|PARK, YAEWON - North Carolina State University|
|ERNST, NICHOLAS - Tulane University|
|FORD, ERICKA - North Carolina State University|
|GIBB, BRUCE - Tulane University|
Submitted to: RSC Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2020
Publication Date: 9/23/2020
Citation: Nam, S., Park, Y., Hillyer, M.B., Hron, R.J., Ernst, N., Chang, S., Condon, B.D., Hinchliffe, D.J., Ford, E., Gibb, B.C. 2020. Thermal properties and surface chemistry of cotton varieties mineralized with calcium carbonate polymorphs by cyclic dipping. RSC Advances. 10(58):35214-35225. https://doi.org/10.1039/D0RA06265K.
Interpretive Summary: A majority of cotton products on the market are made of scoured and/or bleached white fibers. Since scouring and bleaching, which remove waxes, proteins, pectin, and natural color on the fiber surface, cause high chemical oxygen demand and high biological oxygen demand in the textile effluents, the use of non-scoured, non-bleached raw white or colored cotton fibers is receiving growing attention. In this study, raw white and raw brown cottons as well as scoured white cotton were investigated as host materials for the growth of CaCO3 polymorphs to improve and alter their properties for nonwoven applications. The mineralization method employed in this study was a simple route of cyclic dipping to alternatively add calcium and carbonate ions onto cottons. The mineralization of cotton fibers protected them against heat, allowing the fabrics to be heat resistant. The mineralization altered the hydrophobic surface of raw cotton fabrics, which yielded about 130 degrees of a water contact angle, into the hydrophilic surfaces, which immediately absorbed the water droplet. The moisture regains of mineralized cotton fabrics were also increased in nearly twice as compared with those of control fabrics.
Technical Abstract: Calcium carbonate (CaCO3) polymorphs were fabricated onto hydroentangled nonwovens made of various cotton fiber varieties—raw white cotton, scoured white cotton, and raw brown cotton—as host materials. The fabrication involves a cyclic dipping process, in which calcium and carbonate ions were alternatively added to the cottons. Different surface components of cotton influenced the mineralization. Raw white cotton containing non-cellulosic components produced a mixture of calcite and vaterite polymorphs, whereas scoured white cotton having no non-cellulosic components and raw brown cotton having an additional component of tannins predominantly produced calcite. The morphology of calcite was better defined on scoured cotton than on brown cotton. The mineralized cotton nonwovens exhibited improved thermal resistance: slower thermal decomposition of cellulose with decreased activation energies and reduction in heat release capacity up to 40%. The CaCO3 mineralization also transformed the hydrophobic surfaces of raw white and brown cottons to be hydrophilic, increasing moisture regain two-fold and decreasing the water contact angle from 130 to 0 degrees.