Environmental Effects on Strength and Failure Strain Distributions of Sheep Wool Fibers

Abstract

Sheep wool is an eco-friendly, renewable, and totally recyclable material increasingly used in textiles, filters, insulation, and building materials. Recently, wool fibers have become good alternatives for reinforcement of polymer composites and filaments for 3D printing. Wool fibers are susceptible to environmental degradation that could shorten their lifetime and limit applications. This study reports on the mechanical properties of sheep wool fibers under the impact of humid air and UV irradiation. The results of single fiber tensile tests showed a noticeable gauge length effect on the fibers’ strength and failure strain. Long (50 mm) fibers possessed about 40% lower characteristics than short (10 mm) fibers. Environmental aging decreased the elastic modulus and strength of the fibers. Moisture-saturated fibers possessed up to 43% lower characteristics, while UV aging resulted in up to a twofold reduction of the strength. The most severe degradation effect is observed under the coupled influence of UVs and moisture. The two-parameter Weibull distribution was applied for the fiber strength and failure strain statistical assessment. The model well predicted the gauge length effects. Moisture-saturated and UV-aged fibers were characterized by less extensive strength dependences on the fiber length. The strength and failure strain distributions of aged fibers were horizontally shifted to lower values. The results will contribute to be reliable predictions of the environmental durability of sheep wool fibers and will extend their use in technical applications.

Investigation of Physical Properties of Polymer Composites Filled with Sheep Wool

“…It should be noted that the mechanical properties of sheep wool are also affected by the conditioning process. Starkova et al [ 59 ] reported that the long-term conditioning of fibers in a humid environment and under UV irradiation resulted in a significant decrease in tensile strength and elastic modulus. In contrast (see Table 8 ), the elongation at break values for sheep wool and silk are significantly higher than those of other natural fibers.…”

The Application of Sheep Wool in the Building Industry and in the Removal of Pollutants from the Environment

“…In addition, composite materials present complications for recycling. Starkova et al [6] dealt with the effect of the environmental degradation of wool, which can affect the life cycle and useful life of sheep wool fibers. They investigated the influence of moist air and UV radiation individually and synchronously using the two-parameter Weibull distribution [7].…”

“…Tests of the elastic modulus and strength of the fibers showed individual reductions in mechanical degradation characteristics (moisture-saturated fibers up to 43%, UV aging up to 50%), but the simultaneous action of both factors had an even worse effect. The study [6] is a demonstration of the applicability of the Weibull distribution for predicting the service life of sheep wool.…”

Sulfur and Cystine Content in Various Sheep Wool Breeds and Their Correlation with Wool Growth and Strength

“…У процесі переробки вовни, починаючи з її миття, карбонізації, чесання, відбілювання тощо, міцність волокон зазвичай зменшується. На міцність вовни також впливають конституція тварини, її фізіологічний стан, індивідуальні властивості, умови годівлі та утримання (Starkova et at., 2022). Отже, вовна володіє цілим комплексом ознак, що характеризують її фізичні, а отжей технологічні властивості.…”