: : O : || : - N - C - O - | : H urethanePolyurethanes can be classified into the following major groups:
O O || || O=C=N - R - N=C=O + HO - R - OH --> -[- C - N - R - N - C - O - R - O -]- | H diisocyanate diol polyurethaneIsocyanates will react with an amine to form a polyurea:
H H O O | | || || O=C=N - R - N=C=O + H-N - R - N-H --> -[- C - N - R - N - C - N - R - N -]- | | | | H H H H diisocyanate diamine polyureaSynthesis of isocyanates
O O || || R - N - H + Cl - C - Cl ---> R - N - C - Cl + HCl | | H H amine phosgene isocyanate hydrochloric precursor acid O || R - N - C - Cl ---> R - N = C = O + HCl | H isocyanate isocyanate precursor
O H || H | Cl - C - Cl | H N -[- C -]- NH + ----------> O=C=N -[- C -]- N=C=O 2 | 6 2 | H H hexamethylenediamine hexamethylene diisocyanateHDI sees limited use in the preparation of moulding materials.
O C - OH / \ C - O -[- C - C - O -]-m H C - C | epichlorohydrin | n,m range from 1 to 10 ------------> C - OH C - O -[- C - C - O -]-n H diol low molecular weight polyetherThe same trick can be done with glycerol (1,2,3-trihydroxypropane), which would have three polyether chains off the glycerol unit. The molecular weight of this is 1000 to 3000.
O O O O || || || -CO2 || R - N = C = O + R - C - O - H ----> R - N - C - O - C - R ----> R - N - C - R | | H H isocyanate carboxylic acid unstable product amide An amide can react with isocyanate, as seen further on.
O || R - N = C = O + H - O - H ----> R - N - C - O - H ----> R - N - H | | H H isocyanate water unstable product amine An amine can react with isocyanate, as seen further on.
O O O || || || R - N = C = O + R - N - C - O - R -----> R - N - C - N - C - O - R | | | H H H isocyanate urethane allophanate
O || R - N = C = O + R - N - C - N - R ---> What is drawn in the notes does | | not make sense. The word "biuret" H H is used.
O O O || || || R - N = C = O + R - N - C - R ----> R - N - C - N - C - R | | | H H R
O || R - N = C = O + HO - benzene ----> H - N - C - O - benzene | RDimerization of isocyanate
O || C / \ 2 R - N = C = O ---> R - N N - R \ / C || O uretidioneTrimerization of isocyanate
C-C / \ N-C-C-N \ / C-CBoth polyesters and polyethers can be used. However, polyethers are hydrolytically susceptible.??
O / \ -- C - C epoxyApplications of Epoxides include adhesives, paints, coatings, plastics, and extremely strong glues used for woodwork.
base C = C - C + Cl ---> C = C - C - Cl + HCl ----> 2 HOCl O / \ ----> C - C - C - Cl epichlorohydrin (reacts with bugs and humans)Resin Preparation:
CH3 + - | - + Na O - benzene - C - benzene - O Na | CH3And as you would deduce, the reaction of two epichlorohydrins with the above would produce a NaCl byproduct.
O / \ C - C.We've discussed exact stoichiometric match and step polymerization before. It should make sense that if the Bisphenol A to epichlorohydrin to base stoichiometry is exactly 1:1:1, then the whole system would form one molecule.
Molar ratio- epichlorohydrin/Bisphenol A | Molecular Weight | Softening Point |
10 : 1 | 370 | 9 deg C |
2 : 1 | 451 | 43 deg C |
1.4 : 1 | 791 | 84 deg C |
1.33 : 1 | 802 | 90 deg C |
1.25 : 1 | 1133 | 100 deg C |
1.2 : 1 | 1420 | 112 deg C |