Teruo Nakashima

Antibacterial Activity of Cellulose Fabrics Modified with Metallic Salts

This paper deals with the effect of a metallic salt treatment on the antibacterial activity of cellulosic fabrics against three kinds of bacteria: gram-positive bacteria Staphylococcus aureus (S. aureus), gram-negative bacteria Klebsiella pneumoniae (K. pneumoniae), and methicillin resistant Staphylococcus aureus (MRSA). Two kinds of cellulose fabrics are treated with the metallic salts CuSO4 and ZnSO4. The fabrics are pretreated with succinic acid anhydride to make adsorption of metallic salts more effective. This pretreatment is very effective at increasing the amount of metal ions adsorbed, and is more prominent in Cu ion than in Zn ion. The degree of antibacterial activity of samples treated with Cu salt against one of the S. aureus increases with an increasing amount of adsorbed Cu ion. A similar tendency is observed for the samples treated with Zn salt, although its correlation is not as clear as for Cu ion. Antibacterial activity is also confirmed against K. pneumoniae. The degree of antibacterial activity of samples treated with Cu salt against MRSA is almost independent of the amount of Cu ion adsorbed, and the tendency is similar for samples treated with Zn salt. After ten laundering cycles, the effect of the treatment is maintained. We conclude that these treatments are very effective in providing antibacterial activities to cellulose fabrics.

Development of high-strength and high-modulus polyethylene-starch composite films and biodegradation of the composite films

Abstract Composite films of polyethylene with ultrahigh molecular weight (6 × 106) and corn starch were prepared by gelation-crystallization from dilute solutions. The polyethylene-starch compositions chosen were 3/1, 1/1, 1/3, and 1/5. The elongation was carried out in a hot oven at 135°C. The maximum drawability was affected by the composition. The maximum draw ratios of the 1/5 composite reached 80, and the corresponding Youngs modulus was 10 GPa. The values of the films with the 3/1 and 1/1 composites were about 75 and 105 GPa, respectively, which are higher than the moduli of aluminum(70 GPa) and cast iron (90 GPa). In spite of the elongation up to such high draw ratios, most starch particles remained within the composite films. This interesting phenomenon is discussed in terms of the morphology of the composite films as studied by wide-angle x-ray diffraction, small-angle x-ray scattering, and scanning electron microscopy. Furthermore, the composite films with different compositions were put on a d...

Biodegradation of high-strength and high-modulus PE–starch composite films buried in several kinds of soils

The biodegradative behaviors of composite films of ultrahigh molecular weight polyethylene (UHMWPE) (6×106) and starch (ST) particles were investigated. The films were prepared by gelation–crystallization from dilute solutions of PE, in which ST particles were dispersed. The PE–ST compositions chosen were 3/1, 1/1, 1/3, and 1/5. The elongation was done up to 80 times in a hot oven at 135°C under nitrogen. Using the undrawn and drawn specimens, biodegradation of PE was examined by burying the blend materials for 16 months in three kinds of soils, namely, paddy soil, farmyard manure, and red clay. The weight decrease after the degradation was found to be dependent on ST content, draw ratio of original films, type of soils, and burying period. The weight loss was the highest for the specimen buried in paddy soil and lowest for that in red clay. Nevertheless, the changes in the tensile strength and Youngs modulus after degradation were most prominent in the specimen buried in the red clay. This result is of interest since the weight decrease in this specimen was lowest. Drastic morphological changes were observed by scanning electron microscopy for the specimens buried in red clay. Significant chain scission of ultra UHMWPE could be observed. The specimen showed the largest decrease in storage modulus. No degradation, however, was observed for the ultradrawn UHMWPE specimen (1/0) buried in red clay. Thus it turned out that the degradation of PE in the composite materials buried in red clay is induced by the dispersed ST particles.

Segmental Orientation under Simultaneous Biaxially Stretching using a Lattice Model and Application of Oriented Crystallization of Ultra-high Molecular Weight Polyethylene Films Prepared by Gelation/Crystallization from Solution

A lattice model proposed before for uniaxial stretching of polyethylene films was applied to estimate the oriented crystallization of ultra-high molecular weight polyethylene (UHMWPE) dry gel films under simultaneous biaxially stretching. In this model system, the preferred axis associated with the preferred orientation of amorphous chain segments was chosen along the direction between two successive cross-linked points and the preferred axis was assumed to deform in an affine fashion with respect to the stretching direction. As the application of the proposed model, the orientation distribution function of crystallites was calculated on the basis of the lattice model and oriented crystallization model. The oriented crystallization model is based on the concept that a kinetically determined distribution of crystal chain axes as the normalized distribution of clusters found at the saddle point corresponding to a non-uniform orientation under conditions of a steady-state nucleation rate. Of course, the crystallites are oriented randomly with respect to the film normal direction. The parameter fitting for the formulated orientation distribution function of crystallites was done for the film which was prepared by the gelation/crystallization from solution with 0.9 g/100 mL concentration, the solvent being decalin, since the concentration assured the highest drawability under simultaneous biaxially stretching. The calculated orientation distribution functions 2πqj(cosθj) of the reciprocal lattice vector of the crystal planes were in good agreement with the observed ones. Thus the numerical calculations indicate that the orientation of the c-axes depends on that of amorphous chain segments and the orientation behavior of crystallites is strongly affected by their rotation around the c-axis.

Young's Modulus Estimated from Orientation Distribution Functions of Crystal and Amorphous Phases for Simultaneous Biaxially Stretching Ultra-High Molecular Weight Polyethylene Films Prepared by Gelation/Crystallization from Solutions

Youngs modulus of simultaneous biaxially stretched films was much lower than that of uniaxial films with the same draw ratio. To address this problem, a theoretical approach was carried out by using a three-dimensional model. In this model system, the oriented crystalline layers are surrounded by an anisotropic amorphous phase and the strains of the two phases at the boundary are identical. Youngs modulus was calculated by using the generalized orientation factors of crystallites and amorphous chain segments calculated from the orientation function of crystallites and that of amorphous chain segments. The orientation function of crystallites was determined from the orientation functions of the reciprocal lattice vectors of the crystal planes. The theoretical values of Youngs modulus were calculated using the values of elastic compliance proposed by Zehnder. The values were in fairly good agreement with the experimental values of specimens with different draw ratios. Judging from the induced equations, the calculated results provided that the Youngs modulus of simultaneous biaxially stretching film is attributed to the contribution from the compliance associated with shear modulus and consequently the Youngs modulus automatically takes low values.