preparation of polyurethanes

 preparation of polyurethanes Article

20 – 03 – 13

TRY THINGS OUT: - PLANNING OF POLYURETHANES

AIM

Synthesis of polyurethanes

OBJECTIVES

-Mixing a diisocyanate and a diol in polyurethane synthesis of two distinct goods. -Comparing polyurethane material from castor oil to that made from polyethylene glycol. -To establish the sort of foams with regards to rigidity or flexibility.

THEORY

Polyurethanes, also called polycarbamates, participate in a larger class of compounds called polymers. Polymers are macromolecules made up of smaller, echoing units known as monomers. Generally, they incorporate a primary long-chain backbone molecule with attached side organizations.

The preparation of polyurethanes is known as a process of polymerisation whereby a diisocyanate and a dihydroxyl compound react together. Polyurethanes by explanation are thready polymers which may have a molecular backbone containing carbamate teams (-NHCO2). These groups, referred to as urethane, happen to be produced through a direct chemical reaction between efficient groups of a diisocyanate and a Polyol. First designed in late 1930s, polyurethanes are some of the most adaptable polymers. The diisocyanate can either be aliphatic, (hexamethylene diisocyanate) or fragrant like toluene diisocyanate. Types of diols are ethylene glycol or even polyethylene glycols, with greater Mr.

Synthetic polymers, like polyurethane, are made by reacting monomers in a effect vessel. In order to produce polyurethane, a step also called condensation reaction is performed. Through this type of chemical reaction, the monomers that are present contain reacting end teams. One of the crucial reactive supplies required to produce polyurethanes is a diisocyanate, characterized by a (NCO) group, the highly reactive alcohol. Toluene diisocyanate (TDI) is manufactured by chemically adding nitrogen organizations on toluene, reacting these types of with hydrogen to produce a diamine, and isolating the unwanted isomers. The other reacting species necessary to produce polyurethanes are chemical substances that contain multiple alcohol teams (OH), named polyols which are often polyether polyols, which are polymers formed by cyclic ethers. They are typically produced through an alkylene o2 polymerization process. The first step of this reaction ends in the substance linking with the two molecules leaving a reactive alcoholic beverages (OH) on a single side and a reactive isocyanate (NCO) on the other. These types of groups respond further with other monomers to form a larger, much longer molecule. This really is a rapid process which yields high molecular weight supplies even by room heat. Polyurethanes that have important business uses commonly contain other functional groupings in the molecule including esters, ethers, amides, or urea groups

The German chemist, Friedrich Bayer in 1937, produced early prototypes of polyurethanes simply by reacting toluene diisocyanate with dihydric alcohols. From this operate one of the first transparent polyurethane fibers, Perlon U, was developed.

Polyurethanes are high molecular pounds polymers which may have a wide range of viscosity. Various polyether polyols that are used include polyethylene glycol, thermoplastic-polymer glycol, and polytetramethylene glycol. These elements are generally applied when the desired polyurethane will probably be used to make flexible foams or thermoset elastomers

TRIAL AND ERROR

5 grms of castor oil were weighed in a paper glass. The glass was transferred to the storm hood exactly where 2 drops of normal water were added, add later on 2 drops of triethyl amine. The mixture was stirred having a glass fly fishing rod till a creamy emulsion formed. several ml of tolylene-2, 4- diisocyanate were added and stirring was continued. The mixture started to emulsify and bubbles shaped. The mixing rod was removed from the mixture. The mixture was set aside inside the fume hood and polymerisation was permitted to occur. The ideal volume was reached following 4 hours and observations were made. The same process was repeated for your five grams of polyethylene glycol. Observations were noted...

Referrals: Othmer E. 1997 " Encyclopaedia of Chemical Technology”. John Wiley & Sons, pg 627

Carraher T. 2010 " Polymer Chemistry”. 4th edition, New York: Marcel Dekker, pg 233

Anderson J. 2013, Multiple uses of castor oil [online] London. Obtainable from http://www.ars.usda.gov/research/publications/castoroil.htm [Date accessed: 02-04-2013: 1632hrs]

McGuire And. 2011. Taming the castor bean [online]. The American chemistry society. Readily available from http://www.chemistry.org/portal/a/c/s/1/feature_pro.htm [Date accessed: 02-04-2013: 1638hrs]

McMurry M., (2000); " Organic Chemistry Textbook” 5th edition; Brookes and Cole; California UNITED STATES; pg 1272

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