Polyurethane (PU) and Thermoplastic Polyurethane (TPU) differ primarily in their chemical structure and physical properties. PU is typically a thermosetting polymer, which means once it has cured, it cannot be melted and reshaped.
On the other hand, TPU is a type of thermoplastic polyurethane, signifying it can be melted, processed, and remolded multiple times. This key difference makes TPU more flexible and recyclable than conventional, thermosetting PU. TPU's unique structure gives it a combination of rubber-like elasticity and the toughness of plastic.
In contrast, PU is known for its rigidity and resistance to abrasion and solvents once set. In practical applications, TPU is often used in cases where durability and flexibility are needed, like in phone cases or shoe soles. In contrast, PU is used for items like insulation or rigid foams where reshaping is not required after the product is formed.
What are PU and TPU?
PU plastic combines the chemical compounds, diisocyanates, and polyols into a polymer chain. The type of PU plastic produced largely depends on what diisocyanates and polyols are used during this chemical reaction.
These slight changes during the production process have created many different types of PU, each with slightly different characteristics and properties.
TPU, on the other hand, undergoes a similar production process but with one small difference.
TPU is also made by combining diisocyanates and polyols but includes a “chain extender” in the polymer chain, which allows TPU to be melted at extremely high temperatures several times over without the polymer chain breaking down… this is a fancy way of saying TPU is heat resistant!
PU plastic is known for its versatility and durability. There are many types of PU plastic out there with many different uses.
One interesting characteristic of thermoplastics like TPU is that they can be heated and remolded into different shapes, which is why TPU is a popular choice for industry and manufacturing applications. TPU is also known for being extremely elastic and resistant to deformation or environmental factors that might wear or cause abrasions on other kinds of plastic.
Polyurethanes were first invented in the 1930s by German chemist Dr. Otto Bayer. During World War II, there was a shortage of natural rubber products due to military occupations in regions that produced rubber, leading to serious issues in supply chains.
Dr. Bayer and his team saw PU plastic as the solution since it mimicked rubber's durability and flexibility. Over time, more variations of PU came on the market, and it found a place in many different industries, from fashion to furniture to automotive products.
TPU plastic wasn't discovered until the 50s. At this time, more funding was being put into researching how to create new materials from different chemical compositions. TPU quickly gained popularity since it was just like PU, but it was stronger, more resistant to abrasions, and could be heated and remolded, allowing the material to have a longer lifespan.
Common Uses for TPU and PU Plastics
Today, both TPU and PU plastics have tons of uses, including:
- Insulation of refrigerators and freezers
- Building insulation
- Phone cases
- Cushioning for furniture
- Automotive parts (i.e., car bumpers, fuel lines, interior trim, and gaskets)
- Coatings and adhesives
- Composite wood panels
- Shoe and boots
- Clothing and sportswear
- Accessories (i.e., handbags and belts)
- Medical devices (i.e., catheters and surgical instruments)
- Cables and electrical wiring
PU plastic is often used as a “faux vegan leather” in the fast fashion industry. For example, PU is a common vegan fabric substitute for leather called sustainable “vegan leather.” This is greenwashing, if you ask me! I think plant-based leather like cacti leather, apple leather, or pineapple leather is a much more sustainable option and won’t break down into microplastics.
While vegan leather is likely better than regular leather from a sustainability standpoint, it still creates greenhouse gas emissions and pollution during production and disposal.
This leads up to our next point…
Are PU and TPU sustainable? Not exactly.
First, PU and TPU are synthetic plastics, meaning they are not biodegradable or compostable. If either type of plastic were sent to a landfill to degrade, it would break down into tiny microplastics that could enter our waterways and aquatic food webs.
The production of PU and TPU both come with issues as well. Non-renewable resources like crude oil and natural gas must be extracted from the ground to make plastic. This process typically involves drilling or mining the earth and nasty tailing ponds. When not properly managed, the extraction of fossil fuels can have devastating impacts on the surrounding ecosystem.
Once extracted, the fossil fuels are then processed into plastic. This step releases greenhouse gases like carbon dioxide and methane into the atmosphere. If you haven't heard, these two greenhouse gasses are the primary drivers of climate change!
As you can see, the production of plastics (like PU and TPU) and climate change go hand in hand.
Conversely, most municipalities can recycle PU and TPU into new products. However, it’s hard to know how often PU and TPU truly get recycled since 91% of plastic doesn’t get recycled.
Health and Safety
PU and TPU are considered safe for general use since they don’t contain BPA, endocrine-disrupting chemicals, or phthalates. However, when mixed with other additives, exposure to PU and TPU may lead to health problems for individuals with pre-existing medical conditions.
For example, spray PU foam is used for insulation purposes and is known to contain flame retardants or other chemicals that are harmful to human health.
According to the EPA, individuals with a history of skin conditions, respiratory allergies, asthma, or prior isocyanate sensitization should review the product information when using spray PU foam and “consider safer alternatives''.
PU and TPU are considered more affordable than other raw materials like rubber or leather.
Advantages and Disadvantages: PU vs. TPU
Let's look at PU first.
… and TPU?
Is TPU more flexible than PU?
Yup! TPU can stretch and bend into many forms, making it more resistant to cracking or breaking. This characteristic is extremely handy when considering all the different uses of TPU.
Can both PU and TPU be recycled?
Depending on what form it’s in, most recycling facilities can take and recycle PU and TPU plastic. However, I would always recommend double-checking what the recycling facilities in your area will and will not accept since some municipalities have their regulations.
Which is more durable: PU or TPU?
While both PU and TPU are durable plastics, TPU is known for being the most durable since it is made specifically to be more flexible and resistant to wear and tear.
Are there any allergic reactions associated with PU or TPU?
When mixed with other additives, PU or TPU may cause allergic reactions for those with pre-existing health conditions. However, PU and TPU are both considered safe for general use.
Which is more environmentally friendly?
PU and TPU can be recycled; however, because TPU is a more durable material, an item made from TPU is more likely to last longer and won’t need replacing as quickly. Since one of the five R’s of zero waste is “refuse” (new stuff), I will give TPU the win.
How do I care for products made from PU or TPU?
Like all plastics, PU and TPU-based products will last longer when better cared for. I would recommend storing products made from either material in a cool, dry place in your home and avoiding harsh chemicals on your item, as this might cause discoloration over time.
I believe natural cleaning products are how to clean your counters, floors, and stuff!
PU and TPU have their advantages and disadvantages. They are strong, flexible, and durable materials with many different uses. While less affordable, TPU is slightly more elastic and durable and can easily be reprocessed for new uses.
TPU and PU are safe to use and don’t contain BPA, PVC, endocrine-disrupting chemicals, or phthalates. From an environmental perspective, TPU and PU can be recycled. However, at the end of the day, PU and TPU are both plastic, which means they were made using fossil fuels and are not biodegradable.
If you are into sustainable living, I understand wanting to avoid exposure to all plastics whenever possible. Fortunately, there are many substitutes out there that are more sustainable and 100% plastic-free.
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