Natural resistance of raw cotton fiber to heat evidenced by the suppressed depolymerization of cellulose

Authors: Nam, Sunghyun; Condon, Brian; Liu, Yongliang; HE, QINGLIANG - Great Lakes Solutions, Chemtura Corporation

Submitted to: Polymer Degradation and Stability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2017
Publication Date: 3/10/2017
Citation: Nam, S., Condon, B.D., Liu, Y., He, Q. 2017. Natural resistance of raw cotton fiber to heat evidenced by the suppressed depolymerization of cellulose. Polymer Degradation and Stability. 138:133-141.

Interpretive Summary: Scouring and bleaching of cotton fiber conducted as pretreatments to remove waxes, proteins, pectin, and natural color, consume large amounts of water, energy, and chemicals, causing high chemical oxygen demand and high biological oxygen demand in the textile effluents. As an effort to minimize such negative impact on the environment, the use of mechanically purified raw cotton fiber without using water and chemicals is receiving growing attention. However the unique thermal stability of raw cotton, which is important in processes and utilization, is little known. This study shows that the accelerated low-temperature thermal reactions were distinct in the pyrolysis of raw cotton. As compared with scoured cotton, an intensive accumulation of dehydrocellulose in solid products and the enhanced formation of water, carbon dioxide, and char were observed in raw cotton. This catalyzed low-temperature dehydration reactions suppressed the depolymerization of cellulose at high temperatures, which produces levoglucosan, a major constituent of flammable tar.

Technical Abstract: Mechanically purified raw cotton fiber finds a growing range of applications in support of environmental sustainability, but its unique thermal stability, which is important in processes and utilization, is little known. This study shows that at low temperatures (< 300 'C), the accelerated dehydration of cellulose was distinct in the pyrolysis of raw cotton. Compared with in scoured cotton, an intensive accumulation of dehydrocellulose in solid products and the enhanced formation of water, carbon dioxide, and char were observed in raw cotton by FTIR-ATR and TGA-FTIR. The amount of the crystalline region degraded together with the amorphous region was increased in raw cotton. The activation energy for raw cotton determined under isothermal conditions at 200-300 'C was 124 kJ/mol, smaller than 202 kJ/mol for scoured cotton. This catalyzed low-temperature thermal reactions suppressed the depolymerization of cellulose at high temperatures, which produces highly volatile levoglucosan. The levoglucosan detected in raw cotton using Py-GC/MS was two orders of magnitude less abundant than in scoured cotton.