The Optical Behavior of Polyethylene Spherulites

Polyethylene was crytallized from the molten film under temperature gradient. As a result, the optically positive spherulites were observed, though only the negative spherulites had been observed previOusly in polyethylene. When the radial structure units twisted regulary in a spherulite are formed parallel to the surface of the film, the spberulite is usually optically negative in polyethylene. In this study, the temperature gradient normal to the surface of the film gives so significant tilt of the radial structure units formed to the surface of the film that the radial refractive index becomes larger than the tangential one under the transmitted polarized light and the spherulites have optically positive behavior. The optical behaviors of the polyethylene spherulites and the crystallizing condition were studied and discussed

Thermal Study on Adducts of Urea with n-Alkanes and n-l-Alkanols

Crystalline adducts of urea with n-alkanes (C(8)~C(20)) and n-l-alkanols (C(12)~C(18)) were prepared. From thermal analysis and X-ray diffraction study on the adducts, we found that the composition of adducts and the heat of decomposition can be obtained easily from the thermogram of adducts

Two Distinct Types of Spherulite in Poly (ethylene oxide)

Fujiwara's oriented crystallization method was applied to poly (ethylene oxide) to obtain a uniform texture composed of parallel fibrils which correspond to the structure of a radial direction of spherulites. Two different x-ray diffraction patterns in crystallite orientation of the spherulite radius were obtained. From these patterns and crystallization conditions it could be determined that the spherulite radius has a [401] rotation axis below about 50℃ and two [421] and [421]rotation axes above about 50℃. A reasonable interpretation was given for these two ways of spherulitic crystallization, based on the growth features of lamellar crystals of poly (ethylene oxide). That is, it is concluded that a second order transition in poly (ethylene oxide) lamellar crystals near the temperature of 50℃ is responsible for the change of the rotation axis in spherulite radius

Milko-Tester Analysis of Milkfat Content of Churned and Nonchurned Samples from Jersey and Holstein Dairy Cattle

Milk samples from three Jersey and three Holstein herds were used to determine if the degree of churning correlated with the initial milkfat assay, and also to determine if the churned milkfat could be measured as accurately as the initial milkfat using the Milko-Tester. Regression lines for the initial milkfat test versus churned milk- fat test fit polynomial curves. The degree of churning was greater for Jerseys than Holsteins and correlated with the initial milkfat test. The repeatability of initial milkfat tests vas 0.98 for Jerseys and 0.99 for Holsteins. However, the repeatability of churned milkfat tests was lower for both breeds, especially for Jerseys. This indicated that the churned sample could not be measured for its milkfat content as accurately as the nonchurned sample. Churned milkfat samples all tested lower than initial milkfat samples, thus the Milko-Tester Mark III was unable to provide an initial fat test estimate following sample churning. Cows were different from each other in the difference between initia1 and churned milk fat tests. This suggested that cows which produce milk with a higher tendency for churning are apt to receive less reliable milkfat tests from central laboratories than other cows, when all milk samples are subjected to churning conditions

Studies on the electrochemical properties of copolymers of maleic acid, I : potentiometric titration at low ionic strength

In this series, the polydibasic properties of some copolymers of malefic acid are studied from the viewpoint of the neighbor interaction. In the present paper, the potentiometric titrations of two copolymers, malefic acid-vinyl acetate and malefic acid-styrene copolymers, were studied at low ionic strength, with somewhat different experimental methods from Garrett and Ferry. The empirical equations to estimate the average dissociation constants were presented in comparison with that of the monomeric dibasic acids. The average dissociation constants in various polymer concentrations were obtained and the polydibasic properties were discussed

The Molecular Mechanism of Chain Tilt in Poly (ethylene terephthalate) Fibers

The molecular mechanism of chain tilt in poly(ethylene terephthalate) (PET) fibers was proposed. The mechanism was considered basing on the ordering process from the cold drawn state of glassy PET. It was confirmed that the direction of maximum contraction on ordering agrees with the azimuth of chain tilt which varies with annealing temperature. In the stacking structure of irregular folded chain blocks of cold drawn PET, the expansion to the chain direction and the contraction to the lateral direction yield the compressive stress and tensile stress r respectively. The stress revealed as the result of the ordering from the glassy structure to crystalline structure can be relaxed by the rotation of the resulting crystallites. Therefore, we can suggest that the chain tilt is caused by the relaxation process of the stress

A Study on single Crystals of Nylon 12

Single crystals of two crystatalline forms, α and γ, in nylon 12 were obtained from dilute solutions. The single crystals of γ-form from diols solutions are ribbon like lamellae in shape, and that of α-form obtained from solution in water-formic acid are parallelogramic. Electron diffraction study shows that chain packings in single crystals of two crystalline forms are very similar to those of nylon 6, respectivel

Order-Disorder Transition in Urea-Polyethylene Complex

The phase transition of urea complexes whose guest components range from n-paraffin to polyethylene was investigated by DSC thermal analysis. The transition temperatures increased with increasing the chain length; the related heats did not change much with the chain length. An X-ray powder diffractometry for urea-polyethylene complex revealed that the complex undergoes the same kind of phase transition between orthorhombic and hexagonal as urea-n-paraffin complex. The transition is interpreted in terms of an order-disorder transition with respect to the orientation of the guest molecule

Media training of student-teachers in Venda

M.Ed. (Eucational Media)The training of student-teachers in media selection, integration and utilization in Venda is not done according to expectations. To investigate this problem it was necessary to identify problem areas in the theoretical and practical training of media of teachers in Venda. In order to reach possible solutions to the set problem in confirmation of the purpose of the study, a literature survey on teacher education with special reference to pre-service education and media training was undertaken. An empirical study was also conducted which included four groups of respondents, namely: Rectors of Colleges and the Dean of the Faculty of Education at the University. Heads of Departments at these institutions. Lecturers at these institutions. Final year student-teachers at colleges and the university. The research as stipulated above yielded the following results: * The lecturer of student-teachers in training cannot use the available teaching media at the College/University because he himself has not been trained in the'use of available teaching media in the didactic situation. * The training programme of student-teachers is congested, which limits the time for training in and practising of the use of media in didactic situations. * The student-teacher completes his training without enough knowledge on how to use teaching media in a teaching-learning situation. * The rejection of using teaching media by lecturers and student-teachers Js il result of lack of knowledge on how to use teaching media. * There is no in-service training for lecturers and teachers to update them in teaching media. * Mainly three teaching media can be used by student teachers, lecturers and teachers, that is Chalkboard, Maps and Wall Charts. * Schools where student-teachers do teaching practice have a lack of audiovisual materials and other equipment. * The period of teaching practice is not enough to practise teaching media in the real teaching-learning situation, is, where some of the teaching media are available. * Teachers at schools cannot offer guidance to student media during practice * Student-teachers have a good theoretical knowledge but no practical knowledge of teaching media in the didactic situation