To reduce the environmental pollution and meet the needs for wearable electronic devices, new requirements for electromagnetic interference(EMI) shielding materials include flexibility, biodegradability, and biocompat...To reduce the environmental pollution and meet the needs for wearable electronic devices, new requirements for electromagnetic interference(EMI) shielding materials include flexibility, biodegradability, and biocompatibility. Herein, we reported a polypyrrole-coated zein/epoxy(PPy/ZE) ultrafine fiber mat which was inherently biodegradable and skin-friendly. In addition, it could maintain its ultrafine fibrous structure after coating, which could provide the mat with mechanical compliance, high porosity, and a large specific area for high EMI shielding. With the assistance of the epoxide cross-linking, the breaking stresses of the PPy/ZE fiber mats could achieve 3.3 MPa and 1.4 MPa and the strains were 40.1% and 83.0% in dry and wet states, respectively, which met the needs of various wearable electronic devices. Along with the extension in the PPy treatment duration, more PPy was loaded on the fiber surfaces, which formed more integrated and conductive paths to generate increasing conductivities up to 401.76 S·m^(-1). Moreover, the EMI shielding performance was raised to 26.84 dB. The biobased mats provide a green and efficient choice for EMI shielding materials, which may be a promising strategy to address EMI problems in multiple fields.展开更多
Wearable on-skin electrodes or conductors should be vapor permeable,strain-insensitive,isotropically stretchable and stable under cyclic stretching.Various strategies have been proposed to prepare the required conduct...Wearable on-skin electrodes or conductors should be vapor permeable,strain-insensitive,isotropically stretchable and stable under cyclic stretching.Various strategies have been proposed to prepare the required conductors up to now;however,it is a challenge to fabricate them with above properties in a simple manner.In this paper,a highly permeable and stretchable conductor based on electrospun fluorine rubber fiber mat is reported.The fibers are pre-stretched in electric field during electrospinning,and they shrink isotropically by~35-40%in area after being detached from the substrate.The obtained fiber mat conductor demonstrates high stretchability up to~170%,and the resistance changes only 0.8 under 60%strain,which is superior to many other strain-insensitive conductors.The conductor possesses high stability,no cracks or structure damage are observed after washing and cyclic stretching.Moreover,the conductor is vapor permeable with a water vapor transmission rate of~850 g m−2 day−1,which is comparable to the normal water evaporation in ambient conditions,indicating that it would not disturb the sweat evaporation when being used on skin.The conductor is successfully used as stretchable yarns and electromyography(EMG)electrodes,showing high reliability in E-textiles and on-skin applications.展开更多
Impregnation rate of thermoplastic resin(polypropylene)in jute fiber mat and influence of relative factors on impregnation were studied,aiming to develop the continuous melt impregnation technique and to investigate t...Impregnation rate of thermoplastic resin(polypropylene)in jute fiber mat and influence of relative factors on impregnation were studied,aiming to develop the continuous melt impregnation technique and to investigate the effect of impregnation rate and temperature on processing conditions and mechanical properties of natural fiber mat-reinforced thermoplastics.Influence of pressure on porosity of fiber mat and effect of melt viscosity on impregnation rate were also investigated.The modified capillary rheometer was used as apparatus and experimental data were analyzed based on the one-dimension Darcy’s law.Results showed that at a given pressure,the impregnation rate is inversely proportional to melt viscosity and jute fiber mat has higher porosity than glass fiber mat.The architecture,compressibility,permeability and fiber diameter of jute fiber mat were compared with those of glass fiber mat and their effects on impregnation were discussed further.It could be seen that the average diameter of jute fiber is much bigger;the porosity of jute fiber mat is significantly higher and inner bundle impregnation does not exist in jute fiber mat.Therefore,it is not difficult to understand why the impregnation rate in jute fiber mat is 3.5 times higher and permeability is 14 times greater.Kozeny constants of jute and glass fiber mats calculated based on the capillary model are 2950 and 442,respectively.展开更多
基金Fundamental Research Funds for the Central Universities,China(No. 2232022D-13)Fundamental Research Funds of Shanghai Collaborative Innovation Center of High Performance Fibers and Composites (Province-M inistry Joint),China(No. X12812101/015)。
文摘To reduce the environmental pollution and meet the needs for wearable electronic devices, new requirements for electromagnetic interference(EMI) shielding materials include flexibility, biodegradability, and biocompatibility. Herein, we reported a polypyrrole-coated zein/epoxy(PPy/ZE) ultrafine fiber mat which was inherently biodegradable and skin-friendly. In addition, it could maintain its ultrafine fibrous structure after coating, which could provide the mat with mechanical compliance, high porosity, and a large specific area for high EMI shielding. With the assistance of the epoxide cross-linking, the breaking stresses of the PPy/ZE fiber mats could achieve 3.3 MPa and 1.4 MPa and the strains were 40.1% and 83.0% in dry and wet states, respectively, which met the needs of various wearable electronic devices. Along with the extension in the PPy treatment duration, more PPy was loaded on the fiber surfaces, which formed more integrated and conductive paths to generate increasing conductivities up to 401.76 S·m^(-1). Moreover, the EMI shielding performance was raised to 26.84 dB. The biobased mats provide a green and efficient choice for EMI shielding materials, which may be a promising strategy to address EMI problems in multiple fields.
基金supported by the Project funded by China Postdoctoral Science Foundation(2020M682987)the NSFC-Shenzhen Robotics Basic Research Center Program(U2013207)+2 种基金the National Natural Science Foundation of China(U1913601,81927804,62003331)the Natural Science Foundation of Guangdong Province(2018A030313065)the National Key Research and Development Project,MOST(2020YFC2005803).
文摘Wearable on-skin electrodes or conductors should be vapor permeable,strain-insensitive,isotropically stretchable and stable under cyclic stretching.Various strategies have been proposed to prepare the required conductors up to now;however,it is a challenge to fabricate them with above properties in a simple manner.In this paper,a highly permeable and stretchable conductor based on electrospun fluorine rubber fiber mat is reported.The fibers are pre-stretched in electric field during electrospinning,and they shrink isotropically by~35-40%in area after being detached from the substrate.The obtained fiber mat conductor demonstrates high stretchability up to~170%,and the resistance changes only 0.8 under 60%strain,which is superior to many other strain-insensitive conductors.The conductor possesses high stability,no cracks or structure damage are observed after washing and cyclic stretching.Moreover,the conductor is vapor permeable with a water vapor transmission rate of~850 g m−2 day−1,which is comparable to the normal water evaporation in ambient conditions,indicating that it would not disturb the sweat evaporation when being used on skin.The conductor is successfully used as stretchable yarns and electromyography(EMG)electrodes,showing high reliability in E-textiles and on-skin applications.
文摘Impregnation rate of thermoplastic resin(polypropylene)in jute fiber mat and influence of relative factors on impregnation were studied,aiming to develop the continuous melt impregnation technique and to investigate the effect of impregnation rate and temperature on processing conditions and mechanical properties of natural fiber mat-reinforced thermoplastics.Influence of pressure on porosity of fiber mat and effect of melt viscosity on impregnation rate were also investigated.The modified capillary rheometer was used as apparatus and experimental data were analyzed based on the one-dimension Darcy’s law.Results showed that at a given pressure,the impregnation rate is inversely proportional to melt viscosity and jute fiber mat has higher porosity than glass fiber mat.The architecture,compressibility,permeability and fiber diameter of jute fiber mat were compared with those of glass fiber mat and their effects on impregnation were discussed further.It could be seen that the average diameter of jute fiber is much bigger;the porosity of jute fiber mat is significantly higher and inner bundle impregnation does not exist in jute fiber mat.Therefore,it is not difficult to understand why the impregnation rate in jute fiber mat is 3.5 times higher and permeability is 14 times greater.Kozeny constants of jute and glass fiber mats calculated based on the capillary model are 2950 and 442,respectively.
