Well-dispersed fiber suspension is the precondition of good paper formation. Compared with cellulosic fibers, synthetic fibers are prone to flocculate because of their long length and hydrophobic nature, resulting in ...Well-dispersed fiber suspension is the precondition of good paper formation. Compared with cellulosic fibers, synthetic fibers are prone to flocculate because of their long length and hydrophobic nature, resulting in poor paper formation. To solve this problem, dispersants and extremely low forming consistency are typically adopted during the traditional wet-forming process, which cause a large amount of water consumption and treatment cost. Therefore, increasing forming consistency without compromising paper formation remains a challenge for papermakers. In this work, foam forming was adopted to disperse polyimide fibers (PI) with high forming consistency. The results showed that the formation index of handsheets increased when the bubble size and distribution became small and narrow. Compared with traditional wet-forming process with the same consistency (0.4%), the formation index of handsheets by foam forming increased by approximately 100% when C8 alkyl glucoside (APG08) concentration reached 16 g/L. Notably, forming consistency could increase by eight times while keeping the same level of paper formation. Overall, foam forming exhibits great advantages in dispersing long fiber and reducing water consumption and environmental pressure, and has potential applications in specialty paper made of long fibers.展开更多
One of the serious concerns for tungsten materials in fusion devices is the radiation defects caused by helium plasma irradiation since helium is a fusion product. The fiber-formed nanostructure is thought to have a p...One of the serious concerns for tungsten materials in fusion devices is the radiation defects caused by helium plasma irradiation since helium is a fusion product. The fiber-formed nanostructure is thought to have a possible weakness against the plasma heat flux on the plasma- facing component and also may destroy the reflectivity of optical mirrors. In this paper an inter- esting method for the recovery of such tungsten surfaces is shown. The recovery process depends on the grade and manufacturing process of tungsten materials.展开更多
Fiber-metal laminates (FMLs) possess huge potential in mass-reduction strategy of automotive industry. In order to understand behavior of FMLs as they undergo stamp forming processes, finite element analyses of surfac...Fiber-metal laminates (FMLs) possess huge potential in mass-reduction strategy of automotive industry. In order to understand behavior of FMLs as they undergo stamp forming processes, finite element analyses of surface strain evolutions have been carried out. The simulations provide strains at locations within the layers of an FML, allowing better understanding of forming behavior of the composite layer and its influence on the metal layers. Finite element analyses were conducted on two aluminum-based FMLs with different fiber-reinforced composites and benchmarked against monolithic aluminum alloy. The simulation results indicated that high stiffness of the reinforcement constrains flow of the matrix in the composite layer, which can be attributed to the distinguishing behavior of the FMLs compared to the monolithic aluminum alloy.展开更多
This paper investigated stamp forming performance of two aluminum-based Fiber-metal laminates (FMLs) with different fiber-reinforced composites using finite element analysis. Given the inherent thermal-dependent prope...This paper investigated stamp forming performance of two aluminum-based Fiber-metal laminates (FMLs) with different fiber-reinforced composites using finite element analysis. Given the inherent thermal-dependent properties of fiber-reinforced polypropylene, the effect of elevated temperature on its forming behavior is worthy of concern. Furthermore, the elevation in temperature also influences the bonding within the constituent lamina. Both factors were integrated in the modelling. By investigating the through-thickness strain evolution throughout the stamping process, the forming mode of each layer, as well as their interactions, were better understood. Results suggested that the flow of matrix and the rotation at the intersections of fiber strands can be promoted at elevated temperature, which transforms the forming performance of FMLs close to that of monolithic aluminum. These results propose means to improve the forming performance of FMLs.展开更多
The dispersion mechanism of low melting point metal (LMPM) particles in polymers was studied using Cox dilute emulsion model. The critical destruction shear stress sigma of LMPM droplets is sigma greater than 2 v/d. ...The dispersion mechanism of low melting point metal (LMPM) particles in polymers was studied using Cox dilute emulsion model. The critical destruction shear stress sigma of LMPM droplets is sigma greater than 2 v/d. When sigma is small, LMPM droplets were dispersed and deformed ellipsoidal or bar droplets whose orientation direction is always at an angle of 45 degree with the direction of shear rate. When sigma is very big and droplets are very fine, polymer melt elasticity behavior and big boundary tension between a polymer melt and LMPM droplets make further fining LMPM droplets become more difficult. Therefore, LMPM droplets produce tensile flow and form LMPM microfibrils in situ in polymer melt. SEM photographs have shown the results predicted using dilute emulsion model. (Author abstract) 7 Refs.展开更多
Ethyl cellulose (EC), taken as a thermotropic liquid crystalline polymer, was blended with polypropylene (PP), followed by injection molding. Fibre-forming of EC in the PP matrix is analyzed,based on the rheological d...Ethyl cellulose (EC), taken as a thermotropic liquid crystalline polymer, was blended with polypropylene (PP), followed by injection molding. Fibre-forming of EC in the PP matrix is analyzed,based on the rheological data,dynamic mechanical analysis and fracture micrographs of EC/PP blends. The addition of maleated PP, for the modification of the interphasial interaction between the PP matrix and the EC fibrils, did not impair the fiber formation substantially.展开更多
As a high-performance material for preparing composite materials, polyimide fibers suffer from many potential drawbacks, including poor bonding with other substrates, which results in composite materials with poor mec...As a high-performance material for preparing composite materials, polyimide fibers suffer from many potential drawbacks, including poor bonding with other substrates, which results in composite materials with poor mechanical properties. Therefore, this study proposed a simple and rapid technique for obtaining loose, porous polyimide fiber papers by implementing a wet method using equal amounts of polyimide fiber and polyimide fiber paper as reinforcements, respectively. The polyimide resin-based composite materials were prepared by hand lay-up and hot pressing. The results showed that the paper-based reinforcement exhibited high porosity and the fibers were arranged with a uniform pore size distribution. The tensile properties, bending performance, and interlaminar shear performance of the paper-based composite improved by 130%, 108%, and 34.5%, respectively, compared to those of the fiberbased counterpart. The factors affecting the mechanical properties of the composites were analyzed based on the fiber length, fiber beating or lack thereof, and the basis weight of the paper. The increased uniformity of the polyimide fiber paper changed the ordering of the fibers and resolved drawbacks such as difficult dispersion, uneven pore size distribution, and poor mechanical properties related to single fibers in the resin-based composite material.展开更多
Syndiotactic polypropylene （sPP） as-spun fiber （sPP1） and drawn fiber （sPP2） were prepared by melt-spinning and melt-spinning/hot-drawing, respectively. The structure transition of the two fibers induced by anne...Syndiotactic polypropylene （sPP） as-spun fiber （sPP1） and drawn fiber （sPP2） were prepared by melt-spinning and melt-spinning/hot-drawing, respectively. The structure transition of the two fibers induced by annealing at different temperatures and the corresponding mechanical properties were subsequently investigated by the combination of Fourier transform infrared spectroscopy （FTIR）, wide-angle X-ray diffraction （WAXD） and tensile testing. The results indicate that the chain conformation and crystal forms of the two sPP fibers are not obviously changed at low annealing temperature （40℃）. With increasing the annealing temperature, the trans-planar conformation and mesophase in sPP1 and sPP2 fibers can be completely transformed to helical conformation and crystal form I under tension. Upon removing the tension, a small amount of mesophase and trans-planar conformation will be regained. The mechanical properties of the annealed fibers are manifestly dependent on their initial structure and the annealing temperature.展开更多
基金funded by National Key R&D Program of China (2017YFB0308300)Shaanxi Provincial Key R&D Program (2017GY-140)Doctoral Scientific Research Foundation of Shaanxi University of Science & Technology (BJ15-12, 2018BJ-22)
文摘Well-dispersed fiber suspension is the precondition of good paper formation. Compared with cellulosic fibers, synthetic fibers are prone to flocculate because of their long length and hydrophobic nature, resulting in poor paper formation. To solve this problem, dispersants and extremely low forming consistency are typically adopted during the traditional wet-forming process, which cause a large amount of water consumption and treatment cost. Therefore, increasing forming consistency without compromising paper formation remains a challenge for papermakers. In this work, foam forming was adopted to disperse polyimide fibers (PI) with high forming consistency. The results showed that the formation index of handsheets increased when the bubble size and distribution became small and narrow. Compared with traditional wet-forming process with the same consistency (0.4%), the formation index of handsheets by foam forming increased by approximately 100% when C8 alkyl glucoside (APG08) concentration reached 16 g/L. Notably, forming consistency could increase by eight times while keeping the same level of paper formation. Overall, foam forming exhibits great advantages in dispersing long fiber and reducing water consumption and environmental pressure, and has potential applications in specialty paper made of long fibers.
基金supported by a Grant-in-aid for scientific Research (B) (20360414) from JSPS
文摘One of the serious concerns for tungsten materials in fusion devices is the radiation defects caused by helium plasma irradiation since helium is a fusion product. The fiber-formed nanostructure is thought to have a possible weakness against the plasma heat flux on the plasma- facing component and also may destroy the reflectivity of optical mirrors. In this paper an inter- esting method for the recovery of such tungsten surfaces is shown. The recovery process depends on the grade and manufacturing process of tungsten materials.
文摘Fiber-metal laminates (FMLs) possess huge potential in mass-reduction strategy of automotive industry. In order to understand behavior of FMLs as they undergo stamp forming processes, finite element analyses of surface strain evolutions have been carried out. The simulations provide strains at locations within the layers of an FML, allowing better understanding of forming behavior of the composite layer and its influence on the metal layers. Finite element analyses were conducted on two aluminum-based FMLs with different fiber-reinforced composites and benchmarked against monolithic aluminum alloy. The simulation results indicated that high stiffness of the reinforcement constrains flow of the matrix in the composite layer, which can be attributed to the distinguishing behavior of the FMLs compared to the monolithic aluminum alloy.
文摘This paper investigated stamp forming performance of two aluminum-based Fiber-metal laminates (FMLs) with different fiber-reinforced composites using finite element analysis. Given the inherent thermal-dependent properties of fiber-reinforced polypropylene, the effect of elevated temperature on its forming behavior is worthy of concern. Furthermore, the elevation in temperature also influences the bonding within the constituent lamina. Both factors were integrated in the modelling. By investigating the through-thickness strain evolution throughout the stamping process, the forming mode of each layer, as well as their interactions, were better understood. Results suggested that the flow of matrix and the rotation at the intersections of fiber strands can be promoted at elevated temperature, which transforms the forming performance of FMLs close to that of monolithic aluminum. These results propose means to improve the forming performance of FMLs.
文摘The dispersion mechanism of low melting point metal (LMPM) particles in polymers was studied using Cox dilute emulsion model. The critical destruction shear stress sigma of LMPM droplets is sigma greater than 2 v/d. When sigma is small, LMPM droplets were dispersed and deformed ellipsoidal or bar droplets whose orientation direction is always at an angle of 45 degree with the direction of shear rate. When sigma is very big and droplets are very fine, polymer melt elasticity behavior and big boundary tension between a polymer melt and LMPM droplets make further fining LMPM droplets become more difficult. Therefore, LMPM droplets produce tensile flow and form LMPM microfibrils in situ in polymer melt. SEM photographs have shown the results predicted using dilute emulsion model. (Author abstract) 7 Refs.
基金This work is supported by The National Natural Science Foundation of China
文摘Ethyl cellulose (EC), taken as a thermotropic liquid crystalline polymer, was blended with polypropylene (PP), followed by injection molding. Fibre-forming of EC in the PP matrix is analyzed,based on the rheological data,dynamic mechanical analysis and fracture micrographs of EC/PP blends. The addition of maleated PP, for the modification of the interphasial interaction between the PP matrix and the EC fibrils, did not impair the fiber formation substantially.
基金financial support from the Lianyungang 555 Talents Project Program of China (2015-13)
文摘As a high-performance material for preparing composite materials, polyimide fibers suffer from many potential drawbacks, including poor bonding with other substrates, which results in composite materials with poor mechanical properties. Therefore, this study proposed a simple and rapid technique for obtaining loose, porous polyimide fiber papers by implementing a wet method using equal amounts of polyimide fiber and polyimide fiber paper as reinforcements, respectively. The polyimide resin-based composite materials were prepared by hand lay-up and hot pressing. The results showed that the paper-based reinforcement exhibited high porosity and the fibers were arranged with a uniform pore size distribution. The tensile properties, bending performance, and interlaminar shear performance of the paper-based composite improved by 130%, 108%, and 34.5%, respectively, compared to those of the fiberbased counterpart. The factors affecting the mechanical properties of the composites were analyzed based on the fiber length, fiber beating or lack thereof, and the basis weight of the paper. The increased uniformity of the polyimide fiber paper changed the ordering of the fibers and resolved drawbacks such as difficult dispersion, uneven pore size distribution, and poor mechanical properties related to single fibers in the resin-based composite material.
基金supported by the National Natural Science Foundation of China(No.50603029)the Innovation Foundation of Center for Molecular Science,Chinese Academy of Sciences(CMS-Y200724)
文摘Syndiotactic polypropylene （sPP） as-spun fiber （sPP1） and drawn fiber （sPP2） were prepared by melt-spinning and melt-spinning/hot-drawing, respectively. The structure transition of the two fibers induced by annealing at different temperatures and the corresponding mechanical properties were subsequently investigated by the combination of Fourier transform infrared spectroscopy （FTIR）, wide-angle X-ray diffraction （WAXD） and tensile testing. The results indicate that the chain conformation and crystal forms of the two sPP fibers are not obviously changed at low annealing temperature （40℃）. With increasing the annealing temperature, the trans-planar conformation and mesophase in sPP1 and sPP2 fibers can be completely transformed to helical conformation and crystal form I under tension. Upon removing the tension, a small amount of mesophase and trans-planar conformation will be regained. The mechanical properties of the annealed fibers are manifestly dependent on their initial structure and the annealing temperature.
