Inspection for supercritical CO₂ dyeing of poly(m-phenylene isophthalamide) by kinetics and thermodynamics analysis

Abstract

Eco-friendly dyeing by using supercritical carbon dioxide as a medium has already been investigated worldwide due to the advantages of dyeing without water and recyclability of dyes and carbon dioxide. In this article, dyeing mechanism of poly(m-phenylene isophthalamide) was investigated in supercritical carbon dioxide. The obtained results showed that the dye uptake of Disperse Red 60 increased moderately with the temperature raising at constant pressure and achieved dyeing equilibrium after 70 min. By adding the carrier, diffusion coefficients of Disperse Red 60 in the polymer increased significantly in supercritical carbon dioxide. The activation energy for diffusion of Disperse Red 60 with and without carrier was 1165.91 and 1050.66 kJ mol−1, respectively. Moreover, the distribution coefficient, the standard affinity, the standard enthalpy, and the standard entropy of dyeing were also determined in supercritical carbon dioxide. These fundamental data are of vital importance on the green dyeing production of poly(m-phenylene isophthalamide).

Dyeing para‐aramid fabrics in supercritical carbon dioxide with pretreatment of nonthermal plasma induced oil polymers

“…Between the two major types of aramids of meta‐aramids and para‐aramids, the meta‐aramid fibers consist of poly(m‐phenylene isophthalamide) that bind via meta‐linked aromatic rings to result in a semi‐crystalline fiber with the molecular chain oriented along the fiber axis, while the building‐blocks of para‐aramids are poly(p‐phenylene terephthalamide) with stiff para‐linked aromatic rings and densely arranged hydrogen bond donors and acceptors throughout their backbones (Roenbeck et al, 2019). Our literature searches on ScCO 2 dyeing of aramids found that (1) most studies claimed successful dyeing of meta‐aramids, but few of para‐aramids; (2) most studies used disperse dyes because they are soluble in ScCO 2 ; and (3) most studies relied on the addition of auxiliary chemicals, such as dimethyl terephthalate, ethyl alcohol, or CINDYE DNK as carriers, to enhance dyeing performance (Ye et al, 2019; Zheng et al, 2017; Zheng & Zheng, 2014). It is more difficult to dye para‐aramids than meta‐aramids, because the inherent molecular rigidity of para‐aramids, combined with strong intermolecular hydrogen bonding interactions, enables the molecules to achieve excellent alignment with their neighbors, resulting in a highly anisotropic unit cell consisting of covalent bonds, hydrogen bonds, and van der Waals interactions along each fundamental axis, forming a highly crystalline structure (Roenbeck et al, 2017).…”