Epoxy Resins and Polyurethanes example, reaction and common product? the mechanism of epoxy resin and polyurethanes?

Epoxy Resins and Polyurethanes example, reaction and common product?

the mechanism of epoxy resin and polyurethanes?

Solutions

Expert Solution

Epoxy resins are resinous polymeric substances which are prepared by polymerization of 1,2- epoxide like ethylene oxide.

Poly (oxymethylene) glycols is an addition polymer and is obtained by polymerization of ethylene oxide in presence of water and sodium hydroxide as catalyst. Besides this, epoxy resin can also be prepared by reacting epichlorohydrin with bisphenol A in the presence of base.

The polymerization begins by initial attack of phenoxide ion on the epoxide ring. It opens the epoxide ring and a molecule of NaCl is eliminated in next step to regenerate epoxide ring. This molecule again reacts with NaOH to form phenoxide ion which further reacts with epichlorohydrin to form a product having epoxide group at each step. This leads to the formation of epoxy resin.

Polyurethane

Urethane is an ester of carbamic acid (R-NH-COOH). Carbamic acid being unstable decomposes to give amines and CO₂. But, the esters of carbamic acid i. e. Urethane are stable. Urethane are prepared by reaction between alcohol and isocyanate. Thus, polyurethane are condensation polymers which are prepared by reacting diol with diisocyanate. The diol can be ethylene glycol and diisocyanate used is toluene - 2,4-diisocyanate. The polyester having CH₂OH end groups can also be used as diol.

In the second reaction, ethylene glycol reacts with adipic acid forming a polyester ( by loss of water molecule). This polyester reacts with diisocyanate to form polyurethane.

queen_honey_blossom answered 2 years ago

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