Isocyanurate made from HDI by using potassium acetate as catalyst was synthesized and characterized by IR and NMR(1H

13C

1H-1H COSY

13C-1H HMQC

13C-1H HMBC)．The peaks atδ3.29～3.32

δ3.86

δ3.27

δ3.70

δ4.45

δ3.25 and δ3.45 of the 1H-NMR spectrum were attributed to the hydrogen proton on the α carbon atom connected with the nitrogen atom of N=C=O

the hydrogen proton on the α carbon of the HDI trimer

the hydrogen proton on the carbon connected with the nitrogen of urethane

the hydrogen proton on the α carbon of biurea

the hydrogen proton on the carbon connected with the oxygen atom of the carbonyl group of ureido-formate

the hydrogen proton connected with biurea

the hydrogen proton connected with substituted urea

the hydrogen proton connected with the urea carbonyl group of ureido-formate

respectively．The peaks at δ121.46

δ148.58

δ153.60

δ153.91

δ154.36

δ155.44

δ155.93

δ165.29 of the 13C-NMR spectra belonged to the double bonded carbon of N=C=O

the carbon on the carbonyl group of the HDI trimer

the carbon on carbonyl of urethane

carbon on the carbonyl of dual-biurea

the carbonyl of the ureido-formate

the carbon of the carbonyl of biurea

the carbon on the carbonyl of substituted urea．and the carbon on the carbonyl of ureido-formate．The results showed that the main product of HDI self-polymerization was its trimer

isocyanurate．Isocyanurate and isocyanate groups were the main groups in the trimer．Urethane

urethaneurea

urea

biurea groups were also detected in little amount．1D and 2D NMR could differentiate seven sorts of carbonyl groups and one N=C=O group

and establish the connections of all carbon and hydrogen atoms of mixed structures that originated from eight different substitutions．The content of NCO groups was derived from the results of the NMR characterization

it was about 21％．By using the statistical method

the average molecular weight and functionality of the trimerization product were calculated as well

they are 624～632 and 3.1～3.2

respectively．The consistence of the calculated values of isocyanate content

mean functionality and mean molecular weight with the experimental values(20％

3 and 618) demonstrated the correctness of structure characterization．