Flexible HR PU, also known as flexible polyurethane, is a highly versatile material that has become an increasingly popular engineering option for a variety of industrial applications. It has been widely used in the transport industry.

In addition, high resilience polyurethane is a very durable material. This is especially important for the manufacture of products that undergo intense use, such as transport. This makes HR flexible PU an excellent option for manufacturers looking for products of high quality and durability.

The term resilience can be found in different polyurethane foams. In elastomers, resilience is defined as the relationship between the total energy supplied to produce a deformation and the energy restored after that deformation. That is, in general terms, resilience is the percentage of recovery after a deformation and this depends on the deformation speed.

A high resilience indicates that a product completely and quickly recovers its original shape, while a low resilience indicates that a product partially and slowly recovers its original shape. However, in the rest sector, the term resilience refers to materials that combine flexibility, resistance and damping properties. Resilience is a measure with which to rate the comfort that a mattress has, the greater the resilience, the more comfort.

Silicone stabilizers are a relevant part in the formation processes of flexible HR PU. These stabilizers are used to improve the performance of products, while improving their durability. Stabilizers are an essential part of the manufacture of flexible HR PU, since they help prevent the degradation of materials, while defining some properties or others according to customer needs. Silicone surfactants are copolymers formed by a silicone base and polieteres, usually polyethylene oxide chains and polypropylene oxide chains. Surfactants condition the formation of fine cells, thick cells, closed cells and open cells, and these cellular structures influence the final properties of PU foam.


Surfactants for flexible HR PU

Concentrol’s surfactants of the STB PU-12XX range are designed for high resilience HR PU foam. These formulations require stabilization and regulation of efficient cells, which is achieved through TDI systems, MDI or mixtures of both. Therefore, it is necessary to offer a wide variety of additives to meet all needs. These systems are stable and a balanced foam opening is sought.

One of the requirements that are usually requested is a low compression force. The optimal compression level can be achieved with the proper selection of surfactant.

Due to the increasingly strict legislation of the automobile and mattress industries, one of the priorities is to minimize the contribution of volatile compound emissions. These emissions are divided into VOC (volatile organic compounds), FOG (organic compounds of “fogging”), VVOC (very volatile organic compounds) and SVOC (semi-volatile organic compounds). As an example, VOCs easily detach from PU foam when the car is closed and the internal temperature is between 25 °C and 90 °C. FOGs are VOCs plus SVOCs that evaporate at temperatures above 90 °C.

In this way, in recent years Concentrol has investigated the way to reduce VOC, FOG and aldehydes of silicone surfactants with a new generation of products that allow obtaining PU foams with emission values related to stabilizers lower than 20ppm (for a dose of 1pphp).



Phthalates are a group of chemical synthetic plastics. These compounds have received a bad reception in recent years, which has led to the prohibition and elimination of some of them in silicone surfactants.

The regulations do not restrict the use of all phthalates and some surfactants still contain these products. In addition, in some markets there are low smell requirements, mainly attributed to aldehyde compounds. For these reasons, there are currently three types of products within the STB PU-12XX line, although among them there are no performance differences in PU foam:

  • STB PU-12XX: First designed line that carries phthalate compounds.
  • STB PU-12XX PF: Second line designed free of phthalates but with high content of aldehydes and aromatics, aimed at the European market.
  • STB PU-12XX PFJ: Third line designed, free of phthalates with low content of aldehydes and aromatics, aimed at the Asian market, China and Japan especially.

Concentrol carries out constant research to develop surfactants for flexible HR PU that meet the needs of its customers and the market. These products offer innovative solutions for applications related to all types of industry.

Research also allows us to offer response to new regulations and develop products for markets around the world.