminium that is used in pharma packaging can be recycled easily.
“There is no end of life for this material, and around 75% of the aluminium in use today is recycled aluminium,” explains Ermine.
On Datwyler’s side, she adds that the company works with a certified third-party to recover 100% of the waste and scrap generated during flip cap manufacturing. Meanwhile, the company continues to investigate the possibility for a non-virgin pharma-grade aluminium to further lower the carbon footprint of its flip cap design.
“Hopefully in the future we will have a high-quality recycled aluminium we can use, but unfortunately that’s not the case today,” she says.
Quality is king
When it comes to pharmaceutical products, another significant challenge with eco-design is that quality – which often directly correlates to patient safety – always comes first. To this end, Datwyler conducted a variety of tests to verify that the new bio-based flip caps are just as safe and effective as its traditional product, which is manufactured under the exact same conditions as the sustainable alternative. These included functional checks to see whether the cap opens and seals as it should to colour stability and sterilization tests to ascertain whether the new material withstands the sterilization process without degradation or colour changes.
Ongoing aging studies are also underway to observe how the new material performs over its expected lifespan. Datwyler does not expect to witness any changes here. Ultimately, spectroscopy tests have ensured there are no chemical differences that could affect the material’s performance, while certification and equivalency checks from the material provider have also confirmed that the new plant-based polypropylene’s chemical and physical properties match the traditional material exactly.
While quality will always take precedence in pharma’s product design, the growing importance of sustainability is impossible to ignore. As companies seek to minimise the environmental impact of their products’ packaging without impacting its integrity in any way, Datwyler’s latest flip caps show how planet friendly and patient safety can go hand in hand.
