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FULL OF KNOWLEDGE BLOG ONSEN® / Expert Tips

What is polyurethane foam and why is it used in mattresses?

2 grudnia 2021
Pianka poliuretanowa, materace online, materac piankowy, sklep z materacami
Contents
Properties of polyurethane foams
Types of polyurethane foams
Testing of polyurethane foams
Polyurethane foams in mattresses
Every foam used in mattresses is polyurethane foam, also known as PUR foam. This group includes HR, V, and T foams – high-resilience, viscoelastic (memory), and traditional types. PUR foam owes its popularity to its unique physical and chemical properties, which can be easily modified. With the right parameters and a thoughtful combination, it’s possible to create excellent sleeping mattresses. It’s also used in furniture, car seats, and sports accessories, which makes it a common part of everyday life.

The production process of PUR foam generally involves combining two petroleum-based ingredients – polyol and isocyanate. The correct proportions of these substances, along with additives and foaming technology, determine the foam’s final properties. At this stage, its type, firmness, density, and durability are defined, all of which affect the final product’s longevity and comfort.

Bed mattresses made from this material are the only products on which a person spends, in a state of complete unconsciousness, an average of one-third of their life – without being able to influence their function in the moment. Unlike other foam products used consciously and with control, a mattress affects the body for about 8 hours every night. The quality of sleep directly impacts our daily functioning and well-being, making design and composition all the more important.
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Properties of polyurethane foams

It's important to note that polyurethane foams possess chemical and physical properties that allow them to be used even in extreme conditions, as the material withstands temperatures from -50 °C to 100 °C. Additionally, its thermal conductivity is very low. As a result, polyurethane foam offers excellent thermal and acoustic insulation, making it a multifunctional material.

By nature, PUR foam is resistant to mold and mildew and does not attract insects. At ONSEN®, we use only polyurethane foams that maintain their performance for many years, and their hypoallergenic properties have been confirmed by independent European quality certificates such as Oeko-Tex and CertiPUR.

At ONSEN®, we exclusively use HR and V foams, deliberately avoiding T foams. This allows us to create high-resilience ergonomic mattresses, as well as a collection of orthopedic pillows with truly anatomical shapes. The key lies in the careful selection of foam parameters and thoughtful design, along with collaboration with trusted suppliers. All this guarantees a healthy and comfortable sleep on an optimally designed mattress.
Viscoelastic foam is also a type of polyurethane foam.
It’s worth emphasizing that every foam in a mattress is polyurethane foam. Regardless of whether it’s HR, V, or T foam – they all originate from polyurethane. They differ only in foaming methods and parameters, but their chemical foundation remains the same. Of course, the properties of HR, V, and T foams vary significantly.

Unfortunately, many mattress manufacturers try to distort this reality. To differentiate their products from the competition, they assign invented trade names to the foams, which are not based on any standards or real technology. This creates the false impression for the customer that they’re dealing with a different material.

Many mattress sellers also use various tricks. It’s common to hear in stores that only T foam is polyurethane, while other foams fall into different categories. This is, of course, incorrect – all of these foams share a common chemical base: polyols and isocyanates. The production method determines whether it’s an open-cell foam or closed-cell, and influences other key parameters like density and firmness. Making an informed mattress choice requires knowledge of facts, not marketing gimmicks.
Materac hipoalergiczny, materace antyalergiczne, jak spać z uczuleniem, spanie z katarem

Types of polyurethane foams

The types of polyurethane foam available on the market play a key role not only in mattresses but also in upholstery products. While all of them are made from polyurethane, they differ in cell structure, density, and firmness. These differences determine whether polyurethane foam mattresses will be comfortable, durable, and breathable – or quite the opposite, deforming quickly and losing their properties.

The three main types of polyurethane foam produced today are HR, V, and T foams. Each type has different characteristics and applications in foam mattresses. High-resilience foam, marked with HR, is a dynamic open-cell foam. Visco foam, marked with the letter V, is a viscoelastic (memory) foam with variable viscosity. Traditional foams, marked with T, feature a closed-cell structure and lower durability.
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It’s important to remember that polyurethane foams are categorized by type as follows:
  • HR foams – breathable, flexible, and durable, making them the best choice for modern mattresses;
  • V foams – temperature-sensitive and collapse under body heat, which is why they are used in the second layer of the mattress;
  • T foams – relatively inexpensive but not durable, with little to no ventilation and a tendency to compress quickly.
There is also increasing mention of HD foam, which is a type of T foam with increased density.
Pianka poliuretanowa, pianki tradycyjne, materac piankowy, najlepsze materace
T foam (from the English word traditional) is a closed-cell foam in which the cells lack pores. When compressed, the air trapped inside causes the cell walls to rupture. This leads to the mattress quickly collapsing, along with a loss of elasticity and reduced product lifespan. T foam generally does not allow air to pass through, meaning it lacks ventilation.

T foams typically have a density of 14–40 kg/m³ and a firmness of 1.5–5.0 kPa according to the CLD standard. Their rebound elasticity is around 40%, and the tensile strength is at least 80 kPa, though it rarely exceeds that significantly. Their main advantage is low cost, but they quickly lose their performance. For this reason, T foams should not be used in high-quality sleeping mattresses.
Pianka poliuretanowa, pianki wysokoelastyczne, materac piankowy, najlepsze materace
HR foam (from the English high resilience) is an open-cell foam in which the cells are interconnected. This allows for free air circulation, improving mattress hygiene. As a result, high-quality HR foam mattresses are breathable and much better at wicking away moisture. The open-cell structure also gives the mattress a springy and responsive feel.

HR foams usually have a density of 25–40 kg/m³ and a firmness of 2.0–4.0 kPa according to the CLD standard. Their rebound elasticity is at least 55%, and their tensile strength is at least 100 kPa, often much higher. In practice, this means that HR foam mattresses not only offer better body support but also last longer. Additionally, they are hypoallergenic, lightweight, and comfortable for everyday use.
Pianka poliuretanowa, pianki memory, materac piankowy, najlepsze materace
V foam (from the English viscoelastic) is a thermoelastic foam, also known as memory foam. This is a viscoelastic material that responds to pressure and, more importantly, to body temperature. Thanks to this property, a visco foam mattress adapts to the user's body shape, creating a feeling of being gently enveloped. However, it is not a responsive foam and therefore does not actively support the spine. While it does reduce pressure on muscles and joints, this comes at the expense of proper support.

Visco foams typically have a density of 45–50 kg/m³ and a firmness of 1.5 kPa according to the CLD standard. Their rebound elasticity is quite low at around 15%, though their tensile strength is at least 110 kPa. Because of these properties, V foams are often used in anti-bedsore mattresses. Although they don’t support correct spinal alignment, they significantly improve circulation. A notable drawback of visco foams is their reduced breathability, as their cells are partially closed.
Materace piankowe, pianka visco, materac wysokoelastyczny, sklep z materacami

Testing of polyurethane foams

ISO 2439 defines the procedure for testing the indentation hardness of polyurethane foams, which simply refers to the foam’s firmness. The method involves pressing a piston of standardized diameter into a foam sample and measuring the force required to reach a specific depth. The result can be expressed in kilopascals (kPa) or newtons (N). This parameter is crucial when evaluating mattress comfort, as it indicates how the material reacts to body pressure.

ISO 1798 specifies the method for testing a foam’s tensile strength and its elongation at break. The foam sample is stretched in laboratory conditions until it tears. This parameter shows how foam reacts to prolonged stress and deformation, helping to determine its durability. For foam mattresses, it indicates whether the material will withstand intensive use and resist tearing during daily use.

ISO 8067 tests the tear resistance of polyurethane foam, which is also relevant for mattresses. A cut is made in the foam sample, and then the force required to continue tearing is measured. This parameter matters for mattresses, pillows, and upholstery, as such products are naturally subject to mechanical damage like pulling or point pressure in daily use.

ISO 3385 defines the fatigue test, which measures the loss of thickness and firmness after prolonged loading. The foam sample undergoes repeated compressions to simulate years of mattress use. This is a particularly important parameter for evaluating the long-term durability of foam mattresses.
The industry also uses ASTM standards, with ASTM D3574 being one of the most important. It covers a range of polyurethane foam tests, including density, firmness, tensile strength, and fatigue resistance. This standard is commonly used in the automotive, furniture, and mattress industries, particularly in the United States. It allows manufacturers to certify the quality of their products according to international standards.

The German standard DIN 53579 focuses on measuring the indentation hardness of foam in entire foam blocks. Compared to ISO 2439, DIN allows testing not only lab samples but also full components. This is important when evaluating mattresses and furniture, as it provides more practical results related to actual usage.

Another key standard is PN-EN ISO 845:2010, which describes the method for determining the density of polyurethane foams – a factor that directly affects their durability. The test is conducted on a dried sample, and the result helps assess the suitability of the foam for mattress use. Density has a direct impact on longevity, resistance to deformation, and sleep comfort, although it is not related to firmness.
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Polyurethane foams in mattresses

As is well known, the use of polyurethane foams in the mattress industry is extremely widespread. They are found both in low-cost mattresses sold in supermarkets and in premium mattresses offered by smaller manufacturers. However, the difference isn’t just the price – it’s mainly the type and specifications of polyurethane foam used in the mattress. Sometimes, more expensive models use the same foams as cheaper ones, with the higher price resulting only from a retail markup. That’s why it’s crucial for consumers to understand the real foam parameters instead of relying solely on marketing.

In general, polyurethane foam in mattresses should be flexible, resilient, and appropriately firm. The key parameters are foam density and firmness, which must be listed separately. Unfortunately, many sellers intentionally mislead customers by claiming that density and firmness are the same. In practice, foam density directly affects durability and resistance to deformation, while firmness shows how the foam responds to pressure. Making an informed mattress choice requires knowing both values, not just one.

Every foam used in a mattress has an alphanumeric designation based on international standards. Letters indicate the type of foam, while numbers refer to its density and firmness. For example, the label HR3020 refers to high-resilience foam with a density of 30 kg/m³ and a firmness of 2 kPa. In practice, this is a breathable and responsive polyurethane foam that is far more durable than traditional T foam. Understanding these labels helps the customer assess whether a given mattress is truly worth its price.
Materac z pianki poliuretanowej, materace online, sklep z materacami, producent materacy
In spring mattresses, polyurethane foams are typically used as a simple comfort layer that separates the springs from the mattress cover. Unfortunately, many low-cost models use T18, T25, or T30 foams – all of which are traditional closed-cell foams. Manufacturers often promote only the foam density, which is quite low, while omitting the firmness value. Such a mattress may initially feel comfortable, but after just a few months of use, it often develops indentations, back pain, and sleeplessness caused by the deteriorating foam. T foam quickly loses its properties, forcing the user to replace the mattress sooner than expected.
Materac z pianki poliuretanowej, materace online, sklep z materacami, producent materacy
The situation is different in memory foam mattresses. Here, thermoelastic foam is used – commonly known as memory foam or sometimes viscoelastic foam. Its unique and often misleading feature is its response to pressure and body temperature, which causes the foam to soften with heat and mold to the body. This approach reduces pressure points but has significant downsides. Under pressure, visco foam cells close, which restricts the mattress’s breathability and leads to sweating. That’s why the best results come from using visco as a second layer, not the top one.

It’s worth noting that memory foam has a fascinating history. It was developed in the 1960s at NASA’s request, in search of a material capable of absorbing G-forces to enhance safety in space seats. Its unique response to pressure and body heat quickly found applications beyond aerospace. First in hospitals for anti-bedsore mattresses, and shortly afterward – although not originally intended for this – in sleeping mattresses, creating an illusion of comfort. While often marketed today as a novelty, visco foam is over 50 years old, and its use in mattresses is steadily declining internationally.
Materac z pianki poliuretanowej, materace online, sklep z materacami, producent materacy
The best solution is high-resilience mattresses, though not all of them. It's always important to pay attention to the mattress design to ensure it truly provides support and promotes health. HR foam has an open-cell structure, which guarantees ventilation, eliminates the sinking effect, and ensures great responsiveness. Only foams with high density and resilience maintain their properties for many years. However, to fully benefit from HR foam, its layers must be properly combined. That’s why the order, thickness, density, and firmness of each layer in the mattress must be right – these elements determine the final quality.
Materac z pianki poliuretanowej, materace online, sklep z materacami, producent materacy
An excellent example of well-thought-out design is the Osaka Air mattress, which has become a symbol of comfort and wellness. It features several layers of high-quality foam. On the top is open-cell HR30100 foam, which supports the body. The second layer is V50075 foam, which contours the body without causing a sinking sensation. It also includes ventilation channels and an innovative Aero 3D mesh that eliminate heat and moisture build-up. The stable base is made of high-density HR50190 foam, which ensures durability and structural stability. As a result, the Osaka Air mattress is ergonomic, breathable, and resistant to deformation.

We spend an average of 8 hours a day on a mattress – up to 32 times more than behind the wheel of a car. That’s why choosing the right sleeping mattress is more important for your health and wellbeing than choosing a car. The right polyurethane foam is the best material for mattress construction – but only when the foam parameters are clearly stated and properly selected. At ONSEN®, we prioritize full transparency: we don’t hide foam specifications, and our innovative mattresses and orthopedic pillows made from open-cell foams are also certified as Class I medical devices, confirming their health-promoting properties.
We spend up to 32 times more time on a mattress than behind the wheel of a car!
In summary, choosing the right polyurethane foam is crucial for healthy sleep and mattress durability. The cheapest options based on T25 or T30 foam tend to lose their properties quickly. These mattresses sag and cause back pain, which should be avoided. For this reason, such foams should be used only in occasional furniture or low-cost toppers, not in proper sleeping mattresses.

Anyone considering HR foam versus T30 should understand that the difference between these materials is fundamental. HR foam stands out thanks to its open-cell structure, offering ventilation, resilience, and long lifespan. On the other hand, T30 foam, despite its seemingly decent density, deforms quickly and fails to support the spine properly. That’s why informed customers typically steer clear of T foam.

It’s also important to note that a firm foam mattress isn’t necessarily the best choice. The idea that hard mattresses are ideal is a myth. Properly selected firmness levels in HR foams, paired with V foam as a second layer, provide ergonomic support that adapts to the body without the “sinking in” effect typical of memory foam – while still protecting the spine and joints during sleep.

Polyurethane foams are not just mattress sponges; they are advanced materials with specific parameters. Not all foams are the same – differences are substantial. Cheap, closed-cell T foams are non-durable and poorly ventilated, whereas HR and V foams, when used properly, offer modern technology, comfort, and longevity, depending also on mattress design. That’s why, when choosing a mattress, it’s essential to look beyond price and focus on the actual foam specifications.

We also encourage you to explore other articles on the best sleep and health blog, as well as the Encyclopedia of Healthy Sleep prepared by the ONSEN® team of specialists. For those who care about spine health, we recommend a set of spine exercises prepared by our physiotherapist.
Materace piankowe, pianka visco, materac wysokoelastyczny, sklep z materacami

FAQ: Polyurethane foam

What is polyurethane foam used for?

Polyurethane foam, also known as PUR foam, is used across many industries. Polyurethane sponges are found in mattresses, furniture, medical products, and sports accessories. This is due to its versatile physical and chemical properties, which can be easily customized. Its resistance to mold and mildew and low thermal conductivity make it durable, comfortable, and usually hypoallergenic.

Is a mattress made of polyurethane foam good?

Yes, a polyurethane foam mattress can be excellent ? provided the foam type is appropriate. HR and V foams offer ergonomic comfort and durability due to their structure and performance. In contrast, cheap T foams quickly lose their qualities. Key factors include foam density, firmness, and a thoughtful, health-oriented design. It?s best to avoid T foams and also avoid mattresses with V foam as the top layer.

Is polyurethane foam good for sleeping?

Absolutely, as long as it?s the right kind. HR foams (high resilience) are breathable, springy, and durable ? ideal for a hygienic sleep. V foams (memory foam) adapt to the body and reduce pressure points but limit airflow and have low responsiveness. That?s why they work best as a second layer. T foams are the worst option for sleep ? they are not durable and have a closed-cell structure.

What type of foam makes the best mattress?

The best mattresses combine HR foam in the top layer ? for breathability and stability ? with V foam underneath to contour the body. T foams are not suitable due to quick wear and poor ventilation.

What is better for sleep ? foam or springs?

PUR foams (especially HR and V) provide better body contouring, quietness, and hygiene than spring mattresses. Spring mattresses often use T foam as the comfort layer, which wears out quickly and reduces comfort. Polyurethane foam distributes body weight in all directions, while springs only move vertically. As a result, foam mattresses support the spine better ? regardless of whether the springs are classic, pocket, or multipocket, since the spring pockets are usually glued on the sides and top/bottom anyway.

Contents
Properties of polyurethane foams
Types of polyurethane foams
Testing of polyurethane foams
Polyurethane foams in mattresses
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