Keishin Mizoguchi

CO2-induced crystallization of poly(ethylene terephthalate)

Abstract Crystallization of amorphous poly(ethylene terephthalate) (PET) induced by sorbed CO2 has been investigated at several temperatures and pressures up to 50 atm and compared with thermal crystallization. From the results of X-ray diffraction, infra-red spectroscopy and density measurements, it was shown that, by sorption of CO2, crystallization takes place even at temperatures well below the Tg measured in air, and the crystallization rate at temperatures above Tg was greatly increased. This means the sorbed CO2 acts as an intensive plasticizer for PET. From the effects of the sorbed CO2 on the crystalliation rate, the plasticizing ability of CO2 was estimated in terms of temperature, which is equivalent to enhancement of the mobility of the polymer segments. The density of the sample crystallized by sorbed CO2 was smaller than that of a thermally crystallized sample having the same crystallinity determined by infra-red measurements. It is assumed that the sample crystallized by sorbed CO2 contains more microvoids than that crystallized by thermal annealing.

Structural studies on ethylene-tetrafluoroethylene copolymer 1. Crystal structure

Abstract The crystal structure for an ethylene-tetrafluoroethylene (ETFE) alternating copolymer film containing highly ordered crystal regions was determined. The unit cell is orthorhombic with the dimensions: a = 8.57 A , b = 11.20 A , and c ( chain axis ) = 5.04 A . Four planar zigzag chains are packed in the unit cell. The lateral packing mode is similar to that of orthorhombic polyethylene (PE). A study on the mode of double orientation confirmed that the crystal structure of ETFE, which has been assumed to be pseudo-hexagonal, is indeed orthorhombic as described above, although it has paracrystalline disorder.

Structural studies on ethylene-tetrafluoroethylene copolymer: 2. Transition from crystal phase to mesophase

Abstract A thermo-reversible, first-order transition from an orthorhombic crystal lattice to a hexagonal lattice (mesophase) was found in ethylene-tetrafluoroethylene alternating copolymer by using X-ray diffraction. The transition was shown to be the order-disorder transition with a wide pretransitional temperature range, which was caused by rotational motion around the chain axis as often observed in planar zigzag polymers like polyethylene. A characteristic anisotropy of the thermal expansion coefficient of the crystal lattice was observed in the pretransitional range. By combining dilatometric data with the X-ray data on crystal expansion, the copolymer composition, the fraction of ordered orthorhombic region in the crystal phase and the crystallinity were obtained. Furthermore, the relaxations observed in a dynamic viscoelastic measurement were analysed by comparison with the crystal expansion.

Thermodynamic interactions in rubbery polymer/gas systems

The Flory–Huggins interaction parameters χ for 23 gases (He, Ne, Ar, Kr, Xe, H2, N2, O2, N2O, CO2, CH4, C2H4, C2H6, C3H6, C3H8, 1,3-C4H6, four C4H8s, n-C4H10, iso-C4H10, and n-C5H12) in five rubbery polymers (1,2-polybutadiene (PB), poly(ethylene-co-vinyl acetate)) (EVAc), polyethylene (PE), polypropylene (PP), and poly(dimethyl siloxane) (PDMS) were determined from either literature data on Henrys law coefficient and partial molar volume or those on sorptive dilation for each polymer/gas system. Values of χ for the gases increased in the order of PDMS < PP ≡ PB < EVAc ≡ PE. Among the gases except He and H2 whose χ values are not reliable, Ne and Xe have respectively the highest and the lowest values of χ for the polyolefins. The χ values of the hydrocarbons were compared together with previously reported χ values of n-alkanes C3-C10. The dependencies of χ upon concentration and temperature were discussed on the basis of the literature data.

Pressure dependence of gas permeability in a rubbery polymer

The effect of pressure on gas permeability of a rubbery polymer, 1,2-polybutadiene, is investigated for 15 gases with various molecular sizes and solubilities in the ranges of pressure up to 110 atm at 25°C. The permeability for slightly soluble gases (He, Ne, H 2, N 2 , O 2 , and Ar) decreases with increasing pressure, and that for soluble gases (CH 4 , Kr, CO 2, N 2 O, C 2 H 4 , Xe, C 2 H 6 , C 2 H 6 , and C 3 H 8 ) increases with increasing pressure. Logarithms of permeability coefficient versus feed-gas pressure for the slightly soluble gases, CH 4 and Kr, is linear within each pressure range, whereas such plots become convex toward the pressure axis for more soluble gases, such as CO 2, N 2 O, C 2 H 4 , Xe, C 2 H 6 , C 3 H 6 , and C 3 H 8 . By analyzing the pressure dependence of permeability using sorption data of the gases, contributions of concentration and hydrostatic pressure to the gas diffusivity are estimated.

Sorption and partial molar volumes of inert gases in rubbery polymers

Abstract Sorption of inert gases (He, Ne, Ar, Kr, and Xe) in two rubbery polymers, 1,2-polybutadiene (PB) and poly(ethylene-co-vinyl acetate) (EVAc), and dilation of the polymers due to the sorption were measured as a function of the gas pressure at 25°C. For all the gases, the sorption isotherms followed the Henrys law over the pressure ranges examined, and the dilation isotherms were linear in these ranges. From the sorption and dilation data, the partial molar volumes V r of the dissolved gases were determined. A linear relation was found between V r and the van der Waals volume V w ; i.e., V r =1.6V w +20 in cm3/mol. This is much the same the relation for hydrocarbon gases dissolved in the same polymers and that between molar volume and V w for liquid n-alkanes. There also existed a linear relation between V r and the logarithm of Henrys law coefficient for a series of inert gases in the polymers. Sorption and dilation for He/Kr mixtures in PB were measured at various total and partial pressures, and thereby the hydrostatic-pressure dependence of V r for dissolved Kr component was examined. From the dependence, the compressibility of the dissolved Kr molecules was estimated to be ≈ 5×10−4 atm−1.