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When choosing PU foam, you need to consider the following points
Density is a key factor in choosing PU foam. The performance of PU foam varies greatly from one density to another. Low-density PU foam (e.g., density between 10 - 30kg/m³) is usually softer, with good elasticity and cushioning properties. This type of foam is suitable for applications that require a high degree of softness, such as sofa padding and shoe insoles. It can provide a comfortable touch and a certain degree of shock absorption effect.
Higher density PU foam (density of 30 - 100kg/m³ or even higher) is more compact, with better strength and compression resistance. In the need to withstand greater pressure or to provide stable support, such as the seat cushion part of the car seat (especially some high-performance car seats, need to withstand the weight of the driver and passengers as well as in the process of driving a variety of dynamic pressure), sound and heat insulation panels for construction, etc., high-density PU foam is a better choice.
PU foam hardness is generally measured by Shore hardness. Lower hardness foam (Shore hardness of 10 - 30A or so) is soft to the touch, easy to be compressed. This is good for applications that require frequent compression and recovery, such as foldable protective pads, cushioning materials for packaging, etc.
Higher hardness foams (Shore hardness 40 - 80A) are more rigid and perform well in applications where heavier objects need to be supported or shapes need to be stabilized. For example, in the manufacture of molds or some industrial equipment support shims, higher hardness PU foam can provide better shape stability and support.
Elastic recovery rate reflects the ability of PU foam in compression after the return to its original state. For some of the foam products need to be used repeatedly for a long time, such as sports protective gear, mattresses, etc., a high elastic recovery rate is very important. Good PU foam can be compressed quickly and almost completely restored to its original shape and size, which can ensure that it is still able to provide good cushioning and support performance after repeated use. Generally speaking, high quality PU foam elastic recovery rate can reach more than 90%.
Compression permanent deformation refers to the foam at a certain temperature and pressure, after a certain period of time after compression, removal of pressure can not be restored after the degree of deformation. Lower compression permanent deformation is ideal, especially in some of the shape of the higher precision requirements of the application. For example, in the packaging and support of precision instruments, if the compression permanent deformation of PU foam is too large, it may lead to the instrument in the packaging or placement process can not be stable support, thus affecting the safety and accuracy of the instrument.
According to the different application scenarios, PU foam needs to have different temperature resistance. In some high-temperature environments, such as automotive engine compartment seals or industrial equipment insulation materials, the need to choose a higher temperature resistance of PU foam. Generally speaking, the ordinary PU foam temperature range of - 20 ℃ to 80 ℃ or so, but there are special high-temperature resistant PU foam, its maximum operating temperature can reach 120 ℃ or even higher.
In low-temperature environments, such as some outdoor refrigeration equipment insulation materials or cold regions of the building insulation materials, PU foam needs to remain in the low-temperature elasticity and insulation performance, not because of the low temperature and become brittle and hard.
Flame retardancy is an important consideration in many application scenarios, such as building materials, transportation interiors, and electronic equipment. According to different fire rating requirements, you can choose different flame retardant properties of PU foam. Some PU foam has been specially treated with self-extinguishing properties, which can automatically stop burning when encountering an ignition source, preventing the spread of fire. This is essential to protect the safety of life and property.
For some contact with the human body PU foam products, such as shoe insoles, mattresses, sofas, etc., breathability is to be considered. Good breathability allows air to circulate between the inside and outside of the foam, avoiding a stuffy feeling and moisture accumulation. Breathable PU foam contributes to the comfort of the user, especially during prolonged use.
If the PU foam may come into contact with a variety of chemicals, such as in the chemical equipment sealing, automotive parts (may come into contact with fuel, lubricants, etc.) and other application scenarios, you need to consider its chemical resistance. Different PU foams have different resistance to chemicals, some foams can resist acids, alkalis, organic solvents and other chemicals, while others may be more sensitive.
