纺织材料学第一章英文

纺织材料学第一章英文
To analyze and predict a fabric's performance, start with the fiber. Knowledge of fiber properties will help you understand the fiber's contribution to the performance of a fabric and the product made from it. Fiber properties are determined by their physical structure, chemical composition, and molecular arrangement.
Some attributes of fibers are desirable and some are not. The
following list of characteristics of a low-absorbency fiber includes consumer advantages and disadvantages:
• Static cling
• Rapid drying
• Cool and slick hand
• Poor skin-comfort—clammy
• Waterborne soils do not stain
• Evaporation of perspiration may occur by wicking, but fabric is
low in absorbency
Wick: 毛细管作用， wicking: 动名词。

• Dimensionally stable to water
• G ood wrinkle recovery when laundered
• Difficult to dye, but dyes are colorfast when laundered
Fast: 牢固的，耐久的， colorfast: 不褪色的。

While fiber plays a major role in the characteristics of a product, other components are also contributors. Fibers are used to produce yarns. The type of yarn and its structure influence hand and performance.
For example, yarns made from short fibers may be comfortable, but
they tend to pill. The process used to produce the fabric influences the product's appearance and texture, performance during use and care, and cost. Finishes alter the fabric's hand, appearance,
and performance.
These three components (yarn, fabric type, and finish) will be discussed in detail in the chapters in Sections 3, 4, and 5.
Because cotton is a common consumer fiber, it is often used as a standard in the industry. It might be helpful to compare cotton's performance to that of other fibers when examining or studying Tables 3-3 through 3-8.
Fiber properties are determined using specialized equipment and following specified procedures called "standard test methods." Assessment of specific fiber properties is important in selecting an appropriate fiber for the end use.
Physical Structure
The physical structure, or morphology, can be identified by
observing the fiber using a microscope. In this book, photomicrographs
at magnifications of 250 to 1000X are used
to show details of a fiber's physical structure. In addition, fiber dimensions influence fabric characteristics and performance and the process to be used in producing a finished fabric.
Length Fibers are sold by the fiber producer as staple, filament, or filament tow. Staple
fibers are short fibers measured in inches or centimeters (Figure 3-1). They range in length from 2 to 46 cm (3/4 of an inch to 18 inches). Except for silk, all the natural fibers are available only in staple form.
Filaments are long, continuous fiber strands of indefinite length, measured in miles or kilometers. They may be either monofilament (one filament) or multifilament (a number of filaments). Filaments may be smooth or bulked (crimped in some way), as shown in Figure 3-2.
Smooth filaments are used to produce silklike fabrics; bulked filaments arc-used in more cottonlike or wool-like fabrics. Filament tow, produced as a loose rope of several
thousand fibers, is crimped or textured, and cut to staple length.
Diameter Fiber diameter greatly influences a fabric's performance
and hand (how it feels). Large fibers are crisp, rough, and stiff. Large fibers also resist crushing— a
property that is important in products such as carpets. Fine fibers are soft and pliable. Fabrics made with fine fibers drape more easily.
Natural fibers are subject to growth irregularities and are not uniform. In natural fibers, fineness is one factor in determining quality—fine fibers are of better quality.
Fineness is measured in micrometers (a micrometer is 1/1000
millimeter or 1/25,400 inch). The diameter range for these common
natural fibers is 16 to 20 micrometers for cotton, 12 to 16 for flax, 10 to 50 for wool, and 11 to 12 for silk.
In manufactured fibers, diameter is controlled at several points during production. Manufactured fibers can be made uniform in diameter or can be thick-and-thin at regular intervals throughout their length. The fineness of manufactured fibers is described as denier or tex.
Denier is the weight in grams of 9000 meters of fiber or yarn. When used to describe a fiber, denier refers to the fineness or coarseness of the fiber—small numbers
describe fine fibers; large numbers describe coarse fibers. Tex is the weight in grams of 1000 meters of fiber or yarn. Staple fiber is sold by denier and fiber length; filament fiber is sold by the denier of the yarn or tow.
Denier per filament (dpf) is a way of describing fiber size; it is often used when
describing or specifying yarns. Dpf is calculated by dividing the yarn size by the number of filaments: 40 denier yarn/20 filaments = 2 denier per filament. Fine cotton, cashmere, or wool is 1 to 3 denier;
average cotton, wool, or alpaca is 5 to 8 denier; carpet wool is 15 denier.
Apparel fibers range from <1 to 7 denier. Carpet fibers may range
from 15 to 24 denier. Industrial fibers exhibit the broadest range, from 5 to several thousand, depending on the end use. For example, fibers used for weed trimmers and towropes are much larger than those used for absorbent layers in diapers.
Denier is related to end use. For example, apparel fibers do not
make serviceable carpets, and carpet fibers do not make serviceable garments. Apparel fibers are tot) soft and pliable, and carpets made of apparel fibers do not have good crush resistance. Industrial or
technical fibers are produced in various deniers, depending on the end use.
CROSS-Sectional Shape The cross-sectional shape of a fiber affects luster, bulk, body, texture, and hand. Figure 3-3 shows common cross-sectional shapes. These shapes may be round, dog-bone, triangular, lobal, multisicd, or hollow.
The natural fibers derive their shape from (1) the way the cellulose is built up during plant growth (cotton), (2) the shape of the hair
follicle and the formation of protein substances in animals (wool), or (3) the shape of the orifice through which the insect extrudes the fiber (silk).
The shape of manufactured fibers is controlled by the shape of the spinneret opening and the spinning method. The size, shape, luster, length, and other properties of manufactured fibers can be varied by changes in the production process.
Surface Contour Surface contour describes the outer surface of the fiber along its length. Surface contour may be smooth, serrated, striated, or rough, and it affects luster, hand, texture, and apparent soiling of the fabric. Figure 3-3 also shows surface contours of selected fibers.
Climp Crimp may be found in textile materials as fiber crimp or
fabric crimp. Fiber crimp refers to the waves, bends, twists, coils, or curls along the length of the fiber. Fiber crimp increases cohesiveness, resiliency, resistance to abrasion, stretch, bulk, and warmth.
Crimp increases absorbency and skin-contact comfort but reduces luster. Inherent crimp
occurs in wool. Inherent crimp also exists in an undeveloped state
in bicomponent manufactured fibers in which it is developed in the
fabric or the garment (such as a sweater) with heat or moisture during finishing.
Fabric crimp refers to the bends caused by distortion of yarns in a fabric. When a yarn is unraveled from a fabric, fabric crimp can easily
be seen in the yarn. It also may be visible in fibers removed from the yarn.
Fiber Parts Except for silk, the natural fibers have three distinct parts: an outer covering called a cuticle or skin; an inner area; and a central core that may be hollow.
The manufactured fibers are less complex in structure. They usually consist of a skin and a core.
Serviceability
Textile serviceability includes the concepts of aesthetics, durability, comfort, appearance retention, care, environmental impact, and cost that were introduced in Chapter 2.
Properties that relate to each concept are presented in Table 3-1.
Learning the definitions of the properties will contribute to a more in-depth understanding of textile fiber performance. The tables in this chapter compare various performance aspects among fibers. Relating past experience with fabrics made of a specific fiber will contribute to a better understanding of fiber performance and serviceability.
Aesthetic Properties
A textile product should be appropriate in appearance for its end use. Aesthetic properties relate to the way
sion can occur when the fabric is fairly flat, such as walking on a rug. Edge abrasion can occur when the fabric-is folded, as when a pant hem rubs on a sidewalk. Flex abrasion can occur when the fabric is moving and bending, as in shoelaces that wear out where they are laced
through the shoe. Flexibility, the abilitv to bend repeatedly without breaking, is an important property related to abrasion resistance.
Tenacity, or tensile strength, is the ability of a fabric to withstand a pulling force (Table 3-3).'(Brrakiujj tenacity for a fiber is the force, in grams per denier or tex,
required to break the fiber.) The tenacity of a fiber when it is wet may differ from the tenacity- of that same fiber when it is dry. Although fabric strength depends, to a large degree, on fiber strength, yarn and fabric-structure are additional factors affecting fabric strength. Strength may also be described by the force needed to rip a fabric (tearing strength) or to rupture a fabric (bursting strength) Elongation refers to the degree to which a fiber may be stretched without breaking. It is measured as percent elongation at break (Table 3-4). Elongation should be considered in relation to elasticity.
Comfort Properties
A textile product should be comfortable when it is worn or used.
This is primarily a matter of personal preference and individual perception of comfort under different climatic conditions and degrees of physical activity. The complexities of comfort depend on characteristics such as absorbency, heat retention, density, and elongation.
Absorbency is the ability of a fiber to take up moisture from the body or from the environment. It is measured as moisture regain where the moisture in the material is expressed as a percentage of the weight
of the moisture-free material (see Table 3-3). Hydrophilic fibers absorb moisture readily. Hydrophobic fibers have
little or no absorbency. Hygroscopic fibers absorb moisture without feeling wet.
Absorbency is related to static buildup; problems with static are more likely to develop in hydrophobic fibers because they do not conduct electrons readily.
Heat or thermal retention is the ability of a fabric to hold heat (see Table 3-2).
Because people want to be comfortable regardless of the weather, a low level of thermal retention is favored in hot weather and a high
level in cold weather. This property is affected by yarn and fabric structure and layering of fabrics.
Heat sensitivity describes a fiber's reaction to heat (Table 3-5). Since some fibers soften and melt and others are heat resistant, these properties identify safe pressing temperatures.
Density or specific gravity is a measure of fiber weight per unit volume (see Table 3-3). Lower-density fibers can be made into thick fabrics that are more comfortab than high-density fibers made into heavy fabrics.
Appearance-Retention Properties
A textile product should retain its appearance durii use, care, and storage.
Resiliency is the ability of a fabric to return to original shape
after bending, twisting, or crushing (s Table 3-2). An easy test is to crunch a fabric in your haj and watch how it responds when you open your han Fabrics that do not wrinkle easily and spring back afi compression
are resilient and wrinkle resistant. A fab: that wrinkles easily stays crumpled in your hand. When is flattened out, wrinkles and creases are apparent.
Dimensional stability is defined as the ability ol fabric to retain
its original size and shape through u
and care, which is desirable. It includes the properties of
shrinkage resistance and elastic recovery.
Shrinkage resistance is the ability of a fabric to retain its
original dimensions throughout care. It is related to the fabric's reaction to moisture or heat. Items that shrink may no longer be
attractive or suitable for their original end use. Residual shrinkage refers to additional shrinkage that may occur after the first care cycle.
Elasticity or elastic recovery is the ability of a fabric to return
to its original
dimension or shape after elongation (see Table 3-4). It is measured
as the percentage of return to original length. Elastic recovery varies with the amount of elongation and with the length of time the fabric is stretched. Fabrics with poor elastic recovery tend to stretch out of shape. Fabrics with good elastic recovery maintain their shape.
Environmental Impact
Environmental impact refers to the way the production, use, care, and disposal of a fiber
or textile product
affects the environment. Many consumers assume that natural fibers have less of an environmental impact than do manufactured or synthetic fibers. However, the natural fibers' impact on soil conservation, use of agricultural chemicals, disposal of animal waste, water demands, cleaning requirements, and processing create environmental problems. Since very few textile products are disposed of in a manner that allows for bio-degradation, natural fibers do not have that advantage in modern society. The environmental impact of each of the major consumer fibers will be discussed in Chapters 4-9.。