Abstract:

Objective It is reported that supercritical CO₂ fluid (SCF-CO₂) can solubilize many drugs and carry them onto the polymer matrices, which allows to process with thermosensitive drugs and it enables to recover a final impregnated implant free of any solvent residue just by depressurization. Therefore, SCF-CO₂ can be used to process functional viscose fabric. To achieve good drug loading performance, it is necessary to study the structure and property of different drugs-loaded viscose fabrics impregnated by SCF-CO₂.

Method Viscose fabrics loaded with different polar drugs of nicotinamide, resveratrol were processed by SCF-CO₂ at 80 ℃, 20 MPa, 90 min. Scanning electron microscope (SEM) was utilized to analyses the surface morphology of drug-loaded viscose fabric. Fourier transform infrared spectroscopy (FT-IR) was used to monitor the change of the chemical structure of viscose fibre. X-Ray Diffraction (XRD) was applied to measure the crystallinity of drug-loaded viscose fibre. Thermogravimetry (TG/DTA) and INSTRON was respectively utilized to analyse the thermostability and tensile property of viscose fibre.

Results The results showed that the surface morphology of viscose fibre did not change after SCF-CO₂ treatment, and Nicotinamide and resveratrol were observed on the fiber surface in the form of small particles, but the distribution quantity of nicotinamide was more than that of resveratrol. The loading drugs had no effect on the chemical structure of viscose fibre, but it weakened the interaction between viscose fiber molecular chains. As a results, SCF-CO₂ impregnation showed a plasticizing effect on viscose fiber. After the treatment of the pure SCF-CO₂ the crystallinity was virtually changeless, but after being loaded with nicotinamide and resveratrol the crystallinity of viscose fiber was decreased from 41.37% to 29.28%, 23.37%, respectively. It was found that after the viscose fiber was treated with pure SCF-CO₂, the aggregate structure did not change significantly. However, after loading nicotinamide and resveratrol, parts of molecular chains of viscose fiber were changed from the ordered structure into disordered structure and the destruction of the ordered structure of viscose fiber loaded with resveratrol was more significant. It was observed that it had a significant degradation at 300 - 400 ℃ for viscose fibre samples and the quality retention rate was about 10%. The initial decomposition temperatures were 319.8 ℃, 320.2 ℃, 317.3 ℃ and 317.4 ℃, respectively, for untreated viscose fibre, treated viscose fibre by pure SCF-CO₂, viscose fibre loaded with nicotinamide, and viscose fibre loaded with resveratrol. The corresponding thermogravimetric loss rates were 94.29%, 93.69%, 95.36% and 95.67% respectively and the maximum mass loss rate were 30.5%/℃, 30.6%/℃, 31.2%/℃ and 32.2%/℃, respectively. The initial decomposition temperature of viscose fabric was decreased slightly after drug loading, and the thermogravimetric rate and maximum mass loss rate were increased slightly, indicating that the thermal degradation performance of viscose fabric loaded with drugs decreased to a certain extent, but it was not distinctive. The tensile breaking strength and elongation at break of viscose fabric after SCF-CO₂ treatment did not demonstrate distinctive variations.

Conclusion The variations in structure and property of drug-loaded viscose fabrics impregnated by SCF-CO₂ were charactered. It is found that a higher loading capacity of nicotinamide in viscose fibre results in a higher distribution quantity on the surface of viscose fibre than resveratrol. Under the effect of the swelling, penetrating of SCF-CO₂ and the interaction between drugs and viscose fibre molecular chains viscose fibre is plasticized to certain extent, but its chemical structure has no change. The interaction between nicotinamide, resveratrol and viscose fibre molecular chains causes the decreasing of the crystallinity of drug-loaded viscose fibre from 41.37% to 29.28%, 23.37%. After SCF-CO₂ impregnation viscose fabric can still maintain good thermal stability and mechanical property.

Key words: supercritical CO₂ fluid, nicotinamide, resveratrol, viscose fabric, crystallinity, thermal degradation property