Методические указания и контрольные задания для судентов-заочников
|
Скачать 433.32 Kb.
|
F L A XWe know flax to be an annual plant grown in many temperate countries for the production of linseed and linen fibre. In English-speaking countries both the plant and the fibre are called flax, while the yarn and fabric produced from flax are called linen. In the United States the word "linen" is often used to identify tablecloths, towels and similar articles that may or may not be made of flax fibres. We know the use of flax to have a greater antiquity than any other commercial fibre. Some historians claim flax to have been cultivated by the ancient Mexicans in the earliest period of our civilization. Flax was cultivated in prehistoric times, possibly at first for food. We know it to have been found in the ruins of the Stone Age lake dwellings of Switzerland and it is known that the ancient Egyptians made linen cloth from flax fibres. Later flax cultivation spread through Europe and Asia. It reached the United States during the colonial period where it was widely grown for fibre before the invention of the cotton gin in 1792 made cotton a cheaper fabric. The manufacture of linseed oil in the United States began in 1805. While the plant can be grown in nearly every portion of the temperate world, it is produced commercially throughout Europe and in portions of Africa and Asia, Japan, Australia, Canada and the USA. Russia is the world's chief producer of flax fibre; other leading producers include Poland, France, Ireland. Flax is harvested for fibre when the leaves have fallen from the lower two-thirds of the stem . The crop is harvested by pulling the plants from the ground by hand or by pulling machines. The disseeded straw (stems) is retted to dissolve the gum that binds the fibres to the woody portion of the stem. Retting is completed after 7 to 21 days. There are three methods of retting. Dew retting is the simplest, when the straw is spread over the field like hay and retted by dew and by the action of elements. Pool retting is immersing the straw in pools of stagnant water. The pools are dug in the ground for this purpose. Retting in running water is the third method. The fibres separated by retting are bailed and shipped to spinning mills. Flax fibre is strong, lustrous and, when bleached to a sparkling white, produces an attractive appearance for apparel goods as well as tablecloths and napkins. Because of its high strength it is also used in fish nets, sewing thread and fire hose. Fineness of the linen yarns is taken into consideration in choosing them for appropriate end uses. We know fine yarns to be used in weaving high-quality linen fabrics such as laces, household linens and dress goods. Coarse yarns are used for fabrics such as rough toweling, or for making cord or rope. Linen is especially suitable for towels because of its good absorbing power. W O O LThe thick covering of coat of the domestic sheep consists of a mass of fibres called wool. Wool fibres grow in tufts of as many as a dozen fibres. Density of fibre varies widely with the breed and from one part to another of the body of the individual sheep. There are more than 200 different breeds of sheep in the world, representing all grades of wool from the finest to the coarsest. Sheep's wool is classified into five generally recognized types: fine, medium, long, crossbred and carpet (or mixed). Fine wools are produced by Merino sheep while most medium wools are produced by English breeds. Fibres to be obtained from Asiatic sheep are classed as carpet wool. The sheep is sheared to obtain the wool. The fibres are sheared from the living sheep (although some wool is "pulled" from slaughtered sheep) and are then sorted and graded for fibre length, diameter and colour. Wool is sheared from the sheep ordinarily once each year. The wool to be spun into yarn has to be sorted and washed. The use of wool for human clothing reaches far back into antiquity, if not prehistory. Its outstanding qualities of resilience, wrinkle resistance, hygroscopic quality, felting property and lowe heat conductivity lomg ago gave it a high useful- ness not only for human clothing, but for blankets, upholstery, floor covering,etc. The wool to be used for clothing must possess good natural colour. Owing to a whole range of useful proper- ties wool is also used for the production of industrial fabrikc and articles. The most striking characteristic of wool fibre is its felting property. It is caused by the horny scales of the outer layer of the fibre. To convert wool fibres into felt they are subjected to heat, moisture and mechanical agitation. No other fibres possess this property to such a marked degree. But this property may be a disadvantage because wool textiles shrink sonti- nuously if wet laundered. This is why wool garments to be cleaned are treated with organic solvents rather than with water. |
Похожие:
 |
Методические указания и контрольные задания для студентов заочников... Методические указания и контрольные задания для студентов заочников специальности 140448 |
|
Методические указания и контрольные задания по дисциплине «Дендрология и лесоведение» Методические указания и контрольные задания по дисциплине «Дендрология и лесоведение» для студентов-заочников образовательных учреждений... |
 |
Методические указания составлены в соответствии с рабочей программой... Методические указания и контрольные задания для студентов-заочников Салаватского индустриального колледжа |
|
Методические указания и контрольные задания для студентов-заочников образовательных учреждений Пм 02 мдк 02. 02: «Бухгалтерская технология проведения и оформления инвентаризации» |
|
Методические указания и контрольные задания для студентов-заочников... Краткий методический курс для изучения дисциплины и выполнения контрольных работ |
|
Государственное автономное образовательное учреждение среднего профессионального... Методические указания и контрольные задания для студентов-заочников средних профессиональных учебных заведений |
|
Методические указания и контрольные задания для студентов-заочников образовательных учреждений Федерального государственного образовательного стандарта среднего профессионального образования по специальности 38. 02. 01 Экономика... |
|
Методические указания по профессиональному модулю «Организация и... ... |
|
Методические указания и контрольные задания для студентов заочной... Методические указания и контрольные задания для студентов-заочников образовательных учреждений среднего профессионального образования... |
|
Методические указания и контрольные задания для студентов-заочников... В методических указаниях приведены рекомендации по изучению программного материала, вопросы для самоконтроля, рекомендации по выполнению... |
|
Методические указания и задания по выполнению домашней контрольной... Методические указания и задания по выполнению домашней контрольной работы для студентов-заочников |
|
Методические указания и контрольные задания для студентов-заочников... Одобрены на заседании предметной (цикловой) комиссии общепрофессиональных и специальных дисциплин специальности 35. 02. 12 «Садово-парковое... |
|
Программа по технологии лекарственных форм Методические указания по изучению курса И. А. Насырова. Фармацевтическая технология: Методические указания, программа и контрольные задания для студентов заочного отделения... |
|
Методические указания и контрольные задания для студентов-заочников... Государственного образовательного стандарта среднего профессионального образования к минимуму содержания и уровню подготовки выпускника... |
|
Методические указания и контрольные задания для студентов заочников... Для студентов – заочников по специальности 110809 «Механизация сельского хозяйства» |
|
Методические указания и контрольные задания для студентов заочников... Работа состоит из трех заданий, выполняемых в «Тетради для выполнения контрольной работы 2». Ответы па вопросы и решения всех задач,... |