Thermal and Mechanical Characteristics of Polyimide Based Ceramers
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535 Mat. Res. Soc. Symp. Proc. Vol. 405 01996 Materials Research Society
EXPERIMENTAL Solution coated TiO. modified polyimide 3% offset LARCTM IA polyimide powder (Imitech Incorp.) was slowly added to a solution of 10% v/v Titanium (IV) 2-ethylhexoxide (Aldrich) in pentane. The slurry was stirred for 2 h at room temperature, and the solvent removed by rotary evaporation. The coated powder was stirred in distilled water (10% w/w) for 4 h, isolated over sintered glass, and dried at 200° in vacuo for 12 h. Flash imidized SiO, modified polyimide 3% offset
LARCTM
IA amide acid resin, 30% by weight in NMP (Imitech Incorp.),
was diluted to 10% solids with distilled NMP. Equivalent weights of TEOS (Aldrich) and water were added to the flask and the resulting homogeneous mixture was allowed to hydrolyze at room temperature 5 h. The amide acid/alkyl silicate solution was thermally imidized by dropwise addition into refluxing xylene. The reaction was stirred at -240 °C for - 16 h in a resin kettle equipped with a Dean-Stark moisture trap. The powder was isolated and dried at 200 °C in vacuo for 12 h. Characterization Glass transition temperatures (Tg) for all systems were determined using a Shimadzu DSC-50 Differential Scanning Calorimeter, at a heating rate of 20 °C/min. Tg was determined at the half point of the slope change from the baseline of the change in energy (Amw) versus temperature curve. Dynamic thermogravimetric analyses were conducted on a Seiko Tg/DTA 200/220 at a heating rate of 2.5 °C/min to 750 'C in air at a flow rate of 15 cc/min. Percent inorganic was determined by the residual weight after holding the sample 1 h at 750 *C. Scanning electron micrographs were taken of residual inorganic samples on a Hitachi S-510 SEM. Processing Modified powders were melt extruded through a Brabender PL 2000 mixer under nitrogen purge from 315 to 335 *C. The polymers were compression molded in a square stainless steel mold using a hydraulic press equipped with heated platens. Samples were cut into 2.5 x 0.5 inch samples using a diamond saw. Room temperature flexural properties were determined according to ASTM D-790 on a Sintech model 2W screw driven test machine.
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RESULTS The resultant morphology of the hybrid composites composed of LARCTM IA and titanium oxides was such that the inorganic Ti0 2 portion were large platelike flakes of 1-5g.m in two dimensions and
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