| An adjustable assembly of Mg(OH)2 nano-crystals on a flat substrate,which has been extensively used as flame retardant materials,will enhance the functionality of the materials,such as the mechanical,electrical,optical and physical chemical properties.In our study,Mg(OH)2 lamellar nano-crystals has been grown on citric acid modified cotton fabric by secondary crystallization and in-situ crystallization,which can provide the fabric with special properties.Under action of a static electric field the assembly of lamellar Mg(OH)2 nano-crystals on a flat substrate——modified cellulose membrane was also studied,which can provide the fabric with special properties.Firstly,Mg(OH)2 lamellar nano-crystals on citric acid modified cotton fabric by secondary crystallization was investigated.Mg(OH)2 was provided by a simple reaction of MgCl2 and NH3·H2O,without any organic additive or catalyst.The lamellar nano-crystals grown on cotton fabric have been characterized by X-ray diffraction(XRD),scanning electron microscope(SEM), thermal gravimetric analysis(TGA),a Tiniius Olsen Corporation universal strength tester,a vertical flammability test,a DRL-Ⅱthermal conductivity cryoscopy and optical wavelength spectrometer.The XRD studies revealed that Mg(OH)2 was lamellar.The SEM studies showed that the lamellar crystals were perpendicular to the surface of cotton fabric.The TGA,vertical flammability test and thermal conductivity studies indicated that the growth of Mg(OH)2 on modified cotton fabric could be applied to the filed of fire-proof.Through optical wavelength scanning,the radioprotection property was observed.Although citric acid modification damaged the cotton fabric,the Mg(OH)2 crystals coating exhibit enhanced mechanical properties.Secondly,under action of a static electric field the assembly of lamellar Mg(OH)2 nano-crystals on modified cellulose membrane during the in-situ crystallization have been studied. The cellulose membrane was prepared in Urea-NaOH aqueous system;the modified cellulose membrane was prepared by the citric acid;a Dc high voltage generator provided a horizontally oriented field of the intensity 30KV;the membrane was placed in two different directions(parallel or perpendicular to the ground);compared with the assembly of the lamellar Mg(OH)2 nano-crystals without electric field,the effect of the oriented electric field on the assembly of the lamellar Mg(OH)2 nano-crystals on modified cellulose was studied.The lamellar nano-crystals grown on membrane have been characterized by X-ray diffraction(XRD) scanning electron microscope(SEM).The XRD studies revealed that Mg(OH)2 was amorphous.The SEM studies showed that in an oriented electric field,Mg(OH)2 crystals were inclined to grew flatly on the modified membrane after in-situ crystallization,but there is difference between the assembly of Mg(OH)2 paticles on the two directions within a electric field:perpendicular to the ground,most of nano Mg(OH)2 paticles stand upright on the surface of the membrane;parallel to ground,most of lamellar nano Mg(OH)2 paticles are lying down,parallel to the membrane.For study the influence of the oriented field on the functionality of cotton fabric with oriented assembly of nano Mg(OH)2 crystals,modified cotton fabric by in-situ crystallization in electric field was prepared. The tests of cotton fabric with the oriented assembly of Mg(OH)2 nano-crystals indicated that under action of a static electric field the e modified cotton fabric gives the best fire retardant,heat insulation and radioprotection properties.
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