The Adhesive Reaction Of Polyurethane And The Decomposition Of PEG By DFT

Polyurethane products are widely used in aviation, electronics, marine, ships, vehicles, civil construction and textile industry for the excellent performance. The propellant coating of polyurethane has many advantages of good adhesion and mechanical property. In order to improve the coating properties of the liner of solid rocket propellant, it is important to study the adhesive reaction of polyurethane and the ability of plasticizer resistance of the liner by quantum chemical method.In this thesis, Gaussian 09 suit of programs were used to explore the adhesive mechanism in polyurethane reaction system and the ability of plasticizer resistance of the liner. The geometry optimization, vibration frequency analysis, energy calculation, energy surface scan, reaction path analysis, solvation model were performed through the density functional theory?DFT? with the B3LYP/6-31+G?d, p? or 6-31++G?d, p? level.The calculations of the hydrolysis reaction of 2, 4-TDI indicated that the additions across N=C and C=O bonds with water trimer are energetically preferred to the reaction with water dimer and monomer. In addition, the 1, 3-Hydrogen shift following an attack across C=O bond is a fast process with water dimer serving as an efficient proton transporter. In the final decomposition of carbamic acid, water trimer or water tetramer shows an important role to reduce the energy barrier significantly.The calculations of the reaction between isocyanate and stearic acid show that the direct addition of isocyanate and arboxylic acid possess an unexpected low barrier. In addition, the energy barrier is not reduced but increased by including an extra methanol or carboxylic acid molecule erving as an proton transporter. It is indicated that the reaction between isocyanate and stearic acid is auto-catalyzed with carbanyl group of stearic acid acting as a reactive catalyst.The calculations of the reaction between 2, 4-TDI and cellulose show that the direct addition of 2, 4-TDI and cellulose possess an unrealistically high barrier. With a neighboring ?-D-glucose serving as a proton transporter by forming a flexible six-membered ring transition state, the energy barrier of the reaction is significantly reduced; this is in a good accordance with the experimental data. It is indicated that the reaction between 2, 4-TDI and cellulose is auto-catalyzed with a neighboring ?-D-glucose acting as a reactive catalyst.The oxidation mechanism of diethyl ethers by NO₂ follows four steps. Based on the calculations, the third step of the nitrate CH₃CH?ONO?OCHCH₃ can be further decomposed into CH₃CH₂ONO and CH₃CHO is the rate-limiting step with high energy barrier. The results indicate that the high temperature may be required for the oxidation of ethers by NO₂. The calculated oxidation mechanism agrees well with Nishiguchi and Okamoto's experiment and proposal.The study of the NG's migration to coating showed that the materials consist only of carbon/silicon and hydrogen atoms have low binding energies with NG. Because of the strong nitrogen-hydrogen bonds and oxygen--hydrogen bonds, another material that contains oxygen or nitrogen has high binding energies. The polyurethane material cannot resist NG's migration to coating effectively. And then, the experimental results showed that the compound-doped have little impact on the ability of resist NG's migration to coating. Hydroxyl-terminated polybutadiene?HTPB? is a material with good plasticizer resistance.