| Recently,studies on high temperature resistance fabric which can be used as outer mechanical of fire fighter and military uniform have attached extensive attention in the field of material chemistry.This kind of material must have some special properties,such as:1. Resistance to open fire(≥800℃) more than 10 minutes;2.An excellent heat insulation property: 3mm-thick material has a temperature difference of inside and outside more than 450℃tested on temperature of 800℃;3.Flexibility under high temperature.Now,no materials which fully meet all of above properties can be provided.Polysulfonamide has the excellent properties of high temperature resistance,corrosion resistance,radiation protection,electrical insulation and good mechanical properties.Mg(OH)2 has been extensively used as flame retardant and the smoke suppressant in various polymeric materials due to its ability to undergo endothermic dehydration in fire conditions.Both it self and its dehydrated products MgO are environmental friendly flame retardants.According to previous studies in our group,oriented Mg(OH)2 lamellar nano-crystals have been grown on organic polymer fiber materials by original crystallization and secondary crystallization,which can improve the properties of thermal stability and thermal radioprotection.In this research,lamellar magnesium hydroxide nano-crystals were secondary crystallized onto modified polysulfonamide fabric.The influences of the concentration of sodium hydroxide,the original solution system,the time of the secondary crystallization and the condition of the hydrothermal treatment were studied in detail.The best growth condition of Mg(OH)2 lamellar nano-crystals was as follows:the fabric with Mg(OH)2 seeds were put into the saturated system which was obtained by filtering the solution of magnesium hydroxide,then adding NH3·H2O solution(0.1 mol/L) 4mL/h and MgCl2 solution(0.05mol/L) 4mL/h;and the secondary crystallization of Mg(OH)2 on fabric was kept for 7 days,finally the surface were covered with Mg(OH)2 lamellar nano-crystals.Comparing with the fabric with absorbing seeds,the fabric with padded seeds could get denser and vertical crystals after secondary crystallization,and have the better property of radiation protection and heat insulation.The fabrics with different oriented magnesium hydroxide crystals were obtained by changing the concentration of sodium hydroxide.Lamellar magnesium hydroxide can be changed to lamellar magnesia crystals by heat treatment,and keep the same configuration of the crystal. The hydrothermal treatment with Mg(OH)2 saturated solution at 80℃for 6 hours can changed the morphology of Mg(OH)2 lamellar nano-crystals from vertical to horizontal.The polysulfonamide fabrics grown with lamellar Mg(OH)2 nano-crystals have been characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),thermal gravimetric analysis(TGA),heat conduction coefficient detector and optical wavelength spectrometer.The XRD studies revealed that Mg(OH)2 was lamellar.The SEM studies showed that the lamellar crystals were located like vertical fish scales or procumbent scales on the surface of polysulfonamide fabric.The heat conduction coefficient detector studies represented the heat insulation effect of the fabric was improved after secondary crystallization.Through optical wavelength scanning,the radioprotection property was observed.The fabric with padding seeds has the best effects of heat insulation and radioprotection after secondary crystallization.
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