Abstract The aim of this work was to synthesize the porous polyimide nanostructure and coating of it on the polyester nonwoven substrate in a short low-risk process. Porous polyimides have a large specific surface area and excellent thermal stability and mechanical properties. In general, the synthesis of a polyimide porous structure has been challenged by researchers due to the high temperature thermal imidization process. In this work, the porous structure of polyimide based on isocyanate was synthesized by two methods ; ambient method and autoclave-acetone method. In ambient condition, the polyimide structure with the suitable porosity and specific surface area was not achieved. The autoclave-acetone method was based on the swelling of the gel structure with acetone and thermal imidization process was carried out in autoclave to achieve porous polyamide structure.The integrity of this structure was intact. The steps of gelation, ageing and thermal imidization was done together in the autoclave. In this method, two monomers of 4,ʹ4-diphenyl methane diisocyanate (MDI) and pyromelitic dianhydride (PMDA) in a mixture of N-methyl 2-pyrrolidone (NMP) and acetonitrile solvents with the volume ratio of 1:3 were used. The resulting sol was mixed with the acetone. The added acetone in the spaces of the gel led to swell the gel. Gel formation with the stable pores was carried out at the atmospheric acetone pressure in the autoclave. In the second part of this work, the polyester fabric coated with the porous polyimide nanostructure of through in situ. synthesis of porous polyimide structure on the fabric surface. The FTIR, FESEM and SEM tests, BET and mercury porosimetery analyze were used for characterization of polyimide samples. Also, the mechanical peroperties, flame retardant, oil absorption and droplets contact angle of textiles coated with porous polyimide structure were eva‎luated. The optimal sample with a concentration of 15% w/w having a porous structure with the density of 0.1885 g /cm2, the specific surface area of ​​104 m2 /g, porosity of 24%, and average pore diameter of 10 µm and total pore volume of 1265 mm3/g was achieved. The presence of a limited number of mesopores in the structure was confirmed by the results of nitrogen adsorption desorption analysis. The results showed the uniform coating of porous polyimide structure on the surface and thickness of the fabric which improved the tensile strength, flame retardant, hydrophobicity and absorption properties of the fabric. .The Youngʹs modulus of the coated samples increased 8.5 times compared to the non-woven layer.Also, an increase in the toughness of the sample after coating with a porous polyimide structure was observed. The results of the droplet test revealed the wetting time of the fabric increased by 4.5 times (from 126 s to 566 s) due to the porous polyimide coating. The flame retardant properties of the fabric coated with the porous polyimide nanostructure, which was investigated by the flame spread rate eva‎luating, which was significantly improved. Also, the oil absorption properties of coated sample slightly improved.

زهرا طالبي مزرعه‌شاهي

حسين توانايي، اكبر خدامي