Rubber

Abrasion-ResistantElasticPackagingPliantRubberStrongTemperature-ResistantTextilesTuneraWaterproof

WHAT WE SAY:

Synthetic rubbers exploded in popularity after their invention for the same reasons we embraced other plastics – they were cheaper and much more available than the natural materials they were replacing. We know better now and as we move away from synthetic polymers and the environmental problems they bring, it is time to go back to the real thing.

Natural rubber is a renewable resource with endless uses in fashion, construction and packaging. Money does not grow on trees, but the alternative to plastic just might.

Rubber sheet production / Source: Shutterstock

What is Rubber?

Natural rubber – sometimes known as India rubber or Amazonian rubber – is a material almost exclusively derived from the Amazonian rubber tree Hevea brasiliensis.
Natural rubber is harvested as latex – a sticky, white, milky substance – from the rubber tree when it is around six years old and six inches in diameter. To tap the latex, incisions are made in the bark every two days, giving a cupful of latex containing around 50 grams of solid rubber each time.
After being tapped, the latex is strained, mixed with water to coagulate, dried and rolled into rubber sheets for sale.
Because of its strength, elasticity, weather-resistance and grip, rubber is the ideal primary material for car tyres. Over half of all the rubber manufactured every year – and up to 70% of natural rubber produced – is used in automobile tyres.
Other consumer uses for rubber – both natural and synthetic – include shoes, clothes, furniture and toys. Medical uses include: tubes and seals, leads, catheters, diaphragms and prostheses. Rubber is also used in mechanical parts for hoses, belts, gaskets, mountings and washers.
Around one tonne of natural rubber can be produced per acre of land every year, assuming a planting density of 150 rubber trees per acre.
Natural rubber reacts to temperature, getting softer when it is hot and harder when it is cold, and it can also be sticky, smelly and perishable. Vulcanisation is used to harden natural rubber, making it more stable.
Plastic-based synthetic rubbers can take hundreds of years to break down in the environment. By contrast, natural rubber is essentially biodegradable as it comes from a plant. However, in its significantly altered forms, like shoe soles and rubber gloves, this can be a lengthy process, with it taking up to weeks and months for decomposition to start. Perhaps, unsurprisingly, vulcanised rubber takes even longer to break down.

KEY PROPERTIES:

Abrasion-Resistant
Elastic
Strong
Temperature-Resistant
Waterproof

INDUSTRY:

Packaging
Textiles

AVAILABILITY:

Mass Market

DIVE DEEPER:

With natural rubber limited in availability, scientists developed synthetic alternatives. Isoprene was first polymerised in 1909 and in 1930, chemical giant, DuPont developed neoprene, which became the first commercially successful synthetic rubber. Like all plastics, synthetic rubbers are made from petrochemicals.
In 2020, global production of rubber was an estimated 27.4 million metric tonnes. The majority was synthetic; 14.4 million metric tonnes were produced, compared to 13 million metric tonnes of natural rubber.
While the majority of natural rubber is used to manufacture tyres, they are made from a mixture of both natural and synthetic rubbers. Modern car tyres require around seven gallons of oil to make (22 gallons for a truck tyre), and around 800 million of them are discarded across the world every year.
Tyres wear with use and pollute the environment. Research tells us, tyres in the US produce approximately 1.8 million tonnes of microplastics each year
Natural rubber production today takes place mainly in South and Southeast Asia, in Thailand and Indonesia in particular. The Hevea brasiliensis tree is native to the Amazonian rainforest and was traditionally harvested in Brazil and Peru, but serious cultivation there ended in the early 20th century due to South American leaf blight.
Rubber trees can provide latex for over 20 years. Wood from felled rubber trees is prone to fungal and insect attack, so trees were traditionally burned after their productive life. Today, the wood is treated with boron preservatives and kiln-dried to allow it to be made into furniture.
Charles Goodyear developed vulcanisation in 1938. The process involves heating the rubber to 140-160°C with sulphur – often with an accelerator and activator – to form cross-links between long rubber molecules.
Vulcanised rubber has better elasticity, tensile strength, resilience, viscosity, hardness and weather resistance than rubber in its natural state, however it is difficult to recycle vulcanised rubber, which is why discarded tyres are such a blight on the environment. In some cases, they can be broken into smaller parts and used as rubber bark chips, as an additive in rubberised asphalt for roads, pavements and playgrounds, in thermal or acoustic insulation material or in footwear.
Like many natural resources, rubber has links to low pay and poor working conditions. However, in the fashion and footwear world, significant efforts are being made by brands to use fairly traded and sustainable natural rubber. The Rain Boot from Thesus is handmade in Sri Lanka from 100% Fair Rubber Association-Certified natural rubber, with fair trade premiums being used for projects to support local communities.
Waves sells FSC-certified 100% natural rubber flip-flop sandals and recycles discarded flip-flops and offcuts back into its manufacturing process to make new products. Consumers can return old flip-flops for a 10% discount on future purchases. Waves’ own sandals are taken to local rubber recycling, where they are converted into rubber matting.
Yulex produces the only commercially-available FSC-certified pure natural rubber materials. Brand partners include: Allbirds, Finisterre, Hermès, Hunter and Stella McCartney. Patagonia replaced neoprene in its products with Yulex natural rubber in 2016, reducing the carbon dioxide emissions in a wetsuit by up to 80%.
Returning to rubber’s roots, sustainable fashion designer Flavia Amadeu uses FSA wild rubber from the Amazon rainforest, where the trees are tapped less intensively so they can be harvested for generations rather than a couple of decades. Additionally, the rubber is processed using an alternative, chemical-free method developed by the Project Tecbor/Lateq from the University of Brasília.
In 2016, Michelin developed a global policy for sustainable natural rubber alongside the WWF, with fellow tyre manufacturers Pirelli, Bridgestone, Goodyear, Sumitomo, Continental, Yokohama, Hankook and Toyo Tires announcing their own sustainability policies soon after.
In 2018, the Global Platform for Sustainable Natural Rubber (GPSNR), was set up with the goal of bringing together several stakeholders to help make the rubber industry more sustainable, equitable and fair, by offering resources, a policy framework and a code of conduct.
While it is not straightforward and vulcanised rubber cannot be simply returned into its pre-hardened state, processes do exist for cutting the cross linked bonds and essentially ‘devulcanising’ rubber, by chemical, ultrasound, microwave or thermomechanical means. The recovered material is then mixed with virgin rubber for new uses. Martin’s Rubber uses a number of such processes to make its part-recycled Remould rubber products.

KEY FACTS:

28%

Of microplastics in the ocean comes from tyres shedding synthetic rubber.

27.4mn MT

In 2020, global production of rubber was an estimated 27.4 million metric tonnes.

800 million

Around 800 million modern car tyres are discarded across the world every year.

Key Questions to Ask

Could your rubber be driving deforestation?

Due to deforestation caused by land clearance for rubber plantations, the WWF calls for responsible production of rubber on low-quality, degraded land. Taking the time to trace your supply chain back to the plantation is a must to avoiding swapping the impact of synthetics for the impact of deforestation.

Can you use an alternative source of natural rubber?

Bridgestone and others have been experimenting with the evergreen guayule shrub as a new source of natural rubber, which is faster growing than the rubber tree and can grow in arid areas. Meanwhile, Continental is experimenting with taraxgum rubber made from dandelions.

Will you safeguard the future of rubber?

Natural rubber is on the EU’s list of critical raw materials and the risk of pathogens, as well as the inevitable droughts and flooding brought by climate change are threatening the fragile global supply. It would be responsible to engage on-the-ground experts, to help guide the volume and manner of your sourcing, so that you can help sustain rather than deplete resources.

Are you making a product that lasts?

Given that vulcanised rubber is not biodegradable and the raw material is at risk, rubber should only ever be on the table when you have long-term use in mind.