كليدواژه :
پلي يورتان , سينتيك , HTPB , ipdi
چكيده لاتين :
A kinetic study of the reaction between a hydroxyl-terminated poly butadiene (HTPB) and isophorone diisocyanate(IPDI) was carried out by using back titration. At four temperatures 30, 40, 50 and 60 degrees centigrade, the progress of reaction, rate constant and activation energy were obtained. It was shown that reaction has an apparent second -order in terms of HTPB and IPDI concentration. In the second-order plots, a discontinuity was observed. This behavior depends on differences in reactivity of the isocyanate groups at isophorone diisocyanate molecule site. The activation energies for the two parts of the reaction were determined to be 8.3 and 10.1 Kcal/mole.
Next, effects of curing ratio parameter (equivalent ratio of NCO/OH) and ferric Acetyl Acetonate catalyst for butadiene polymerization were investigated. Results of this research shows that a discontinuity exist at second-order plots. The IPDI molecule is a cycloaliphatic diisocyanate that includes a group of first type isocyanate (CH2-NCO) and a group of second type isocyanate (CH-NCO). This activity difference of these groups produce a discontinuity at second-order plots. In the next phase of the study , effect of temperature, type of isocyanate and catalyst on the reachen system was investigated. Finally, a comparative kinetic study between the three different diisocyanates ,i.e, Toluene diisocyanate (TDI), hexametylene diisocyanate (HMDI) and isophorone diisocyanate), was carried out. It was observed that the order of reactivity for diisocyanates was aromatic, aliphatic and cycloaliphatic. Considering this finding, we can select adiisocyanate appropriate for the reaction in question..
