Task 3 To describe the properties of natural protein fibers描述天然蛋白质纤维
General information Natural protein fibers天然蛋白质纤维
Proteins are complex，high-molecular-weight compounds containing amino acids.They are essential for the growth and repair of all animal tissue.The protein fibers are naturally occurring animal products.The two major protein fibers are wool and silk.Wool is the fiber from the fleece of a sheep or lamb or the hair of a fur-bearing animal；silk is the fiber extruded by the silkworm，in the form of a cocoon，for protection in its pupal stage.Spider silk，which is extruded by the spider to form a web，sometimes is classified as a textile fiber.
Wool fibers are more widely used；they provide warmth，a pleasant hand，attractive appearance，good absorbency，and resiliency.Silk，noted for its lustrous appearance and unique hand，has always been considered a luxury fiber.
The oldest examples of wool fabrics in Europe come from archaeological digs in Germany and date from about 1500 B.C.Fabrics from Danish sites have been dated about 1300 to 1000 B.C.；these fabrics have a rough，coarse texture.
New Words and Expressions
protein 蛋白质
complex 复杂的
high-molecular-weight 高分子量
compound 化合物
contain 包含
amino acids 氨基酸
repair 修补，恢复
tissue 组织
occur 出现，存在
fleece 毛被，套毛
fur-bearing animal 毛皮动物
extruded 挤压的
silkworm 蚕
cocoon 蚕茧
pupal 蛹的
resiliency 弹性，回弹
lustrous 有光泽的，光亮的
archaeological考古学的
dig 出土物
Danish 丹麦的
Notes
1.The protein fibers are naturally occurring animal products.
蛋白质纤维是天然的来自动物的产品。
2.for protection in its pupal stage：蚕茧对蛹有保护作用。
3.spider silk：蜘蛛丝（非洲马尔加什一种蜘蛛所吐，外形与蚕丝相似，但不适合纺织应用，仅用于光学仪器工业）。
4.They provide warmth，a pleasant hand，attractive appearance，good absorbency，and resiliency.
羊毛具有暖感，舒适的手感，吸引人的外观，好的吸湿性和弹性。
5.Silk，noted for its lustrous appearance and unique hand，has always been considered a luxury fiber.
“Noted…hand”这个过去分词短语修饰前面的silk；
该句可译为“以光亮的外观和独特的手感著称的蚕丝，经常被认为是一种华贵的纤维”。
Exercises
Part 1 Put the following expressions into Chinese
1.Protein s are complex，high-molecular-weight compounds containing amino acids.
2.Wool is the fiber from the fleece of a sheep or lamb or the hair of a fur-bearing animal.
3.But their unique properties make them an important object of study in textile science.
4.The oldest examples of wool fabrics in Europe come from archaeological digs in Germany.
5.George Washington encouraged the importation of Merino sheep from Spain in the late 1700s.
Part 2 Questions
1.What are the two major protein fibers?
2.Which protein fibers are more widely used?
3.Why has silk always been considered as a luxury fiber?
4.Where come from the oldest examples of wool fabrics in Europe?
Unit 1 Wool羊毛
Wool was probably the first animal fiber to be made into cloth.The art of spinning wool into yarn developed about 4000 B.C.and encouraged trade among the nations in the region of the Mediterranean Sea.
The major wool producers in the world are Australia，Argentina，China and South Africa.
Wool is a protein fiber with 18 amino acids.Its cross section may be nearly circular，but most wool fibers tend to be slightly elliptical or oval in shape.Wool fibers have a natural crimp，a built-in waviness.The crimp increases the elasticity and elongation properties of the fiber and also aids in yarn manufacturing.The wool morphology is shown in Fig.1.6.
Fig.1.6 Observation under microscope
The supply of wool available to the world every year amounts to about 5，000 million pounds.After scouring，this is reduced to about 3，000 million pounds of pure wool.The wool crop is insufficient to meet the world needs.Pure wool is often mixed with other type fibers and recovered wool to meet the demand.
The qualities of different wools vary greatly.The merino sheep of Australia，South America and South Africa produce very fine and soft wool.The quality of wool from these sources depends upon the conditions and heritage of the sheep.Port Philip wool is the finest in Australia and is used to produce the highest quality woolen and worsted fabrics.
Merino wool has been successfully raised in Germany，France，Spain and the United States，and is of high quality.
Wool is attacked by hot sulphuric acid and decomposes completely.It is generally resistant to most other mineral acids of all strengths.Wool will dissolve in caustic soda solutions that would have little effect on cotton.
Properties of the wool：
Wool fiber has extremely high absorbency and high moisture regain.
It has soft hand high thermal insulation（low thermal conductivity）and low flammability.
Its elastic recovery is excellent.
It is lightweight and versatile.
It is resistant to dirt and wear and tear.
New Words and Expressions
spinning纺纱，细纱，纺丝
breed品种，血统
amino acid氨基酸
oval卵形，椭圆形的
crimp皱缩，卷曲
tear撕破
thermal insulation热绝缘
flammability可燃性
elastic recovery弹性回复
versatile多功能的，通用的
morphology形态
worsted 精纺毛织物
woolen 粗纺毛织物
sulfuric acid 硫酸
caustic soda 苛性
Unit 2 Specialty and fur fibers特种毛
Fibers from animals other than sheep frequently are referred to as specialty fibers.Most specialty fibers come from members of the goat（Fig.1.7）and camel families，which are indigenous to countries other than the United States（although small numbers are being raised in this country，primarily for the use of hand-spinners and weavers）.Both specialty and fur fibers are similar to sheep’s wool in chemical and physical properties.They are added to wool fabrics primarily to give softness，color interest，and value.
Fig.1.7 Goat
Mohair
Mohair is from the Angora goat and is highly resilient and strong.Mohair’s luster，not softness，determines its value.They have very good abrasion resistance and are quite durable.
Mohair is used in home decorating fabrics as well as garment fabrics including tropical worsteds.
The United States and South Africa are the major sources of mohair fibers.Mohair fibers are circular in cross section and range 10～90 μm in diameter.The mohair morphology is shown in Fig.1.8.
Fig.1.8 Observation under microscope
Cashmere
Cashmere is a soft，fine fiber obtained from the cashmere（Kashmir）goat of Asia.The fiber is combed，rather than sheared，from the animals.A single goat yields only 114 grams（4oz）of good fiber.Because supply of the fiber is limited and demand for it is high，cashmere fiber is quite expensive.The fiber cross-section is regular round.The cashmere morphology is shown in Fig.1.9.
Cashmere is more sensitive to the action of alkalies than wool.Cashmere fibers longer than 7.5 cm（3 in）may be somewhat stiff and coarse.The fiber has very small，barely protruding scales.Complaints from consumers and importers about labeled cashmere fabrics are investigated via careful microscopic evaluation to determine whether cashmere fibers are present in the amount specified on the label.
Fig.1.9 Observation under microscope
The fiber is used primarily for apparel such as scarves，sweaters，suits，and coats when a luxurious，soft fabric is desired.It is often blended with wool to reduce the cost of the products.
Camel hair
Camel hair，is an animal fiber obtained from the camel（Fig.1.10）and belonging to the group called specialty hair fibers.Camel hair fiber has greater sensitivity to chemicals than wool fiber does.Its strength is similar to that of wool having a similar diameter but is less than that of mohair.Fabric made of camel hair has excellent insulating properties and is warm and comfortable.Camel hair is mainly used for high-grade overcoat fabrics and is also made into knitting yarn，knitwear，blankets，and rugs.The coarse outer fiber is strong and is used in industrial fabrics such as machine beltings and press cloths employed in extracting oil from oilseeds.
Fig.1.10 Camel
The fiber cross section is circular to oval.Medulla is narrow and continuous.The fiber morphology is shown in Fig.1.11.
Fig.1.11 Observation under microscope
Alpaca
Alpacas（Fig.1.12）are domestic members of the camel family from the altiplano region of South America，prized for the production of fine fleece.
A cross section of an alpaca fiber will reveal microscopic air pockets.These pockets of air add to the insulating qualities as well as the light weight of a garment made from alpaca.The fiber morphology is shown in Fig.1.13.
Fig.1.12 Alpaca
Alpaca fiber offers the following benefits and qualities.
It’s extremely fine with little guard hair.
The fiber is compatible with either the woolen or worsted systems.
Fig.1.13 Observation under microscope
It has excellent insulative or thermal qualities.
It has a rich silky sheen which has high visual appeal in the apparel industry.
It has a higher tensile strength than wool.
It can be carded and blended with other natural or synthetic fibers.
New Words and Expressions
fur fibers毛皮纤维
indigenous本土的，本土生长的
primarily最初的
hand-spinner手工纺纱
mohair马海毛
Angora goat安哥拉山羊
shear剪毛
label 标签
identify鉴定，识别
abrasion磨蚀，磨损
aesthetic美观的，美感的
cashmere山羊绒
comb梳理
yield生产
sensitive敏感的，灵敏的
coarse粗糙
barely仅仅，几乎没有
protruding突出的
evaluation评价，估价
specify指定，详细说明
camel hair骆驼毛，驼绒毛
bactrian camel双峰驼
underhairs下层纤维
insulating绝缘的
medulla毛髓，髓质
pluck摘，拔
tan棕褐色，棕黄色
reddish微红的
brown棕色，褐色
subsequently随后的，后来的
shade色泽，色光
gray灰色
navy海军蓝
specialty hair fibers特种毛发纤维
altiplano高原
alpaca羊驼，羊驼毛
rug地毯，毯子
rope绳索
microscopic极小的，微观的
air pocket气穴，气孔
Unit 3 Silk丝
Silk is a continuous strand of two filaments cemented together forming the cocoon（Fig.1.14）of the silkworm.
For centuries silk has had a reputation as a luxurious and sensuous fabric，one associated with wealth and success.Silk is one of the oldest textile fibers known to man.
Fig.1.14 Cocoon
It is supposed to have been discovered in 2640 B.C.by a Chinese princess.It is also became a valuable commodity both in Greece and Rome.During the Roman Empire，silk was sold for its weight in gold.
Silk is the only natural filament fiber，triangular in cross section with rounded corners.The silk morphology is shown in Fig.1.15.
Silk is a protein fiber with 15 amino acids.It has no cross linkages and no bulky side chains.The molecular chains are packed closely to form high molecular orientation，which contributes to its higher strength.
Fig.1.15 Observation under microscope
Silk Properties：
It has a tenacity of 2.4 to 5.1 grams per denier when dry，wet strength is about 80 to 85 percent of the dry strength.
It has medium resiliency.Creases will hang out relatively well，but not so quickly or completely as for wool.
It has a relatively high standard moisture regain of 11 percent.
It has a poor resistance to sunlight exposure.
The elastic property of silk is better than those of cotton or rayon but is not as good as wool’s.Like wool，silk absorbs moisture readily and can take up a third of its weight of water without feeling wet to the touch.It has a regain of 11.0%.
Silk will withstand higher temperature than wool without decomposing.It will withstand a high temperature of 140℃ for prolonged periods.However，it will decompose at 175℃.
Silk is less readily damaged by alkali than wool and like wool it is also insoluble in common solvents.
New Words and Expressions
silk丝，蚕丝，丝织品
filament长丝
cocoon蚕茧
silkworm蚕
triangular三角形的
molecular chain分子链
molecular orientation分子取向
crease折印，折痕
Extension of practice&reading Spider silk蜘蛛丝
Spider silk is a protein fiber spun by spiders（Fig.1.16）.Spiders use their silk to make webs or other structures，which function as nets to catch other animals，or as nests or cocoons for protection for their offspring.They can also suspend themselves using their silk.
Spider silk is one of the 7 great wonders of the animal kingdom.That a small animal，often less than a millimeter across can make a substance that we humans with all our technology are unable to reproduce，a substance that is tougher，stronger and more flexible than anything else we can make is surely a humble reminder of the fact that nature created us and not the other way around.
Fig.1.16 Spider
Each spider and each type of silk has a set of mechanical properties optimized for their biological function.Most silks，in
particular dragline silk，have evolved exceptional mechanical properties.They exhibit a unique combination of high tensile strength and extensibility（ductility）.This enables a silk fiber to absorb a lot of energy before breaking（toughness，the area under a stress-strain curve）.
Spider silk is both light and strong.In fact，it is stronger than Steel，even stronger than Kevlar，the material that makes bullet-proof jackets.And because it is natural，it is biodegradable and can be produced pollution-free.Furthermore，one of the most important qualities of spider silk is its endless versatility.Spider silk，synthetically made，could be used in countless applications with significant commercial impact and improvement to human life.
New Words and Expressions
spider silk蜘蛛丝
flexible柔韧的，易弯曲的，灵活的
dragline silk拖丝
extensibility伸长性，延伸性
ductility延展性，韧性
stress-strain curve应力应变曲线
Kevlar凯夫拉纤维
bullet-proof jacket防弹衣
biodegradable生物所可降解的
pollution-free无污染的
Comprehensive Training
1.What are the two major protein fibers?
2.Describe the structure characteristics of wool such as length，width，cross section，shape.
3.Describe the processing of wool.
4.Describe the process from cocoon to the silk yarn.
5.Say something about the properties of the silk.
6.Where are the major sources of mohair fibers?
7.Why is cashmere fiber quite expensive?
8.Can you say something more about Alpaca?
9.Can you say something more about Camel fiber?
10.Give some more examples about specialty animal fibers.
11.Write a paper about the major properties of spider fiber.