The Experts below are selected from a list of 2493 Experts worldwide ranked by ideXlab platform
Hatsuo Ishida - One of the best experts on this subject based on the ideXlab platform.
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effect of phenol substitution on the network structure and properties of linear Aliphatic Diamine based benzoxazines
Polymer, 2009Co-Authors: Douglas J. Allen, Hatsuo IshidaAbstract:Abstract A series of Aliphatic Diamine-based benzoxazines with different phenolic substitutions have been synthesized and characterized. Molecular structure of the monomers is verified by 1H and 13C NMR, FTIR, and elemental analysis. The site of polymerization is regiospecified and the type of linkage in the network structure is manipulated by selectively blocking the ortho, para, and meta positions in the aromatic rings of the monomer. The controlled network structures and their properties are compared to those formed by the polymerization of Aliphatic Diamine-based benzoxazines prepared from unsubstituted phenol in order to provide insight into their structures. Investigation on the melting point, polymerization kinetics, gelation, and Tg and sub-Tg thermal transition is all reported on these systematically controlled structure polybenzoxazines.
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effect of fiber surface modification on the mechanical properties of sisal fiber reinforced benzoxazine epoxy composites based on Aliphatic Diamine benzoxazine
Journal of Applied Polymer Science, 2007Co-Authors: Suchada Tragoonwichian, Nantaya Yanumet, Hatsuo IshidaAbstract:Sisal fibers were incorporated into a mixture of benzoxazine and bisphenol A type epoxy resins to form a uni- directionally reinforced composite. Surface modifications of the sisal fibers were carried out with sodium hydroxide, g-amino- propyltrimethoxysilane, and g-glycidoxypropyltrimethoxysi- lane. The surface treatments led to changes in the morphology, chemical groups, and hydrophilicity of the fibers. The effect of the fiber surface treatments on the fiber-matrix interfacial adhe- sion and mechanical properties of the composites were also studied. The results showed that surface treatments with so- dium hydroxide and a silane coupling agent led to improved fiber-matrix adhesion; this could be seen in the scanning elec- tron micrographs of the fractured surfaces from mechanical testing and the reduction in the impact strength of the compo- sites made from treated fibers. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 106: 2925-2935, 2007
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Polymerization of linear Aliphatic Diamine-based benzoxazine resins under inert and oxidative environments
Polymer, 2007Co-Authors: Douglas J. Allen, Hatsuo IshidaAbstract:A series of linear Aliphatic Diamine-based benzoxazine monomers have been studied. Reaction times and purification procedures have been optimized for each individual Diamine. The structure of these Diamine-based benzoxazine monomers has been characterized by 1 H and 13 C NMR, and infrared spectroscopy. The rate of polymerization has been studied by Fourier transform infrared spectroscopy as a function of the chain length of the Aliphatic amines. The glass transition temperatures (Tg) of the polybenzoxazines from these monomers are also studied. The short chain amine polybenzoxazine exhibits the Tg of around 170 � C. The influence of the polymerization environment for these linear Aliphatic Diamine-based series of benzoxazine monomers has been studied under air and inert atmosphere. Differential scanning calorimetry is used to determine the melting points of these benzoxazines and the temperature of the peak polymerization exotherm. An anomalous polymerization behavior of ethylene Diamine-based polybenzoxazine is also reported. 2007 Elsevier Ltd. All rights reserved.
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Physical and mechanical properties of flexible polybenzoxazine resins : Effect of Aliphatic Diamine chain length
Journal of Applied Polymer Science, 2006Co-Authors: Douglas J. Allen, Hatsuo IshidaAbstract:A series of linear Aliphatic Diamine-based benzoxazine monomers has been polymerized into transpar- ent, crosslinked specimens that are free of voids and have good mechanical integrity. The density of these polybenzo- xazines is measured as a function of the amine chain length. Dynamic mechanical analysis of these linear Aliphatic poly- benzoxazines shows two, chain length dependent transi- tions. Properties, such as room temperature modulus, glass transition temperature, crosslink density, thermal degrada- tion temperature, and char yield, of the polybenzoxazines are investigated as a function of the chain length. All these properties exhibit strong dependence on the chain length. These Aliphatic amine-based polybenzoxazines are found to be much more flexible than the bisphenol-type polybenzox- azines. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2798 -2809, 2006
Dujin Wang - One of the best experts on this subject based on the ideXlab platform.
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triple shape memory epoxy based on diels alder adduct molecular switch
Polymer, 2016Co-Authors: Xiao Kuang, Xia Dong, Dujin WangAbstract:Abstract In this work, we report a novel tripe-shape memory (TSM) strategy using glass transition and thermally reversible Diels–Alder (DA) reaction as two distinct switch units in a network. Based on this principle, a series of TSM epoxy materials were facilely prepared through the reaction of a conventional epoxy oligomer, an Aliphatic Diamine and a Diamine DA adduct cross-linker via a one-pot approach. The thermal and thermal dynamic properties of the reversible–irreversible dual cross-linking epoxy network were studied by differential scanning calorimetry (DSC) analysis and dynamic mechanical thermal analysis (DMTA), respectively. The thermal reversibility of DA adduct was revealed by Fourier transform infrared spectroscopy (FTIR). The TSM effect of the epoxy materials was demonstrated and quantitatively studied by DMTA. The development of thermal-responsive DA adduct as a molecular switch provides a new insight into the design and functionalization of multi-shape memory polymers.
Tadayuki Uno - One of the best experts on this subject based on the ideXlab platform.
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Potent DNA photocleavage by zinc(II) complexes of cationic bis-porphyrins linked with Aliphatic Diamine.
Bioorganic & medicinal chemistry, 2002Co-Authors: Yoshinobu Ishikawa, Naoki Yamakawa, Tadayuki UnoAbstract:Abstract We have prepared zinc(II) complexes of cationic bis-porphyrins, as one of the attempts to improve less DNA photocleavage activities of the metal-free bis-porphyrins composed of two H 2 TMPyP-like chromophores, linked with a series of Aliphatic Diamines. The less activities seemed to be derived from their intermolecular self-aggregation properties in aqueous solution. The zinc(II) insertion into the metal-free cationic bis-porphyrins completely removed their self-aggregation properties, most probably due to steric hindrance between axial ligands of zinc(II) chromophores of the cationic bis-porphyrins. The DNA photocleavage activities of the zinc(II) complexes were fully enhanced, which were three times larger than that of the lead compound H 2 TMPyP. Quantitative analysis of singlet oxygen production by photosensitization of cationic bis-porphyrins was performed using 1,3-diphenylisobenzofuran, and the singlet oxygen productivities of them were found to be related to their solution properties. There is a good relationship between the activities and the productivities, which will provide insights into the further development of more effective DNA photocleavage agents.
Jie Yang - One of the best experts on this subject based on the ideXlab platform.
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polyamide derived from 4 4 thiobis methylene dibenzoyl chloride and Aliphatic Diamine interfacial synthesis and characterization
Polymer Bulletin, 2013Co-Authors: Gang Zhang, Yan Zhang, Guangshun Huang, Xiaojun Wang, Jie YangAbstract:A series of processable semi-aromatic polyamides containing thioether and methylene units were synthesized through the reaction of 4,4′-thiobis(methylene)dibenzoyl chloride and Aliphatic Diamine by the method of interfacial polycondensation. These polyamides had excellent thermal properties with glass transition temperatures (T g) of 104.3–130.6 °C, melting temperatures (T m) of 300.3–303.8 °C, and initial degradation temperatures (T d) of 405.2–410.3 °C. They had wider processing windows than traditional semi-aromatic polyamides (such as PA6T can not be processed by melting) and can be processed by melting method. They had better tensile strengths of 57.6–64.1 MPa, low-temperature mechanical properties, low water absorption of 0.19–0.27 %, low dielectric constants of 3.11–3.95 at 100 kHz, and better melt flowability properties of 232–60.7, 301.9–78.8, and 423.1–83.6 Pa s under a shear rate ranging from 20 to 1,170 s−1, respectively. In addition, these polyamides showed good corrosion resistance, they did not dissolve in solvents such as NMP, DMSO, hydrochloric acid (6 mol/l), and solution of NaOH (1 mol/l) and so on.
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Polyamide derived from 4,4′-thiobis(methylene)dibenzoyl chloride and Aliphatic Diamine: interfacial synthesis and characterization
Polymer Bulletin, 2012Co-Authors: Gang Zhang, Yan Zhang, Li Dongsheng, Guangshun Huang, Xiaojun Wang, Jie YangAbstract:A series of processable semi-aromatic polyamides containing thioether and methylene units were synthesized through the reaction of 4,4′-thiobis(methylene)dibenzoyl chloride and Aliphatic Diamine by the method of interfacial polycondensation. These polyamides had excellent thermal properties with glass transition temperatures (T g) of 104.3–130.6 °C, melting temperatures (T m) of 300.3–303.8 °C, and initial degradation temperatures (T d) of 405.2–410.3 °C. They had wider processing windows than traditional semi-aromatic polyamides (such as PA6T can not be processed by melting) and can be processed by melting method. They had better tensile strengths of 57.6–64.1 MPa, low-temperature mechanical properties, low water absorption of 0.19–0.27 %, low dielectric constants of 3.11–3.95 at 100 kHz, and better melt flowability properties of 232–60.7, 301.9–78.8, and 423.1–83.6 Pa s under a shear rate ranging from 20 to 1,170 s−1, respectively. In addition, these polyamides showed good corrosion resistance, they did not dissolve in solvents such as NMP, DMSO, hydrochloric acid (6 mol/l), and solution of NaOH (1 mol/l) and so on.
Abdel-karim Maaroufi - One of the best experts on this subject based on the ideXlab platform.
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An innovative reaction model determination methodology in solid state kinetics based on variable activation energy
Thermochimica Acta, 2014Co-Authors: Muhammad Azeem Arshad, Abdel-karim MaaroufiAbstract:Abstract Determination of appropriate reaction model(s) in solid state reactions has been confronting with serious discrepancies over the decades. The dilemma in the choice of reaction models originates from the use of facile methods to handle the complicated multi-step kinetics. In order to minimize these discrepancies, an advanced reaction model determination methodology is put forward which deals with variable energy of activation concept. This methodology is expected to fairly simulate single step as well as multi-step reaction kinetics. The fresh expressions for the well known reaction models under this methodology are derived and their validity conditions are discussed. The methods for determining pre-exponential factor(s) in single step and multi-step processes are also reviewed. The proposed methodology is experimentally verified by taking an experimental example of non-isothermal curing kinetics of the polyepoxy formation (by the reaction between DGEBA and an Aliphatic Diamine) under constant as well as variable energies of activation. The obtained results are compared and effectively interpreted. The precautions while using the said methodology and its prospective applications are also discussed.
