| Eco-friendly stiffening agent is a formaldehyde-free,green security finishing agent with excellent initial stiffened effect and storage stability.It is widely used in curtains,bags and special finishing fields,and has extremely high application value.However,the fibers or layer of stiffening agent on stiffened fabric is usually subjected to hygroscopic in the subsequent storage process,and caused the problem of softening of the handle.Therefore,how to avoid and reduce the softening of the handle of stiffened fabrics has become one of the research focuses in this field.Although the soft feeling of the handle is generally found in the finishing process of the eco-friendly stiffening agent,but the softening mechanism has not been effectively studied,and the degree of softness of the handle is not accurately determined.Therefore,quantitatively judging the degree of softening of the fabric,understanding the softening mechanism,and designing a method to suppress the softening of the fabric,has an important practical significance for improving the performance of the stiffened fabric.Firstly,the hygroscopic behavior of polyvinyl acetate(PVAc)stiffened polyester fabric in different storage environments was studied.The hygroscopic rate of PVAc stiffened polyester fabric during hygroscopic and under different environmental conditions was determined by gravimetric method.The Freundlich and Langmuir isotherm adsorption model was used to fit the hygroscopic isotherm curve of PVAc stiffened polyester fabric.It was found that the water molecule adsorption process is more in line with Freundlich's multilayer physical adsorption model.The quasi-first-order dynamic equation and the quasi-second-order dynamic equation are used to fit the hygroscopic process.It is found that the hygroscopic process of pure polyester fabric is more in line with the quasi-first-order kinetic equation,and the water molecules produce a simple physical adsorption process on the fiber surface;the hygroscopic process of PVAc stiffened polyester fabric is more in line with the quasi-second-order kinetic equation,it has undergone complex processes including the adsorption of water molecules on the surface of the fibers and the adsorption or diffusion to the finished film.Finally,according to the model fitting,the hygroscopic mechanism of PVAc stiffened polyester fabric was obtained.Based on the study of the hygroscopic behavior of polyester fabrics stiffened by PVAc.The fabric handle value after hygroscopic and before hygroscopic were determined,and a new method for evaluating the softness of the handle was established.The verification experiment shows that the method is suitable for the softness evaluation of cotton and polyester fabrics stiffened by different stiffening finishing agents.The mechanism of hygroscopic and softening of PVAc stiffened polyester fabric was studied.Scanning electron microscopy(SEM)was used to characterize the microscopic morphology of the fabric before and after hygroscopic.It was found that the interface and bond failure between the PVAc stiffening agent film and the polyester fiber appeared after hygroscopic;by differential scanning calorimetry(DSC)and Shore hardness tester characterizes the Tg and Shore hardness values of the stiffener film after hygroscopic.It is found that the Tg and Shore hardness values of the stiffener film decrease after hygroscopic.In the hygroscopic-drying cycle experiment,the completely non-hygroscopic polyester stiffened fabric has a high stiffness value(116).During the hygroscopic cycle,the stiffness value of the re-dried fabric is almost maintained at about 107.The stiffness value of the un-dried fabric was almost maintained at around 102,that is,the fabric had a decrease in irreversible stiffness value after the first hygroscopic process.Impact-damage experiments on fabrics have shown that the interface and bond failure between the stiffener film and polyester fibers results in a decrease in the stiffness value and is unrecoverable.Therefore,the hygroscopic softening of the PVAc stiffened polyester fabric is caused by the decrease in the hardness of the reversible stiffener film and the destruction of the irreversible combination of t fiber and stiffener film.The mechanism of hygroscopic and softening of PAcr stiffened cotton fabric was studied.The study found that cotton fabrics are highly hygroscopic fabrics,and stiffness value decreased during the hygroscopic process is test by intelligent style instrument tester.The DSC and Shore hardness tests showed that the Tg and Shore hardness values of the stiffener film decreased after hygroscopic process,similar to the PVAc film.The SEM showed that there was no interface damage and bond failure between the PAcr stiffening agent film and cotton fibers.In the hygroscopic-drying cycle experiment,compare with the stiffness value of the fabric under the initial non-hygroscopic condition,the stiffness value of the sample re-dried after the hygroscopic cycle were consistent,indicating that the softness of the handle can be recovered by drying process.Therefore,the softness of the PAcr stiffened cotton fabric is mainly caused by the reversible plasticization of stiffener film and the cotton fibers.In this paper,a model for the distribution of water molecules on the surface of stiffened fabrics is proposed.Based on this,a new evaluation method for hygroscopic and softening of stiffened fabrics is established,which solves the problem that the fabrics in the industry cannot be accurate and quantitative evaluation.On the basis of the mechanism of hygroscopic and softening of PVAc stiffened polyester fabric and PAcr stiffened cotton fabric was obtained,which was instructive for the suppression of fabric softening and the development of new stiffening finishing agent in actual production. |
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