Preparation And Performance Of Cross-linked Starch-enhanced Shear Thickening Gel And Its Composite Fabric

In order to meet the market's requirements for lighter,stronger,and softer protective materials,various soft protective materials have been continuously introduced.Shear thickening gum(STG),a new type of protective material,has excellent energy absorption benefited from its viscosity conversion under different shear conditions.It is easy to prepare,stable in nature,low-density,lightweight,and easy to transport and store.The field of protection is getting more and more attentions.However,STG also has shortcomings such as low initial viscosity,storage modulus,and low yield stress,which limits the application range of STG.At present,the blending method is mainly used to add functional fillers or composite with highperformance fabrics to improve the mechanical properties of STG.In this thesis,sodium trimetaphosphate(STMP)was used as the crosslinking agent to prepare high crosslinking degree sodium trimetaphosphate crosslinked starch(CS).It was blended and heated with high-viscosity hydroxy silicone oil(HV-PDMS)and boric acid(H3BO3)to obtain a cross-linked starch-enhanced shear thickening glue(CS-STG).A rotary rheometer was used to test the rheological properties of the product.In the steady-state test,CS-STG has significant advantages,and its shear modulus far exceeds that of Ca CO3 and Si O2 modified STG samples,even reaching 28.24 times that of STG.CS-STG performs well in large oscillation mode,and its energy dissipation capacity is greatly enhanced.The area of the hysteresis curve of CS-STG-50 is 15.49 times that of STG.The storage modulus and loss modulus of CS-STG increase with the increase of CS addition,and there are significant differences between the samples after statistical analysis(p<0.05).The storage modulus and loss of CS-STG-50 The maximum modulus is 10.40 times and 10.43 times that of STG,respectively.Therefore,in order to study the reinforcement mechanism of CS to STG,X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectrometer(FTIR)were used for characterization.The XPS results confirmed that CS can form the Si-O-C covalent bond by the grafting reaction with low-viscosity hydroxy silicone oil(LV-PDMS).At the same time,FTIR confirmed that the two molecules interacted to form a hydrogen bond.Under the combined effect of the two,the rheological properties of CS-STG have been significantly improved.Based on the good shear thickening effect of CS-STG,it is introduced into Kevlar fabric(Aramid 1414,Kevlar)to enhance the protective ability.The Kevlar fabric was pretreated with a low-temperature plasma treatment device,and the CS and STG were respectively compounded with the pretreated Kevlar fabric using the "two-step method" to prepare CS-STGKevlar.Using SEM to observe the surface morphology of the sample,it was found that the surface of the Kevlar fabric after plasma treatment became rough.XPS data shows that plasma treatment increases the proportion of oxygen on the surface of the sample and produces a large number of oxygen-containing groups.This provides reaction sites for the formation of Si-OC covalent bonds between the surface of Kevlar fiber and Polydimethylsiloxane(LV-PDMS)at the interface.Improve the interface compatibility of Kevlar fabric and STG.The experimental data of single yarn tensile strength show that CS-STG can not increase yarn strength.However,the experimental data of single yarn pull-out test shows that CS-STG enhances the protective performance of Kevlar fabric,mainly due to the shear thickening effect that occurs under high load,increases the interweaving resistance,reduces the slip between adjacent yarns,and makes the fabric It tends to be more integrated in the impact,and has a higher specific energy absorption in the hammer impact test.In addition to improving the mechanical properties of Kevlar,the substrate can also enhance the water-repellent and heat-resistant properties of the composite fabric.PDMS is attached to the Kevlar surface,and the contact angle test results show that the waterproof performance of the fabric is improved.STG reduces the thermal weight loss of composite materials within 320 ? in the thermal weight loss test.Therefore,CSSTG-Kevlar can be used as a multi-functional composite material for human protection under extreme conditions,such as firefighting,extreme sports,and military application.