Tsunetaka Matsumoto

Effect of particle size on fracture toughness of epoxy resin filled with angular-shaped silica

Abstract The effect of particle size on the fracture behaviour of cured epoxy resin filled with angular-shaped silica was studied. Angular-shaped silica particles were prepared by crushing fused natural raw silica and were classified into six groups with different mean sizes ranging from 2 to 47 μm. Critical stress intensity factor ( K c ) and critical strain energy release rate ( G c ) of the cured epoxy resin filled with these silica particles were measured. Both K c and G c values increased with an increase in particle size of the silica. Scanning electron microscopic observations of crack tips and fractured surfaces showed that the damage zone was formed at the crack tip by particle fracture and by crack diverging. This phenomenon became more pronounced with increase in the particle size. The higher K c and G c values appear to be derived from the dispersion of the stress concentrated at the crack tip due to the crack diverging and from energy absorption due to the formation of a damage zone.

Effect of particle size on the fracture toughness of epoxy resin filled with spherical silica

Abstract The effect of particle size on the fracture behaviour of cured epoxy resin filled with spherical silica particles was studied. Five kinds of spherical silica particles prepared by hydrolysis of silicon tetrachloride having different mean sizes, ranging from 6 to 42 μm, were used. The critical stress intensity factor (Kc) and the critical strain energy release rate (Gc) of the cured epoxy resins filled with the silica particles were measured. Both Kc and Gc values increased with particle size. Scanning electron microscope observation shows that the main crack propagation was hampered by large particles and a damage zone was formed at the main crack tip region in the large particle filled resin due to crack diversion and debonding of particle/matrix interfaces. The higher Kc and Gc values seem to be derived from these phenomena.

Production of anomalously shaped carboxylated polymer particles by seeded emulsion polymerization

Anomalous polymer particles with a partial protuberance like “octopus ocellatus” were produced under alkaline conditions by seeded emulsion copolymerization for styrene and butyl acrylate, with styrene-butyl acrylate-methacrylic acid terpolymer emulsion as seed. The mechanism of production of the polymer particles was studied. By transmission electron microscopic observation of the particles at each conversion, it was observed that the anomalous polymer particles were produced by partial growth of each of the individual seed particles throughout polymerization. Ionization of the carboxyl groups and low viscosity in the growing particles during the process of polymerization were important factors for partial growth.

Effect of particle size on impact properties of epoxy resin filled with angular shaped silica particles

Abstract The effect of particle size on the impact properties of cured epoxy resin has been studied. This resin is filled with angular shaped silica particles that were prepared by crushing fused natural raw quartz. These particles were sorted into six groups having different mean sizes ranging from 2 to 47 μm. Specimens having a U-shaped blunt notch were prepared. The impact properties were measured by an instrumented Charpy type impact tester which can record a load-displacement curve at impact fracture. The impact absorbed energy increased with a decrease in silica particle size. The fractured surfaces were studied using a scanning electron microscope to clarify the initiation point of fracture.

Immunoactivity of polymer microspheres with their hydrophilic/hydrophobic heterogeneous surface sensitized with an antibody

Styrene/2-hydroxyethyl methacrylate polymer microspheres consisting of various polymer compositions were produced by emulsifier-free seeded emulsion polymerization technique. Using these microspheres, which should have hydrophilic/hydrophobic heterogeneous surface, the effects of surface hydrophilicity on the main, fundamental requirements for an immunomicrosphere — high colloidal stability, sensitive immunologic agglutinability and insensitive non-specific agglutinability — were studied in detail. There was a region of the surface hydrophilicity that satisfied the three requirements simultaneously.

Adsorption of trypsin onto styrene-2-hydroxyethyl methacrylate copolymer microspheres and its enzymatic activity

Effects of the surface hydrophilicity of styrene-2-hydroxyethyl methacrylate (S-HEMA) copolymer microspheres on the adsorption immobilization of trypsin and on its enzymatic activity were discussed. In the case of a polystyrene (PS) microsphere, the amount of adsorption was large, whereas the enzymatic activity of the adsorbed trypsin was low. On the other hand, in the case of an S-HEMA copolymer microsphere whose HEMA content was 10 mole %, the maximum specific activity of trypsin adsorbed was nearly equal to that of free trypsin, although the amount of adsorption decreased to about 65 % of that in PS. Accordingly, total activity, which is the product of the amount of adsorption and the specific activity, could be enhanced by controlling the surface hydrophilicity of the microsphere.

Covalent immobilization of trypsin onto poly(2-hydroxyethyl methacrylate)/polystyrene composite microspheres by cyanogen bromide method and its enzymatic activity

Covalent immobilization of trypsin onto poly(2-hydroxyethyl methacrylate)/ polystyrene composite microspheres, produced by emulsifier-free seeded emulsion polymerization technique, was carried out using the cyanogen bromide method under various conditions. The highest enzymatic activities of the trypsin immobilized in this study against N-α-benzoyl-L-arginine ethyl ester and N-α-benzoyl-L-arginine-p-nitroanilide, as low-molecular substrates and casein as a high-molecular substrate, were high, as corresponding to 80%, 85% and 50% of those of free trypsin, respectively.

Temperature dependence of the elastic modulus of crystalline regions of Poly(ethylene terephthalate)

Abstract The temperature dependence of the elastic modulus E1 of crystalline regions of poly(ethylene terephthalate) (PET) in the direction parallel to the chain axis has been investigated by x-ray diffraction. The axial chain contraction coefficient is constant from 25°C to 200°C, and correspondingly the value of E1 (108 GPa) remain unchanged up to 215°C. This is in contrast with the temperature dependence of E1 values of various polymers previously reported. It is considered for PET that the axial thermal molecular motions which cause the decrement of E1 do not take place in the crystalline regions, and that the force constant of bond stretching and that of bond angle bending are constant over both the temperature and the stress range studied. It is reasonable to conclude that the mechanical structure of drawn PET is composed of the series model.

Transcrystalline Region of Polypropylene: Its Formation, Structure and Mechanical Properties

Abstract The question of the dominant factors in the production of a transcrystalline region (TCR), an “interphase,” in crystalline polymers on solidifying in contact with a substrate is investigated for isotactic polypropylene (PP) using polarization microscopy and scanning electron microscopy. Several uncoated substrates, and the same substrates coated with certain vacuum-evaporated metals and carbon, as well as surface replicas of these made with cellulose acetate, are compared as nucleating surfaces. It is concluded that TCR formation is not dependent on the species of substrates or their surface energy but on the geometrical morphology or surface roughness. In fact, the rough surface produced by abrasion with carborundum powder creates a TCR for every substrate used. An all-transcrystalline (TC) film of PP more than 300μm thick is obtained by hot pressing the PP between two sheets of PTFE. Wide-and small-angle X-ray analysis of the film reveals a “cross-hatch” structure of lamellae. Micro-beam X-ray ...

Crystal growth of Co ferrite on fine acicular γ-Fe2O3 particles

Abstract Highly coercive magnetic powder was obtained by growing cobalt ferrite on the surface of γ-Fe 2 O 3 particles in highly alkaline suspensions containing cobalt and ferrous ions in a Co/Fe molar ratio = 1 2 . The mechanism of the growth and the structure of cobalt ferrite on γ-Fe 2 O 3 were studied by X-ray diffraction and electron diffraction techniques. Results show that crystals of cobalt ferrite CoFe 2 O 4 with a spinel type crystal structure of lattice constant 8.415 A grew epitaxially on γ-Fe 2 O 3 . The acicular direction of the epitaxially grown Co-γ-Fe 2 O 3 as well as γ-Fe 2 O 3 was in the [ 1 01] direction. It was found that from the lattice constant value and the half width of X-ray diffraction peaks, the lattice constant epitaxially grown Co γ-Fe 2 O 3 may be attributed to two kinds of crystals, viz., seed γ-Fe 2 O 3 ( a = 8.35 ∼ 8.37 A ) which was partly reduced to Fe 3 O 4 , and surface layer CoFe 2 O 4 ( a = 8.415 A ). The crystal growth in the interface between the seed crystals and the growth layer was affected by the crystal structure of the seed crystals. The lattice constant of CoFe 2 O 4 which was located in the vicinity of the interface was almost equal to that of the seed crystals.