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what is pvc and calcium carbonate
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Yarn pilling occurs due to friction, causing small balls of fiber to form on the fabric surface. Yarns that pill the least are tightly spun and made from long-staple fibers. Merino wool, high-quality cotton, silk, and synthetic fibers like acrylic can show lower tendencies to pill because of their fiber composition and structure. Tightly woven or knitted fabrics also resist pilling better. Additionally, blends designed for durability and less pilling, such as those combining synthetic fibers with natural ones, tend to maintain a smoother appearance over time. Choosing the right yarn for your project, considering the yarn’s fiber content, yarn construction, and the anticipated amount of wear and friction the finished item will encounter, can significantly minimize pilling.
Spun yarn is a type of yarn made by twisting and binding fibers together to create a cohesive thread. This can involve various fibers such as wool, cotton, flax, or synthetic materials. The process begins with carding the fibers to align them, followed by spinning, which twists the fibers into yarn. Spinning can be done by hand using tools like spindles and spinning wheels, or industrially with machines. Spun yarn is used extensively in textiles for knitting, weaving, and sewing. The properties of the yarn, such as strength, elasticity, and warmth, vary based on the type of fibers used and the tightness of the spin. Spun yarns offer a natural and versatile option for many textile applications, ideal for creating a wide range of products from clothing to home furnishings.
To draw stress-strain curves for polymers, start with preparing a sample of the polymer and fitting it into a tensile testing machine. The main steps include:
1. **Initialization**: Initiate the test by applying a gradual force to stretch the polymer, ensuring the machine records both the force applied (stress) and the polymer's elongation (strain).
2. **Elastic Region**: Initially, the polymer will exhibit an elastic behavior where it stretches and returns to its original shape upon release. This part of the curve is relatively linear.
3. **Yield Point**: With increased stress, the material reaches a yield point where it begins to deform plastically, meaning it will not return to its original shape entirely. This is indicated by a noticeable deviation from the linear path.
4. **Strain Hardening**: After yielding, certain polymers might show a strain hardening region where the curve becomes steeper again, indicating an increase in tensile strength with strain.
5. **Necking and Failure**: Eventually, the material will start to "neck", localizing deformation in a narrow region, followed by fracture. This final part of the curve drops sharply.
For accuracy, ensure the polymer’s temperature is controlled since its mechanical properties can significantly vary with temperature. Plotting multiple curves at different temperatures or strain rates can provide a comprehensive understanding of the material’s behavior.
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