Porous Polyimide Films Research Articles

高耐熱性ポリイミド多孔膜

高耐熱性ポリイミド多孔膜

Preparation of porous carbon films by the pyrolysis of poly(urethane-imide) films and their pore characteristics

Porous carbon films were prepared by the pyrolysis of poly(urethane-imide) films that were prepared by a reaction between phenol-terminated polyurethane prepolymer and poly(amide acid) obtained from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA). Upon thermal treatment of the poly(urethane-imide) films at 300 to 400°C, the thermally less stable urethane domains decomposed, leaving porous polyimide films. The porous polyimide films were further pyrolyzed at 900°C for 1 h to give porous carbon films. The formation of macropores was confirmed from scanning electron microscopy (SEM) of the surface and the cross-section of the films. The size distribution of the macropore was relatively narrow. With the increase of urethane content, the size of the macropore increased. The average pore size was found to be controlled between 0.6 μm and 10 μm by changing the ratio of the imide and the urethane components. It was also revealed from nitrogen adsorption isotherms that macroporous carbon films also contain micropores that were formed during the pyrolysis of the polyimide films. The progress of the micropore formation was studied by measuring nitrogen adsorption isotherms of the carbonized films treated at various temperatures.

Preparation and Properties of Porous Polyimide Films Prepared from a Polymer Blend of Polyol and Poly(amide acid).

Porous polyimide films were prepared by thermally treating a polymer blend film of polyol and poly(amide acid) obtained from pyromellitic dianhydride (PMDA) and oxydianiline (ODA). Upon thermal treatment of the films at 300 to 400°C, the thermally less stable polyol domains decomposed, leaving porous polyimide films. The presence of pores was confirmed from the scanning electron microscope (SEM) of the surface and the cross-section of the films. The size distribution of the pore was narrow. With the increase of polyol content, the average pore size increased from 2-3 μm to 6-7μm. The porous polyimide films had excellent physical properties in spite of the porous structure. Viscoelastic analyses showed that all the porous polyimide films had high glass transition temperature at above 400°C, and storage moduli were maintained up to 400°C. Carbonization of the porous polyimide films at 900°C for 1h gave porous carbon films maintaining the pore structure.

Preparation and Properties of Porous Polyimide Films

Porous polyimide films were prepared in two steps. The first step was the preparation of poly(urethane-imide) films by a reaction between a phenol-terminated polyurethane prepolymer and poly(amide acid) obtained from pyromellitic dianhydride (PMDA) and oxydianiline (ODA) followed by thermal treatment at 200 °C. The second step was the pyrolysis of the poly(urethaneimide) films. Upon thermal treatment of the poly(urethane-imide) films at 300 to 400 °C, the thermally less stable urethane domains decomposed, leaving porous polyimide films. The presence of pores was confirmed from the scanning electron microscope (SEM) picture of the surface and the cross section of the films. The size distribution of the pores was narrow. With increasing urethane content, the apparent density decreased but the size of the pore did not increase so much. Instead, the number of pores increased. Tensile measurements revealed that, with increasing urethane component the tensile modulus did not vary very much, but the elongation and thus the tensile strength decreased. Viscoelastic analyses showed that all the porous polyimide films had a high glass transition temperature, above 400 °C, and storage moduli were maintained up to 400 °C.

Preparation and Properties of Porous Polyimide Films Prepared by the Pyrolysis of Poly(urethane-imide) Films.

Porous polyimide films were prepared by 2 steps. The first step is the preparation of poly(urethane-imide) films by a reaction between phenol-terminated polyurethane prepolymer and poly(amide acid). Polyurethane prepolymer was prepared from the reaction of polyethylene adipate and hexamethylenediisocyanate. Poly(amide acid) was obtained from pyromellitic dianhydride and oxydianiline. The second step is the pyrolysis of the poly(urethane-imide) films. Upon thermal treatment of the poly(urethane-imide) films at 300 to 400°C, the thermally less stable urethane domains decomposed, leaving porous polyimide films. The presence of pores was confirmed from the scanning electron microscope of the surface and the cross-section of the films. The size distribution of the pore was narrow. With the increase of urethane content, the size of the pore increased. Tensile measurements revealed that, with the increase of urethane component, tensile modulus did not vary so much, but elongation and thus tensile strength decreased. Viscoelastic analyses showed that all the porous polyimide films had high glass transition temperature at above 400°C, and storage moduli were maintained up to 400°C.