In this study, the mechanical and structural characteristics of wool fibers were examined, and the contributions of the microfibrils and matrix to the deformation processes were analyzed. The experiments were carried out on single wool fibers. To understand the structural changes at different deformation levels, the wool fibers were treated with a complex mechanical regime. One of the most significant results from the mechanical tests was the estimation of the modulus of the matrix, which changed from 0.07 to 1.6 GPa during stretching. This result proves the proposal of the netlike structure of the matrix. On the basis of the obtained experimental data and the structural model, where the microfibrils and matrix play the role of a reinforcing phase and a filler, respectively, the rigidity of the microfibrils in the initial unstretched state was determined to be equal to about 20 GPa. The experimental data obtained from the Fourier transform infrared–attenuated total reflectance spectroscopy method proved the α–β conformational transition both in the yield and postyield regions and revealed the presence of the stable β form, which was not sensitive to stretching. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Uniaxially oriented commercial films of isotactic polypropylene were strained with ends keeping fixed and subjected to the heat treatment at temperatures from 50 to 2008C. The rigidity of annealed samples was characterized by the value of tangent modulus, E t , determined graphically at the initial portions of stress-strain curves. The structural changes in the samples were studied with the help of the IR and low-frequency Raman spectroscopies. The smallest E t values were obtained for the low-strained films, while the tangent moduli measured for highly strained samples exceeded the value for the original (untreated) film. The most prominent positive effect was achieved after annealing the samples at 908C.

No abstract

No abstract

No abstract

Single wool fibers were coated with TiO 2 by using the sol-gel method. The uniaxial tensile properties of TiO 2 coated single wool fibers heated at different temperatures from 25 to 200 C were investigated and compared with those of uncoated single wool fibers. It was observed that the shape of the stress-strain curve of TiO 2 coated wool fibers became the same as uncoated wool fibers and showed a similar tendency of change to uncoated wool fibers with increasing temperature. But, the TiO 2 coated wool fibers obtained higher rigidity than uncoated wool fibers and up to their rupture points; they obtained higher stress levels in three deformation regions in the stress-strain curves, which indicates stronger wool fibers. Although the breaking extension of TiO 2 coated wool fibers decreased little by about 8%, the Young's modulus of TiO 2 coated wool fibers increased significantly by 19%, which was caused mostly by an increment in the stiffness of the cuticle layer of the wool fiber, and remained relatively higher than that of uncoated wool fibers after heat treatments. Structural changes in both uncoated and TiO 2 coated single wool fibers due to thermal effect, which caused the changes in the uniaxial tensile properties and the thermal behaviors of these fibers were discussed by using spectroscopic and thermal analysis methods in detail.

A series of reactor powders of ultrahigh molecular weight (UHMW) polyethylenes with different morphology was melted at 1608C for 5 min and cooled in ice water. Low-frequency Raman spectroscopy was used to characterize the straight-chainsegment (SCS) length distribution of both initial and melt-crystallized materials. A bimodal SCS length distribution was found in the melt-crystallized sample originated from the reactor powder with a very tenuous amorphous phase. In other samples recrystallized from powders with more ordered structure, the SCS length distribution was unimodal and approximately identical. The result is explained in terms of perfection of lamellar crystals formed under limited time and thermal conditions from differently organized initial structure.

No abstract