Hitoshi Fujimatsu

Adhesion between high strength and high modulus polyethylene fibers by use of polyethylene gel as an adhesive

The use of polyethylene gels to adhere high strength and high modulus polyethylene fibers together has been investigated. It was found that the joint strength obtained using high density polyethylene (HDPE) gel in decalin or tetralin depended on the heating temperature and time of the gel. When heated at 100°C for 30 min, the gel showed such a high joint strength that polyethylene fibers were torn, and this should be enough for practical uses. The results of the present study demonstrate that utilization of the polyethylene gel as an adhesive is an extremely effective method when polyethylene fibers are used in composite materials.

Lower critical solution temperature (LCST) and theta temperature of aqueous solutions of nonionic surface active agents of various polyoxyethylene chain lengths

Cloud points of aqueous solutions of homogeneous poly(oxyethylene)dodecyl ether derivatives (C12(OE)n: n=2–8) and the apparent theta temperatureTθap were determined from the abrupt changes in optical transmittance and the temperature dependence of the second virial coefficient obtained by light scattering measurements. It was found that the lower critical solution temperature (LCST) shifts to a lower temperature and lower concentration as the number of oxyethylene units in a molecule decreases. Because of this behavior of LCST, the modified Flory-Schultz plot of phase separation was applied to the present nonionic surfactant-water system, and its theta temperature obtained. The dependence ofTθap on the number of oxyethylene units suggests that the polyoxyethylene chain has different effects on the solubility of C12(OE)n in water forn less than or equal to 3 from those forn greater than or equal to 4.

Temperature dependences of micellar molecular weight and radius of nonionic surface active agent in the aqueous solution

Abstract The molecular weight and diffusion constant of poly(oxyethylene) dodecyl ether (C 12 OE 9·3 ) micelles with an average of 9.3 oxyethylene group were determined from light-scattering measurements and free boundary experiments over a wide temperature range. It was found that micelles formed by C 12 OE 9·3 were monodisperse in the temperature range studied. Plots of the logarithms of micellar molecular weight and micellar radii estimated from the diffusion constants against the temperature have a break point around 45°C. This temperature agrees with a theta point where the second virial coefficient obtained from light-scattering measurements is zero. Although the number of the molecules participating in micelle formation increases with temperature, the size of the micelle remains constant up to the temperature corresponding to the theta point, because the spherical micelle is packed with increasing tightness. The increase in the size and weight beyond that point may be attributed to a departure from spherical shape.

Sensitized photoisomerization of cis-stilbazoliumions intercalated in saponite clay layers

Sensitized photoisomerization of the cis-stilbazolium ion 1 by ruthenium tris-2,2′-bipyridine [Ru(bpy)32+] was studied in saponite clay layers. The reaction yield was 100 times higher than the reaction yield in a homogeneous solution. The Stern–Volmer constant of the luminescence of Ru(bpy)32+ by 1 was 3.4×105 d mol-1, which made the quenching rate constant faster than the diffusion limiting rate. The fast quenching rate implies a static quenching by 1 in the vicinity of Ru(bpy)32+. The reaction efficiency showed a maximum when 70 mol% of 1 was intercalated on the basis of the cation exchange capacity (CEC), where the ruthenium complex and 1 are suitably arranged in the saponite layer for effective photoelectron transfer and subsequent electron relay.

Adhesion of molded polyethylene using polyethylene gels by microwave heating

Adhesive effect of polyethylene gels on the molded polyethylene by heating with microwaves has been investigated. Polyethylene gels in polar organic solvents such aso-xylene, chlorobenzene,o-dichlorobenzene,m-dichlorobenzene, 1,1,1,2-tetrachloroethane, and 1,1,2,2-tetrachloroethane were used as adhesives. All of these gels showed adhesive effect when heated with microwaves. In particular, the gels in 1,1,2,2-tetrachloroethane showed such strong adhesion that polyethylene plates of 3 mm in thickness and 20 mm in width gave rise to necking by heating for 8 min in a 500 W (2450 MHz) microwave oven.

Immobilization of β-Galactosidase with Polyvinyl Alcohol

Abstract Immobilization of β-galactosidase with PVA (polyvinyl alcohol) hardened by freezing-thawing was attempted and the stability of the immobilized enzyme was investigated. Afterwards the freezing-thawing procedure, leakage of the enzyme from PVA hydrogel beads, and faster activity drop of the gel beads were observed during prolonged incubation. The stability of the immobilized enzyme treated with boric acid at an adequate concentration restored to the extent of the free enzyme, although higher concentrations of boric acid inhibited the free enzyme.

Effect of solvents on adhesion between polyethylene moldings and molten polyethylenes

The effect of a variety of solvents on adhesion between polyethylene moldings and molten polyethylenes has been investigated. The adhesive strengths between the molten polyethylenes heated in the range of 250 to 300°C and the polyethylene moldings, on which organic solvents, such as xylene, decalin, tetralin and o-dichlorobenzene were precoated, sharply increased, and indicated stable high values. This effect was evident for such molten polyethylenes as LDPE, HDPE and HMWPE. This results from the local dissolution of the polyethylene surface and molten polyethylenes, and subsequent recrystallization of polyethylene molecules in both the surface of the molten polyethylene and polyethylene moldings as the solvents evaporate.

Swollen polyethylene films as adhesives to bond polyethylene moldings

The adhesive effect of swollen polyethylene films to bond polyethylene moldings have been investigated. It was found that low density polyethylene (LDPE) films swollen in decalin and tetralin show an adhesive effect when heated over 70° C for 2 h. The joint strength increased as the heating temperature was raised. When heated at 120° C, it showed such a strong joint strength (over 36 kg/cm2) that the polyethylene plates gave rise to necking, and this should be enough for practical uses.

Adhesive effect of low-density polyethylene gels on polyethylene moldings

Adhesive effect of low density polyethylene (LDPE) gels in organic solvents such as decalin, tetralin, ando-dichlorobenzene on high density polyethylene (HDPE) moldings has been investigated by shearing tests, electron microscopy, and DSC measurements. When heated at 110°C for 2 h, all of the gels showed strong adhesive strengths around 30 kg/cm2, which is sufficiently strong for practical uses. It has been found that the adhesive strength increases with the heating temperature and that the temperature at which the heated gel begins to exhibit the adhesive effect depends upon solvents and is about 30° lower than that of the HDPE gels.

Thermochromism of poly-1-butene gels

Poly-1-butene gels in some solvents of benzene-derivatives show a colouring phenomenon. The colour changes from blue to yellow under irradiation of natural light as the temperature rises from the melting point of the solvent to the sol-gel transition temperature. The colouring phenomenon is due to selective scattering, but not to optical absorption. The apparent characteristics of the phenomenon resemble the thermochromism of cholesteric liquid crystals, although poly-1-butene itself is colourless and has no asymmetric carbons.