Cotton
| Infobox on Cotton | |
|---|---|
| Example of Cotton |  |
| Facts | |
| Origin |
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| Stowage factor (in m3/t) |
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| Humidity / moisture |
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| Oil content | 0.4 - 1.0% (waxes) |
| 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 flooring/ceiling are too damp or the temperature is too high. The heat has then to be dissipated and ventilation should proceed as follows: - Air exchange rate: 6 changes/hour (airing) - Moisture must then be eliminated, to reduce mold and bacterial activity. - Since cotton very readily absorbs oxygen, before anybody enters the hold, it must be ventilated and a gas measurement carried out, since a shortage of oxygen may endanger life. |
| Risk factors | Reference is made to the relevant IMO regulations on hazardous cargo. |
Cotton
Contents
Description
Cotton is a soft, fluffy staple fibre that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fibre is to aid in seed dispersal.
The plant is a shrub native to tropical and subtropical regions around the world, including the Americas, Africa, and India. The greatest diversity of wild cotton species is found in Mexico, followed by Australia and Africa.
The fibre is most often spun into yarn or thread and used to make a soft, breathable textile.
Cotton is shipped in fully pressed bales, pressed to a considerable density, without harm. Bales vary in size, according to country of origin, in weights between 100 kgs and 330 kgs., and are compressed to varying degrees, strapped by steel bands or wire and covered with cotton, jute or synthetic fibre, and sometimes plastic sheet.
There are four main factors to be considered when purchasing raw cotton:
a) Grade – Cotton is graded by cleanliness or colour. Badly ginned cotton contains more ‘trash’ – dirt, leaf, cut seed, stains, etc., which means higher wastage for the spinner. ‘Stain’ is caused by climatic conditions during growing. Lightning, for instance, will cause a yellow stain on the mature bolls.
b) Staple – The length of the fibres. Evennes of fibre length is an important consideration.
c) Micronaire – A term used to describe the thickness and the maturity of the fibre.
d) Strength – the tenacity of the fibre at breaking point tested by instruments such as Pressley, Stelometer or the High Volume Instrument (HVI).
In addition to the long fibres, cotton also contains cotton-linters. Cotton linters are fine, silky fibres which adhere to the seeds of the cotton plant after ginning. These curly fibres typically are less than 3 mm long. The term also may apply to the longer textile fibre staple lint as well as the shorter fuzzy fibers from some upland species. Linters are traditionally used in the manufacture of paper and as a raw material in the manufacture of cellulose. In the UK, linters are referred to as "cotton wool". This can also be a refined product which has medical, cosmetic and many other practical uses.
Applications
Cotton is used to make a number of textile products. These include terrycloth for highly absorbent bath towels and robes; denim for blue jeans; cambric, popularly used in the manufacture of blue work shirts (from which we get the term "blue-collar"); and corduroy, seersucker, and cotton twill. Socks, underwear, and most T-shirts are made from cotton. Bed sheets often are made from cotton. Cotton also is used to make yarn used in crochet and knitting. Fabric also can be made from recycled or recovered cotton that otherwise would be thrown away during the spinning, weaving, or cutting process. While many fabrics are made completely of cotton, some materials blend cotton with other fibres, including rayon and synthetic fibres such as polyester. It can either be used in knitted or woven fabrics, as it can be blended with elastine to make a stretchier thread for knitted fabrics, and apparel such as stretch jeans.
In addition to the textile industry, cotton is used in fishing nets, coffee filters, tents, explosives manufacture (see nitrocellulose), cotton paper, and in bookbinding. The first Chinese paper was made of cotton fiber. Fire hoses were once made of cotton.
The cottonseed which remains after the cotton is ginned is used to produce cottonseed oil, which, after refining, can be consumed by humans like any other vegetable oil. The cottonseed meal that is left generally is fed to ruminant livestock; the gossypol remaining in the meal is toxic to monogastric animals. Cottonseed hulls can be added to dairy cattle rations for roughage.
Shipment / Storage / Usage
Having regard to the main characteristics mentioned, and the method of packing, there are five main causes of partial loss:
a) Fire
b) Water
c) Contamination with sticky or other harmful substances
d) Burst bales
e) Internal damp
Fire
Cotton, either in dry or wet condition, is incapable in itself of spontaneous combustion, except when the cotton will, and does generate heat, but this temperature is far short of the point of ignition. Fire to baled cotton is usually caused by a) bursting of bands contacting other ferrous metal and creating sparks, b) smoking, cigarettes, matches, etc., c) electrical faults, d) spread of fire from other commodities.
When baled cotton is involved in fire, the extinguishing of the outbreak will leave a coating of charred cotton on the exterior of the bale, varying in depth according to the density of the fire. In most cases because of the density of the pressed bale the inroads into the bale by the fire are not excessive, making for much sound cotton inside the bale.
Because of the make-up of the cotton fibre much oxygen remains in a bale after pressing, and this allows, in many cases, the rekindling of the fire, days or even weeks after seemingly having been extinguished. After a fire has been extinguished, the charred coating on a bale of cotton when dry forms a hard surface of carbon, which to a certain extent protects the undamaged interior of the bale and further stops the interior cotton from taking in more oxygen. Only in exceptional circumstances is it advisable to break open bales when fighting a fire.
Where bales are damaged by fire and water, or water alone, it is advisable to contact a reputable reconditioning firm with a cotton press, have all the bales opened up and the damaged cotton removed and sound cotton re-pressed. Loss would be on the basis of value of damaged cotton, plus picking and re-pressing charges. The grade in the salvaged cotton should in no way be affected by this operation. Pickings may realise a small salvage value.
Country damage
This type of damage may be caused by rain, flood, mud, sand, bales standing on wet or damp ground, or any combination of these causes. There is also the added damage that can be caused by insects, particularly ants and termites. Surveyors at destination should readily be able to identify ‘country damage’ which, by its nature, will be external in origin, extending inwards, depending upon the extent of the damage and density of the bale, as against damage originating from the interior of the bale, referred to under ‘Internal Damp’.
Country damage can usually be assessed in two ways, i.e. the amount of damage on the bale is estimated plus the cost of labour in removing the damage and an allowance granted per bale ‘in lieu of picking and mending’, or arranging for the bales to be removed to a reputable reconditioning firm for ‘’ picking and mending’, with the same procedure and settlement as for bales damaged by fire.
Contamination
Pressed bales of cotton from most producing countries are covered by hessian on bilges and ends only, leaving the flats of the bales uncovered. Therefore, these exposed places are susceptible to damage by other commodities, mainly due to bad stowage during transit. The main offenders of contamination are Carbon Black, Sugar, Coal, Coffee, Sisal, Ores and Yellow Ochre. Most of these commodities cause superficial damage by staining, which in most instances can be removed by brushing. Those pickings brushed off during this process are usually of no commercial value. An allowance should be given to cover the cost of the brushing and pickings removed, or a flat allowance per bale granted ‘in lieu of picking and mending’. Where damage cannot be brushed or an allowance ‘in lieu of picking and mending’ is not acceptable, then a reconditioning firm should be found for ‘picking and mending’.
Cotton is liable to damage if in contact with oil; and should not be stowed in the same compartment as any commodity which may contain vegetable, animal or other oils, in the same stowage as goods which, because of possible leakage or seepage, might bring oil in contact with the cotton.
Burst Bales
When bales burst during transit, this does not, in most cases, cause damage to the cotton, but does often result in a loss of cotton. This loss can be ascertained by the bale being re-pressed or repaired and then weighed. The average weight per bale of the sound cottonm should then be used against the weight of the burst bales, to assess the weight loss involved.
Internal Damp
This type of damage is normally not detectable from the exterior of the bale, but usually found when the bales are opened at the spinner’s mill. This damage is caused at the time of pressing, when either too much water is used in the press, or the cotton has been excessively wet when pressed. Damage is usually in pockets spread evenly throughout the various layers of cotton, which will be warm to hot according to the heat generation in the bale, and in most cases is accompanied by mildew or mould created by the heat generation. The damaged portion of the bales should be removed, and these pickings to be sold at best.
Water
Normally, wetting of bale cotton has no effect on the cotton fibres if drying follows quickly, but should the wetting, caused either by rain, sea water or sweat, remain on the bales for a period of time, it will penetrate slowly into the bale and cause staining and rotting in the affected fibres. Normally, baled cotton contains moisture up to 8,5%, the maximum allowed. In temperatures below freezing, there is very little chance of wetting causing deterioration or rotting of the fibres, due to the low temperatures arresting the decay process. In some cases where delay in dealing with the cotton could not be avoided it has been put into cold storage to prevent the development of decay.
If bales have been thoroughly wetted, the cutting of the bands to release the pressure should be considered, as heating will increase in compressed cotton whereas the opening of the bales will arrest the process of deterioration.
Where wetting has not penetrated very deeply into the bales they may be left in the open under drying conditions, which should be sufficient to restore them, but if they are thoroughly wetted then the bales should be opened up and dried as soon as possible. Artificial drying may sometimes be detrimental to the final appearance of the cotton as it may become spotted or yellow-stained. The natural process of drying, if available, is to be preferred, the main question in the case of wet-damaged cotton being to deal with it as promptly as possible.
Fumigation should not ordinarily be detrimental to cotton.
Cotton is subject to loss or gain in weight.
Some bales of cotton when opened may contain pockets of burnt cotton. The cause of this is usually traceable to the gins and compresses using the sawgin, with the cotton passing through a pneumatic conveyor system to the press, during which process sparks caused by friction ignite the cotton, which finds its way into the interior of the bale. Then, by virtue of its own oxygen content, the cotton continues to burn for a period of time before extinguishing itself.
Cotton Batting
Sheets of cotton obtained by combing of the cotton. Liable to spontaneous combustion.
Cotton Linters
Inferior quality cotton fibres obtained by the cleaning of the seeds. Handle as cotton.
Additional advice
Owing to the great risk of fire which is ever present with cotton cargoes, the handling, stowage, and carriage of same calls for the greatest care and attention. The National Cargo Bureau have issued Rules which govern the loading of cotton in all U.S.A. ports, and these may, with advantage and confidence, be adopted when loading cotton in ports where no specific rules are enforced.
Fire Extinguishers — before commencing to receive cotton, the ships fire fighting system should be thoroughly examined. Fire extinguishers should be placed adjacent to working hatch. Stevedores forklift truck should be battery driven and checked that arresters are in proper and good condition. While loading or discharging cotton, the fire hoses should be connected and ready for use. "No Smoking" notices conspicuously displayed, and the order rigidly enforced, "spark arresters" fitted on main and galley funnels and the use of forges or naked lights prohibited. Wet cotton, if stowed in a confined space, will heat and deteriorate but no danger of spontaneous ignition is to be expected. Wet and dry cotton should not be stowed together. On the other hand, cotton which is or has been in contact with oil or grease is very liable to spontaneous combustion, for which reason holds, and especially spar ceiling, should not be painted shortly before loading cotton unless it is certain that there is sufficient time for the paint to harden before cotton is stowed up against it.
Receiving — bales of cotton must be carefully examined on wharf or lighter, and all wet, damp or oil stained bales, also those with wrappers torn off and marks missing, or, with burst or missing bands should be rejected. Loose cotton should never be received on board. When bales are wrapped in hessian wrappers, as usually is the case, many countries (Canada especially) insist on bales being fumigated before entry is permitted where second-hand material has been used for wrapping. It is therefore advisable for a certificate to be obtained from Shippers certifying the wrapper used to be new material and that such be visaed by the consul of the country of destination. Where bales are partly opened up for sampling and grading only new material should be used to replace parts of wrappers cut off for that purpose.
Stowing — the bales stow on flat, edge or end according to which arrangement will ensure the greatest number being carried in the compartment, the particular arrangement depending on dimensions of bales and depth of compartment.
Cotton fires — in the event of a fire breaking out in a cotton cargo at sea, prompt measures are necessary:
- Batten down and close all apertures by which air may find its way into the holds
- turn on the C02
Cotton goods
Mildew and decay in cloth may be avoided by the use of suitable antiseptics. A starch finish may support traces of mould growth, producing organic acids which lead to spotting of the fabric. This spotting should not be confused with damage due to exterior causes. If cotton cloth is subjected to conditions of high humidity or is warm at the time of packing, these conditions are conducive to and may result in the formation of mould. Also if cloth is wrapped in moisture-proof wrappers and unsuitable antiseptics have been used or the cloth has been packed warm or under conditions of high humidity, mould growth immediately below the wrappers may develop to some considerable extent during the course of transit.
Cotton Fabrics
In all cases of damage by sea water, immediate cleaning is essential. If proper facilities are not immediately available, the material should be thoroughly washed in fresh cold water.
Grey Cloth
Packed in hessian-wrapped bales secured by steel bands. Grey cloth is sometimes delivered at destination suffering from mould damage. This usually falls into three different categories:
a) Bales which are externally wet, generally from exposure to rain prior to shipment. Hessian wrappers are stained and the steel bands surrounding the bal;es in the vicinity of the stain. Should the moisture be sufficient to penetrate the packing, the cloth in the vicinity of the wetting becomes brown-stained and mildew forms around the stains. The remaining pieces in the bales are usually in good order.
b) Packages externally in normal condition. The hessian wrappers in these instances may be affected by quay dirt or dust picked up during handling operations, but without evidence of external wetting, and the steel bands free of rust. On opening, it may be found that the top and bottom pieces are uniformly mildewed on the outer surface, the mildew penetrating the pieces to varying degrees, sometimes throughout. The adjoining pieces are mildewed on their edges or folds, but in some cases the mildew is present only on the external surfaces of the pieces and does not emanate from the interior.
c) Bales which are stained in places, but where the external moisture has not penetrated the interior packing, yet the top and bottom pieces are heavily mildewed and the intervening pieces are affected on the edges or folds, precisely similar to the contents of the bales which are not externally stained.
There are several different methods of packing, and these appear to have a direct bearing on the cause of the mildew. It is only the interior packing which varies, all bales being hessian wrapped and secured by steel bands. The interior packing may be one of the following:
a) Plain brown paper covering the cloth, and then covered with one or two layers of bitumen-lined paper, and the hessian cover places over all.
b) Plain brown paper covering the cloth, plaited cane matting over the tops and bottoms and part way down the sides and ends, one or two layers of bitumen-lined paper over the matting, and a final hessian cover.
c) The cloth covered at tops and bottoms with a sheet of polythene material which extends part way down the sides and ends and a hessian wrapper over all.
Examinations have revealed that in most instances where bales are externally unstained and brown paper and bitumen-lined paper only are used as interior protection, the cloth is in good order. Where cane matting is employed, or the cloth is covered with a polythene wrapper, mildew has developed and it is noticeable that where the matting or polythene does not cover the cloth there is no mildew. It would appear that while the packing has successfully excluded external moisture it has at the same time prevented the escape of any internal moisture which may have been present at the time of packing. Very little normal moisture need be present to set up a mildew growth on grey cloth, given suitable conditions, and it is possible that the subjection of pieces to a highly humid atmosphere prior to packing is alone sufficient when the appropriate conditions are present to produce an excess of moisture which cannot escape. Alternatively, a somewhat similar result can be obtained through the cloth being warm when packed, and when the bales are subjected to a lower temperature, light condensation takes place on the moisture-proof wrapping, resulting in mildew.
Cotton Duck Cloth
Investigations into the causes of yellowish discoloration of a shipment of Indian duck cloth revealed that the discoloration was not due to mould growth but to incomplete removal of oils and waxes in the lye treatment. The lye boiling is the most important operation in the bleaching process. It removes such impurities as oils, waxes, mineral oils, proteins, etc. Owing to incomplete lye boiling, yellowish discolorations occur because of unremoved oils and waxes. Unremoved wax may not be apparent directly after the bleaching process, but when the goods are stored, it works its way to the surface, giving the goods a yellow tint. The light grey and yellow discoloration in the cloth under test was possibly due to incomplete bleaching of the fabric owing to the presence of the unremoved waxes.
When cotton fabric has undergone efficient lye treatment, the ether extract from the material should not exceed 0,01%
Cotton Piece Goods
Care should be exercised in attributing the cause of water staining to contact with sea water, as an analysis of undamaged material may produce the same result, for the reason that salt is sometimes used in the dressing and/or filling used to bring the cloth up to a specified weight.
Dyed Cotton Piece Goods
May give off strong odor similar to that of kerosene, especially when packed in polythene bags. The odour is present in some dyes used and will disappear on full airing.
Baled Cottons
Bales are sometimes lined with an inferior water-proof paper in which bitumen of a very low melting point has been used between the two layers of paper. From 60°C to 65°C, the bitumen is freed and this, combined with pressure, causes soiling of the goods.
Cotton Yarn
If wetted yarn is immediately reconditioned, the damage should be confined to the reconditioning expenditure. Dyed yarn is more susceptible to damage. When cotton yarn is shipped in cone form, reconditioning is seldom economical and the wetting will weaken the fibre and render the cones useless.
Risk factors
- Self-heating / Spontaneous combustion
- Odor
- Contamination
- Mechanical influences
- Toxicity / Hazards to health
- Insect infestation / Diseases
- Wetness / mold growth caused by heat and moisture may start even in the cotton field. This leads to a reduction in value by staining and discoloration due to rot.
Cotton Waste – Spontaneously combustible
Clean cotton waste can be satisfactorily shipped providing the moisture content is below 13%. If there is an excess of moisture, the pressure of the press-packing will cause the waste to degenerate rapidly from the centre of the bale due to heat, the damaged waste having the appearance of discolored wood pulp. Will withstand contact with water if dried out quickly before mildew ensues.
Will heat if kept damp or in contact with oils. Should be stowed in a dry, well ventilated space away from heat. Oily waste is dangerous and liable to catch fire if the oil content exceeds 5%. Contact with water may also render the waste liable to spontaneous combustion.
Reference is made to the relevant IMO regulations on hazardous cargo.