Thiourea synthesis

Thiourea is manufactured by heating ammonium thiocyanate at 140-145°C for about 4 hours; equilibrium is established when about 25% of the thiocyanate is converted to thiourea.Thiourea may also be prepared by the interaction of cyanamide and hydrogen sulphide:

Thiourea closely resembles urea in that reaction with formaldehyde gives methylol derivatives and then resinous condensates which on continued heating yield network structures. Thiourea-formaldehyde resins are slower curing than urea-formaldehyde resins and the hardened products are more brittle and more water-resistant. At one time thiourea-formaldehyde resins were added to urea-formaldehyde resins to give mouldings and laminates with improved water-resistance. These mixed resins have now been largely superseded by melamine-formaldehyde resins which give products with better resistance to heat.