| Spandex is developed as a novel self-adaptive fiber to Z-pinch for its high elasticity,corrosion resistance and oxidation resistance,while it was already used in special medical equipments,seat belt,sports apparatus and garment textile etc.Along with the widely use and rapid developing requirements,it's significant to ensure materials safe in use.In this paper,to obtain the optimal material,microstructures of spandex were studied under different preparation conditions.Besides,its service life was infered by thermal stability of spandex under high temperature,where opinions were provided to ensure spandex safe in use.(1)Polytetramethylene ether glycol(MDI),ethylenediamine/propylamine(EDA/PDA)and 4,4'-diphenylmethane diisocyanate(PTMG)were used as hard segments,chain extenders and soft segments respectively.To study the effect of preparation on the microstructure and properties of spandex,different R value(nMDI/nPTMG)and PTMG molecular weight were used,where the hydrogen bonding degree was characterized by Fourier infrared spectroscopy(FTIR),microphase separation was tested by dynamic mechanical analysis and small angle X-Ray scattering,mechanical properties were obtained by the universal material testing machine,and the effect of the microphase separation degree on properties of spandex were analyzed.Following conclusions were drawn: When the R value increased from 1.66 to 1.86 or the PTMG molecular weight increased from 1400 to 3000,the hydrogen bonding degree,the microphase separation degree,and the breaking strength all increased first and then decreased.When the R value was 1.76 and the PTMG molecular weight was 2,200,the greatest properties were showed,such as the hydrogen bonding degree,the microphase separation degree,the breaking strength,300% elastic recovery rate,and internal friction.(2)Disperse blue 56 dye,dispersant MF,acetic acid solution(1mol/L),sodium acetate(1mol/L)buffer solution and sodium hydroxide solution were used to dye spandex under various dyeing pH values,dyeing temperatures,and dyeing time.The effect of dyeing process on spandex structure and mechanical properties were obtained by a series of test including FTIR,the X-ray diffraction test,the surface color depth test,the color fastness rating,and a universal material testing machine.Finally,the optimal dyeing process under low damage and high dyeing property was about 125?~130?,30 min,and pH 5~6.(3)The thermal decomposition characteristics of spandex in nitrogen and air were studied,where the life-temperature curve in nitrogen and air was calculated using the temperature of 5% weight loss as a standard to calculate the service life.Results showed that: 1)The thermal decomposition temperature range of spandex in nitrogen was approximately 240? to 450?,where it was about 250? to 550? in air with more complex reaction process.Besides,with the increase of heating rate,the thermal decomposition curves of spandex under both atmospheres would show hysteresis effects and move to high temperature areas.2)According to Kissinger method,the activation energy in air is 169.4726kJ/mol lower than 186.9516kJ/mol which is in nitrogen.The activation energy obtained by OFW method and Friedman method showed similar activation energy curves.The average activation energy in nitrogen and air is 151.1530kJ/mol~155.1406kJ/mol and 133.4204kJ/mol~135.7947kJ/mol respectively,indicating that spandex was more easily decomposed in air than in nitrogen.3)The relational expression between temperature and use time in nitrogen and air was derivated that the life of spandex was 62.17 years in nitrogen at room temperature(25?)respectively,while the life was only 3.80 years in the air and as the temperature rises,the life expectancy decreases in both atmospheres,indicating that high temperature and oxygen had a serious aging effect on spandex which directly affected its service life. |
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