Preparation Of Thermal Protective Polysulfonamide Textiles Based On Crystal Growth And Aerogel Technology

With the development of society,the demand for protective clothing with thermal insulation and fire resistant properties is increasing in metallurgy,fire,military and other fields in China.However,the existing protective clothing does not possess the excellent protective property to ensure the wearer safe when they access to the fire ground.The improvement of the thermal insulation property and fire resistant performance of materials plays a decisive role on developing high-performance protective clothing.In this research,the polysulfonamide（PSA）fabric was used as the substrate,the thermal insulated and flame resistant PSA/SiO₂/Mg（OH）₂ composite was prepared based on the crystal growth technology;the thermal insulated and flame resistant PSA/ aerogel composites,including PSA/aluminum hydroxide aerogel composite,PSA/silica-aluminum hydroxide composite,and PSA/magnesium-aluminum double hydroxide aerogel composite,were prepared on the basis of the aerogel technology.Compared with the original PSA fabric,the thermal insulation and flame resistance properties of all the composites were improved greatly.The main work was as follows.The thermal insulated PSA fabrics were prepared based on the crystal growth theory,and their properties were studied.The thermal insulated and flame resistant PSA composite fabrics wrapped by magnesium hydroxide and silica（PSA/SiO₂/Mg（OH）₂）were prepared by growing Mg（OH）₂ crystal seed on the PSA fabrics finished with silica and then carrying on the second growth of Mg（OH）₂ crystals.Through controlling the growth conditions such as growth time,raw material concentration,the particle size and solution concentration of silica and so on,the surface of PSA fabrics were wrapped successfully by silica and Mg（OH）₂ crystals of different morphologies,for example,lodging flake,erect petal,honeycomb,inverted triangular pyramid,inverted triangle platform and rod-like shape,etc.The initial decomposition temperature and the maximum thermal decomposition temperature of the PSA fabric coated by silica and Mg（OH）₂ were elevated greatly,and the PSA coated by silica and honeycomb-shaped Mg（OH）₂ had the highest initial decomposition temperature with the value of 451.2 °C,and the maximum thermal decomposition temperature of the composite material was as high as 483.6 °C.The thermal conductivity coefficient and vertical burning damage length of the composite fabrics were decreased by wrapping the PSA fabrics with silica and Mg（OH）₂ crystals,which indicated that the thermal insulation and flame resistance properties of composites were improved.The morphology of Mg（OH）₂ has an important effect on the thermal conductivity coefficient of the composites.The thermal conductivity coefficient was tested by TC-3000 hot wire thermal conductivity tester at 25 °C.The results showed that when the morphology of Mg（OH）₂ crystal on the fabric surface was inverted triangular pyramid-like mixed with inverted triangular platform-like and rod-like,the thermal conductivity coefficient of the prepared PSA/SiO₂/Mg（OH）₂ composite fabric was the lowest with the value of 0.0553 W/（m·K）.When the morphology of Mg（OH）₂ crystal on the fabric surface was honeycomb-like,the thermal conductivity was 0.0559 W/（m·K）.When the morphology of Mg（OH）₂ crystal on the fabric surface was triangle platform-like,the thermal conductivity coefficient was 0.0568 W/（m·K）.They were all lower than the thermal conductivity coefficient of the original PSA fabric with the value of 0.0975 W/（m·K）.The PSA/SiO₂/Mg（OH）₂ composite fabric had excellent flame resistance and its damage length was 1.20 cm,and it belonged to the nonflammable material.The porous structure was beneficial to improve the thermal insulation property of the materials,to further improve the thermal insulation property of the PSA fabrics,aluminum hydroxide aerogels were prepared by sol-gel method and ambient drying method,and they were successfully finished on the surface of PSA fabrics.The pore structure and the apparent density of aerogels affected the thermal insulation property.With the increase of the pore volume or the decrease of the apparent density,the thermal insulation coefficient of the composites became lower.The pore structure and apparent density of aerogels were regulated and controlled by changing the raw material ratio.The white translucent bulk aluminum hydroxide aerogels were obtained.The apparent density was 0.172⁰.645 g/cm3,the pore volume was 0.717².325 cm3/g,the specific surface area was 292.703⁴08.696 m2/g,and the average pore diameter was 10.9²1.8 nm.The aerogel was crystallized in γ-Al OOH boehmite crystal form,and its spatial network structure consisted of interconnected nanometer-sized fibrous particles.PSA/aluminum hydroxide aerogel composite fabrics were successfully prepared by sol-gel forming method and ambient drying method.The properties of thermal insulation and flame resistance of the composite fabrics were characterized by the thermal conductivity at 25 ℃ and the vertical burning damage length.Compared with the original PSA fabric,the thermal conductivity coefficient of the composite fabric was decreased from 0.0975 W/（m·K）to 0.0599 W/（m·K）,and the vertical burning damage length was shorted from 4.90 cm to 1.25 cm.In short,the thermal insulated and flame resistant properties of the composite fabric were improved greatly.In order to further decrease the apparent density and the pore volume of the aerogel,tetraethyl orthosilicate was added in the preparation course of aluminum hydroxide aerogel and the white translucent bulk silica-aluminum hydroxide aerogel was obtained.Its apparent density was 0.140 g/cm3,the specific surface area was 366.686 m2/g,the pore volume was 2.798 cm3/g,and the average pore diameter was 28.3 nm.The silica-aluminum hydroxide aerogel was the composite of γ-Al OOH boehmite crystal and amorphous SiO₂,and its spatial network structure consisted of interconnected nanometer-sized leaf-like particles.The PSA/silica-aluminum hydroxide aerogel fabric composite was successfully fabricated by the sol-gel forming method and the ambient drying method.The properties of thermal insulation and flame resistance of PSA/ silica-aluminum hydroxide aerogel composite fabric were characterized by the thermal conductivity at 25 ℃ and the vertical burning damage length,which were tested by the TC-3000 hot wire thermal conductivity tester and the vertical combustion tester respectively.Compared with the original PSA fabric,the thermal conductivity coefficient of the composite fabric was decreased from 0.0975 W/（m·K）to 0.0581 W/（m·K）,and its vertical burning damage length was shorted from 4.90 cm to 2.85 cm.In short,the thermal insulated and flame resistant properties of the PSA/silica-aluminum hydroxide aerogel composite fabric were improved greatly.In order to further improve the thermal insulation property of aluminum hydroxide aerogel,the white bulk magnesium-aluminum hydroxide aerogels were prepared by sol-gel method and ambient drying-vacuum drying method.The phase composition,the apparent density and the pore structure of magnesium-aluminum hydroxide aerogels were regulated and controlled by changing the raw material ratio.Magnesium-aluminum hydroxide aerogels with different phase compositions were obtained,the apparent density was 0.108⁰.689 g/cm3,the pore volume was 0.655².430 cm3/g,the specific area was 177.514⁴59.376 m2/g,and the pore diameter was 5.1³2.4 nm.The spatial network structure consisted of interconnected nanometer-sized lamellar particles or spherical flower-like particles which were composed of interlaced and superposed flakes.PSA/magnesium-aluminum double hydroxide aerogel composite fabrics were successfully prepared by the sol-gel forming method and the ambient drying-vacuum drying method.The properties of thermal insulation and flame resistance of PSA/aerogel composite fabrics were characterized by the thermal conductivity at 25 ℃ and the vertical burning damage length,which were tested by the TC-3000 hot wire thermal conductivity tester and the vertical combustion tester respectively.Compared with the original PSA fabric,the thermal conductivity of the composite fabric was decreased from 0.0975 W/（m·K）to 0.0532 W/（m·K）,and the vertical burning damage length was shorted from 4.90 cm to 2.10 cm.In short,the thermal insulated and flame resistant properties of the PSA/magnesium-aluminum double hydroxide aerogel composite fabric were improved greatly,and the composite fabric belonged to thermal insulated and non-flammable materials.Comparing the thermal insulated and flame resistant properties of PSA/SiO₂/Mg（OH）₂ composite fabrics,PSA/aluminum hydroxide aerogel composite fabrics,PSA/silica-aluminum hydroxide aerogel composite fabric and PSA/magnesium-aluminum double hydroxide aerogel composite fabrics,it could be seen that the thermal insulation property of the PSA/magnesiumaluminum double hydroxide aerogel composite fabric was the best,and its thermal conductivity coefficient was as low as 0.0532 W/（m·K）.The flame resistant property of the inverted triangle platform-like magnesium hydroxide wrapped PSA/SiO₂/Mg（OH）₂ composite fabric was the best,and the vertical burning damage length was as low as 1.20 cm.The research results of this paper can provide the reference for the development of thermal protective textiles which have high heat insulation property and excellent fire resistance performance.