BPDA

Abstract: We report the first synthesis of polyimide aerogels cross-linked through a polyhedral oligomeric silsesquioxane, octa(aminophenyl)silsesquioxane (OAPS). Gels formed from polyamic acid solutions of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), bisaniline-p-xylidene (BAX) and OAPS were chemically imidized and dried using supercritical CO2 extraction to give aerogels having density around 0.1 g/cm3. The aerogels are greater than 90 % porous, have high surface areas (230 to 280 m2/g) and low thermal conductivity (14 mW/m-K at room temperature). Notably, the polyimide aerogels cross-linked with OAPS have higher modulus than polymer reinforced silica aerogels of similar density and can be fabricated as both monoliths and thin films. Thin films of the aerogel are flexible and foldable making them an ideal insulation for space suits, and inflatable structures for habitats or decelerators for planetary re-entry, as well as more down to earth applications.

Abstract: Carbon nanotubes (CNTs) have high strength and modulus, large aspect ratio, and good electrical and thermal conductivities, which make them attractive for fabricating composite. The poly(biphenyl dianhydride-p-phenylenediamine) (BPDA/PDA) polyimide has good mechanical and thermal performances and is herein used as matrix in unidirectional carbon nanotube composites for the first time. The strength and modulus of the composite increase by 2.73 and 12 times over pure BPDA–PDA polyimide, while its electrical conductivity reaches to 183 S/cm, which is 1018 times over pure polyimide. The composite has excellent high temperature resistance, and its thermal conductivity is beyond what has been achieved in previous studies. The improved properties of the composites are due to the long CNT length, high level of CNT alignment, high CNT volume fraction and good CNT dispersion in polyimide matrix. The composite is promising for applications that require high strength, lightweight, or high electrical and thermal conductivities.

Abstract: A BPDA−pp‘ODA polyimide film was formed on the outer surface of a porous alumina support tube (outside diameter, 2.4 mm; inside diameter, 1.8 mm; void fraction, 0.48; and average pore size, 140 nm) and was then carbonized at an optimized temperature of 700 °C. Membranes prepared by repeating this process two and three times respectively exhibited permeances of approximately 1 × 10-8 mol·m-2·s-1·Pa-1 for C2H4 and 2 × 10-9 mol·m-2·s-1·Pa-1 for C2H6 at 100 °C. Permeances to C3H6 and C3H8 at 100 °C were 4 × 10-9 and 1 × 10-10 mol·m-2·s-1·Pa-1, respectively. The selectivities were 4−5 for C2H4/C2H6 systems and 25−29 for C3H6/C3H8 systems. When the permeation temperature was decreased to 65 and 35 °C, permeances decreased and selectivities increased to 5−7 for C2H4/C2H6 systems and 33−56 for C3H6/C3H8 systems. The permeance and selectivity for an equimolar mixture of C3H6 and C3H8 were nearly the same as those for the single-component gases.