Polyurethane foam explained

Polyurethane foam is a specialist material used for thermal insulation and other applications. It is a solid polymeric foam based on polyurethane chemistry.

Flexible polyurethane foam

The so-called flexible polyurethane foam (FPF) is produced from the reaction of polyols and isocyanates, a process pioneered in 1937.[1] FPF allows for some compression and resilience that provides a cushioning effect. Because of this property, it is often used in furniture, bedding, automotive seating, athletic equipment, packaging, footwear and carpets.[1]

Rigid polyurethane foams

Rigid polyurethane foam has many desirable properties which has enabled increased use in various applications, some of which are quite demanding.[2] [3] These properties include low thermal conduction making it useful as an insulator. It also has low density compared to metals and other materials and also good dimensional stability.[4] A metal will expand on heating whereas rigid PU foam does not. They have excellent strength to weight ratios.[5] Like many applications, there has been a trend to make rigid PU foam from renewable raw materials in place of the usual polyols.[6] [7] [8]

They are used in vehicles, planes and buildings in structural applications.[9] They have also been used in fire-retardant applications.[10]

Space shuttles

Polyurethane foam has been widely used to insulate fuel tanks on Space Shuttles. However, it requires a perfect application, as any air pocket, dirt or an uncovered tiny spot can knock it off due to extreme conditions of liftoff.[11] Those conditions include violent vibrations, air friction and abrupt changes in temperature and pressure. For a perfect application of the foam there have been two obstacles: limitations related to wearing protective suits and masks by workers and inability to test for cracks before launch, such testing is done only by naked eye.[11] The loss of foam caused the Space Shuttle Columbia disaster. According to the Columbia accident report, NASA officials found foam loss in over 80% of the 79 missions for which they have pictures.[11]

By 2009 researchers created a superior polyimide foam to insulate the reusable cryogenic propellant tanks of Space Shuttles.[12]

Notes and References

  1. Web site: What Is Flexible Polyurethane Foam?. Polyurethane Foam Association. 1 February 2023.
  2. McIntyre . A. . Anderton . G. E. . 1979-02-01 . Fracture properties of a rigid polyurethane foam over a range of densities . Polymer . en . 20 . 2 . 247–253 . 10.1016/0032-3861(79)90229-5 . 0032-3861.
  3. Chen . W. . Lu . F. . Winfree . N. . 2002-03-01 . High-strain-rate compressive behavior of a rigid polyurethane foam with various densities . Experimental Mechanics . en . 42 . 1 . 65–73 . 10.1007/BF02411053 . 1741-2765.
  4. Tu . Z. H . Shim . V. P. W . Lim . C. T . 2001-12-01 . Plastic deformation modes in rigid polyurethane foam under static loading . International Journal of Solids and Structures . en . 38 . 50 . 9267–9279 . 10.1016/S0020-7683(01)00213-X . 0020-7683.
  5. Thirumal . M. . Khastgir . Dipak . Singha . Nikhil K. . Manjunath . B. S. . Naik . Y. P. . 2008-05-05 . Effect of foam density on the properties of water blown rigid polyurethane foam . Journal of Applied Polymer Science . en . 108 . 3 . 1810–1817 . 10.1002/app.27712.
  6. Chian . K. S. . Gan . L. H. . 1998-04-18 . Development of a rigid polyurethane foam from palm oil . Journal of Applied Polymer Science . en . 68 . 3 . 509–515 . 10.1002/(SICI)1097-4628(19980418)68:3<509::AID-APP17>3.0.CO;2-P . 0021-8995.
  7. Hu . Yan Hong . Gao . Yun . Wang . De Ning . Hu . Chun Pu . Zu . Stella . Vanoverloop . Lieve . Randall . David . 2002-04-18 . Rigid polyurethane foam prepared from a rape seed oil based polyol . Journal of Applied Polymer Science . en . 84 . 3 . 591–597 . 10.1002/app.10311 . 0021-8995.
  8. Guo . Andrew . Javni . Ivan . Petrovic . Zoran . 2000-07-11 . Rigid polyurethane foams based on soybean oil . Journal of Applied Polymer Science . en . 77 . 2 . 467–473 . 10.1002/(SICI)1097-4628(20000711)77:2<467::AID-APP25>3.0.CO;2-F . 0021-8995.
  9. Menges . G. . Knipschild . F. . August 1975 . Estimation of mechanical properties for rigid polyurethane foams . Polymer Engineering and Science . en . 15 . 8 . 623–627 . 10.1002/pen.760150810 . 0032-3888.
  10. Zhu . Menghe . Ma . Zhewen . Liu . Lei . Zhang . Jianzhong . Huo . Siqi . Song . Pingan . 2022-06-10 . Recent advances in fire-retardant rigid polyurethane foam . Journal of Materials Science & Technology . en . 112 . 315–328 . 10.1016/j.jmst.2021.09.062 . 1005-0302.
  11. Web site: Get Your Foam On. Slate. Michelle Tsai. 13 August 2007. 1 February 2023.
  12. Web site: Insulating Foams Save Money, Increase Safety. NASA. 2009. 1 February 2023.

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