The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Jinsong Leng - One of the best experts on this subject based on the ideXlab platform.
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Shape-Memory Polymers with Adjustable High Glass Transition Temperatures
Macromolecules, 2015Co-Authors: Xinli Xiao, Xueying Qiu, Liwu Liu, Yanju Liu, Deyan Kong, Wenbo Zhang, Shen Zhang, Fenghua Zhang, Yang Hu, Sheng Zhang, Jinsong LengAbstract:Shape-memory polymers (SMPs) are synthesized with adjustable glass transition temperature (Tg) ranging from 299 to 322 °C, higher than those reported previously. The Polyimide containing thermal stable but flexible linkages within the backbone act as reversible phase, and high molecular weight (Mn) is necessary to form physical cross-links as fixed phase of thermoplastic shape-memory Polyimide. The critical Mn is 21.3 kg/mol, and the relationship between Mn and Tg is explored. Thermoset Polyimides show higher storage modulus and better shape-memory effects than thermoplastic counterparts due to covalent cross-linking, and the effective cross-link density with the influence on their physical properties is studied. The mechanism of high-temperature shape-memory effect of Polyimide on the basis of chain flexibility, molecular weight, and cross-link density is proposed, which will benefit further research on high-temperature SMPs. Shape-memory polymers (SMPs) are synthesized with adjustable glass transition temperature (Tg) ranging from 299 to 322 °C, higher than those reported previously. The Polyimide containing thermal stable but flexible linkages within the backbone act as reversible phase, and high molecular weight (Mn) is necessary to form physical cross-links as fixed phase of thermoplastic shape-memory Polyimide. The critical Mn is 21.3 kg/mol, and the relationship between Mn and Tg is explored. Thermoset Polyimides show higher storage modulus and better shape-memory effects than thermoplastic counterparts due to covalent cross-linking, and the effective cross-link density with the influence on their physical properties is studied. The mechanism of high-temperature shape-memory effect of Polyimide on the basis of chain flexibility, molecular weight, and cross-link density is proposed, which will benefit further research on high-temperature SMPs.
A.b. Frazier - One of the best experts on this subject based on the ideXlab platform.
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Recent applications of Polyimide to micromachining technology
IEEE Transactions on Industrial Electronics, 1995Co-Authors: A.b. FrazierAbstract:In this paper, applications of Polyimide materials to micromachining technology are reviewed. First, the use of Polyimide-based materials as sensor materials are discussed. In this case, the Polyimide material is used as an integral part of the micromachined devices. Emphasis is given to the development and characterization of a piezoresistive composite of Polyimide and graphite particles. The composite material is characterized for the mechanical properties (Young's modulus, residual stress) and the electromechanical property (piezoresistive coefficient). Second, the use of both photosensitive and nonphotosensitive Polyimides as electroplating molds for the fabrication of thick and high aspect ratio metallic microstructures is presented. Extensions of the basic micromolding process, which enable the fabrication of controlled gaps between metallic microstructural components and higher aspect ratio microstructures, are presented. Electroplated metallic microstructures realized using these technologies are shown. In addition, various applications of the Polyimide micromolding technologies are discussed.
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Recent Applications of Polyimide
1995Co-Authors: A.b. FrazierAbstract:Absbuct-In this paper, recent applications of Polyimide materials to micromachining technology are reviewed. First, the use of Polyimide-based materials as sensor materials are discussed. In this case, the Polyimide material is used as an integral part of the micromachined devices. Emphasis is given to the development and characterization of a piezoresistive composite of Polyimide and graphite particles. The composite material is characterized for the mechanical properties (Young’s modulus, residual stress) and the electromechanical property (piezoresisthe coefficient). Second, the use of both photosensitive and nonphotosensitive Polyimides as electroplating molds for the fabrication of thick and high aspect ratio metallic microstructures is presented. Extensions of the basic micromolding process, which enable the fabrication of controlled gaps between metallic microstructural components and higher aspect ratio microstructures, are presented. Electroplated metallic microstructures realized using these technologies are shown. In addition, various applications of the Polyimide micromolding technologies are discussed.
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Uses of Polyimide for micromachining applications
Proceedings of IECON'94 - 20th Annual Conference of IEEE Industrial Electronics, 1994Co-Authors: A.b. FrazierAbstract:In this paper, applications of Polyimide materials to micromachining technology is reviewed. First, the use of both photosensitive and nonphotosensitive Polyimides as electroplating molds for the fabrication of thick and high aspect ratio metallic microstructures is presented, Electroplated microstructures of different metals realized using these technologies are shown. In addition, various applications of this technology that have been realized are discussed. Second, the use of Polyimide materials as integral parts of micromachined devices is presented. Emphasis is given to the development of a piezoresistive composite of Polyimide/graphite for sensor applications. >
Xinli Xiao - One of the best experts on this subject based on the ideXlab platform.
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Shape-Memory Polymers with Adjustable High Glass Transition Temperatures
Macromolecules, 2015Co-Authors: Xinli Xiao, Xueying Qiu, Liwu Liu, Yanju Liu, Deyan Kong, Wenbo Zhang, Shen Zhang, Fenghua Zhang, Yang Hu, Sheng Zhang, Jinsong LengAbstract:Shape-memory polymers (SMPs) are synthesized with adjustable glass transition temperature (Tg) ranging from 299 to 322 °C, higher than those reported previously. The Polyimide containing thermal stable but flexible linkages within the backbone act as reversible phase, and high molecular weight (Mn) is necessary to form physical cross-links as fixed phase of thermoplastic shape-memory Polyimide. The critical Mn is 21.3 kg/mol, and the relationship between Mn and Tg is explored. Thermoset Polyimides show higher storage modulus and better shape-memory effects than thermoplastic counterparts due to covalent cross-linking, and the effective cross-link density with the influence on their physical properties is studied. The mechanism of high-temperature shape-memory effect of Polyimide on the basis of chain flexibility, molecular weight, and cross-link density is proposed, which will benefit further research on high-temperature SMPs. Shape-memory polymers (SMPs) are synthesized with adjustable glass transition temperature (Tg) ranging from 299 to 322 °C, higher than those reported previously. The Polyimide containing thermal stable but flexible linkages within the backbone act as reversible phase, and high molecular weight (Mn) is necessary to form physical cross-links as fixed phase of thermoplastic shape-memory Polyimide. The critical Mn is 21.3 kg/mol, and the relationship between Mn and Tg is explored. Thermoset Polyimides show higher storage modulus and better shape-memory effects than thermoplastic counterparts due to covalent cross-linking, and the effective cross-link density with the influence on their physical properties is studied. The mechanism of high-temperature shape-memory effect of Polyimide on the basis of chain flexibility, molecular weight, and cross-link density is proposed, which will benefit further research on high-temperature SMPs.
X.t. Dong - One of the best experts on this subject based on the ideXlab platform.
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Wideband average power handling capability of coupled microstrips on Polyimide and Polyimide/GaAs substrates
IEE Proceedings - Microwaves Antennas and Propagation, 2004Co-Authors: X.t. DongAbstract:The wideband average power handling capabilities (APHC) of coupled microstrips on a single-layer Polyimide substrate and also on a Polyimide and GaAs double-layer substrate are studied. Since the thermal conductivity of Polyimide materials is only about 0.2 W/m °C, the APHC of the coupled microstrips is severely limited by the Polyimide thickness. As a first step to obtaining the APHC, the ohmic and dielectric losses of even and odd modes need to be calculated. The rise in temperature is determined using a proposed thermal model in which the lateral heat dissipation on the neighbouring microstrips is appropriately treated. Numerical results are presented to show the effects of microstrip conductivity and thickness, and Polyimide thickness on the APHC for different coupled microstrip configurations. Several ways to effectively enhance the APHC are suggested, which could be useful in the design of coupled microstrips on, or embedded in, Polyimides.
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Wideband average power handling capability of coupled microstrips on Polyimide and Polyimide/GaAs substrates
IEE Proceedings - Microwaves Antennas and Propagation, 2004Co-Authors: X.t. DongAbstract:The wideband average power handling capabilities (APHC) of coupled microstrips on a single-layer Polyimide substrate and also on a Polyimide and GaAs double-layer substrate are studied. Since the thermal conductivity of Polyimide materials is only about 0.2 W/m /spl deg/C, the APHC of the coupled microstrips is severely limited by the Polyimide thickness. As a first step to obtaining the APHC, the ohmic and dielectric losses of even and odd modes need to be calculated. The rise in temperature is determined using a proposed thermal model in which the lateral heat dissipation on the neighbouring microstrips is appropriately treated. Numerical results are presented to show the effects of microstrip conductivity and thickness, and Polyimide thickness on the APHC for different coupled microstrip configurations. Several ways to effectively enhance the APHC are suggested, which could be useful in the design of coupled microstrips on, or embedded in, Polyimides.
Kenichi Okamoto - One of the best experts on this subject based on the ideXlab platform.
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novel sulfonated Polyimides as polyelectrolytes for fuel cell application 1 synthesis proton conductivity and water stability of Polyimides from 4 4 diaminodiphenyl ether 2 2 disulfonic acid
Macromolecules, 2002Co-Authors: Jianhua Fang, Xiaoxia Guo, Satoshi Harada, Tatsuya Watari, Hidetoshi Kita, Kazuhiro Tanaka, Kenichi OkamotoAbstract:A sulfonated diamine monomer, 4,4‘-diaminodiphenyl ether-2,2‘-disulfonic acid (ODADS), was successfully synthesized by direct sulfonation of a commercially available diamine, 4,4‘-diaminodiphenyl ether (ODA), using fuming sulfuric acid as the sulfonating reagent. A series of sulfonated Polyimides were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), ODADS, and common nonsulfonated diamines. The resulting sulfonated Polyimides displayed much better stability toward water than those derived from the widely used sulfonated diamine 2,2‘-benzidinedisulfonic acid (BDSA). This is because ODADS-based Polyimide membranes have a more flexible structure than the corresponding BDSA-based ones. Fenton's reagent test revealed that ODADS-based Polyimide membranes also had fair good stability to oxidation. Polyimide membranes with good water stability as well as high proton conductivity were developed. NTDA−ODADS/BAPB(1/1) coPolyimide membrane (BAPB refers to 4,4‘-bis(4-aminophenoxy)biphenyl)), for ex...
