Properties of polyimide shells made using vapor phase deposition

Hollow polyimide shells, to be used in inertial confinement fusion experiments, were fabricated by codepositing monomer precursors onto spherical mandrels. Polyimide shells with 700 to 950 mu m diameters and 4 to 13 mu m wall thicknesses were produced. The shell wall shrunk 20-30% due to imidization. Burst and buckle pressure tests on these shells yielded estimated mechanical strength properties: similar to 15 GPa elastic modulus and similar to 300 MPa tensile strength. The permeability of D-2 through polyamic acid at 298 K was 7.4 x 10(-17) mol.m/m(2).Pa.s and increased to 6.4 x 10(-16) mol.m/m(2) .Pa.s upon curing the shell to 150 degrees C. The permeability of D-2 at 298 K through vapor-deposited polyimide flat films was 240 times greater than through polyamic acid.