A new sustainable line calls time on damaging aerosols

Aerosols are nearly a century old: the first patent was granted in 1927. Until 1989 the main propellants were chlorofluorocarbons (CFCs). In 1989 CFCs were banned as they played a role in damaging the ozone layer. In the majority of products CFCs were replaced by volatile organic compounds (VOCs) such as butane and propane. These VOCs are highly flammable, are precursors to smog formation and are associated with a wide range of respiratory disorders. Furthermore, aerosols containing flammable VOCs tend to blow up when the cans are crushed during recycling. VOC propellant gases are no longer environmentally or socially sustainable.

The challenge to produce a sustainable alternative has occupied Triple Line Technology's founders, Mark Nicmanis and Michelle Gothard, for some time. Mark, an Australian, who came to the UK in 1995 to study chemical engineering. "My interest in multi-phase systems began during my PhD where I studied the behaviour of particulate systems using population balance equations," he says.

After graduating he joined Unilever's R&D division where he worked on "the development of novel ice cream, laundry granule, aerosol anti-perspirant, hair care and beverage products. He then was recruited by TTP working for six years, and followed that by three years at Cambridge Consultants."

Michelle has a PhD in physical chemistry and has worked extensively in materials understanding, and the development of sustainable processes, technologies, and products, in areas as diverse as crop agronomy, biomaterials, value recovery from waste, foods production, and biofuels

"We both worked at Cambridge Consultants - and Unilever, where our terms overlapped," says Michelle. "After Unilever I worked as a technical consultant, and for processing technology companies, then finally Cambridge Consultants.

"Mark and I have both worked on interfacial phenomena and multiphase systems for most of their professional careers. We are familiar with the technological and regulatory barriers of some of the existing approaches.”

Mark explains the main alternative to non-VOC foam generation “Tiny bubbles or small droplets can be made by drawing a membrane through a tiny orifice. Eventually the membrane elongates to the point where it becomes energetically more favourable to exist as separate droplets. This phenomenon is known as the Rayleigh-Taylor instability and is the basis of many of the inkjet technologies that have been pioneered in the Cambridge tech cluster.

“The problem with using the Rayleigh-Taylor instability to generate small bubbles is that the bubbles tend to be around the same size as the orifice used to create them. So, if you wanted to generate 40 micron sized bubbles you need an orifice roughly 40 micons in diameter. Such tiny orifices are prone to clogging, are expensive to manufacture and require really high pressures to generate tiny bubbles.”

To overcome these difficulties Triple Line Technology has invented a way to use an alternating series of shear fields that elongate fluid membranes and tear off tiny bubbles to create a micro-foam. In this way they can create micro-foams consisting of bubbles typically smaller than 40 micron. The flow channels in which this phenomena occur have dimensions in millimetres rather than microns. Components with millimetre sized flow channels are easily manufactured using standard injection moulding, they also overcome issues with clogging and can create very fine bubble structures using very modest pressures.

I notice the bubbles in the foam are so fine you can hardly see them. The foam generation technology is contained in a small component where compressed air from the head-space of the can is drawn up with the foamable formulation to form a gas and liquid mixture. This mixture then goes through the mechanism and a fine foam comes out the aerosol nozzle.

"We've patented the geometries which cause this phenomenon. It's a new physical pheonomena we have not previously seen."

“We both immediately saw that our new foam generation technology overcomes many of the limitations of the existing methods of creating very small bubbles,” adds Michelle. "Not only is our new foam technology environmentally friendly (since it does not require VOCs), but it also overcomes the issues associated with attempting to create foams with a small orifice or fine mesh. The consumer goods industry is moving to remove VOC propellants from its aerosol products by 2025 or 2030. Though there are some alternative technologies in the pipeline for spray aerosols, there isn't much out there yet for generation of aerosol foams without using VOCs."

Mark and Michelle demonstrate Triple Line Technology’s aerosols technology. There is no difference to the user from a standard aerosol, although there's a proprietary technology hidden within the aerosol packaging. The mechanism can be implemented in the actuator (button), or within the dip-tube/valve assembly of the aerosol can.

Their business plan to license, or co-develop the technology with major industrial and consumer goods companies is going well. They are currently working on applications of their technology with a few large multinationals and a few start-ups. These upcoming products are being developed under non-disclosure agreements (NDAs), but the general principles are delightfully straightforward.

"Until now you've needed liquified gas propellant to create foam from an aerosol," says Mark. "Ours uses compressed air, which is safer and environmentally friendly. We're looking to partner with major brands and license the technology to a brand or component manufacturer. "

"There's possibilities for packaging, processing and medical devices," says Michelle, "so far we have only scratched the tip of the iceberg with regards to interesting new applications of our technology."

"The timing of launches based upon our technology comes down to the internal processes of a large company," notes Mark. "From the time they start talking to you to the time they start building the product is typically a minimum of a year. They have to develop formulations that work with our technology - that consumers like and are affordable. Then the industrial tools have to be cut. This can take as long as 16 weeks. Then pilot manufacturing and storage trials - the package integrity has to be established, to make sure it's safe - and then verify the business proposition before scale up and market launch. "

It can cost several million pounds to set up a new production line for aerosols - a fate avoided by Triple Line: "This aerosol technology can be filled on standard filling lines, at no extra cost for the manufacturer."

Triple Line has also advanced its technology without requiring external investment, which makes it easier to continue making progress during the pandemic.

"We're still 100 per cent self-financed," Marks says. "and have been progressing our developments with a very low burn-rate compared to many start-ups.”

There's a long haul to pull this sustainable product through the industrial schemata - through the storage trials, FDA approval and safety approvals - but, with the backing of a larger company, those milestones are sharply redacted. With applications in personal care (shaving foam, suntan lotions, hair mousses), home care (carpet shampoos), medicine (advanced delivery mechanisms, "tissue scaffolds for regenerative medicine"), industrial (including gas scrubbing, insulation and fire extinguishers) and agriculture - where foam, unlike general crop-spraying, can be targeted - Triple Line is on target for a prominent role is a new generation of climate-friendly foam products.