Isolation and characterization of lignins extracted from flax shives using pressurized aqueous ethanol.

High-molecular weight lignins (HML) and low-molecular weight lignins (LML) were extracted from flax shives using pressurized 30% aqueous ethanol, and isolated by precipitation and ultrafiltration. The isolated lignin samples and two commercial lignins were assayed for monolignol content and functional groups, solubility assays, thermal analysis using differential scanning calorimetry (DSC), size exclusion chromatography (SEC), and Fourier transform infrared spectroscopy (FT-IR). The highest yield of HML was 13.5 g/100 g of flax shives, and this was about six times higher than the LML yield. SEC of lignin samples revealed that the molecular weights of HML and LML are about 30,000 and 8749 Da, respectively. The DSC results of HML show that this lignin has a glass transition temperature near 160 degrees C. HML contains fewer carboxyl groups and more phenolic hydroxyl groups than LML. The higher molecular weight and higher thermal stability of HML makes it an excellent candidate for industrial applications.

Extraction and characterization of latex and natural rubber from rubber-bearing plants.

Consecutive extraction of latex and natural rubber from the roots of rubber-bearing plants such as Taraxacum kok-saghyz (TKS), Scorzonera tau-saghyz (STS), and Scorzonera Uzbekistanica (SU) were carried out. Latex extraction was carried via two methods: Blender method and Flow method. The results of latex extraction were compared. Cultivated rubber-bearing plants contained slightly higher latex contents compared to those from wild fields. Several creaming agents for latex extraction were compared. About 50% of total natural rubber was extracted as latex. The results of the comparative studies indicated that optimum latex extraction can be achieved with Flow method. The purity of latex extracted by Blender method ( approximately 75%) was significantly lower than that extracted by Flow method (99.5%). When the latex particles were stabilized with casein, the latex was concentrated significantly. Through concentrating latex by flotation, the latex concentration of 35% was obtained. Bagasse contained mostly solid natural rubber. The remaining natural rubber in the bagasse (left after the latex extraction) was extracted using sequential solvent extraction first with acetone and then with several nonpolar solvents. Solid natural rubber was analyzed for gel content and characterized by size exclusion chromatography (SEC) for molecular weight determinations. SEC of solid natural rubber has shown that the molecular weight is about 1.8E6 and they contain less gel compared to TSR20 (Grade 20 Technically Specified Rubber), a commercial natural rubber from Hevea brasiliensis.

Fractionation of flax shives by water and aqueous ammonia treatment in a pressurized low-polarity water extractor.

Fractionation of flax shives into cellulose, hemicellulose, and lignin with a two-stage extraction process using water and aqueous ammonia was carried out in a pressurized low-polarity water extractor operated at different temperatures, flow rates, and ammonia concentrations. During the first stage with water, 84% of hemicellulose and 32% of lignin were removed at 190 degrees C at a flow rate of 1.5 mL/min for 30 min. During the second stage with aqueous ammonia, more than 77% of the lignin was removed, and hemicellulose removal reached 95% at 200 degrees C at a flow rate of 0.5 mL/min and with a solvent/feed ratio of 40 mL/g. The temperature and flow rate had a significant effect on lignin removal. The impact of additives (anthraquinone and hydrogen peroxide) and modifications (overnight soaking, reduced particle size, and elevated temperature) on lignin extraction was also studied. The combination of higher temperatures and reduced particle sizes resulted in enhanced lignin extraction. The extraction profiles of free phenolics (vanillin, acetovanillone, and vanillic acid) during the two-stage processing were monitored and compared with those of lignin.