三种胺类防老剂对丁羟聚氨酯老化防护机理的分子模拟

Molecular Simulation of Three Kinds of Amine Antioxidants on the Aging Protection Mechanism of Hydroxyl-terminated Polybutadiene Polyurethane

为探究三种不同防老剂N-(1,3-二甲基)丁基-N'-苯基对苯二胺(4020)、N-异丙基-N'-苯基对苯二胺(4010NA)、N-苯基-2-萘胺(D)在丁羟聚氨酯(HTPB-TDI)体系中的防老机理与防老性能优劣,采用量子力学(QM)模拟、分子动力学(MD)模拟、蒙特卡洛(MC)模拟分别对HTPB-TDI体系与各组分的解离自由能、扩散系数、溶度参数与渗透系数进行了计算。结果表明:三种防老剂的解离自由能大小顺序为ΔG_(D)>ΔG_(4010NA)>ΔG_(4020),并且均小于HTPB-TDI的最小解离自由能345.63 kJ·mol^(-1),说明三种防老剂均能优先与HTPB-TDI中的活性自由基反应并且减缓HTPB-TDI中自由基连锁反应的进行;防老剂4020的扩散系数及其与HTPB-TDI的溶度参数差值最小,说明防老剂4020迁移能力差且与HTPB-TDI相容性好,从而能在HTPB-TDI中稳定均匀存在;氧气在三种丁羟聚氨酯-防老剂体系中的渗透系数大小顺序为P_(HTPB-TDI/D)>P_(HTPB-TDI/4010NA)>P_(HTPB-TDI/4020),表明防老剂D的阻氧能力最差。综合三种防老剂的化学反应难易程度、迁移性大小、相容性优劣以及氧气的渗透性好坏,可得三种防老剂的防老性能优劣为4020>4010NA>D。

To explore the aging mechanism and performance of antioxidants N-(1,3-dimethyl)butyl-N'-phenyl-p-phenylenediamine(4020),N-isopropyl-N'-phenyl-p-phenylenediamine(4010NA),N-phenyl-2-naphthylamine(D)in hydroxyl-terminated polybutadiene polyurethane(HTPB-TDI)system,quantum mechanics(QM)simulation,molecular dynamics(MD)simulation,monte carlo(MC)simulation were used to calculate the dissociation free energy,diffusion coefficient,solubility parameter and permeability coefficient of the HTPB-TDI system and each component.Results show that the order of the bond dissociation free energy of the three antioxidants is ΔG_(D)>ΔG_(4010NA)>ΔG_(4020),and they are all less than the minimum free energy of dissociation of HTPB-TDI(345.63 kJ·mol^(-1)),indicating that the three antioxidants can preferentially react with the active free radicals in HTPB-TDI and slow down the progress of the free radical chain reaction in HTPB-TDI.The difference of diffusion coefficient and solubility parameter between antioxidant 4020 and HTPB-TDI is the smallest,which shows that antioxidant 4020 has poor diffusion ability and good compatibility with HTPB-TDI,so it can exist in HTPB-TDI stably and uniformly.The order of the permeability coefficient of oxygen in the three kinds of hydroxyl-terminated polybutadiene polyurethane antioxidant systems is P_(HTPB-TDI/D)>P_(HTPB-TDI/4010NA)>P_(HTPB-TDI/4020),which manifests that D has the worst oxygen barrier ability.According to the chemical reaction difficulty,mobility,compatibility and oxygen permeability of the three kinds of antioxidants,the order of antiaging properties of the three kinds of antioxidants is 4020>4010NA>D.