Wool
| Infobox on Wool | |
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| Example of Wool |  |
| Facts | |
| Origin |
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| Stowage factor (in m3/t) |
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| Humidity / moisture |
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| Oil content | 10 - 20% (wool grease) |
| Ventilation | If the product is loaded for shipment in a dry state, it does not have any particular ventilation requirements. Problems arise if the product, packaging and/or ceiling/flooring are too damp; an air exchange rate of 10 changes/hour (airing) is then recommended. |
| Risk factors | Raw wool is an animal fiber. Wool is sensitive to unpleasant and pungent odors. Wool is particularly susceptible to mechanical damage, contamination and insect attack. Damp bales may also develop mildew due to mold and mildew stains due to bacteria. |
Wool
Description
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits.
Wool has several qualities that distinguish it from hair or fur: it is crimped, it is elastic, and it grows in staples (clusters).
Characteristics
Wool's scaling and crimp make it easier to spin the fleece by helping the individual fibers attach to each other, so they stay together. Because of the crimp, wool fabrics have a greater bulk than other textiles, and retain air, which causes the product to retain heat. Insulation also works both ways; Bedouins and Tuaregs use wool clothes to keep heat out and protect the body.
The amount of crimp corresponds to the fineness of the wool fibers. A fine wool like Merino may have up to 100 crimps per inch, while the coarser wools like karakul may have as few as 1 to 2. Hair, by contrast, has little if any scale and no crimp, and little ability to bind into yarn. On sheep, the hair part of the fleece is called kemp. The relative amounts of kemp to wool vary from breed to breed, and make some fleeces more desirable for spinning, felting, or carding into batts for quilts or other insulating products, including the famous tweed cloth of Scotland.
Wool fibers are hydrophilic, meaning they readily absorb moisture, but are not hollow. Wool can absorb moisture almost one-third of its own weight. Wool absorbs sound like many other fabrics. It is generally a creamy white color, although some breeds of sheep produce natural colors, such as black, brown, silver, and random mixes.
Wool ignites at a higher temperature than cotton and some synthetic fibers. It has lower rate of flame spread, low heat release, low heat of combustion, and does not melt or drip; it forms a char which is insulating and self-extinguishing, and contributes less to toxic gases and smoke than other flooring products, when used in carpets. Wool carpets are specified for high safety environments, such as trains and aircraft. Wool is usually specified for garments for firefighters, soldiers, and others in occupations where they are exposed to the likelihood of fire.
Wool is resistant to static electricity, as the moisture retained within the fabric conducts electricity, so wool garments are much less likely to spark or cling to the body. The use of wool car seat covers or carpets reduces the risk of a shock when a person touches a grounded object. Wool is considered by the medical profession to be hypoallergenic.
Shearing
Sheep shearing is the process by which the woolen fleece of a sheep is cut off.
After shearing, the wool is separated into four main categories: fleece (which makes up the vast bulk), broken, bellies, and locks. The quality of fleeces is determined by a technique known as wool classing, whereby a qualified person called a wool classer groups wools of similar gradings together to maximize the return for the farmer or sheep owner. In Australia and New Zealand, before being auctioned, all Merino fleece wool is objectively measured for micron, yield (including the amount of vegetable matter), staple length, staple strength, and sometimes color and comfort factor.
Scouring
Wool straight off a sheep, known as "greasy wool" or "wool in the grease", contains a high level of valuable lanolin, as well as dirt, dead skin, sweat residue, pesticide, and vegetable matter. Before the wool can be used for commercial purposes, it must be scoured, a process of cleaning the greasy wool. Scouring may be as simple as a bath in warm water, or as complicated as an industrial process using detergent and alkali, and specialized equipment. In commercial wool, vegetable matter is often removed by chemical carbonization. In less-processed wools, vegetable matter may be removed by hand, and some of the lanolin left intact through use of gentler detergents. This semigrease wool can be worked into yarn and knitted into particularly water-resistant mittens or sweaters, such as those of the Aran Island fishermen. Lanolin removed from wool is widely used in cosmetic products such as hand creams.
Quality
The quality of wool is determined by its fiber diameter, crimp, yield, color, and staple strength. Fiber diameter is the single most important wool characteristic determining quality and price.
Merino wool is typically 3-5 inches in length and is very fine (between 12 and 24 microns). The finest and most valuable wool comes from Merino hoggets. Wool taken from sheep produced for meat is typically more coarse, and has fibers 38 to 150 mm in length. Damage or breaks in the wool can occur if the sheep is stressed while it is growing its fleece, resulting in a thin spot where the fleece is likely to break.
Wool is also separated into grades based on the measurement of the wool's diameter in microns and also its style. These grades may vary depending on the breed or purpose of the wool.
Any wool finer than 25 microns can be used for garments, while coarser grades are used for outerwear or rugs. The finer the wool, the softer it is, while coarser grades are more durable and less prone to pilling.
Applications
Most wools are processed in the textiles sector. They are classified as follows, depending on intended use or production purpose:
- Carded wools or wools for heavy woolen fabrics
- Worsted wools
- Carpet wools
Shipment / storage
Wool is packed for shipment in bales covered with jute or plastic, pressed to varying densities. Size and weight of bales varies depending on country of export. The most frequent cause of damage to wool is contact with moisture, both fresh and salt. In a humidity of 95 hygrometer degrees, wool will charge itself up to 25 to 30%. Moisture absorption varies with its different physical states. With washed wool 17% is taken as a basis, carded wool 18,25% and wool not thoroughly washed 18%.
Absorption of atmospheric humidity provokes an increase in the temperature of a mass of fibre. Wool when packed must not be excessively compressed in the bale as, due to the hygroscopic property of the fibre, a considerable rise of temperature in the interior of the mass may take place, causing enervate. It is known that water, even when cold, makes the wool fibre turgit. Excessive humidity affects the external stratum of the fibre, destroying it rapidly, causing it to take a yellowish shade, and lowering its resistance to strain.
Greasy raw wool in its original state, and fibres which have not been defatted, are liable to be affected by moulds and bacteria at a lower humidity degree than that at which they have appeared on washed wool. These bacteria first destroy the superficial cells of the fibre and then penetrate the wall of the surface cells and finally disintegrate the cohesive texture. Wool affected by bacteria presents a higher affinity for acid and direct colouring matter, which it absorbs in a non-uniform manner. It gets more rapidly wet than sound fibre and suffers a higher loss of weight when subjected to washing, dyeing and bleaching. Bacteria causing discolouration and deterioration are likely to develop when the wool is wet and exposed to the air, as on a sheep’s back in rainy weather, or during an interval between wet processing. So far as is known there is no chemical treatment as protection against bacteria and mould which does not result in discoloration of the wool. Where wool has been in contact with salt water as a result of damping with sea water, subsequent immersion in a water solution will provoke a greater swelling of the fibre than in the case of rain-water damage.
Where moisture in bales and coverings has been ascertained, an analysis of samples and wrappings will determine whether the moisture and stains evident in the sample parts of the covering have been caused by rain water or by salt water. Research into the existence of marine salts must not be carried out by processing the liquid that results from washing the covering and the wool by aid of distilled water, but by analyzing the preparation obtained by previously reducing the fibre and covering to ashes in a refractory receptacle.
Wools after contamination by salt water require to be opened up and washed or scoured with fresh water. Unless this is done, the wool will not dry out properly and is always liable to collect moisture from the air. Wool which has been wetted by fresh water should also be opened up for drying. All wool, especially greasy wool, remaining in bales in a wet condition will heat in a few days and become mouldy and discoloured, showing brown stained tips of staples. This discoloration, if bad, cannot be eradicated. In all cases of water damage, speed in treatment is essential. All burned or charred wools should be warm water washed and dried only, not scoured with hot water and harsh soaps. Changes in the fibre caused by self-heating or by various fermentative agents latent at the time of the examination of the consignment require particular attention as to the colours and resistance of the fibre.
Chemical research will show the components responsible for the degeneration of the keratin, and a careful examination of the fibre under a microscope will reveal the condition of the scales and of the walls of the cortial cells and connecting texture. Some variations of weight are likely due to drying out during transit.
Favorable travel temperature range: 5 - 25°C. As wool grease may melt if heated (melting point 34°C), it must be stowed away from heat sources. Every hold should be equipped with means for measuring temperature. Measurements must be performed and recorded daily.
Greasy Wool
Usual packing is gunny-covered bales. The covering is liable to staining by the greasy wool. This may be mistaken for water damage. Water-damaged greasy wool sometimes generates heat and weakens the tensile strength of fibres, and immediate treatment such as opening and re-processing is recommended. Greasy wool damaged by sea water requires washing in order to extract salt, but even sound greasy wool requires washing prior to processing or manufacture at the mill. The hair of the wool is often covered by a wet, yellowish substance and some hair is often colourless and bristly. This damage occurs prior to shipment, the first by sheep mange and the second to hair being already dead when clipped. If greasy wool is packed in wet or damp condition, there is a possibility of spontaneous combustion.
Instances have occurred where greasy wool has suffered contamination from diesel oil. It was shown that in the case of the heavily damaged wool, diesel oil having penetrated the fibre cells, the harsh treatment of washing in volatile solvents discoloured the wool and made the fibres tender. While the wool may be suitable for some purposes it would in such condition not be suitable for others. It can, however, be reclassified as discoloured scroured fleece wool. The less damaged wool was treated in a similar manner but with the addition of extra soap and alkali solutions, and was not found to have suffered to the same extent, being reclassified as scoured (average) fleece wool. It will be seen that a proper segregation of the heavily damaged from the less damaged wool may result in the loss being minimized.
Greasy wool should not be stowed near heat sources (engine room bulkhead, heated tanks), since the wool grease may run.
Scoured Wool
Has not the same susceptibility to damage as greasy wool due to its being thoroughly dry before being packed.
Wool Shoddy
Contains 5% to 10% natural oil, according to grade and variety. Salt water damaged wool shoddy requires immediate washing to prevent further deterioration, but 10% to 15% may be lost in this operation. Shoddy damaged by fresh water does not usually require washing, but should be immediately aired and dried.
Sliped Wools
This class of wool is not scoured in process, merely being washed and machine dried before packing. Still contains a large percentage of grease.
Alpaca
Normal moisture content is from 8% to 12%, which usually increases during transit. When baled wet rot may set in in the centre of the bale, discolouring and damaging the fibre, which may lose in strength. Sea-water damaged bales should be opened up to be dried or scoured as soon as is possible.
Peruvian Sheep’s Wool
May contain 16% moisture without being considered wet. It usually gains weight during transit but may lose weight depending on the moisture content at the time of baling.
Woolen Fabrics
In all cases of damage by sea-water immediate cleaning is essential. If proper facilities are not available the material should be thoroughly washed in fresh cold water.
Woolen Goods (Baled Blankets
Bales are sometimes lined with an inferior waterproof paper in which bitumen of a very low melting point has been used between the two layers of paper. Above 60°C the bitumen is freed and this combined with pressure causes soiling of the goods.
Woolen Knitting Yarn
All wool and worsted commodities, from the raw material to the finished product, contain a certain proportion of moisture, and therefore normal loss by evaporation may be quite high. This needs to be taken into account, and the surveyor should calculate what is commonly known as ‘regain’ to ascertain the weight that the bales would have shown had they still had a normal moisture content.
Wool Presscloth
White wool presscloth which has been damaged by salt water will be found to be stained, mildewed, rotten, crumbly and emitting a bad odour. Damaged presscloth of this nature should, if possible, be processed without delay.
Reference is made to the relevant IMO regulations on hazardous cargo.
Risk factors
- Moisture / Self heating
- Mechanical influences
- Contamination
- Odors
- Toxicity / Hazards to health
- Shrinkage / Shortage
- Insect infestation / Disease