Silk fibroin solution was prepared by dissolving the silk fibroin in triad solvent CaCl2 · CH3CH2OH · H2O. In this article we tested and analyzed the state of frozen silk fibroin solution and fine structure of freeze dried porous silk fibroin materials. The results indicated that the glass transition temperature of frozen silk fibroin solution ranges from −34 to −20°C, and the initial melting temperature of ice in frozen solution is about −8.5°C. When porous silk fibroin materials are prepared by means of freeze drying, if freezing temperature is below −20°C, the structure of silk fibroin is mainly amorphous with a little silk II crystal structure, and if freezing temperature is above −20°C, quite a lot of silk I crystal structure forms. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2185–2191, 2001

Porous silk fibroin materials, with average pore size 10 ∼ 300 μm, pore density 1 ∼ 2000/mm2, and porosity 35 ∼ 70%, were prepared by freeze drying aqueous solution of silk fibroin obtained by dissolving silk fibroin in ternary solvent CaCl2 · CH3CH2OH · H2O. Pore size distribution of such materials mostly accorded with logarithmic normal distribution. It is possible to control the aforementioned structural parameters and the physical properties of moisture permeability, compressibility, strength, elongation, etc., by adjusting freezing temperature and concentration of silk fibroin solution. Above glass transition zone (−34 ∼ −20°C) of silk fibroin, the freezing temperature has more significant effect on the structure and properties of porous silk fibroin materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2192–2199, 2001

The influence of repeated freeze–thawing on pore structural characteristics and physical properties of porous silk fibroin materials prepared by freeze drying were studied. It showed that when quick‐frozen silk fibroin solution was repeatedly thawed and frozen before being vacuum dried, thus pore size of prepared porous silk fibroin materials increased from 67 µm to about 120 µm, and pore density decreased from 80 per square millimeter to about 28 per square millimeter; at the same time compression ratio and moisture permeability increased from 22.7% and 230 g/m2 hr to about 33.7% and 308 g/m2 hr, respectively, tensile strength and dissolvability in hot water decreased from 20.2 N/cm2 and 42.7% to about 12.5 N/cm2 and 26.1%, respectively. Both the times of repeated thawing and the thawing temperature had a certain influence on the above‐mentioned pore characteristic parameters and physical properties. Copyright © 2001 John Wiley & Sons, Ltd.

ABSTRACT:The variance of fiber morphology along a fiber and the natural and artificial flaws in the fiber structure represent the primary reasons for the weak link of fibers. Accordingly, the fiber weak link can be divided into two types, that is, the geometrical thinnest part and the structural weak point. Scanning electron microscopic observation was used to characterize the morphological features of the fiber weak points whose forms are the normal thin sections, natural flaws, and artificial damage. Both the fiber profile morphology and the tensile behavior of wool fibers have been measured using a single-fiber analyzer (SIFAN) and an optical microscope with a CCD camera plus an XQ-1 fiber tensile tester (OM ϩ XQ). The results from the SIFAN and OMϩXQ methods indicate that the fibers breaking at their minimum diameters represent only one part of the broken fibers. The percentage of this kind of breakage is in the range of 40 -60%. A new approach is presented to identify the weak-point breakage relying on the fiber tensile behavior. The experimental results show that the probabilities of weak-point, normal, and thinnest-part breakage evaluated by these methods approximate 40, 60, and slightly more than 80%, respectively.

Wool/polyester blended tops with different blend ratios are collected and made into fiber-bundle specimens for tensile testing. From the specific stress-extension curves of the blended bundles measured by the Sirolan-Tensor, the characteristics of the tensile curves are analyzed and the relationships between these characteristics and the blend ratios are discussed. Typical tensile curves, particularly the tail part of the curves, are used to evaluate the blend ratios of the fiber bundles. Three new approaches, the stress, work, and modulus methods, are developed for estimating fiber bundle blend ratios. The various parameters and algorithms of each method are defined in detail. The blend ratios calcu lated from the three methods are compared with the experimental values and with each other. There is a high coincidence between the experimental and theoretical results. The tensile behavior of WOOI/PET blended fiber bundles depends directly on their blend ratios.