A new vegan sustainable film could replace single-use plastic in many consumer products, scientists say.
Made at the University of Cambridge, the film is inspired by spider silk, one of nature’s strongest materials.
It has the strength of man-made synthetic polymers in plastic bags and foil packaging, but decomposes completely naturally, without harming the environment.
The new product will be commercialized by Xampla, a spin-out company from the University of Cambridge that develops replacements for single-use plastics and microplastics.
Xampla will introduce a range of single-use sachets and capsules later this year, which could replace the plastic used in everyday products such as dishwasher tablets and detergent capsules – many of which are still in individual plastic packaging.
The company is also testing the vegetable film in food packaging such as sandwich containers and salad boxes.
Developed by Cambridge spinout company Xampla, the film is shown here in food packaging, dishwasher tablets and detergent capsules
WHY ARE SPIDER WEBS SO STRONG?
The strength of a biological material like spider silk lies in the configuration of structural proteins, which have small clusters of weak hydrogen bonds that work together to withstand force and dissipate energy.
This structure makes the lightweight natural material as strong as steel, although the ‘glue’ of hydrogen bonds that hold spider silk together is 100 to 1000 times weaker at the molecular level than the strong glue of the metal bonds of steel.
It is also working on developing edible films, which could be used for applications such as oral drug delivery.
Non-fading ‘structural’ color can also be added to the polymer and can also be used to make water resistant coatings.
The production method can be scaled up to industrial scale, the experts claim.
“Other researchers have worked directly with silk materials as a substitute for plastic, but it remains an animal product,” said study author Rodriguez Garcia of the University of Cambridge.
“In a way we came up with ‘vegan spider silk’ – we made the same material without the spider.”
The material can be composted at home, while other types of bioplastics require industrial composting facilities to break down.
It also requires no chemical modifications to the natural building blocks, so it can be safely broken down in most natural environments.
The material was created using a novel approach to assembling plant proteins into materials that mimic silk at the molecular level.
Spiders are master builders, skillfully weaving strands of silk into intricate webs that serve as the spider’s home and hunting ground.
Xampla introduces a range of single-use sachets this year for storing food ingredients (pictured) and cleaning products
Spider webs are as strong as steel, even though the “glue” of hydrogen bonds that hold spider silk together at a molecular level is 100 to 1000 times weaker than the strong glue of steel’s metal bonds.
The researchers became interested in why materials like spider silk are so strong when they have such weak molecular bonds.
“We found that one of the key features that gives spider silk its strength is that its hydrogen bonds are regularly arranged in space and at a very high density,” said study author Professor Tuomas Knowles at Cambridge.
The team began looking at how this regular self-assembly could be replicated in other proteins.
Researchers created the film by mimicking the properties of spider silk, one of nature’s strongest materials
POLYMERS AND MONOMEN
Most plastics are made of polymers, chains of hydrogen and carbon, obtained from petroleum products such as crude oil.
Polymers are composed of shorter strands called monomers.
Many plastics cannot be recycled because of additives mixed with them, making them difficult to remove because the monomers cannot separate from them.
Each replacement for plastic requires a different polymer.
The team replicated the structures found on spider silk by using soy protein isolate (SPI), which is readily available as a byproduct of soybean oil production.
Proteins have a tendency towards molecular self-organization and self-assembly.
‘Because all proteins are made up of polypeptide chains, under the right conditions we can assemble vegetable proteins themselves, just like spider silk’, says Knowles.
‘In a spin, the silk protein is dissolved in an aqueous solution, which then combines into an immensely strong fiber via a spinning process that costs very little energy.’
However, plant proteins such as SPI are poorly soluble in water, making it difficult to control their self-assembly into ordered structures.
The new technique thus uses an environmentally friendly mixture of acetic acid and water, combined with ultrasonication and high temperatures, to improve the solubility of the SPI.
This method produces protein structures with enhanced ‘intermolecular interactions’, guided by the unique and ultra-strong hydrogen bond formation.
In a second step, the solvent is removed, resulting in a water-insoluble film.
The researchers used soy protein isolate (SPI) as their test plant protein, as it is readily available as a by-product of soybean oil product
The material has a performance equivalent to high-performance engineering plastics such as low-density polyethylene – one of the most widely produced plastics in the world.
Polyethylene, also known as #1 plastic, is used in a wide variety of products, from plastic bags, plastic milk jugs and shampoo bottles to corrosion-resistant pipes, wood-plastic composite lumber and plastic furniture.
The polymer is found in about a third of all plastics produced and is worth around $200 billion (£142 billion) a year worldwide.
Professor Knowles has been researching the behavior of proteins for years, but in relation to degenerative diseases.
Much of his research has focused on what happens when proteins misfold or ‘misbehave’, and how this primarily relates to dementia.
“Normally we study how functional protein interactions allow us to stay healthy and how irregular interactions play a role in Alzheimer’s disease,” Knowles says.
‘It was a surprise to find that our research could also tackle a major sustainability problem: plastic pollution.’
The results are reported in the journal nature communication.
Only 20 companies produce 55% of the world’s plastic waste – with ExxonMobil topping the list, contributing 5.9 MILLION tons a year, the report reveals
Just 20 companies produce 55 percent of the “disposable” single-use plastic that ends up as waste worldwide, according to a May 2021 report.
Texas oil company ExxonMobil tops the list of polymer producers producing single-use plastic waste, contributing 5.9 million tons in 2019 – equivalent to the weight of 5,700 blue whales.
ExxonMobil was closely followed by Michigan chemical company Dow and Chinese oil company Sinopec, which contributed 5.6 and 5.3 million tons respectively in 2019.
These three companies together account for 16 percent of global single-use plastic waste, according to the newly published gepubliceerd Index of plastic waste makers.
At 44kg, the UK is also the fourth largest producer of single-use plastic per capita worldwide, the report finds.
Read more: Just 20 companies produce 55% of the world’s plastic waste, report reveals