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  • Bale cover materials

    Chapter 2 - Cotton value addition - Cotton bale packaging 

     
     
    Protective wrapping materials are constructed of fabrics made from cotton, jute (burlap), polyethylene film and woven polypropylene. Bagging choices, like those of density and banding materials, involve weighing many factors including packaging costs, and levels of protection. The primary purpose of bagging is to shield cotton fibre from external contamination. Secondary benefits are reduction of lint loss and a decrease in fire risk from sparks or other ignition sources. If it were not for the need for these safeguards, cotton could be shipped bare, with no cover.

    Increased automation has accelerated the adoption of bags that cover the entire bale. In addition to the labour-saving advantages of application at the gin or warehouse, advantages also accrue to the textile mill; full bags, being on the outside of the band, can be removed without the need for removing straps. Complete bag removal by mill personnel is labour-saving as well as reducing the risk of contamination. Bales may be thoroughly cleaned before band removal.

    Each bagging material has advantages as well as disadvantages. Cotton bagging is desirable from the cotton consumption standpoint as well as reducing the concern of lint contamination from the packaging. The best cotton bagging is made of at least 270 g/m2 (1.4 kg/bale) materials. Cotton bagging meeting those weight requirements performs its intended duty of protecting the bale under normal handling practices. Cotton bagging can be woven or knitted to form bags. Unfortunately, the cost of good cotton bagging is a limiting factor. Experimental non-woven cotton bagging materials have also been used. Non-woven materials formed by hydro entanglement, needle punch and nylon stitch bonding have been used, providing varying degrees of performance. Lighter weight bags of as low as 135 g/m2 have been used with marginal success. As a general rule, higher fabric weights assure better protection. If price and performance were not factors, cotton bagging would be the cover of choice for all cotton bales.

    Woven burlap is used considerably in the form of large bags that enclose the entire cotton bale as well as sheets or panels placed underneath the bands. Mill attitudes to burlap are mixed. Some mills claim that burlap fibres are contaminants. Other mills report that burlap is preferable to plastic materials, because burlap fibre is composed of cellulose similar to cotton. They claim that burlap fibres, if accidentally entrained in cotton yarn, can be bleached and dyed along with cotton. Others show evidence of yarn breaks caused by burlap fibres entering the cotton lint stream. Burlap allows for free atmospheric moisture equilibrium, unlike impermeable films which retard moisture vapour movement. Burlap disposal is handled in two ways. In some facilities, burlap fabrics are recycled and made into other bags. In other cases, burlap is disposed of along with other organic wastes. Burlap, like cotton, is a natural organic product that degrades naturally in the environment.

    Polyethylene film, after cotton, is often chosen by textile mill owners for bagging. Its transparency allows cotton bale fibre to be visually inspected for moisture or other damage. Film also prevents dust, external moisture and similar contaminants from staining the fibre. Polyethylene film often is recyclable by the scrap plastics industry. Service businesses such as warehouses that have the responsibility for storing, handling and loading bales typically complain that polyethylene represents an increase in cost because its toughness and durability are not as good as woven polypropylene. Polyethylene film is recyclable by waste plastic businesses.

    Woven polypropylene bagging is the toughest, and has the highest tensile and tear resistance of all bale bagging materials. Woven polypropylene is usually the product preferred by warehousers and handlers of cotton bales as they perceiveit as protecting the fibre better than other materials. Textile millers do not universally agree on the attributes of woven polypropylene because of the fear of a strand of plastic yarn becoming entrained in raw cotton lint and causing yarn and fabric defects. Because of those concerns, woven polypropylene specifications for United States cotton bales mandate that all woven polypropylene fabrics be stabilized with a laminate coating to minimize yarn and fabric fraying. Woven polypropylene is recyclable, but recycling businesses may not exist in every textile mill area. Otherwise plastics must be disposed of in land fills, or incinerated. Pound for pound, when burned for energy plastic materials produce the same amount of energy as petroleum fuels.

    While plastic materials in cotton fabrics represent a significant cost to world textile mills, by far the most contaminants originate at the cotton field or near the gin. Plastic strings, ropes and sacks that become entrained in seed cotton and passed into the ginning process generate millions of fibres that are not detected until cotton yarn and fabrics are made. There is only scant evidence that woven polypropylene bagging at the textile mill is a contaminant of consequence. In order to assess the risk of woven polypropylene yarns on the outside of the bagging at the textile mill, numerous investigations have been conducted to determine the risks and benefits of plastic bagging on spinning efficiency and fabric quality. Since 1975, United States textile mills represented on the United States cotton industry bale packaging committee (the body that conducts evaluations and recommends specifications to the USDA) have processed over 100 million bales of United States cotton wrapped in woven polypropylene with only minimal evidence of contamination confirmed to be from bagging. Woven polypropylene fabrics made to mandatory United States industry specifications require a chemical trace element to be used for investigating contamination. From dozens of investigations, virtually no evidence exists that bagging was a source of contamination. Laboratory and textile mill experiments also have demonstrated a low risk of contamination from woven polypropylene bagging made to United States industry specifications. Nevertheless, because of many other sources of plastic contamination experienced by textile mills worldwide, operators persist in their concern about woven plastic bagging being a contaminant. 
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