Preparation,Performance And Application Of Nano Silver/Biomass Conductive Rubber Film

Rubber,as a traditional flexible material,has shifted its research from mechanical enhancement to the development of functional applications.For example,after endowing it with conductive function,it can be used in wearable flexible sensing,soft robots,and intelligent health monitoring.However,traditional processing methods is difficult to distribute conductive fillers to form a special conductive filler network structure.Therefore,the functionalized applications of the prepared conductive rubber are relatively single,and currently most of them are concentrated in strain sensing.Introducing biomass rich in polar groups（natural small molecules,natural polymer and their derivatives,etc.）into conductive rubber can provide additional functional applications such as humidity response and self-healing.Based on this,in this paper,conductive network structure is designed by using biomass and nano silver to study its structure-performance relationship,and explore its functional applications.The specific research content is as follows:（1）A composite was prepared by carboxylated styrene butadiene rubber（XSBR）latex and natural small molecule citric acid（CA）which used as a reinforcing and moisture sensitive material.The effect of CA on the microstructure and morphology of the composite material was investigated.In the composite with a content of 60 wt%CA,the tensile strength and Young’s modulus could reach 7.83 MPa and 31.2 MPa,which were 4.1 and 60 times higher than XSBR,respectively.However,high content of CA would produce crystallization,which was not conducive to the conductive application.We chose to introduce silver nitrate of 2 wt%into a system with lower CA content to prepare silver nanoparticles（Ag NPs）in situ.By utilizing the volume exclusion effect of rubber latex particles,we constructed a conductive pathway and prepared a conductive rubber with a conductivity of 10^-6 S/m.The conductive pathway gradually underwent damage or reconstruction with the stretching and relaxation of the rubber matrix which was used as a strain sensor to monitor finger joint movement.In addition,a large number of polar groups on the CA molecule made the composite exhibit strong hydrophilicity and hygroscopicity.Within 10 minutes of relative humidity changes,the current changed significantly.In addition,CA and Ag NPs could synergistically inhibit the growth of Escherichia coli and Staphylococcus aureus,and exhibited long-term antibacterial effects.In the turbidity method antibacterial experiment,they showed an antibacterial effect of more than 96 h.（2）Due to the inability of CA to form a network structure that run through the entire rubber matrix,the application of conductive rubber in humidity sensing was limited.In addition,zero-dimensional Ag NPs were difficult to form more continuous conductive pathways,which affected the composite’s conductivity.Therefore,aldehyde modified carboxymethyl starch sodium（ACMS）was replaced with CA,and[Ag（NH₃）₂]⁺solution was introduced into the system.Based on the reducibility of ACMS,silver nanosheets（Ag NFs）were prepared by silver mirror method.After mixing with XSBR latex to form a composite,a more continuous conductive pathway was constructed to prepare conductive rubber.The conductive rubber had a higher conductivity,with a conductivity of 0.0550 S/m when Ag NFs were 30 wt%.The application of polar groups on ACMS molecular chains in humidity sensing based on their hydrophilicity was explored.Compared to commercially available electronic hygrometers,it exhibits a faster response speed:the response time for humidity to changed from 25%RH to 27%RH is only 1 s,and it only took 134 s to reach the ambient humidity（61%RH）.And its application in respiratory detection was explored.This work provides a new approach for the application of biomass with active groups in humidity sensing materials.（3）Based on the above system,Ag NPs were introduced into the system,and a synergistic conductive network structure was constructed between Ag NPs and Ag NFs in rubber/ACMS.This structure endowed conductive rubber with strain insensitivity.In addition,the introduction of Ag NPs brought photothermal conversion performance to conductive rubber.The effect of nano silver content on microstructure was studied,and the relationship between synergistic conductive network structure and strain insensitive resistance was examined,and the mechanism of strain insensitive resistance formation was explained.Two dimensional large-sized Ag NFs could overlap with each other,forming stable conductive pathways.Whenε<9%,the maximum value of（R-R₀）/R₀ was only0.001.When 9%<ε<At 143%,slightly agglomerated Ag NPs were separated into individual Ag NPs with a diameter of 20.07 nm,which was conducive to forming additional conductive path contact points and forming electron tunnels to maintain stable conductivity.Therefore,within this strain range,the composite had a high quality factor（Q=9.09）.Based on the photothermal effect of Ag NPs,the composite material had a maximum photothermal conversion efficiency of 78.6%when the nano silver content is 30 wt%.its application in the field of photothermal generators was explored,which could output a voltage of 0.44 V under near-infrared radiation of 0.67 W/cm².The"light-thermal-electric"and"thermal-electric"conversion properties of conductive rubber was explored,and their applications in infrared light sensing and wearable temperature sensing were studied.This work proposes an innovative approach for designing strain-insensitive resistance materials.（4）Due to the high cost of constructing conductive rubber networks with nano silver,conductive rubber materials with self-healing properties were prepared to extend their service life.Selecting flexible natural rubber（NR）as the matrix,a self-healing rubber masterbatch with reduced molecular weight and increased carboxyl content was prepared by grafting natural rubber latex（NRL）with 2-methylacrylic acid.By mixing with NR,nano zinc oxide,and peroxides,the self-healing rubber material was successfully prepared by adjusting the vulcanization time.The ion supramolecular network in the matrix could endow rubber materials with self-healing properties,and its strain self-healing efficiency could reach 95.6%.To prevent the damage of conductive fillers to the self-healing rubber structure,high aspect ratio silver nanowires（Ag NWs）were uniformly attached to the surface of self-healing rubber by spraying method,endowing the self-healing rubber with conductive function.When the content of Ag NWs was only 4 wt%,its conductivity could reach up to 92400 S/m.The interface interaction between Ag NWs and self-healing rubber was characterize,and the effect of microcracks on resistance changes during the tensile process was study.Based on the application of microcracks,conductive rubber had a very high gauge factor（GF=191）.When used in strain sensors to monitor human pulse,it could clearly distinguish pulse waveforms（P wave,T wave,and D wave）to determine the health status of the radial artery.（5）The bonding strength between the Ag NWs conductive network constructed by spraying method and the substrate interface was not ideal,and it was prone to damage during multiple deformations.Based on the coating method,a self-healing conductive rubber with an integrated layered structure was constructed to solve this problem,which was divided into a light controlled self-healing rubber layer and a conductive rubber layer.The photo controlled self-healing rubber layer is prepared by blending oxidized modified NRL（o NRL）,sodium alginate（SA）aqueous solution,and a small amount of carboxylated carbon nanotubes（CNT）;The conductive rubber layer is prepared by blending o NRL,SA aqueous solution with Ag NWs.The integrated layered structure of conductive rubber and the dispersion of Ag NWs were characterized.The mechanical properties,conductivity,and photo controlled self-healing performance of integrated layered conductive rubber were studied,and its application in the field of wearable strain sensing was explore.Under near-infrared light irradiation for 3 min（0.37 W/cm²）,the incision was almost invisible.Under SEM observation,the conductive layer showed satisfactory repair effect.In terms of sensing,the GF of conductive rubber could reach 19.33,and it could respond to 9.8%resistance change within 190 ms.