High impact absorption composite flooring materials

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As a market and technology leader in polyurethane-based materials, BASF has successfully combined its diverse product range with its application-driven R&D to develop a composite flooring material with excellent absorption. shock and high rebound properties. This polyurethane-based flooring structure can be used in public areas, indoor and outdoor tracks and children’s play areas.

Active lifestyles and increased sports participation in Europe, North America and the Asia-Pacific region are creating demand for multi-functional and safe sports facilities, where high-efficiency absorbent materials can help athletes, casual users and children achieve their best performance, while at the same time reducing the risk of exercise-related injuries.

BASF’s shock-absorbing flooring material combines properties previously thought to be incompatible, such as exceptional softness, cushioning and excellent resilience. To achieve this, the company used thermoplastic polyurethanes (TPUs), which are one of the most versatile engineering thermoplastics.

Basic research leads to high performance absorbent materials

TPU is a block copolymer with a macromolecular chain composed of alternating soft and hard segments. During processing, due to the distinct polarity of soft and hard segments, partial phase separation occurs in the bulk material, which leads to the formation of a microdomain structure. The hard domains act as physical crosslinkers and contribute to the mechanical strength, while the soft domains give the elastic properties of the material.

This fundamental knowledge allowed BASF scientists to tune the properties of TPU by changing the domain ratio. The result is a wide range of materials that range from thermoplastic elastomers to rigid thermosetting foams and adhesive compounds that can be reprocessed or recycled like any other thermoplastic material due to their lack of covalent cross-linking.

Click to learn more about vibration and shock test systems.

Application of the new material as a shock absorbing flooring surface requires the elasticity of an elastomer (rubber) to provide excellent shock absorption and rebound, ease of application (with varying thickness ), highest possible wear resistance, low maintenance and resistance to various weather, oil and water conditions.

Thermoplastic polyurethane foams provide excellent flexibility and durability

At the heart of the excellent shock absorption properties of the newly developed flooring material is the world’s first expanded thermoplastic polyurethane (E-TPU) marketed by BASF in 2013 under the name Infinergy®.

Expansion (foaming) is particularly beneficial for TPU and helps overcome its relatively high cost and high hardness. Foaming of the material results in reduced material consumption (due to volume expansion) and hardness can be effectively reduced without the addition of plasticizers.

The high demand for low-density TPU foams (more than 23 million tons in 2019) and their various applications as lightweight and highly flexible absorbent materials with high cushioning effect and rapid energy restoration after compression have concentrated extensive academic research and industrial research and development on polymer foam technologies. As one of the technology leaders in the field, BASF offers a wide range of particle foams, from rigid foam, such as expanded polystyrene (EPS), to soft and stretchy E-TPU.

Closed cell foam particles with exceptional elasticity and shock absorption

A special grade of BASF’s closed-cell elastic particle foam, produced by expanding the well-established Elastollan® TPU and Infinergy®SP brand, combines the properties of TPU with the advantages of foams, making it as elastic as rubber. rubber but much lighter.

The closed cell structure of the foam particles prevents water absorption, making it particularly suitable for all-weather sports flooring applications. E-TPU provides significantly higher rebound height than EPS and Expanded Polypropylene (EPP).

In a high frequency fatigue test (5 Hz at a maximum pressure of 250 kPa), Infinergy® retained 92.5% of its original thickness (still returning almost all of the energy that was to it). applied) after 40,000 cycles. At the same time, foams of homologous particles remained permanently compressed.

Especially for outdoor applications, even at temperatures of -20°C, Infinergy® does not lose its elastic properties. Table 1 summarizes the basic physical characteristics of Infinergy® and its counterparts.

Table 1. Overview of key physical properties of Infinergy® E-TPU

Equipment

Infinergy®

EPP

PES

Density [kg m-3]

110 – 320

20 – 200

15 – 30

Ultimate Tensile Strength [kPa]

600

270-1930

80 – 900

Water absorption (in 24h) [% vol.]

Working temperature range [°C]

-20 to +40

-40 to +60

-150 to +80

Bounce (ball bounce test) [%]

55

30

20

Elongation at break [%]

100 – 150

BASF’s impact-absorbing flooring solutions are based on Elastan® and Elastocoat® series of TPU coatings and adhesives combined with Infinergy®SP particulate E-TPU foam. This combination results in a variety of porous and non-permeable surfaces suitable for walkways, athletic tracks, school grounds and playgrounds.

Durable Polyurethane Flooring Structures

Polyurethane-based flooring structures offer superior tensile strength and durability and consist of a layer of Elastocoat® in which Infinergy®SP is embedded (with Elastan® as a binder) for excellent dirt absorption. shocks and excellent rebound.

Thanks to the exceptional cushioning effect of the E-TPU particles, the ground surface absorbs the kinetic energy generated when the runner’s feet land. It returns part of the energy to the runner, while cushioning the impact. In this way, it provides a safer sports experience and a reduced risk of sports injuries.

When used in playgrounds, the high performance surface softens drops very effectively and provides a safe play environment.

Low environmental impact and high sustainability

The absorbent material also gets high scores for durability. Its manufacture is entirely based on ethylene diphenyl diisocyanate (MDI), which means that the production cycle does not require additional solvents, chlorinated paraffin (as a plasticizer), heavy metal catalysts or methylene orthochloroaniline (MOCA) as curing agents.

It is also free of polycyclic aromatic hydrocarbons (PAHs), is fully recyclable and can be applied with conventional tools. Thanks to its low weight, the material can be used in places where terrain restrictions apply. It is suitable for indoor and outdoor use as it can be applied in both water permeable and waterproof formulations. All of this makes new polyurethane-based flooring structures a top choice for modern, durable and safe sports fields, playgrounds, gymnasiums and running tracks.

References and further reading

Advanced flooring solutions. [Online] www.basf.com. Available at: https://www.basf.com/gb/en/who-we-are/core-topics/urban-living/advanced-flooring-solutions.html (accessed April 2, 2020).

Infinergy® – Small pearls, big possibilities. [Online] www.basf.com. Available at: https://plastics-rubber.basf.com/global/en/performance_polymers/products/infinergy.html (accessed April 02, 2020).

Floor structures for sports fields and playgrounds. [Online] www.basf.com. Available at: https://plastics-rubber.basf.com/asiapacific/en/performance_polymers/products/sportsflooring.html (accessed April 2, 2020).

Gama, N.V., et al. (2018) Polyurethane foams: past, present and future. Materials11, 1841. Available at: https://doi.org/10.3390/ma11101841

Sun, X., et al. (2015) Manufacture of highly expanded thermoplastic polyurethane foams using microcellular injection molding and gas-filled granules. Polymer Engineering and Science55, 2643-2652.

Somarathna, HMCC, et al. (2018) The Use of Polyurethane for Structural and Infrastructural Engineering Applications: A State of the Art Review. Construction and building materials, 190, 995-1014. Available at: https://doi.org/10.1016/j.conbuildmat.2018.09.166

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