What is polyurethane?

The origin of polyurethane

Polyurethane sounds like an unfamiliar name, but is it really unfamiliar? We use polyurethane in one form or another every day in our lives and can be found in homes, offices and cars, for example: edges of refrigerators and freezers, building insulation, furniture cushioning, pillows, mattresses , auto parts, insoles, decompression toys, etc. These products play a vital role in making our lives more convenient, comfortable and environmentally friendly.

Polyurethane foam is a porous, cellular-structured, synthetic material made from the reaction of polyols and diisocyanates. Its structure is a composite of a solid phase and a gas phase. The solid phase is made from polyurethane elastomer, while the gas phase is air brought about by blowing agents.

The huge gas phase of polyurethane foams has good thermal and acoustic insulation, high force absorption, low density, and flexibility. Polyurethane foams are sometimes referred to as foam rubber, a broader type of material that include foamsmade from latex, neoprene, and silicone.

The history of polyurethane

The discovery of polyurethanes is attributed to Otto Bayer, dating back to the year 1937 together, and his coworkers at the laboratories of I.G. Farbenindustrie A.G. in Germany. The first polyurethane was formed by the reaction between a diamine-forming polyurea and an aliphatic diisocyanate. The polyurea was later replaced by glycol due to the enhanced properties of the polyurethane created.

The first patent for flexible polyurethane foam preparation was obtained by Zaunbrecher and Barth in 1942. The flexible polyurethane foam was created through simultaneous polyurethane synthesis and gas generation by combining organic toluene diisocyanate (TDI), aliphatic polyester, water, and catalyst. In this one-step process, polyurethane was formed by the reaction of the isocyanates with the hydroxyl-functional groups from the polyester, while its gas phase was formed by the generation of carbon dioxide. Carbon is a product of the reaction of diisocyanates with water. This one-step process was highly exothermic and resulted in scorching and fires, so it was then later transformed into a two-step process. This two-step process starts with the polymerization process (prepolymer preparation) and is followed by gas generation.

Polyether polyols in the form of poly tetramethylene ether glycol (PTMEG) were introduced in 1956 by DuPont. Later, BASF and Dow Chemicals developed polyalkylene glycols. Since then, polyether polyols have become the major polyols in the polyurethane manufacturing industry. Initially, polyurethane foam production was done in a two-step process. But with the development of catalysts andsurfactants, this was replaced by a one-step process. Further refining of blowing agents, polyether polyols, and polymeric isocyanates led to the advancement from flexible polyurethane foams to rigid polyurethane foams.

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