ObstractThe biodegradable aliphatic oligoester oligo(trimethylene separate) (OTS) was synthesized by polycondensation and used to plasticize poly(lactic acid) (PLA). Casting films of PLA and PLA/OTS with concentrations of 1, 5 and 10 wt.% were prepared, and these films were characterized by thermal analyses, crystallinity, rheology and mechanical tests. DSC revealed the decrease in the T g of PLA films with addition of the oligomer and a partial immiscibility. Addition of OTS to PLA slightly decrease the thermal stability as well as increase the degree of crystallinity of these films. Dynamic-mechanical analyses of casting films showed that the PLA/OTS system presented lower storage modulus than PLA and mechanical test revealed an increased in the elongation at break for PLA films containing the oligoester. The results make possible to conclude that the oligomer synthesized from bio-based monomers acts as a plasticizer of PLA increasing the PLA ductility.
Keywords: plasticization poly(lactic acid), oligoesters, trimethylene sebacate, cast films.Aiming to investigate the efficiency of oligoester as PLA biodegradable plasticizers, a oligoester based on two
Summary: Bovine hemoglobin (HbBv) was isolated from whole blood and additionally purified by anion exchange chromatography. To obtain derivatives potentially suitable as oxygen carriers, oxidized trehalose was used as cross-linking reagent. Intra-and intermolecular bonds were formed by reaction between reactive aldehyde groups of oxidized trehalose and primary amine groups on the protein surface. After reduction of the Schiff bases formed, the HbBv derivatives were characterized by high performance liquid chromatography (HPLC), electrophoresis and by ultraviolet spectroscopy to evaluate methemoglobin contents.
Isolation and purification of bovine hemoglobin (HbBv) was carried out after reaction of whole blood with carbon monoxide. Washing/centrifugation steps were used to eliminate leukocytes, platelets, and plasma proteins. Hypotonic media and ultrasound radiation were used to lyse red blood cells. Lyse by ultrasound was shown to lead to solutions at the highest concentrations in HbBv, and the least concentrations in major phospholipids contaminants. Additional purification procedures were performed to remove membrane proteins and phospholipids. In the first case, proteins were denatured by thermal treatment, and filtered. To eliminate phospholipids, liquid chromatography was used with strong anion exchangers. Purity of HbBv was evaluated by normal phase high performance liquid chromatography (HPLC), electrophoresis, and size-exclusion HPLC.
The biodegradable aliphatic oligoester oligo(trimethylene malonate) (OTM) is synthesized by polycondensation and used to plasticize poly(lactic acid) (PLA). Casting films of PLA and PLA/OTM with concentrations of 1, 5,and 10 wt.% are prepared, and these films are characterized by thermal analyses, rheology, and mechanical tests. DSC revealed that the Tg of PLA films decreases with addition of the oligomer. A decrease of about 10 °C in the Tg is attained when 10 wt% of the oligomer is added to the polymer. Addition of OTM to PLA slightly decreases the thermal stability and does not change significantly the degree of crystallinity (Xc) of the films. Dynamic‐mechanical analyses of these casting films show that the PLA/OTM systems presented lower storage modulus than PLA and mechanical test shows an increased in the elongation at break for PLA films containing the oligoester up to 200%. The results make possible to conclude that the oligomer synthesized from bio‐based monomers acts as a plasticizer of PLA increasing the PLA flexibility.
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