Search

Chitosan/gelatin and chitosan/gelatin/zeolite films prepared by solvent casting method are impregnated with a mixture of thymol and carvacrol using a green solvent, supercritical carbon dioxide at 35 °C and 30 MPa, during 18 h. Proposed method enables preparation of biocompatible and biodegradable blends with strong antioxidant and antibacterial activity, whereby amounts of loaded thymol/carvacrol (TC) mixture are in the range from 3.3% to 6%. After initial burst release, both types of films exhibit gradual release of bioactive compounds, with around 72% and 96% of impregnated TC mixture released in water and phosphate buffered saline solution (pH 7.4) during tested period of 10 days, respectively. Results of water vapor transmission rate (>76 g m−2 day−1) confirm that prepared composites are suitable for wound dressing application. Thermal analysis shows superior properties of prepared TC loaded films compared to control samples. In addition, mechanical and structural properties, as well as solubility and swelling behavior of the obtained films are investigated in detail. [ABSTRACT FROM AUTHOR]

This study discusses the possibility of supercritical solvent impregnation of polypropylene and polyamide fabrics as well as cellulose acetate in the form of beads and films with pyrethrum extract in order to fabricate functionalized materials with repellent properties. Impregnation experiments were performed at temperature of 40 °C and pressures of 10 and 20 MPa in supercritical carbon dioxide. The time of impregnation was varied from 0.5 to 18 h. Loadings of pyrethrum extract into polypropylene fabrics and cellulose acetate films higher than 30% were attainable at 10 MPa. In the case of polyamide fabrics and cellulose acetate beads, the pressure of 20 MPa was needed for obtaining the loadings higher than 11%. Pyrethrum extract release study revealed different capabilities of the tested materials for the repellent release, implying a variety of their possible applications. The impregnated solids were characterized by SEM, DSC, FTIR, Mercury intrusion porosimetry analyses and HPLC analyses. [ABSTRACT FROM AUTHOR]

This study discusses a possibility of cotton fabric impregnation with pyrethrum extract as a tick repellent in supercritical carbon dioxide. A solubility of pyrethrum extract in supercritical carbon dioxide has been determined at 35 and 40 °C and pressures ranging from 8 to 20 MPa. The highest solubility of 48.69 kg/m 3 was obtained at temperature of 35 °C and pressure of 20 MPa. Density-based equations of Chrastil, Adachi-Lu and del Valle-Aguilera were employed to correlate the experimental data. Based on the solubility data, conditions for the impregnation of cotton fabric were selected. Conditions at 40 °C and 8 MPa provided targeted quantities of the impregnated extract of 0.5% and 1% after 1 h and 2 h of the impregnation, respectively. The presence of pyrethrins on the cotton fabric’s surface was confirmed by FTIR analysis. Repellent activity of both impregnated cotton fabrics (pyrethrum extract contents of 0.5% and 1%) was proven against ticks. [ABSTRACT FROM AUTHOR]

Like ester type biodiesel fuel, green diesel is a next generation transportation fuel emerging due to the need for a renewable replacement of internal combustion engine fuel, which is also fully compatible with existing automotive powertrain systems. Besides other limitations, the main obstacle for wider application of such renewable fuels is their relatively high production cost, depending mainly on the raw material cost and the application of more efficient processing technology. Green diesel and ester type biodiesel can be produced from waste vegetable oil by catalytic hydrogenation, homogeneous alkali catalysed transesterification and supercritical non-catalytic transesterification. Techno-economic analysis and the sensitivity analysis reveal that economics of these production technologies strongly depend on the process unit capacity and the cost of feedstock. Green diesel production by catalytic hydroprocessing located in a petroleum refinery appears to be the most cost effective option for unit capacity close to and above 200,000 tonnes/year. Conventional ester biodiesel process and non-catalytic ester biodiesel process under supercritical conditions are less profitable at specified capacity. Unit capacities of the investigated processes which are below 100,000 tonnes/year are likely to result in negative net present values after 10 years of project lifetime. [ABSTRACT FROM AUTHOR]

Outbreak of surgical infections and bacterial resistance against synthetic antibiotic has prompted research towards development of antibacterial medical devices. For that purpose, absorbable surgical sutures were impregnated with natural compound thymol using an environmentally friendly medium. The supercritical solvent impregnation process was performed at 35 °C and 10 MPa during 1, 2, 3 and 6 h, resulting in thymol loadings of 3.9–5.6%. All tested samples expressed antibacterial activity against E. coli and S. aureus. Release tests in PBS at 37 °C showed that impregnated material released loaded thymol in a gradual manner. While sutures impregnated during 6 h released complete amount of loaded thymol during 6 days, shorter impregnation process resulted in sutures that retained significant thymol amounts (~ 20–40%) after 10 days of release test. The effect of proposed process on final material properties and its application were explained in detail using characterization techniques SEM, FTIR, DSC and DMA. [Display omitted] • SSI process enabled preparation of surgical sutures effective against E. coli and S. aureus. • Mild process conditions (35 °C, 10 MPa, 1–6 h) allowed thymol loadings up to 5.9%. • Impregnated sutures released thymol in a controlled manner during 10 days. • Mechanical properties of sutures were negligible affected by the proposed SSI process. [ABSTRACT FROM AUTHOR]

In the present study, supercritical solvent impregnation (SSI) has been applied to incorporate thymol into bio-composite polymers as a potential active packaging material. Thymol, a natural component with a proven antimicrobial activity, was successfully impregnated into starch-chitosan (SC) and starch-chitosan-zeolite (SCZ) films using supercritical carbon dioxide (scCO2) as a solvent. Experiments were performed at 35 °C, pressures of 15.5 and 30 MPa, and an impregnation time in the range of 4–24 h. The highest impregnation yields of SC films with starch to chitosan mass ratios of 1:1 and 1:2 were 10.80% and 6.48%, respectively. The addition of natural zeolite (15–60%) significantly increased the loading capacity of films enabling thymol incorporation in a quantity of 16.7–27.3%. FTIR and SEM analyses were applied for the characterization of the films. Mechanical properties and water vapor permeability of films before and after the impregnation were tested as well. Thymol release kinetics in deionized water was followed and modeled by the Korsmeyer-Peppas and Weibull model. SCZ films with thymol loading of approximately 24% exhibited strong antibacterial activity against E. coli and methicillin-resistant Staphylococcus (S.) aureus (MRSA). [ABSTRACT FROM AUTHOR]

Biodegradable polymers with antibacterial properties are highly desirable materials for active food packaging applications. Thymol, a dietary monoterpene phenol with a strong antibacterial activity is abundant in plants belonging to the genus Thymus . This study presents two approaches for supercritical CO 2 impregnation of poly(lactic acid)(PLA)/poly(ε-caprolactone)(PCL) blended films to induce antibacterial properties of the material: (i) a batch impregnation process for loading pure thymol, and (ii) an integrated supercritical extraction-impregnation process for isolation of thyme extract and its incorporation into the films, operated in both batch or semi-continuous modes with supercritical solution circulation. The PCL content in films, impregnation time and CO 2 flow regime were varied to maximize loading of the films with thymol or thyme extract with preserving films' structure and thermal stability. Representative film samples impregnated with thymol and thyme extract were tested against Gram (−) ( Escherichia coli ) and Gram(+) ( Bacillus subtilis ) model strains, by measuring their metabolic activity and re-cultivation after exposure to the films. The film containing thymol (35.8 wt%) showed a strong antibacterial activity leading to a total reduction of bacterial cell viability. Proposed processes enable fast, controlled and organic solvent-free fabrication of the PLA/PCL films containing natural antibacterial substances at moderately low temperature, with a compact structure and a good thermal stability, for potential use as active food packaging materials. [ABSTRACT FROM AUTHOR]