preparation of polyurethanes
20 – 03 – 13
EXPERIMENT: - PREPARATION OF POLYURETHANES
AIM
Synthesis of polyurethanes
OBJECTIVES
- Mixing a diisocyanate and a diol in polyurethane synthesis of two distinct products.
- Comparing polyurethane from castor oil to that made from polyethylene glycol.
- To establish the type of foams in terms rigidity or flexibility.
THEORY
Polyurethanes, also known as polycarbamates, belong to a larger class of compounds called polymers. Polymers are macromolecules made up of smaller, repeating units known as monomers. Generally, they consist of a primary long-chain backbone molecule with attached side groups.
The preparation of polyurethanes is a process of polymerisation whereby a diisocyanate and a dihydroxyl compound react together. Polyurethanes by definition are linear polymers that have a molecular backbone containing carbamate groups (-NHCO2). These groups, called urethane, are produced through a direct chemical reaction between functional groups of a diisocyanate and a Polyol. First developed in late 1930s, polyurethanes are some of the most versatile polymers. The diisocyanate can either be aliphatic, (hexamethylene diisocyanate) or aromatic like toluene diisocyanate. Examples of diols are ethylene glycol or even polyethylene glycols, with greater Mr.
Synthetic polymers, like polyurethane, are produced by reacting monomers in a reaction vessel. In order to produce polyurethane, a step also known as condensation reaction is performed. In this type of chemical reaction, the monomers that are present contain reacting end groups.
One of the key reactive materials required to produce polyurethanes is a diisocyanate, characterized by a (NCO) group, which is a highly reactive alcohol. Toluene diisocyanate (TDI) is produced by chemically adding nitrogen groups on toluene, reacting these with hydrogen to produce a diamine, and separating the undesired isomers. The other reacting species required to produce polyurethanes are
EXPERIMENT: - PREPARATION OF POLYURETHANES
AIM
Synthesis of polyurethanes
OBJECTIVES
- Mixing a diisocyanate and a diol in polyurethane synthesis of two distinct products.
- Comparing polyurethane from castor oil to that made from polyethylene glycol.
- To establish the type of foams in terms rigidity or flexibility.
THEORY
Polyurethanes, also known as polycarbamates, belong to a larger class of compounds called polymers. Polymers are macromolecules made up of smaller, repeating units known as monomers. Generally, they consist of a primary long-chain backbone molecule with attached side groups.
The preparation of polyurethanes is a process of polymerisation whereby a diisocyanate and a dihydroxyl compound react together. Polyurethanes by definition are linear polymers that have a molecular backbone containing carbamate groups (-NHCO2). These groups, called urethane, are produced through a direct chemical reaction between functional groups of a diisocyanate and a Polyol. First developed in late 1930s, polyurethanes are some of the most versatile polymers. The diisocyanate can either be aliphatic, (hexamethylene diisocyanate) or aromatic like toluene diisocyanate. Examples of diols are ethylene glycol or even polyethylene glycols, with greater Mr.
Synthetic polymers, like polyurethane, are produced by reacting monomers in a reaction vessel. In order to produce polyurethane, a step also known as condensation reaction is performed. In this type of chemical reaction, the monomers that are present contain reacting end groups.
One of the key reactive materials required to produce polyurethanes is a diisocyanate, characterized by a (NCO) group, which is a highly reactive alcohol. Toluene diisocyanate (TDI) is produced by chemically adding nitrogen groups on toluene, reacting these with hydrogen to produce a diamine, and separating the undesired isomers. The other reacting species required to produce polyurethanes are
References: Othmer K.1997 “Encyclopaedia of Chemical Technology”. John Wiley & Sons, pg 627 Carraher S. 2010 “Polymer Chemistry”. 4th edition, New York: Marcel Dekker, pg 233 Anderson J. 2013, Multiple uses of castor oil [online] London. Available from http://www.ars.usda.gov/research/publications/castoroil.htm [Date accessed: 02-04-2013: 1632hrs] McGuire N. 2011. Taming the castor bean [online]. The American chemistry society. Available from http://www.chemistry.org/portal/a/c/s/1/feature_pro.htm [Date accessed: 02-04-2013: 1638hrs] McMurry J., (2000); “Organic Chemistry Textbook” 5th edition; Brookes and Cole; California USA; pg 1272