Main Difference – Urethane vs Polyurethane
Polymers are macromolecules that are made out of small units called monomers. Monomers should have either a double bond or at least two functional groups in order to undergo polymerization. Polyurethane is such a polymer that is made out of two monomers (isocyanates and polyols) and has many applications in industry. Polyurethane is made out of organic units that are joined by urethane linkages. Although it is not composed of urethane monomers, it is given the name polyurethane due to the presence of these urethane linkages. Urethane is a crystalline compound in which a carbonic acid group is composed of both an amide group and an ester group. Sometimes, urethane is used to name polyurethanes and carbamate, which is a compound derived from carbamic acid. However, the term urethane actually represents ethyl carbamate. The main difference between urethane and polyurethane is that urethane is soft and flexible whereas polyurethane is rigid and hard.
Key Areas Covered
1. What is Urethane
– Definition, Reactions and their Applications
2. What is Polyurethane
– Definition, Reactions and their Applications
3. What is the Difference Between Urethane and Polyurethane
– Comparison of Key Differences
Key Terms: Amide Group, Carbonic Acid, Ester, Ethyl Carbamate, Isocyanate, Polymer, Polyols, Polyurethane, Spar Urethane, Urethane
What is Urethane
Urethane is a chemical compound having both an ester group and an amide group along with a carbonic acid. Ethyl carbamate is the IUPAC name for urethane. The chemical structure of urethane can be given as R1-O-(CO)-NR2-R3 where R1, R2 and R3 are alkyl groups. R1 is attached to the oxygen atom that has a single bond with the carbon atom. R2 and R3 are attached to the Nitrogen atom. Therefore, -COOR1 indicates the ester group and –CONR1-R3 indicates the amide group.
Figure 1: Urethane Structure
Urethane is a flexible and malleable chemical compound. Therefore, urethane can be molded into different shapes in order to produce desirable products. The major applications of urethane include the production of insecticides, veterinary medicine, and other pharmaceutical products; sometimes it is used as a solvent, in some cases, urethane is used to produce plastics.
According to researchers, urethane is a toxic compound and it has been found that urethane can cause cancers in small animals. In addition, urethane can be used as spar urethane that is a type of varnish. Spar urethane is made for outdoor applications. This would be the best choice for outdoor furniture since it is highly water resistant. The melting point of urethane may vary from 46oC to 50oC depending on the alkyl group attached to the nitrogen atom.
What is Polyurethane
Polyurethane is a polymer that is composed of organic units (isocyanates and polyols) that are linked via urethane linkages. Here, urethane units are linked together from polymerization. Although urethane linkages are present in polyurethane, it is not made of urethane monomers.
Figure 2: Polyurethane ( blue colored parts show urethane linkages)
Two monomers are used in the production of polyurethanes. They are an isocyanate, having more than one reactive isocyanate group, and an alcohol with at least two hydroxyl groups. The exothermic reaction between these two monomers forms polyurethane. The linkage between –N=C=O of isocyanate and –OH of alcohol will form a urethane linkage. This urethane linkage is slightly different from urea linkage.
Figure 3: Urethane and Urea Linkages
Polyurethane is stiff and rigid. Polyurethane can be applied to plastics and metal surfaces. However, the most common applications of polyurethane use its rigid properties. These applications include the formation of rigid foam for cushioning, foot wear production, etc. Unlike urethane, polyurethane is non-toxic.
Polyurethane is a thermosetting polymer. Therefore, when this compound burns instead of melting when heated. Therefore, polyurethane does not have a melting point.
Difference Between Urethane and Polyurethane
Definition
Urethane: Urethane is a chemical compound having both an ester group and an amide group along with a carbonic acid.
Polyurethane: Polyurethane is a polymer that is composed of organic units linked via urethane linkages.
Physical Properties
Urethane: Urethane is soft and flexible.
Polyurethane: Polyurethane is hard and rigid.
Melting Point
Urethane: The melting point of urethane is about 50oC.
Polyurethane: Polyurethane does not have a melting point since it is a thermosetting polymer.
Toxicity
Urethane: Urethane is toxic.
Polyurethane: Polyurethane is non-toxic or less toxic.
Uses
Urethane: Urethane is used for the production of insecticides, veterinary medicine, and other pharmaceutical products.
Polyurethane: Polyurethanes are used the for production of solid materials such as foam, and foot wear.
Conclusion
Urethane and polyurethane have many applications in the industry. Urethane is a crystalline compound that is flexible and malleable. Polyurethane is a hard and rigid compound. This is the main difference between urethane and polyurethane. According to these properties, their applications may vary.
References:
1. Lazonby, John. “Polyurethanes.” The Essential Chemical Industry online. N.p., n.d. Web. Available here. 11 Aug. 2017.
2. “Urethane Vs. Polyurethane.” Sciencing. N.p., n.d. Web. Available here. 11 Aug. 2017.
Image Courtesy:
1. “Urethan” Av NEUROtiker – Eget arbete (Public Domain) via Commons Wikimedia
2. “Polyurethane-allg” Von Roland.chem – Eigenes Werk (CC0) via Commons Wikimedia
3. “Ureathane linkages” By Prabhachatterji at Malayalam Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
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