Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2009
Publication Date: 4/27/2010
Citation: Byler, R.K., Jordan, A.G. 2010. Model of Cotton Bale Weight Changes Related to Bagging. Applied Engineering in Agriculture. 26(2): 203-208. Interpretive Summary: After cotton is baled at the gin, the bales are placed in bags to protect them from contamination during handling and storage. Traditionally, the bagging has been porous and the relatively dry cotton gained weight during storage as the fiber gained moisture. This higher moisture content fiber was actually stronger and better for spinning at mills. Non-porous plastic based bags have increasingly been used because they are lighter in weight and less expensive. The industry has asked that plastic bags be produced with holes to improve moisture gain during storage but many of these bags allow only low levels of moisture transfer. In this study, bales were formed from relatively dry cotton and placed in selected bags made of cotton, burlap, and polyethylene with various predetermined hole patterns. The cotton and burlap bags were very porous and did not restrict weight gain by the bales. A mathematical model was developed for the weight change of bales in polyethylene bags which predicted the change based on the percentage of open area of the bag. This equation will allow bag manufacturers to know how many holes of a given size will be required to achieve a specified rate of bale weight change. The resulting bags will adequately protect the bales produced in the US while allowing a reasonable moisture transfer. This packaging will allow the US cotton industry to remain competitive in the worldwide market.
Technical Abstract: Traditionally, bagging used for cotton bales has been permeable to moisture but more recently relatively impermeable material has been adopted by the industry. This impermeable bagging has significantly affected the moisture changes that occurred during storage. In many cases, holes have been punched in the bagging in an effort to increase the permeability. To better understand the effect of the different bagging materials on bale weight changes, Universal Density cotton bales were formed with relatively dry lint and covered with different types of bale bagging materials. The bales were stored in a humid environment and weighed periodically for between 63 days, for high permeability bagging, to 155 days, for low permeability bagging. The bale coverings which were studied included coated woven polypropylene with micro-perf holes, linear low density polyethylene film with different hole patterns, woven cotton, woven burlap, and no bale bagging. The bale weights were modeled temporally using a nonlinear exponential model. Different bales stored in the same bagging type changed weight consistently. A mathematical model was developed for polyethylene bagging that accurately related the rate of bale weight change with the percentage of bag surface removed as holes. The rate of bale weight change obtained from the regression was used to calculate a half-time to equilibrium, in days, for each bagging type. This weight change half-time will simplify communication of the effect bale bagging has on the cotton bale weight change during storage.