Mechanical and dielectric relaxations of epoxide resins containing spiro‐ring structure

Ochi, Mitsukazu; Shimbo, Masaki; Saga, Motoo; Takashima, Naoichi

doi:10.1002/polb.1986.090241003

Cited by 52 publications

(28 citation statements)

References 19 publications

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“…process for the CTBN could be accurately chara~t e r i z e d .~~ Using plots of tan 6{ = d'/ t' ) , it was possible in the case of DGEBA/DDM/CTBN to locate both processes and a set of values for the activation energy of this process were calculated using these data33 (Table VI) . The value obtained for the pure resin is in good agreement with 81.3 kJ/mol quoted by Mangion and Johari2* and Ochi et al 47 Changes that occur to the 0 process can best be compared from plots of the dielectric loss as a function of concentration ( Fig. 7 and 8) at -20 and -30°C.…”

supporting

confidence: 69%

Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems

Delides¹,

Hayward

Pethrick

et al. 1993

J of Applied Polymer Sci

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SYNOPSISReal-time and equilibrium dielectric measurements, covering the frequency range lo-'-lo6 Hz, are reported on a series of rubber-modified epoxy resins, based on reaction of the diglycidyl ether of bisphenol A (DGEBA) with either triethylenetetramine (TETA) or diaminodiphenylmethylene ( DDM ) . The rubber modifier used was a carboxyl-terminated butadiene acrylonitrile ( CTBN) reactive oligomer and the phase-separated structure, the results of which was examined using both dielectric and electron microscopic techniques. The mixture was initially homogeneous, but after a short period of time, it underwent phase separation and this process was marked by the appearance of a dielectric peak associated with ion-charge migration within the occluded rubbery phase. Analysis of the peak provided information on the morphology of the system and these data were compared with information obtained from scanning electron microscopy. A phase-separated morphology was observed consisting of spherical rubber particles dispersed in an epoxy matrix. For high concentrations of rubber 2 10 wt %, precipitation of epoxy domains within the rubbery phase was observed. Detailed dielectric studies of the peak associated with phase separation revealed that in the case of the TETA system the peak continued to shift after vitrification, whereas in the case of DDM, it was invariant with time. The point at which the peak appears was used to determine the time at which phase separation occurred. Differences observed in the lower temperature dielectric spectra were associated with variations in the form of the phase structure and possibly reflect different degrees of densification of the matrix. Good agreement was observed between the predictions of the Maxwell-WagnerSillers (MWS) theory and experimental observation for these systems. 0 1993

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supporting

confidence: 69%

Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems

Delides¹,

Hayward

Pethrick

et al. 1993

J of Applied Polymer Sci

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“…However, a 15°C difference in the average peak values of the lower temperature ȕ-transition was observed between the two composite types (-72 ± 3 °C and -57 ± 3 °C for the thermally and microwave cured composites respectively). The low ȕ-transition in epoxy systems has been observed between -80°C to -40°C [37][38][39]. More specific in epoxy-amine curing, lowtemperature relaxations are mainly associated with the molecular motion of the hydroxyether portion of the molecule [40].…”

Section: Resultsmentioning

confidence: 99%

Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating

Papargyris

Day

Nesbitt

et al. 2008

Composites Science and Technology

138

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2008) "Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating". Composites Science and Technology,, [1854][1855][1856][1857][1858][1859][1860][1861] Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating AbstractMicrowave processing holds great potential for improving current composite manufacturing techniques, substantially reducing cure cycle times, energy requirements and operational costs. In this paper, microwave heating was incorporated into the resin transfer moulding technique. Through the use of microwave heating, a 50% cure cycle time reduction was achieved. The mechanical and physical properties of the produced carbon fibre/epoxy composites were compared to those manufactured by conventional resin transfer moulding. Mechanical testing showed similar values of flexural moduli and flexural strength for the two types of composites after normalisation of the corresponding data to a common fibre volume fraction. A 9% increase of the interlaminar shear strength (ILSS) was observed for the microwave cured composites. This enhancement in ILSS is attributed to a lowering of resin viscosity in the initial stage of the curing process, which was also confirmed via scanning electron microscopy by means of improved fibre wetting and less fibre pull-out. Furthermore, both types of composites yielded minimal void content ( properties of the produced carbon fibre/epoxy composites were compared to those manufactured by conventional resin transfer moulding. Mechanical testing showed similar values of flexural moduli and flexural strength for the two types of composites after normalisation of the corresponding data to a common fibre volume fraction. A 9% increase of the interlaminar shear strength (ILSS) was observed for the microwave cured composites. This enhancement in ILSS is attributed to a lowering of resin viscosity in the initial stage of the curing process, which was also confirmed via scanning electron microscopy by means of improved fibre wetting and less fibre pull-out. Furthermore, both types of composites yielded minimal void content (<2%). Dynamic mechanical thermal analysis revealed comparable glass transition temperatures for composites produced by both methods. A 15 °C shift in the position of the ȕ-transition peak was observed between thermally and microwave cured composites, suggesting an alteration in the cross-linking path followed.

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“…The raw material of the epoxy resin is the dihydric phenol derivative which is the reaction product obtained from the dehydration condensation of vanillin and pentaerythriol. 143,144 Cardanol, a major component of cashew nut shell liquid, is a phenol derivative having a meta substituent of a C 15 unsaturated hydrocarbon chain with one to three double bonds. It has drawn considerable attention from many researchers for the production of phenolic resins under different sets of conditions.…”

Section: Iii1 Epichlorohydrin Synthesis Of Phenolic Epoxy Prepolymersmentioning

confidence: 99%

The use of lipases as biocatalysts for the epoxidation of fatty acids and phenolic compounds

et al. 2014

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Lipases are versatile enzymes that can be used for various kinds of biocatalyzed reactions. Owing to their selectivity and their mild reaction conditions, they can be often considered as more interesting than classical chemical catalysts. Besides their application in oil and fat processes, these enzymes have proved to be very attractive for other lipase-catalyzed reactions. This review discusses the latest results where lipases are used for the epoxidation of lipid substrates (namely fatty acids and their derivatives) and phenolic compounds. This chemo-enzymatic process involves a two step synthesis where the biocatalyst acts as a perhydrolase to produce peracids, which then act as catalysts to epoxidize double bonds. Various factors govern the efficiency of the reaction in terms of kinetics, yields and enzyme stability.These parameters are evaluated and discussed herein. (Résumé d'auteur

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Mechanical and dielectric relaxations of epoxide resins containing spiro‐ring structure

Cited by 52 publications

References 19 publications

Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems

Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems

Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating

The use of lipases as biocatalysts for the epoxidation of fatty acids and phenolic compounds

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