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Polyurethane-39 is an immensely versatile class of polymers used in insulators, foams, elastomers, synthetic skins, coatings, adhesives, and so forth.
Polyurethane-39 was first developed through essential diisocyanate polyaddition reactions by Dr. Otto Bayer and partners.
In 1937, Polyurethane-39 reached industrial-scale synthesis and was established in the market in the 1950s.
CAS: 9009-54-5
MF: C3H8N2O
EINECS: 210-898-8
Synonyms
Polyisocyanurate resins;Polyurethanes, cellular;PU foam;The following companies react isocyanates or prepolymers with polyols to produce polyurethane foams. The list is incomplete.;POLYURETHANEOLIGOMERS;POLYURETHANEVARNISH;POLYURETHANELACQUER;Polyurethane foam: (Urethane polymers)
Polyurethane-39 a class of polymers containing-NHCOO-repeating structural units in the backbone of polyurethane polyurethanes.
English abbreviation PU. From the isocyanate (monomer) and hydroxyl compound polymerization.
Because of the strong polar carbamate group, insoluble in non-polar groups, has good oil resistance, toughness, wear resistance, aging resistance and adhesion.
Materials suitable for a wide temperature range (-50 to 150 °c) can be prepared from different starting materials, including elastomers, thermoplastic resins and thermosetting resins.
Polyurethane-39 Chemical Properties
Stability: Stable. Combustible. Incompatible with strong oxidizing agents.
InChI: InChI=1S/C3H8N2O/c1-2-5-3(4)6/h2H2,1H3,(H3,4,5,6)
InChIKey: RYECOJGRJDOGPP-UHFFFAOYSA-N
CAS DataBase Reference: 9009-54-5
IARC: 3 (Vol. 19, Sup 7) 1987
Polyurethane-39 foams are resistant to a wide range of solvents.
In this respect, polyester foams are generally superior to polyether foams, particularly in resistance to dry cleaning solvents.
Polyurethane-39 foams are subject to degradation by aqueous acids and alkalis and steam.
Ester, amide and urethane groups represent sites for hydrolytic attack.
Since the ether group is not readily attacked, polyether foams are generally more resistant to hydrolysis than polyester foams.
Uses
Polyurethane-39 resins and foams are two important industrial polymers.
They can be produced as rigid, semirigid, or elastic foams or resins, which give PUR many versatile commercial uses.
Polyurethane-39 can be found in furniture, bedding material, automotive sealing material, adhesives, carpet, packaging material and coatings, and many other products.
Polyurethane-39 is favored industrially because of its resistance to oil, light, and solvents, in addition to its strength and flexibility.
Polyurethane-39 is formed by polyaddition reactions between a diisocyanate and a polyhydroxyl compound, such as a polyol.
Several isocyanates (tolylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, etc.) are used in preparing polyurethanes.
The aromatic isocyanates are more reactive than the aliphatic isocyanates and are widely used in urethane foams, coatings, and elastomers.
The cyclic structure of aromatic and alicyclic isocyanates contributes to molecular stiffness in polyurethanes.
Flexible Polyurethane-39 foams are open-cell structures which are usually produced with densities in the range 24-48 kg/m3 (1.5-3Ib/ft3).
The major interest in flexible foams is for upholstery applications and thus the loadcompression characteristics are of importance.
Used in aviation, railway, construction, sports and other aspects; Used for wooden furniture and metal surface finish; Used for storage tank, pipe, cold storage, beer, fermentation tank, fresh-keeping barrel insulation Insulation and cold preservation, building insulation and waterproof, can also be used for prefabricated polyurethane board; Can be used for the manufacture of plastic products, wear-resistant synthetic rubber products, synthetic fiber, hard and soft foam plastic products, adhesives and coatings; for all types of wood, chemical equipment, telecommunications equipment and instruments and surface finishing of various transport tools.
Preparation
Polyurethane foams are produced by forming a Polyurethane-39 polymer concurrently with a gas evolution process.
Provided these two processes are balanced, bubbles of gas are trapped in the polymer matrix as Polyurethane-39 is formed and a cellular product results.
The matching of the two reactions is essential for the formation of satisfactory foams.
If the evolution of gas is too rapid, the foam initially rises well but then collapses because polymerization has not proceeded sufficiently to give a matrix strong enough to retain the gas.
If polymerization is too fast, the foam does not rise adequately.
By selection of appropriate reactants, Polyurethane-39 is possible to prepare foams of varying degrees of cross-linking.
Slightly cross-linked products are flexible whilst highly cross-linked products are rigid.
Both flexible and rigid Polyurethane-39 foams are of commercial importance.
Production Methods
Castable Polyurethane-39 are fabricated from polyurethane prepolymers, which are obtained by reacting an excess of diisocyanate with high-molecular-weight diols.
These NCO-terminated oligomers (prepolymers) are commercially available under a variety of trade names and in numerous types depending upon the types of diisocyanates and polyols that are used to synthesize them.
The NCO content of these prepolymers can vary from less than 3% to as much as 20%.
A cast polyurethane fabricator mixes these liquid prepolymers with approximately stoichiometric quantities of a curing agent (or a blend of curing agents) such as an appropriate low-molecular- weight diol or diamine.
Generally a prepolymer is heated to reduce its viscosity before mixing it with a liquid or a molten curing agent.
The prepolymer curing agent blends have a limited working time (pot life) during which they are still liquid and can be poured into molds.
The liquid prepolymer/curing agent blend is degassed and then poured into molds, which are often heated to expedite curing.
After curing, the solid Polyurethane-39 articles are removed from the mold and are sometimes finished by keeping them at elevated temperature to complete the cure and to maximize mechanical properties.
