The total birefringence of crystalline polymer for cylindrical symmetric orientation can be represented as follows; on the basis of simple additivity of the crystalline and non-crystalline contribution. The intrinsic birefringence of uniaxially stretched polyvinyl alcohol are evaluated by simultaneous measurements of x-ray diffraction, visible dichroism and birefringence. We transform the above equation to fallowing equation, and then, the slope and intercept on ordinate, we can evaluate the intrinsic birefringences of crystalline and non-crystalline phases, experimentally. On the other hand, by using of Lorentz-Lorenz's equation, we determine the ratio of the intrinsic birefringence of crystalline and non-crstalline phases, and moreover substitute the ratio into the additive equation of birefringence. The symplified equation can be represented as follows; where Δco is KΔao. This equation shows the linear relation of Δt against Δao, therefore we can determine the intrinsic birefringence of non-crystalline phase from the slope of the line. Employing above two methods in our experimental results, following results are reached. 1) The average intrinsic birefringence of crystalline and non-crystalline phases are found as follows; Δco=51.8×10-3Δao=43.8×10-3 2) The principal refractive indices of crystalline and non-crystalline phases are found as follows;
The previous report (part 5) in this series has shown the effects of crystalline orientation on the mechanical properties of the biaxially stretched polypropylene films prepared by dry-process, and successively this report shows the effects of molecular orientation and noncrystalline chain orientation. In this study the samples, stretching system and stretching conditions are also the same as those described in the previous reports. The behaviors of molecular orientation in these stretched films were followed up by the birefringence measurement and the infrared dichroism. In the birefringence measurement a tilting specimen-method was used. The following results were obtcined: (1) The molecular orientation in the films uniaxially stretched under free width is uniaxial with cylindrical symmetry around the stretching direction, and the crystalline orientation improves preferably to the amorphous. (2) In the films uniaxially stretched under constant width, however, the molecular orientation is roughly biaxial. The orientation of amorphous region gives rise to the characteristic elongation to beak the films. (3) In the two-way successively biaxially stretched films, the molecular orientation changes during the second-direction stretching. The crystalline orientation is better than that of the amorphous segments. Therfore, for the crystalline polymer films as polypropylene, it is difficult to make all mechanical properties in balanced state by two-way successive biaxial stretching. (4) In the simultaneously biaxially stretched polypropylene films, the molecular chain orientation is in balance in the machine and the transverse direction at all stretch ratio, and the planar orientation distributed at random is resulted. And, the molecular chain orients in the same direction to the crystal c-axis. The mechanical properties of the films have no directional specificity. This phenomenon is veryfied from the fact that the crystalline and the amorphous chains, are randomly oriented in the plane.
The effects of molecular orientation and crystallization on the dynamic viscoelastic properties of the biaxially stretched polypropylene films were investigated. The specimens were prepared by stretching T-die extruded films to various ratio by various methods at 145°C at a rate of 1600%/min in a circulating hot-air bath. The stretching methods of films were uniaxial under the conditions of free and/or constant width, two-way successivebly biaxial and simultaneously biaxial stretching. The temperature dependence of tanδ, dynamic modulus, E′, and dynamic loss, E″, of the stretched films were measured at 100 c. p. s. using a Viscoelastic Junior Spectrometer. The following results were obtained: (1) The stretched films by each process show characteristic dynamic viscoelastic properties due to the orientation and crystallization. (2) The peak value of tan δ in the αa-absorption region, E′ and E″ values, of the stretching direction (MD) were higher than those of transverse direction (TD) for the uniaxially stretched films. These tendency is observed in the two-way successively biaxially stretched films. These values of MD and TD are some for the simultaneously biaxially stretched films. (3) The molecular chains in the biaxially stretched films seem to be more extended than in the uniaxially stretched films. (4) The temperature of tan δmax changes with the stretching conditions. This is due to the fact that the temperature depends not only on the degree of orientation but on the orientation mode and the orientation direction.
Stress relaxation measurements under various strain from 1 to 5%, have been carried out for polyethylene films having different degree of crystallinity at various temperatures from -20°C to near melting point. Stress relaxation modulus can be described approximately by a power series polynomial in strain. Validity of time-temperature superposition for the coefficients Fn(t) of polynomial have been examined (n=1, 2 for low density and n=1, 2, 3 for high density polyethylene). The stress relaxation master curves of Fn (t) were obtained by a digital computer by means of the mini-max method in a temperature range of -20°C to 60°C for low density and to 110°C for high density sample. Temperature dependence of shift factor aT gave two straight lines, when plotted in log aT vs 1/T, intersecting at about 40°C for low density and 70°C for high density sample. The master curves of the first coefficient F1 (t) were compared with the results of the linear viscoelastic region obtained by Fujino and others. It was found that there were good agreement between both curves. These facts suggest that the relaxation mechanism observed for the nonlinear region seemes to be same as that of the linear region.
The single fibers of silk fibroin were treated with various transition bivalent metal ammine complexes in solution under various conditions, i. e. pH and ion concentration in the bath, treating temperature, species of anion and metal ion, such as copper (II), nickel (II), zinc(II) and silver (I). Adsorbed amounts of metal ion for fibroin fiber were determined by atomic absorption analysis. For the structural analysis, the following methods were used: X-ray diffraction infrared spectra, optical microscopy, load-extention, thermal gravimetric analysis (TGA) and difierential thermal analysis (DTA). The results are as follows; (1) Adsorbed amounts of metal ion for silk fibroin single fiber treated with metal ammine complexes in aqueous solution were larger in comparison with those treated with metal nitrate at lower pH. (2) X-ray diffraction studies showed that the decrystallization of silkfibroin occurs during the treatment. (3) Tensile strength and elongation of the fibroin decreases after the treatment. (4) Silk fibers treated with metal amine complexes were more stable thermally than those untreated. The heat stabilities of silk fibroin treated with various transition bivalent metal amine complexes aqueous solution change depending on the kinds of metal ion, and the effect is ordered as follows: Ag (I)>Cu (II)>Ni (II)>Zn (II).