Dynamic Viscoelasticity And Safety Analysis Of Spandex Under Different Preparation Conditions

Spandex fiber is a viscoelastic material.Thanks to its unique soft and hard block molecular structure,it has excellent properties such as high resilience,wear resistance,oxidation resistance and oxidation resistance.The spandex molecule has a variety of microscopic phenomena such as hydrogen bonding,microphase separation,and crystallinity.These changes in microstructure directly affect its viscoelasticity.Based on its wide application,its dynamic viscoelasticity is studied in order to prepare suitable spandex materials according to their use and application scenarios,so as to ensure the safe,reliable and efficient operation of materials on components.This study is guided by intrinsic safety.And different spandex fibers with different molecular weights,different N,N-dimethylethylenediamine?N,N?24?-EDA?and propylenediamine?EDA?ratio spandex and different Luola ratios are prepared.Their mechanical and microscopic characterizations were carried out,and their viscoelastic data are obtained by dynamic mechanical analysis test to study the relationship between dynamic viscoelasticity and preparation conditions.The main research contents are as follows:1)The spandex is prepared by dry spinning,and PTMG with molecular weights of 1.4k,1.8k,2.2k,2.6k and 3.0k is selected;N,N?24?-EDA:EDA ratios are 0/68,8/60,11/57 and 14/54chain extender;changing the ratio of Luola to 1.3,1.4,1.5 and 1.6 to obtain three groups of13 kinds of spandex fiber.2)After testing its microstructure and mechanical properties,it is found that with the increase of the molecular weight of the soft segment of spandex fiber,the breaking strength first decrease and then increases.When the molecular weight is 2.2k,the maximum value is62.79 cN.The rate of the urethane group?X_b?and the crystallinity?X_c?are both increased first and then decreased.As the ratio of N,N?24?-EDA/EDA chain extender increases,the elongation at break gradually decreases,and the breaking strength first decrease and then increase,the degree of urethane group X_b gradually increases,and the change of X_c is opposite to the change of glass transition temperature?T_g?of the soft segment,X_c gradually decreases.When the Luola ratio increases continuously,both urea carbonyl X_b and X_c increased first and then decreased,and the maximum values are 63.79%and 24.29%,respectively.3)By analyzing its dynamic mechanical temperature spectrum,it is found that with the increase of molecular weight of PTMG,the initial storage modulus(E^?24?)decreases first and then increases,the minimum value is 37.51 N/Tex,and the peak value of loss modulus?E^??exhibits the same law of,and the minimum value is 2.98 N/Tex.As the ratio of N,N?24?-EDA/EDA increases,the initial E^?24?of the fiber decreases gradually,the minimum value is32.78 N/Tex,and the peak value of E^?decreases with N,N?24?-EDA,soft segment.The T_g showed a trend of increasing in turn;the half-peak width on tan tantalum increased with the increase of the chain extender ratio,and the heat resistance of the fiber became better.As the ratio of the Luola increased,the initial E^?24?of the fiber increased first and then decreases.The maximum ratio of the molar ratio is 51.47 N/Tex at 1.4,and the peak value of E^?decreases with the increase of the molar ratio.The T_g of the soft segment decreases first and then increases.4)The temperature spectra of the three spandex fibers at 1 Hz,5 Hz,10 Hz and 25 Hz are shifted to the right as the frequency increases,and T_g increases in turn.The main curve obtained by superposition of the time-temperature equivalent principle spans 20 orders of magnitude.When the frequency increases from 10^-2 to 10¹⁸ Hz,the storage modulus gradually increases from the minimum value of 3.98 N/Tex to the maximum value of 39.81N/Tex.Using the relaxation time spectrum calculation method of Williams and Ferry to obtain the relaxation spectrum,it is found that the relaxation time of the molecular segment is mainly concentrated in the vicinity 10^-1010^-15 s.By calculating the relaxation activation energy??35?H?of the four spandex,the?35?H of the spandex is in the range of 238.01²68.15kJ/mol.