Porous nonwoven calendered fabrics (membranes) based on electrospun prepolymers of modified polyimides

The article presents data on the method of obtaining porous nonwoven polyimide fabrics (membranes), their deformation and strength characteristics, heat resistance, and surface properties. The membranes are produced as a result of a multistep processing of copoly(urethane-imides) prepolymers that includes the synthesis of copoly(urethane-ami & scy; acids) of a given chemical composition, the molding of nonwoven fabrics (mats) by electrodeposition of copoly(urethane-amic acids), the compaction of the volumetric structure of electrodeposited nonwoven fabrics by calendering on hot rollers, the thermal cyclization (imidization) of amic acid units of copolymers during calendering to form imides, and the controlled selective thermal destruction of the urethane groups in the copolymers conditioning the transition from poly(urethane-imides) to polyimides, which is accompanied by the formation of pores in nonwoven polyimide fabrics, resulting in porous polyimide webs with specific properties. In the synthesis of the polymers studied, polycaprolactone diol, 2,4-toluene diisocyanate, 4,4 '-oxydianiline, pyromellitic dianhydride, and 3,3 ',4,4 '-oxydiphthalic anhydride were used. The polymers were characterized using X-ray, 1H NMR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, and scanning electron spectroscopy. The deformation and strength properties of the nonwoven polyimide fabrics were also determined. Chemical composition of the synthesized polymer systems and the conditions for creating porous polyimide nonwoven fabrics influence the physical properties of the resulting fabrics. Porous polyimide nonwoven fabrics hold promise for the development of advanced filtration materials with enhanced strength, heat resistance, and resistance to aggressive amide solvents, which could be used in the pharmaceutical and biotechnology industries. The nonwoven fabrics are based on copoly(urethane imides) in terms of dimethylformamide (DMF) permeability and phthalocyanine rejection with a diameter of 240 nm. The DMF permeability was 280 kg/m2 h bar, the phthalocyanine rejection was 98%.Highlights Nonwoven poly(urethane-amic acid) materials were obtained by electrodeposition. Nonwovens were rolled at high temperatures and pressure. The materials were compacted and acquired the structure of poly(urethane-imides). Porous polyimide materials were obtained by annealing poly(urethane-imides). The obtained materials have the properties of ultrafiltration membranes.