The main quality index of chemical fiber
Fineness is the thickness of a fiber. There are two kinds of direct and indirect indicators. Direct indexes generally expressed in the fiber diameter and cross-sectional area, because the fiber cross-sectional area is irregular, and not easy to measure, usually expressed in direct index when the thickness is not much, reason often said by indirect indicators. Indirect indicators are determined by the quality or length of the fiber, that is, the quality (length) or length (weight) of the fiber when the length is fixed or the weight is fixed.
In the production of chemical fiber, because of the fluctuation of raw materials, equipment running condition and technological conditions, the strips of unstretched and stretched wires are not even dry. Article, therefore, the determination of fiber along the length direction of the dry uniformity is an important indicator of measuring fiber quality change, which affect the physical and mechanical properties of fiber and dyeing properties, but also influence on the performance of the fiber textile processing and fabric appearance.
Moisture absorption is one of the physical performance indicators of fiber, and it is usually called absorption of moisture by fiber materials from the gaseous environment. Indicators of hygroscopic properties include:
1. Moisture regain and Moisture content: Moisture content in fiber materials, i.e., absorbed water content, is usually expressed with Moisture regain or Moisture content. The former refers to the percentage of the moisture content of the fiber and that of the dry fiber, while the latter refers to the percentage of the moisture content of the fiber and the actual quality of the fiber. In the chemical fiber industry, the strength of the hygroscopic properties of the fiber is generally expressed by the moisture recovery rate.
2. Standard condition of moisture regain and male will regain: actual moisture regain of different fibres with environment temperature and humidity changes, in order to compare various moisture absorption ability of fiber material, put it in a unified standard atmospheric conditions (20 ℃, 65% relative humidity) after a certain period of time, make their moisture regain in "the moisture absorption process reaches a steady state value, then the moisture regain of the moisture regain of standard condition.
In the trade and cost calculation, fiber material is often not in standard condition, for the convenience of weight and the need of nuclear price, need to make artificial moisture regain of all kinds of fibre materials uniform, called male moisture regain. The moisture regain rate of the main textile fibers is as follows:
Fiber density (densities), refers to the mass (weight) of fiber per unit volume, the common unit is g/cm3. Composition and macromolecular arrangement due to the packing and the fiber morphological structure is different, the density of all kinds of fiber is different, the main variety of chemical fiber, polypropylene fiber density of the smallest, the density of viscose fiber is the largest. The density of the main textile fibers is as follows: