M. M. El-Tonsy

Automatic measurement of the absolute CTE of thin polymer samples: I—effect of multiple processing on thermal expansion of polypropylene films

Abstract A new design for a light spot position sensor is suggested. Details of the setup and calibration of the sensor are described. The sensor is used to enhance the efficiency of an optical dilatometer by automating its operation. The modified dilatometer is used to measure the coefficient of thermal expansion, CTE, of some thin metallic and polymeric samples. Thermal hysteresis behavior and CTE of multiple-reprocessed polypropylene films are measured and discussed. The discussion is supported by some morphological investigations for the reprocessed samples. It is found, in general, that reprocessing of polypropylene reduces its CTE by 6–22% in a temperature range up to 100 oC. Polypropylene films that have been reprocessed three times showed minimum thermal expansion.

Low cost technique for measuring thermal expansion of thin polymer samples

Abstract A simple low cost thermomechanical analyzer is described. The device is used to optimize the traction applied for straightening the sample. Optimization was carried out by plotting residual thermal elongation after cooling against degree of traction. With the optimum traction, it was possible to measure the sample’s linear thermal expansion coefficient, nearly free from the creep effect. CTE’s of some widely used polymers (polystyrene, polypropylene, polyethylene and polycarbonate) are measured and compared with the published values. The performance of the measuring system (sensitivity, accuracy and reproducibility) are presented and discussed. Advantages and limitations of usage of the system are given as a conclusion.

Opto-thermal properties of fibres: Part 4: Correlation of the density and loss tangent change with some physical parameters of annealed nylon-6 fibres

Abstract Nylon-6 fibres were annealed at various temperatures (90–175°C) for time intervals from 1 to 10 hours. An acoustic method has been used for measuring the density and the mechanical loss factor of these fibres. The variation of refractive indices and birefringences of nylon-6 fibres was studied by two interferometric techniques: the multiple-beam interferometric method in transmission and the two-beam method by using the Pluta polarizing interference microscope. The X-ray diffraction technique was used to interpret the variations in optical and mechanical parameters obtained due to thermal treatments. Relations between the optical data, mechanical loss factor and density with different annealing conditions are given for these fibres. Illustrations are given using graphs and microinterferograms.

Optothermal properties of fibers. VI. Effect of annealing on some of the optical and dynamic mechanical parameters of polyester fibers

Changes in the structure of annealed polyester fibers (Egyptian manufacture) at a constant time of 5 h and different temperatures (80-190°C) were studied interferometrically. The Pulta polarizing interference microscope was used for determining the mean refractive indices and mean birefringence of these fibers. The multiple-beam Fizeau fringes in transmission was also used for determining the refractive indices of the skin and core of these fibers. Also, the acoustic method was used for measuring the density and mechanical loss factor of these fibers. Relations between the mean refractive indices, birefringences polarizabilities per unit volume, and mechanical parameters of annealed polyester fibers with different temperatures are discussed to clarify the thermal effects. Illustrations are given using graphs and microinterferograms.

Optothermal properties of fibers. VII. Optical investigation of annealed nylon-6 fibers

The influence of annealing on the birefringence of nylon-6 fibers was examined. These fibers were found to show considerable optical anisotropy. Three independent techniques were used to study the optical anisotropy in these fibers. The first technique to determine the diameter of the fiber from the diffraction pattern was using a He-Ne laser beam. The second technique was the application of the Becke-line technique to study the effect of annealing on the skin layer of these fibers at different temperatures for a constant time of 5 h. The third is the application of a double-refracting interference microscope ( the Pluta polarizing interference microscope). The double-beam technique is considered as the most suitable technique for determining the mean refractive indices and the double refraction of the annealed samples at different temperatures. (155 and 175°C and at two constant times 7 and 9 h). Microinterferograms and curves are given for illustration.

Optothermal properties of fibers. II. Annealing effect on the birefringence variations of polyester fibers

The variation of refractive indices and birefringences of Egyptian-manufactured polyester fibers with different annealing times at constant temperature 160°C are studied by interferometry. The polarizing interference microscope is used for determining the mean refractive indices and mean birefringence of these fibers. The results are used to calculate optical orientation function and the angle of orientation. Also, the acoustic method has been used for measuring the density and the mechanical loss factor of these fibers. Relations between the mean refractive indices, birefringence, polarizabilities, mechanical loss factors, and densities with annealing time are given for these fibers. Illustrations are given using graphs and microinterferograms.

A contribution to the study of optical properties of cylindrical step-index fibres

Abstract Both two-beam and multiple-beam interferometric techniques were used to determine refractive indices and birefringence of polypropylene fibres. The aim of this work is to suggest a method to calculate the value of refractive indices and birefringence of the fibre from the interferograms when it is difficult to detect the connection between the interference fringe in the liquid region and inside the fibre. Results are compared with those adopted from other interferometric methods and found to be in good agreement. Illustrations are given using microinterferograms.

Optothermal properties of fibers. X. Temperature dependence of the skin—core structure of nylon‐6 fibers

Refractive indices and birefringence for skin and core changes with annealing, produced by different annealing conditions in nylon-6 fibers, were measured interferometrically. Applications were carried out using multiple-beam Fizeau fringes in transmission to determine Cauchys constants and dispersive coefficients for the fibers. The resulting data were used to calculate the polarizability per unit volume for each layer. By optical microscopy, the geometrical parameters of the fiber cross section were found. The effect of temperature and time of annealing on the refractive index and birefringence for each layer were also investigated. The relationships between temperature and time of annealing with the optical parameters were drawn. Illustrations are given using microinterferograms and curves.

Dependence of physical properties of linear low-density polyethylene on the silicon dioxide filler size

In the current work, the influence of filler particle size on the performance of the composites was studied. Some physical parameters were measured for linear low-density polyethylene (LLDPE) films reinforced with silicon dioxide (SiO2) powder. Samples filled with SiO2 of different particle sizes and concentrations were prepared. It was found that fillers with small size caused an increase in mechanical properties of LLDPE at lower concentration than that of particles with bigger size. This was confirmed experimentally by measuring different physical parameters such as yield strength, coefficient of thermal expansion, thermal conductivity, melting temperature, and structural morphology. Therefore, filler sizes ranged from nano to micro could help in reducing the amount of the usage of filler, which could overcome the recycling problems of the filled polymers without affecting the end-use properties of the composite. Illustrations are given using figures, images, and tables.

Interferometric determination of the refractive indices, birefringence and homogeneity of a polymer thin film

Abstract An experimental illustration using microinterferometry is given as a qualitative and quantitative method for determining the refractive indices, birefringence and estimating of the homogeneity of polymer thin film. Multiple-beam Fizeau fringes in transmission were applied for sliced polymer of rectangular cross-sectional shape. Thin film optical parameters could be determined from the shape of Fizeau fringes obtained experimentally. The applicability and advantage of this method have been discussed from the point of view of thin film microscopy. Illustrations were made using photomicrographs.