Hajime Kishi

© 2015 International Committee on Composite Materials. All rights reserved. Within several candidates of matrix polymers for carbon fiber reinforced thermoplastic composites (CFRTP), acrylic polymers have high potential in terms of low-temperature processing. We focused on the improvement in the interfacial adhesive properties between CFs and the acrylic polymers using several functional monomers for the co-polymerization with methyl methacrylate (MMA). Several functional acrylic monomers were co-polymerized with the MMA, and applied as the matrix polymers of the acrylic CFRTPs. It was observed that the copolymer matrices well-adhered to the surfaces of CFs, compared to the pure PMMA. The copolymer with acrylamide (AAm) indicated higher interfacial adhesive strength than that with hydroxyethyl acrylate (HEA). The hydroxyethyl acrylamide (HEAA) copolymer having both amide groups and hydroxyl groups showed very high adhesive strengths to CFs, which resulted in the high flexural strengths of the CFRTPs. The flexural strength of the pure PMMA CFRTP was 450 MPa. On the other hand, the co-polymerized acrylic matrices gave the increase in the flexural strength for the CFRTPs. Especially, the 3mol% HEAA copolymer achieved the two-fold flexural strength (900 MPa) on the acrylic CFRTP. The strength was equivalent level to the epoxy CFRP. The fatigue resistance of the HEAA copolymerized CFRTPs were also evaluated, in relation to the interfacial adhesive strength.

© 2015 International Committee on Composite Materials. All rights reserved. Epoxy resins are utilized in various industrial areas as adhesives and matrix of composite materials because of the higher stiffness, strength and heat resistance. Toughening with rubber particles is one of the most popular method to enhance the fracture toughness. For the structure uses, the fatigue resistance is very important property as well as the static mechanical properties. In this study the effect of molecular weight between crosslinks (crosslink density) on the fatigue crack propagation properties of rubber-toughened epoxy resin. Several DGEBA epoxy resins with different average molecular weight were used in this study. Core shell rubber (CSR) particles, the diameter of 100nm, were well dispersed in the epoxy. The fracture toughness of Core Shell Rubber-modified epoxy monotonously enhanced with increasing molecular weight between crosslinks, and the effect of core-shell rubber became larger as the molecular weight between crosslink increased. On the other hand, the fatigue threshold had a peak against molecular weight between crosslinks. Whereas there is positive effect of core shell rubber in fatigue resistance for molecular weight between crosslink of 1440g/mol, the fatigue threshold of the core shell rubber modified epoxy is lower than that of unmodified one for molecular weight between crosslinks of 3040g/mol. TEM observation from the side surface of the crack tip revealed that the size of the plastic deformation zone was well related to the fatigue resistance. The core shell rubber particles enhanced the shear plastic deformation region at the crack tip for molecular weight between crosslinks of 1440g/mol, and the particles largely lowered the deformation region. These results was caused by the deformation ability of the epoxy resin under plane-stress state.

In this study the aim is to clarify the effect of molecular weight distribution on the microstructure and the mechanical properties of the epoxy resins with same average molecular weight. Four types of epoxy blends with the different molecular weight distribution were formulated using commercial Bisphenol-A diglycidyl ethers. The microstructure and the mechanical properties of the blends were investigated. Dynamic mechanical analysis and microscopic observation revealed that difference of the crosslink density in the resin and the size of the repeated heterogeneous structure became larger as the molecular weight distribution was broader. In particular, the epoxy blend with the widest distribution had a co-continuous phase structure in submicron-scale as a result of reaction-induced phase separation. Whereas the flexural modulus and the flexural strength were insensitive to the molecular weight distribution and the morphology of the cured resin, the fracture toughness enhanced as the molecular weight distribution broadened and the heterogeneity of the crosslink density increased. Fracture mechanisms were discussed using proposed microstructure models.

Stability of nanostructures of epoxy/acrylic triblock copolymer blends was studied. PMMA-b-PnBA-b-PMMA triblock copolymers (acrylic BCPs) having several compositions on the ratio of the block chains and the molecular weight were initially prepared and were blended with diglycidyl ether of bisphenol-A epoxy thermosets. The blends were cured using phenol novolac with tri phenyl phosphine (TPP) as the catalyst. Several nanostructures, such as spheres, cylinders, curved lamellae, were observed in the cured blends. The nanostructures were controlled by the molecular weight of the immiscible PnBA-block chain and the ratio of the PnBA in the blends. Moreover, the effect of the gel time to the nanostructures was examined by altering the trace amount of the TPP in the blends. The types of the nanostructures were almost kept irrespective of the gel time of the blends when the composition of the blends was maintained. This suggested the stability of the nanostructures of the epoxy/acrylic BCP blends made via the self-assembly mechanism, therefore a phase diagram of the cured blends was proposed.

Effects of gamma-ray irradiation on a cyanate ester/epoxy resin composed of dicyanate ester of bisphenol A (DCBA) and diglycidyl ether of bisphenol A (DGEBA) were investigated by changes in physicochemical and mechanical properties after the gamma-ray irradiation with dose of 100 MGy as maximum at around 40 degrees C under vacuum. After the irradiation, gases of hydrogen, carbon monoxide and carbon dioxide were evolved, glass transition temperature decreased, and flexural strength also decreased. It was concluded that ether linkages bonded to cyanurate, isocyanurate and oxazolidinone structures are mainly decomposed by the irradiation. After 100 MGy irradiation, the flexural strength of DCBA/DGEBA was maintained more than 170 MPa which is 90% of initial value of 195 MPa. Flexural modulus and density slightly increased to the values of 3.9 GPa and 1.211 g/cm(3) from initial values of 3.4 GPa and 1.199 g/cm(3), respectively. (C) 2014 Elsevier Ltd. All rights reserved.

Fatigue resistance of toughened epoxy resins with preformed polymer particles were studied in terms of the fatigue threshold and the fatigue crack propagation (FCP). The toughening modifiers were polyamide-12 (PA12) and core-shell rubber (CSR). The PA12 toughened epoxy achieved higher stress intensity factor range (AK) than the pure epoxy, irrespective of the molecular weight between cross-links (Mc) of the epoxy matrices. The crack bridging of the PA12 particles was the major mechanism of the fatigue resistance. Meanwhile, the fatigue behavior of the CSR / epoxy resins depended on the Mc. The whole FCP curve of the CSR / epoxy with low Mc was in the high AK. However, the fatigue threshold of the CSR / epoxy with high Mc was in the lower AK than that of the pure epoxy. The plastic deformation of the epoxy matrix with high Mc was localized, which decreased the fatigue resistance.

The influence of tackifier structure on the temperature dependence of tack for a polystyrene block copolymer/tackifier system was investigated. A blend of polystyrene-block-polyisoprene-block- polystyrene triblock and polystyrene-block-polyisoprene diblock copolymers was used as the base polymer. Four different tackifiers were used: special rosin ester resin (RE), rosin phenolic resin (RP), hydrogenated cyclo-aliphatic resin (HC), and aliphatic petroleum resin (C5). Tack at 20 degrees C increased with the tackifier content for both RE and HC tackifier systems. Tack is affected by two factors: the work of adhesion at the adherend interface and the viscoelastic properties of the adhesive. The good balance of these two factors brought high tack. The adhesive with 10 wt.% tackifier exhibited the highest tack at 20 degrees C, whereas those with 30 and 50 wt.% tackifier were lower than those systems with 10 wt.% of the RP or C5 tackifiers. The adhesive with overly high hardness lowered the work of adhesion and the tack was not improved with more than 30 wt.%. A compatibility test in toluene solution and in solid state showed that tackifier RE has good compatibility with both polyisoprene and polystyrene, whereas tackifier RP has lower compatibility. Tackifiers HC and C5 had good compatibility with polyisoprene, but poor compatibility with polystyrene, and that of C5 was poorer. Pulse nuclear magnetic resonance (NMR) analyses indicated that tackifiers RE and HC effectively restrict the molecular mobility of polyisoprene phase.

a- and b-axis-oriented Bi3. 25Nd0. 75Ti3O12 (BNT) nanoplates, 3. 0-μm thick, were fabricated on conductive Nb:TiO2(101) substrates with 0. 79 mass% Nb at 650 °C by high-temperature sputtering. Successively, the fabrication of inorganic-organic composites was carried out by introducing an epoxy resin to the spaces between the BNT nanoplates. The fourier transform infrared spectroscopy (FTIR) and the energy dispersive X-ray (EDX) elemental mapping results confirmed that the fabricated composites were inorganic-organic hybridized materials with cured epoxy resin introduced into the spaces between the BNT nanoplates. Piezoelectric response measurements of the fabricated BNT-epoxy resin composites by using piezoresponse force microscopy (PFM) showed that the composites have potential as piezoelectric microelement materials. © 2013 The Korean Physical Society.

Peel adhesive strengths of multi-layered laminates composed of two polypropylene (PP) sheets and an inserted polyethylene (PE) layer (the middle layer) between the PP layers were evaluated. PE-glycidyl methacrylate (GMA) copolymers and a maleic-anhydride grafted PP (MAPP) were compared to the PE homopolymer and the PP homopolymer. The peel adhesive strength of PE-GMA/MAPP laminates was much higher than that of PE homopolymer/PP homopolymer laminates. Meanwhile, the blends composed of the PE-GMA and three types of PE homopolymer (PE-GMA+LDPE, PE-GMA+MDPE, PE-GMA+HDPE) were formulated as the PE middle layer of the multi-layered laminates. The PE blends had the same amount of glycidyl groups, and the deformation capacity was different in each. Namely, the PE blend of LDPE had higher elongation to break than the PE blend of HDPE. The peel adhesive strength of the multi-layered laminates with the middle layer of the LDPE blend was highest among the three types of laminates with the middle layer of the PE blends. Scanning electron microscopy on the fractured surfaces revealed that the large plastic deformation of the LDPE blended middle layer was responsible for the high energy absorption, and resulted in the high peel strength.

Multi-layered laminates composed of two polyethylene (PE)-glycidyl methacrylate copolymers sheets and an inserted polypropylene (PP) sheet were fabricated, and the peel adhesive strengths of the laminates were evaluated. The surfaces of PP sheet were pre-treated by O2-plasma to make reactive groups on the surfaces. The relation between the amount of reactive groups and the peel adhesive strength was evaluated. Also, the mechanisms of peel adhesive strengths were discussed using scanning electron microscopy of the fracture surfaces. The interfacial adhesion of PE/PP was improved with the amount of the reactive groups. As the results, the dilatational plastic deformation including cavitation occurred in the PE layer at the vicinity of the interface of PE/PP, where mechanical constraint would be strong. The plastic deformation of the bulk PE layer by the improvement of the interfacial adhesion is responsible for the energy absorption, which resulted in the increased peel adhesive strengths.

New wood-based epoxy resins were synthesized from alcohol-liquefied wood. Wood was first liquefied by the reaction with polyethylene glycol and glycerin. The alcohol-liquefied wood with plenty of hydroxyl groups were precursors for synthesizing the wood-based epoxy resins. Namely, the alcoholic OH groups of the liquefied wood reacted with epichlorohydrin under alkali condition with a phase transfer catalyst, so that the epoxy groups were put in the liquefied wood. The wood-based epoxy resins and the alcohol-based epoxy resins as reference materials were cured with polyamide amine. The glass transition temperature (Tg), the tensile strength, and the modulus of elasticity of the wood-based epoxy resin were higher than those of the alcohol-based epoxy resin. Also, the shear adhesive strength of the wood-based epoxy resin to steel plates was higher than those of the alcohol-based epoxy resins, which was equivalent to the level of petroleum-based bisphenol-A type epoxy resins. The higher Tg of the wood-based epoxy resin than that of the alcohol-based epoxy resin is one of the evidences that the wood-derived molecules were chemically incorporated into the network structures. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 745-751, 2011

Phase structures and mechanical properties of epoxy/acryl triblock copolymer alloys using several curing agents were studied. PMMA-b-PnBA-6-PMMA triblock copolymers synthesized by living anionic polymerization were applied as the toughening modifiers for the epoxy resins. An aromatic amine, an acid anhydride and an anionic polymerization catalyst as curing agents resulted in macro-phase separation in the epoxy/triblock copolymer blends during the cure process. However, a phenol novolac as the curing agent created nano-phase structures in the epoxy blends. The size of the spherical phases or cylindrical phases was about 40 nm in diameter, and the main component in the nano-phases was the PnBA of the triblock copolymer. The fracture toughness of the epoxy/triblock copolymer alloys with the nano-cylindrical phases reached 2530 J/m(2). The fracture toughness was more than twenty fold relative to the unmodified epoxy resin, and was equivalent to the toughness of polycarbonates. (C) 2010 Elsevier Ltd. All rights reserved.

FID signal of the macroscopic magnetization obtained by measurement of a pulsed NMR is data with very much amount of information of molecular structure，a degree of crystallinity，entanglement，etc. We havecomposed a program of calculating a relaxation spectrum by carrying out numerical differentiation of this FID signal directly.This relaxation spectrum has a close relation to the viscoelastic property of a acromolecule. So， we measured the pulsed NMRand dynamic mechanical analysis of the styrene block co-polymer，and analyzed the relation between a relaxation spectrumand the temperature dependency of a dynamic mechanical analysis (DMA) . As a result，the followings became clear. (1) In a low-temperature region，The temperature where a loss modulus changes is the same as the temperaturewhich thepeak value time of a relaxation spectrum shifts greatly. These results show that pulsed NMR and DMA have measured a flowability change of a macromolecule. (2) The relaxation spectrum of 40 µs or less shows that PS block exists as a hard phase near 100℃. From the result of DMA data， it became clear that the flow have taken place with the state where PS domains are formed，in the polymer with many SI diblock contents.

Because of the weak adhesion between the different materials, the polymer lamination using the different materials is normally brittler than the single polymer by the occurrence of delamination. Similarly in rotational molding, the two layers of polyethylene(PE) and polypropylene (PP) could not get the enough peel strength, and are dolaminated. However, in the case of inserting the dryblended powder of PE and PP as the middle layer between PE layer and PP layer, the peel strength of the multi layer rotational molding was much improved. The peel strength was changed by the density of PE in the middle layer. We observed the state of the middle layer in the rotational molding and the delaminated surface by scanning electron microscopy. Moreover, the mechanism of improved peel strength and the deformation capacity of PE in the middle layer were investigated and discussed.

Composites consist of carboxyl-terminated butadiene acrylonitrile rubber (CTBN) / epoxy resin blends and carbon-black (CB) were formulated. The impact-energy absorbability of the composites depended on the kneading temperature of the resin and the CB. Strong interaction at the interface between CTBN and CB particles was the key factor to achieve the high impact-energy absorbability.

Wood-based epoxy resin was synthesized from resorcinol-liquefied wood. First, wood components were depolymerized and liquefied by reaction with resorcinol. The resorcinol-liquefied wood with plenty of hydroxyl groups could be considered as a precursor for synthesizing wood-based epoxy resin. Namely, the phenolic-OH groups of the liquefied wood reacted with epichlorohydrine under alkali condition. By the glycidyl etherification, epoxy functionality was introduced to the liquefied wood. The wood-based epoxy resin was cured with 4, 4'-diamino diphenyl sulphone (DDS) and the thermal and mechanical properties were evaluated. The flexural modulus and strength of the cured wood-based epoxy resin were comparable to those of the petroleum-based bisphenol-A type epoxy resin (diglycidyl ether of bisphenol-A: DGEBA). The mechanical and adhesive properties of the wood-based epoxy resins suited well for matrix resins of fiber reinforced composites. Therefore, biomass composites consist of ramie fibers and the wood-based epoxy resin were fabricated. The flexural modulus and strength of the biomass composites were equivalent to those of the same fiber reinforced bisphenol-A type epoxy composites.

Epoxy resins have high solvent resistance and high creep resistance in consequence with the network structure. However, the network structure may be the source of the brittleness. In order to improve the fracture toughness of the epoxy resins, several types of modifications have been applied. Initially in this review, reaction-induced phase separation method and particle-addition type toughening technology are compared from viewpoints of industrial application. Then, the mechanisms of particle-addition type toughening technology (ex. rubber particles, glass particles and thermoplastic particles) are individually discussed, which followed by the discussions on the role of the particulate modifiers and the epoxy resins as matrix in the toughening mechanisms.

Resin coatings and linings are very useful methods for corrosion prevention of steel structure exposed to hot steam or acid liquid. Vapor permeation is one of the most important properties for corrosion resistant coatings. Nano filler dispersion is well known to improve the vapor permeation for the nylon and the other plastic materials, and is expected to reduce the vapor permeation of the coating resin and expand the lifetime of the coating system. The aim of this study is to clear the effect of the nano filler on the vapor permeation property of the vinyl ester resin. One montmorillonite clay and three organophilic clays with different surface treatment were dispersed in the bisphenol vinyl ester resin system. Scanning electron microscopy and optical microscopy revealed that the different surface treatment resulted in the different dispersion characteristic. The vapor permeation of the nanocomposites was measured under 40°C, showing that the nano filler addition reduced the vapor permeation and the nanocomposite with the better dispersion of the clay had the lower permeation rate. The undispersion index, defined as the area ratio of the residual aggregate particles on the surface, showed the fairly good correlation with the permeation rate. The mechanism of the vapor permeation of the nanocomposites was discussed.

Carboxyl-terminated butadiene acrylonitrile (CTBN) rubber/ epoxy (diglycidyl ether of bisphenol-A) / diamino diphenyl methane polymer blends with 60 wt% of CTBN were formulated to evaluate the viscoelasticity and the damping properties. When the blend resins had micro-phase separated morphologies composed of epoxy-rich dispersed phases larger than 500 nm in diameter surrounded by a rubber-rich continuous phase, the loss factors (eta) of the steel laminates adhered with the resin significantly depended on the environmental temperature and the resonant frequencies. The resins with epoxy-rich phases smaller than 200 urn in diameter had broad glass-transition temperature range that resulted in the high loss factor (eta > 0.1) of the steel laminates in the broad temperature range. Inhomogeneous nano-gel structures with 20 similar to 30 nm sizes were observed in more compatible resins by scanning probe microscopy, although appreciable micro-phase separation was detected by none of SEM and TEM. Pulse NMR suggested that the fraction of interfacial phase in the resins increased with increasing the compatibility of the blends. The large interfacial phase in the inhomogeneous nano-gel structures seems to play an important role in the damping mechanisms.

Carboxyl-terminated butadiene acrylonitrile (CTBN) rubber/ epoxy (diglycidyl ether of bisphenol-A) / diamino diphenyl methane polymer blends with 60 wt% of CTBN were formulated to evaluate the viscoelasticity and the damping properties. When the blend resins had micro-phase separated morphologies composed of epoxy-rich dispersed phases larger than 500 nm in diameter surrounded by a rubber-rich continuous phase, the loss factors (η) of the steel laminates adhered with the resin significantly depended on the environmental temperature and the resonant frequencies. The resins with epoxy-rich phases smaller than 200 nm in diameter had broad glass-transition temperature range that resulted in the high loss factor (η &gt 0.1) of the steel laminates in the broad temperature range. Inhomogeneous nano-gel structures with 20-30 nm sizes were observed in more compatible resins by scanning probe microscopy, although appreciable micro-phase separation was detected by none of SEM and TEM. Pulse NMR suggested that the fraction of interfacial phase in the resins increased with increasing the compatibility of the blends. The large interfacial phase in the inhomogeneous nano-gel structures seems to play an important role in the damping mechanisms. ©2008 The Society of Rheology.

The degradation mechanism in molecular order by electron beam (EB) irradiation for three types of thermosetting polymers (bisphenol type vinylester, Novolak-type vinylester and tetra functional epoxy resin) is confirmed by dynamic mechanical thermal analysis (DMTA) and the swelling test in this study. The level of degradation in molecular order is quite high. The same result was observed in Novolak-type vinylester but not in tetrafunctional epoxy resin. The results of the swelling test showed that the cross-linking networks were destroyed by gamma- or electron beam irradiation remarkably for both the vinylester resins. For the tetrafunctional epoxy resin, gamma- or electron irradiation does not give any effect even in molecular order in high radiation intensity such as 20 MGy. However, the mechanical properties such as bending strength, modulus and fracture toughness of all composites (both vinylester resin and tetrafunctional epoxy resin composites) reinforced by a chopped-strand glass mat or flake-like mica change a little after 20 MGy EB irradiation. (c) 2007 Curtin University of Technology and John Wiley & Sons, Ltd.

Carboxyl-terminated butadiene acrylonitrile (CTBN) liquid rubber/epoxy (diglycidyl ether of bisphenol-A: DGEBA) / diamino diphenyl methane (DDM) resins, in which CTBN was 60 wt % as the major component, were formulated to evaluate the damping and adhesive properties. In cases where acrylonitrile (AN) was 10 similar to 18 mol % as copolymerization ratio in CTBN, the blend resins showed micro-phase separated morphologies with rubber-rich continuous phases and epoxy-rich dispersed phases. The composite loss factors (q) for steel laminates, which consisted of two steel plates with a resin layer in between, depended highly on the environmental temperature and the resonant frequencies. On the other hand, in the case where AN was 26 mol % in CTBN, the cured resin did not show clear micro-phase separation, which means the components achieve good compatibility in nano-scale. This polymer alloy had a broad glass-transition temperature range, which resulted in the high loss factor (eta > 0.1) for the steel laminates and excellent energy absorbability as the bulk resin in a broad temperature range. Also the resin indicated high adhesive strengths to aluminum substrates under both shear and peel stress modes. The high adhesive strengths of the CTBN/epoxy polymer alloy originated in the high strength and the high strain energy to failure of the bulk resin. (c) 2007 Wiley Periodicals, Inc.

Dicyandiamide (DICY)-cured epoxy resins are important materials for structural adhesives and matrix resins for fiber reinforced prepregs. The objective of this study was to examine the mechanical and physical properties as well as the gel structures of the cured resins and discuss the relationships among them. Diglycidyl ether of bisphenol-A (DGEBA) oligomers were chosen as the common chemical structure of the epoxy resins. Four kinds of resin mixtures were formulated using the seven types of DGEBA oligomers having different molecular weight distributions. Three resin formulations having bimodal-type molecular weight distributions were designed to have almost identical rubbery plateau values of the storage modulus in dynamic mechanical analyses after curing, means that they had almost equivalent average crosslink density and basic chemical structure. However, the toughness, ductility, and environmental (heat and solvent) resistance of these three formulations were different. Atomic force microscopy revealed the existence of inhomogeneous nanoscale gel structures in these cured resins. The morphological differences in the gel structures in terms of their size, the connectivity, and the relative magnitude of the heterogeneity would cause the difference in several properties of the DICY-cured epoxy resins. (C) 2007 Wiley Periodicals, Inc.

This study includes the development of a high heat-resistant FRP whose matrix is T_g-less epoxy resin which can be cured by anionic polymerization with potassium carboxylate salts as initiators. First, various epoxy resins with different chemical structures were evaluated to find an epoxy resin composition which has the least decrease in elastic modulus even at an elevated temperature. As a result, R, which is defined as the ratio of the modulus at 250°C to that at 25°C, exhibited the highest value of 44.5% in the combination of bisphenol A type epoxy resin with a multi-functional glycidyl ether derived from multi-functional phenols. The GFRP whose matrix was this T_g-less epoxy resin composition exhibited high heat-resistant property of R≥80% at 34 vol% of glass fiber content. The FRP had also excellent corrosion-resistance because the chemical structure of its matrix is hard to be hydrolyzed even under acidic or alkaline conditions.

A novel adhesive, consisting of well-formulated epoxy resins and thermally expansive fillers has been developed. The cured adhesive resin showed characteristic viscoelasticity with both the storage modulus higher than 3 GPa in the glassy state under the glass transition temperature (Tg) around 100 °C and the rubbery modulus less than 2 MPa over the Tg. As the results, the joint bonded with the adhesive was strong at ambient temperature under 80 °C and they could be dismantled easily at high temperature due to the expansion force caused by expandable graphite as the fillers. The technique of the dismantlable adhesive joints should be important in terms of material recycling because carbon fiber reinforced plastics (CFRP) has to be separated in the recycling process from the other materials such as steel or aluminum alloy used as parts of automotives, for example.

A T-g-less epoxy resin was easily obtained by curing with ionomer. In this system, the storage modulus did not drop and maintained a high level as if it were in a glassy state even at an elevated temperature of 300 degrees C. Investigation of the curing process for the epoxy resin mixture with ionomer, using DSC and FT-IR, revealed that the curing reaction was initiated from the nucleophilic addition of - COO- to the epoxy group to form an ester linkage, and that the chain propagation subsequently occurred by anionic ring opening polymerization of the epoxy group to form an ether linkage. On the basis of the results, the mechanism of 'T-g-disappearing phenomenon' is also discussed. (C) 2007 Curtin University of Technology and John Wiley & Sons, Ltd.

Impact energy absorbability of carbon fiber reinforced composites (CFRPs), in which carboxyl terminated butadiene acrylonitrile rubber (CTBN)/ epoxy reactive blend resins were used as the matrix resins, was evaluated. As the matrix resins, 2 types of CTBN/epoxy blends, in which microphase separated morphologies composed of epoxy-rich phase and rubber-rich phase exist, and 1 type of CTBN/epoxy blend, in which no phase separation was observed by electron microscopy, were compared. The rank order of energy absorbabilily of the resins was consistent with the rank order of that of the CF fabric composite laminates. However, the elastic moduli of the resins decreased with the increase of the energy absorbability. The trade-off relationship between the modulus of elasticity and the energy absorbability was also shown in the CF fabric composite laminates. Then, hybrid composite laminates which consist of the CF fabric prepregs impregnated with CTBN/epoxy blends and uni-directional CF reinforced prepregs impregnated with conventional rigid epoxy resin were fabricated. The hybrid laminated composites indicated improved balance on the modulus of elasticity and the energy absorbability.

One of the conventional methods to develop biodegradable plastics at a reasonable cost is manufacturing the blend of expensive polycaprolactone (PCL) and lower-priced starch. However, past studies have shown that the amount of starch blended with plastics is relatively small and the dynamic properties are not sufficiently improved. This study focuses on the improvement of physical properties of starch, including thermal plasticity, compatibility with PCL and dynamic properties. Starch was blended with glycerine and water to achieve thermal plasticity and improve compatibility with PCL. Addition of maleic anhydride to PCL improved compatibility, which resulted in improved dynamic properties. Addition of clay results in dispersed thermo plastic starch, which improves compatibility with PCL. In addition, it was clarified that addition of clay accelerates the positive effect of electron irradiation on the blend. Copyright (c) 2006 John Wiley & Sons, Ltd.

Wood-based epoxy resins were synthesized from resorcinol-liquefied wood. Wood was first liquefied in the presence of resorcinol with or without a sulfuric acid catalyst at high temperature. Because of the hydroxyl groups, the resorcinol-liquefied wood was considered as a precursor for synthesizing wood-based epoxy resin. Namely, the phenolic OH groups of the liquefied wood reacted with epichlorohydrin under alkali condition. By the glycidyl etherification, epoxy functionality was introduced to the liquefied wood. The epoxy functionality of the resins was controlled by the concentration of phenolic OH groups in the liquefied wood, which would be a dominant factor for crosslink density and properties of the cured epoxy resins. The flexural strength (150-180 MPa) and the modulus of elasticity (3.2 GPa) of the highly crosslinked wood-based epoxy resin were equivalent to those of the commercially available epoxy resin, diglycidyl ether of bisphenol A (DGEBA). Also, the shear adhesive strength of the wood-based epoxy resin was higher than that of DGEBA when plywood was used as the adhesive substrates. The mechanical and adhesive properties suggested that the wood-based epoxy resins would be well suited for matrix resins of natural plant-fiber reinforced composites. (c) 2006 Wiley Periodicals, Inc.

The damping properties and the adhesive properties of carboxyl-terminated butadiene acrylonitrile rubber (CTBN)/epoxy (diglycidyl E bisphenol-A: DGEBA) polymer blends, including 60 wt% CTBN, were evaluated. In cases when the acrylonitrile (AN) contents in CTBN were 10-18 mol%, the blend resins showed micro-phase separated morphologies with rubber-rich continuous phases and epoxy-rich dispersed phases. The composite loss factors (η) for steel laminates, which consisted of two steel plates with the resin layer in between, depended strongly on the environmental temperature and the resonant frequencies. Moreover, in the case that the acrylonitrile (AN) content in CTBN was 26 mol%, the compatibility in the blend was enhanced and the resin did not indicate clear micro-phase separation in nanoscale. The temperature dependence of the tan δ of the resin was small, which resulted in the high loss factor (η &gt 0.1) for the steel laminate over a broad temperature range, with several resonant frequencies. The resin also indicated high adhesive strength values in both shear mode and peel mode. The temperature dependence of η and the order of η among resin formulations could be explained according to the mode proposed by Ross, Unger, and Kerwin.