Task 2 To describe the natural cellulosic fibers描述天然纤维素纤维
General information Natural cellulosic fibers天然纤维素纤维
Being derived from a wide variety of plant sources，natural cellulosic fibers are classified into various types，each possessing distinctive qualities or properties that distinguish it from others and make it especially suitable for certain end uses.
The general characteristics of natural cellulosic fibers as a class or group can be summarized as follows：
·Physical Properties
The density of cellulosic fibers tends to be relatively high，which makes fabrics woven from these fibers feel comparatively heavy.As a result of their having relatively low elasticity and resilience，they wrinkle easily and do not recover from wrinkling readily.Absorbency and moisture regain are generally good.Most cellulosic fibers are，therefore，slow to dry after wetting，comfortable to wear，and easy to dye.
Cellulosic fibers are good conductors of heat and electricity.As good conductors of heat，they carry warmth away from the body and are favored for use in hot weather and warm climates.Since they conduct electricity，cellulosic fibers neither build up static electricity nor produce shocks when worn.
Cellulosic fibers tend to burn easily，with a quick yellow flame，much as paper.Most cellulosic fibers can，however，withstand fairly high dry heat or ironing temperatures before they scorch.
·Chemical properties
Chemical properties of cellulosic fibers include good resistance to alkalis.Excessive bleaching will harm cellulosic fibers，although carefully controlled bleaching is less detrimental.Such properties as the withstanding of high water temperature permit laundering of cellulosic fibers with strong detergent，controlled bleaching，and hot water temperatures.
The unique combination of properties—durability，low cost，easy washability，and comfort—has made cotton not only a material desirable for summer clothes，work clothes，towels，and sheets，but also a standard for great masses of the world’s people who live in warm and subtropical climates.Even though the man-made fibers have encroached on the markets that were dominated by 100 percent cotton fibers，the cotton-look is still maintained and cotton forms up to 65 percent of the fibers in blended fabrics.
New Words and Expressions
cellulosic 纤维素的
source 来源，起源
derive 引出
miscellaneous 各种的
summarize 概述
density 密度，比重
comparatively 比较地
elasticity 弹性
resilience 弹力，回弹
wrinkle 折皱
readily 容易地
absorbency 吸水性
recover 回复
comfortable 舒服的
withstand抵挡，经受住
ironing熨烫
shock 电击
scorch 烫焦
alkali 碱
bleach 漂白
detrimental 损害的，有害的
excessive 过度的，过量的
launder 洗涤
detergent 洗涤剂，净洗剂
washability 易洗性
subtropical 亚热带的
encroach 侵入
maintain保持，维持
unique 独特的，唯一的
blend 混合，混纺物
dominate 统治，控制
wrinkle recovery 折皱回复度
end use 最终用途
moisture regain 回潮率
Notes
1.Being derived from a wide variety of plant sources…
由于来自不同的植物源……
2.classify into 把……分类。
3.…and the like，each possessing distinctive qualities or properties that distinguish it from others and make it especially suitable for certain end uses.
“……等等，每一种纤维都具有使自己与其他纤维相区别并使之特别适合于某些最终用途的品质或性能”。
“and the like”等等；like 在这里是名词，需与定冠词the 连用。each possessing…end uses 系独立分词结构，逻辑主语为each，作状语，表示伴随情况。
4.…much as paper：……这种情况与纸张（易于燃烧，烧着呈黄色的火焰）十分类似。
much as作“……几乎一样”解。接近于“just as”这是一个方式状语从句，much系副词作状语。paper后省略了“tends to burn easily，with a quick yellow flame”。
Exercises
Part 1 Put the following expressions into Chinese
1.distinguish it from others and make it especially suitable for certain end uses
2.Absorbency and moisture regain are generally good.
3.They carry warmth away from the body and are favored for use in hot weather and warm climates.
4.withstand fairly high dry heat or ironing temperatures before they scorch
5.durability，low cost，easy washability，and comfort
Part 2 Questions
1.What are natural cellulosic fibers classified into?
2.What are the general characteristics of natural cellulosic fibers?
3.How about the burning conditions of cellulosic fibers?
4.Talk about the properties of cotton fiber.
Unit 1 Cotton棉
Cotton today is the most used textile fiber in the world.Its current consumption market share is approximately 56 percent for all fibers used for apparel and home furnishings and sold in the U.S.It is generally recognized that most consumers prefer cotton personal care items to those containing synthetic fibers.The earliest evidence of using cotton is from India and the date assigned to this fabric is 3000 B.C.Cotton cultivation first spread from India to Egypt，China and the South Pacific.Even though cotton fiber had been known already in Southern America，the large-scale cotton cultivation in Northern America began in the 16th century with the arrival of colonists to southern parts of today’s United States.With this new technology，it was possible to produce more cotton fiber，which resulted in big changes in the spinning and weaving industry，especially in England.
Cottons are generally classified according to their length：⑴Sea Island cotton ⑵Upland cotton ⑶Egyptian cotton.
Cotton，as a natural cellulosic fiber，has a lot of characteristics，such as：Comfortable soft hand；Good absorbency；Color retention；Prints well；Machine-washable；Dry-cleanable；Good strength；Easy to handle and sew.
Cotton fiber appears as a long，thin，irregular，convoluted（复杂的）and flattened（扁平的）tube.The cross section of a mature fiber shows a thin cuticle（表皮）and primary wall on the outside and a hollow collapsed（塌陷的）cavity（空腔）in the center of the fiber（See in Fig.1.1）.
Fig.1.1 Observation under microscope
The moisture regain（回潮率）of cotton is about 7.1%～8.5%and the moisture absorption is 7%～8%.
Cotton is attacked by hot dilute or cold concentrated acid（酸）ions（离子）.Cold weak acids do not affect it.The fibers show excellent resistance to alkalis（碱）.
The cotton buyer usually selects species and grades of cotton to produce specific yarns.If a fabric such as a part wool blanket is to be produced，the cotton buyer will select Peruvian，China，or Indian cottons which have a harsh，rough，wool-like handle.Where extremely fine texture，silkness and great strength are desired，the cotton buyer may choose Sea Island staple or Egyptian cotton.
During the past 200 years，cottons have evolved hybridization to become the industrial cottons today.In the Practice United States，they are closely related to Sea Island cotton which came into prominence along the coast of South Carolina and to the Egyptian-type species which gained popularity of its high-quality fiber for use in the fine counts.
American-grown cottons are divided into grades according to length of staple，uniformity，strength，color，cleanliness and flexibility.These are compared with a standard supplied by the United States Department of Agriculture.
A cotton mill often averages up the various grades of cotton to produce a fairly uniform yarn.
All normal cotton fibers have a soft creamy tint and some of the long staple fibers like the Egyptian cotton，are more creamy in color than the Upland and the Sea Island cotton.Cotton is never truly white and the nature of the pigment responsible for the color is really not known.
New Words and Expressions
approximately 近似
convoluted 复杂的
convoluted 复杂的
flattened（扁平的）
collapsed 塌陷的
cavity 空腔
moisture regain回潮率
acid 酸
alkalis碱
Peruvian 秘鲁
harsh 粗糙的
rough 毛糙的，粗糙的
desire 要求，愿望
evolve进化
yarn 纱线
count 支数，号数
fabric 织物
blanket 毛毯
handle 手感
texture 织物质地
silkness 像丝绸一样的
Sea Island staple 海岛棉
hybridization 杂交
staple 短纤维
pigment 色素，颜料
uniformity 均匀度
flexibility 柔软度
Notes
1.species and grades of cotton：不同种类和等级的棉花。
2.harsh，rough wool-like handle：像羊毛一样粗糙的手感。
3.fine structure：织物细密的质地。
4.come into prominence：占主要地位。
5.fine count：较细的支数。
6.soft creamy tint：柔和的奶油色泽。
7.color，fiber：均为美国用法，英国用法相应为：colour，fiber.
Questions
1.What factors should be taken into account when choosing cotton species and grades?
2.What are the main considerations in working out the cotton grades in U.S.A.?
3.Give several famous cotton species you know in the world.
4.Write a paper in at least 500 words to say something about the cotton.
Unit 2 Flax亚麻
The use of linen，or“flaxen cloth”，dates back to people who lived about 10，000 years ago.Fragments of the cloth and nets have been discovered in Switzerland.Linen has served man as a textile for thousands of years，and it has been more important in the past than it is today.
In cross section the fibers of flax are polygonal，with rounded edges，show a large cavity and a relatively thin cell wall.The flax fiber morphology is shown in Fig.1.2.
Fig.1.2 Observation under microscope
Flax Properties：
Flax fibers have silky luster much more pronounced than that of untreated cotton.
It is stronger than cotton，the normal tenacity ranges between 5.5 and 6.5 grams per denier，and its tensile strength increases when the fiber is wet.
It is less elastic than cotton.
It is better than cotton as a conductor of heat，it carries heat away from the body faster.
Its moisture regain is 6%～12%（absorb moisture quickly）.
It is composed chiefly of cellulose，but it has 15%～30%natural impurities.It is not as durable as cotton，has poor drape，elasticity and resiliency，it is attacked by mildew and silverfish.
New Words and Expressions
flax亚麻
fragment碎片，碎块
linen亚麻布
date back to可追溯到，始于（某时期）
morphology形态，形态学
tenacity强度
tensile strength拉伸强力，断裂强力
elastic有弹性的
natural impurity天然杂质
durable耐久的，耐用的
resiliency回弹，弹力
mildew发霉，霉变，霉菌
silverfish蠹虫
polygonal多角形的，多边形的
pronounced显著的
Unit 3 Ramie苎麻
China grass，or ramie，is a bast fiber that has been cultivated for hundreds of years in China.Long before cotton was introduced in the Far East.In most recent times it has been of interest to many other countries.
The cross section is elliptical in shape，and the lumen appears open，and frequently contains granular matter.The ramie fiber morphology is shown in Fig.1.3.
Fig.1.3 Observation under microscope
Ramie Properties：
The long，fine ramie fibers are naturally white and lustrous with an almost silky appearance.
It has poor resiliency and wrinkles easily，high absorbency.It is comfortable to wear.
It has high resistance to alkalies，rotting，light and mildew，insects.It can be damaged by concentrated acids.
New Words and Expressions
ramie苎麻
bast fiber韧皮纤维
sieve-like像筛子一样的
wrinkle折皱
porous多孔的，可渗透的
elliptical椭圆的
granular matter 颗粒物质
ribbon-like带状
Unit 4 Jute黄麻
Jute is a bast fiber like flax.It is one of the cheapest and the strongest of all natural fibers and considered as fiber of the future.It has been used since the dawn of the civilization.Today，jute is one of the most widely used fibers in the world.India，Bangladesh，China and Thailand are the leading producers of Jute.It is also produced in southwest Asia and Brazil（Fig.1.4）.
Fig.1.4 Jute
In cross section the jute fiber shows a bundle of several elements bound together，these being more or less polygonal in outline，with sharply defined angles.The jute fiber morphology is shown in Fig.1.5.
Jute Properties：
It is coarse and harsh with good resistance to microorganisms and insects.
It has moderate dry strength but low wet strength.
It has low elongation.
Its fiber length is very short.
Fig.1.5 Observation under microscope
New Words and Expressions
jute黄麻
resistance抵抗，反抗
elongation伸长，伸长率
microorganism微生物
Comprehensive Training
1.Write a paper in at least 300 words to say something about cotton.
2.Describe the shape and character of the cotton fiber.
3.Give a report about the items made of flax you know.
4.Say the major properties of the flax fiber.
5.What are the major properties of ramie fiber?
6.Say something about jute products.