Direct carbamation of cellulose fiber sheets.

The paper is on introducing carbamate groups in sheets of cellulose fiber assemblies by pad-dry-cure treatments with aqueous solutions of polyethylene glycol, amide and salt. The effects of process variables-on carbamation levels and on mechanical properties of the substrate-are reported. Depending on treatment conditions, the nitrogen contents in substrates are in the range 0.668-2.252 wt%, corresponding to nominal degrees of carbamate group substitution of 0.08-0.28. The carbamation is initiated at 140 °C curing, and the levels rise with temperature up to 220 °C, but decrease at higher temperatures. The duration of curing also exerts an influence. There is a catalytic effect of sodium acetate on the carbamation, but the salt also induces a brown coloration in samples, which is likely a result of Maillard-type reactions. The treatments cause hydrolytic degradation in substrates, but there are options to adjust treatment conditions and minimize damage. Pad-dry-cure treatments are a common operation in the textile and paper industries, and the process may be adopted in commercial-scale operations to create derivatized paper or fabrics (woven, knitted or non-woven) for utilization in applications such as adsorbents for heavy metals from waste water, in hygiene products, in the creation of flame retardant products, or in creating all-cellulose composites by further treatment with alkali. [ABSTRACT FROM AUTHOR]