Studies On The Preparation And Properities Of Flame Retardant Polyamide 6 Fibers

Because of their excellent properties such as high tensile strength,abrasion resistance,and superior resilience,polyamide 6(PA6)fibers are extensively used in a variety of fields including civil,industrial and military.However,the limiting oxygen index(LOI)of PA6 fibers is about 21,which make them burn easily.In recent years,with the increasing applications of the PA6 fibers,the fire hazards caused by their flammability are also increasing.Thus,to improve the flame retardancy of PA6 fibers has essential research value and can expand their potential usefulness.Melamine cyanurate(MCA)is a classic flame retardant used for PA6,and we still use it in this study.But the difference is we change the way that MCA was introduced into PA6 by designing a serious of reactions.The MCA/PA6 composite were prepared successfully,then the flame retardant PA6 fibers were prepared by melt spinning.The main contents and conclusions of the thesis are as follows:(1)Cyanuric acid-hexane salt(CA-HMDA salt)and adipic acid-melamine(ADA-MEL salt)were prepared by the reaction of cyanuric acid with equimolecular amount of hexane diamine and adipic acid with equimolecular amount of melamine at aqueous environment,respectively.The effect of the reaction factors such as reaction temperature,reaction time and the amount of solvent were investigated.Within the limits of experiment,the optimal reaction condition for preparation of CA-HMDA salt are:temperature:75 ?,time:2.5h,and for CA-HMDA salt are:temperature:85?,time:2h,solvent:600ml.Fourier transform infrared spectroscopy(FT-1R)indicated that the associative structures existed in the two kinds of salt.Thermogravimetric analysis(TGA)data showed the thermal stability of the salts can meet the requirements for polymerization temperature.The solubility experiment results demonstrated the solubility of CA-HMDA salt and ADA-MEL salt were improved comparing with CA and MEL.(2)The CA-HMDA salt and ADA-MEL salt were introduced into the melt s-caprolactam,and then synthetize the MCA/PA6 composite by hydrolytic polymerization.The structure of the MCA/PA6 composite were characterized by FTIR and wide angle X-ray diffraction(WAXD),and the results indicated that the self-assembly reaction between CA and MEL was complete and the MCA/PA6 composite was prepared successfully.The intrinsic viscosity demonstrated that the introduction of MCA reduce the relative molecular weight of PA6.The research on the interface structure showed that there were chemical bonds combining MCA and PA6.Both vertical burning test(UL94 test)and limiting oxygen index test(LOI test)indicated the flame retardant performance of MCA/PA6 was significantly greater than that of PA6.When the content of MCA was 8wt%,the UL94 level was V-0 rating and the LOI was 29.3%.(3)Based on the TGA and differential scanning calorimetry(DSC)data,the thermal degradation kinetics and non-isothermal crystallization kinetics of PA6 and MCA/PA6 composite were investigated.According to the results,the thermal degradation activation energies of MCA/PA6 were lower than PA6,and increased with the increase of conversion rate.The Ozawa analysis failed to provide an adequate description of the nonisothermal crystallization of the samples due to the process of secondary crystallization.The method developed by Mo was successful in describing the nonisothermal crystallization of the samples,the results indicated that the introduction of MCA into PA6 weaken the crystallization.The activation energy for nonisothermal crystallization of PA6 and MCA/PA6,based on the Kissinger method and the Takhor method respectively,were evaluated,and it was concluded that the absolute value of activation energy for MCA/PA6 is higher than PA6.(4)In the reasonable process conditions,the MCA/PA6 was a kind of good fiber-forming composite and had excellent spinnability.The package build was good and the drawing was easy to control.By SEM,sound velocimeter,strength and elongation tester,the structures and properties of PA6 and MCA/PA6 fibers were characterized and investigated The results showed the tensile strength,orientation,degree of crystallinity of the MCA/PA6 fibers were lower than PA6 fibers.It was found that the crystal size increased,but the crystal space changed a little.The boiling water shrinkage and dry shrinkage ratio of MCA/PA6 fibers increased.In general,the MCA/PA6 fibers could reach the criterion of the clothing and household fabrics.