Study On The Viscoelasticity Of Spandex Based On Structural Characterization And Its Application Safety Analysis

Spandex due to its microphase separation structure and the presence of a large number of hydrogen bonds,it has a lot of excellent properties,such as excellent weather resistance,corrosion resistance,low temperature flexibility and high elastic recovery.Therefore,spandex plays an important role in the fields of textile,biology,medical treatment,physics,and national defense.However,in different application scenarios,spandex needs to meet the corresponding conditions of use in order to ensure the accuracy,reliability,and safety of related components.As we all know,the performance of polymer materials is closely related to its structure,and the structure has a close relationship with the types of raw materials for preparing polymer materials,raw material ratios,and process flow.Therefore,in this paper,spandex spinning method was used to prepare spandex with different spinning dope concentration and different mixed chain extender ratios.The effects of these two preparation factors on the structure of spandex were studied by a variety of characterization methods.Viscoelastic,select the best preparation conditions for the corresponding application field to ensure the safety and reliability of spandex in the use process.The main research content is as follows:1)PTMG with a molecular weight of 1800 is selected as the soft segment,MDI,EDA and 1,2-PDA is a hard segment,and five kinds of spandex were prepared by a dry spinning method with concentrations of 28%,30%,32%,34%,and 36%,respectively,and five kinds of mixed chain extenders were prepared(EDA: 1,2-PDA)spandex with a molar ratio of 3.4:1,4.5:1,6.3:1,10:1,and 21:1.2)The microstructure of spandex was characterized by FTIR,XRD,DSC,AFM,and SAXS.The results showed that:(1)as the concentration of spinning dope increased from 28% to 36%,the spandex index,micro-phase separation degree,and crystallinity of spandex were gradually increased,(2)as the ratio of the mixed chain extender increases from 3.4 to 21,the spandex index,the degree of micro-phase separation,the distance between hard segments,and the radius of rotation of the hard segment will gradually increase.3)The effects of spinning solution concentration and mixed chain extender ratio on the stress relaxation and creep of spandex were studied.The results show that:(1)the total stress relaxation rate of spandex decreases with the increase of the concentration of spinning solution or the ratio of mixed chain extender small,(2)analysis of generalized Maxwell model parameters with n=2 known that the greater the spinning stock concentration or the ratio of mixed chain extender,the greater the elastic modulus of elasticity and the smaller coefficient of viscosity,(3)by fitting the parameters of the spandex generalized Maxwell model under different strains,the formula for predicting the stress relaxation in the strain range from 50% to 500% was obtained,(4)the greater the spinning stock concentration or the greater the spandex ratio,the lower the creep strain level and the higher the creep recovery rate.4)The influence of concentration of spinning solution and ratio of chain extender on dynamic viscoelasticity of spandex was studied.The principal curve of spandex storage modulus E ? and loss modulus E ? ? was superimposed using time temperature equivalence principle.The results show that:(1)the greater the concentration of spinning dope,the smaller the mechanical loss,(2)with the increase of the ratio of the mixed chain extender,the span of the main curve gradually decreases,and at the same frequency,the storage modulus and the loss modulus increase with the increase of the chain extender ratio,(3)the molecular weight distribution becomes narrower as the ratio of the mixed chain extender increases,and the larger the ratio of the mixed chain extender,the greater the number or the "concentration" of the segmental moving units of the spandex containing the same relaxation time,making the mixing the viscoelasticity of spandex,which has a higher chain extender ratio,is more sensitive to frequency and less sensitive to temperature.5)For the safety analysis of the use of spandex,the appropriate preparation conditions should be selected according to the actual application scenario of spandex.For example,when spandex is used in the area where dimensional stability is required,the concentration of spinning dope should be selected to be 36%.The spandex ratio was 21 to produce spandex.Only in this way can we guarantee a more reliable and safer product.