| 초록 |
Polyimides have been used widely in aerospace, electronics and other industries for their excellent thermal, chemical and physical stability. Aromatic polyimides are generally prepared in two step procedure by ring opening polymerization of aromatic diamines to aromatic dianhydrides giving soluble polyamic acid, followed by thermal or chemical imidization. In the present study, semi-rigid structure polyimides having carbonyl (-C=O-), sulfonyl (-S=O-), thionyl (-S-), ether (-O-), and methyl (-CH2-) swivel groups were synthesized using various dianhydrides and diamines via two-step polymerization. Thermo- and chemical oxidative stability of these polyimides were investigated and compared with each other in terms of kind of swivel groups. For thermo-oxidative stability, thermal gravimetric analysis (TGA) was used under inert and air atmosphere, and simultaneously the evolved gases at each decomposition step were observed via mass spectroscope (MS). For chemical oxidation, accelerated peroxide radical stability tests were carried out using 3wt% H2O2 + 0.1wt% ferrous ammonium sulfate peroxide. The oxidation stability of polyimides to aggressive HOO· radicals attack was investigated by observing the changes in film appearance, mechanical strength, flexibility, and gas permeability. |
