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Li J Kong M Cheng XJ Dang QF Zhou X Wei YN Chen XG 《International journal of biological macromolecules》2012,51(3):221-227
Chitosan grafted poly(lactic acid) (CS-g-PLA) copolymer was synthesized and characterized by FT-IR and elemental analysis. The degree of poly(lactic acid) substitution on chitosan was 1.90 ± 0.04%. The critical aggregation concentration of CS-g-PLA in distilled water was 0.17 mg/ml. Three methods of preparing CS-g-PLA nanoparticles (diafiltration method, ultrasonication method and diafiltration combined with ultrasonication method) were investigated and their effect was compared. Of the three methods, diafiltration combined with ultrasonication method produced nanoparticles with optimal property in terms of size and morphology, with size ranging from 133 to 352 nm and zeta potential from 36 to 43 mV. Also, the hemolytic activity and cytotoxicity of the CS-g-PLA based nanoparticles was tested, and results showed low hemolysis rate (<5%) and no significant cytotoxicity effect of these nanoparticles. 相似文献
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Technological and economic potential of poly(lactic acid) and lactic acid derivatives 总被引:24,自引:0,他引:24
Rathin Datta Shih-Perng Tsai Patrick Bonsignore Seung-Hyeon Moon James R. Frank 《FEMS microbiology reviews》1995,16(2-3):221-231
Abstract: Lactic acid has been an intermediate-volume specialty chemical (world production ∼ 40,000 tons/yr) used in a wide range of food processing and industrial applications. Lactic acid has the potential of becoming a very large volume, commodity-chemical intermediate produced from renewable carbohydrates for use as feedstocks for biodegradable polymers, oxygenated chemicals, plant growth regulators, environmentally friendly 'green' solvents, and specialty chemical intermediates. The recent announcements of new development-scale plants for producing lactic acid and polymer intermediates by major U.S. companies, such as Cargill, Ecochem (DuPont/ConAgra), and Archer Daniels Midland, attest to this potential.
In the past, efficient and economical technologies for the recovery and purification of lactic acid from crude fermentation broths and the conversion of lactic acid to the chemical or polymer intermediates had been the key technology impediments and main process cost centers. The development and deployment of novel separations technologies, such as electrodialysis (ED) with bipolar membranes, extractive distillations integrated with fermentation, and chemical conversion, can enable low-cost production with continuous processes in large-scale operations. The use of bipolar ED can virtually eliminate the salt or gypsum waste produced in the current lactic acid processes. Thus, the emerging technologies can use environmentally sound processes to produce environmentally useful products from lactic acid. The process economics of some of these processes and products can also be quite attractive. In this paper, the recent technical advances in lactic and polyactic acid processes are discussed. The economic potential and manufacturing cost estimates of several products and process options are presented. The technical accomplishments at Argonne National Laboratory (ANL) and the future directions of this program at ANL are discussed. 相似文献
In the past, efficient and economical technologies for the recovery and purification of lactic acid from crude fermentation broths and the conversion of lactic acid to the chemical or polymer intermediates had been the key technology impediments and main process cost centers. The development and deployment of novel separations technologies, such as electrodialysis (ED) with bipolar membranes, extractive distillations integrated with fermentation, and chemical conversion, can enable low-cost production with continuous processes in large-scale operations. The use of bipolar ED can virtually eliminate the salt or gypsum waste produced in the current lactic acid processes. Thus, the emerging technologies can use environmentally sound processes to produce environmentally useful products from lactic acid. The process economics of some of these processes and products can also be quite attractive. In this paper, the recent technical advances in lactic and polyactic acid processes are discussed. The economic potential and manufacturing cost estimates of several products and process options are presented. The technical accomplishments at Argonne National Laboratory (ANL) and the future directions of this program at ANL are discussed. 相似文献
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The electrospinning of stereocomplex nanofibers of high-molecular-weight poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA) (PLLA/PDLA = 1:1) was carried out with chloroform as the spinning solvent. The stereocomplex nanofibers with diameters of 830-1400 and 400-970 nm were successfully obtained at voltages of -12 and -25 kV, respectively. Wide-angle X-ray scattering indicated that with an increasing absolute value of voltage from 0 to 25 kV the crystallinity of homo-crystallites composed of either PLLA or PDLA decreased from 5% to 1%, whereas the crystallinity of stereocomplex crystallites increased slightly from 16% to 20%. The obtained results reveal that electrospinning is an effective method to prepare stereocomplex nanofibers with a negligibly small amount of homo-crystallites, even when high-molecular-weight PLLA and PDLA are used, and that the orientation caused by high voltage (or electrically induced high shearing force) during electrospinning enhances the formation and growth of stereocomplex crystallites and suppresses the formation of homo-crystallites. 相似文献
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E. Fortunati I. ArmentanoQ. Zhou A. IannoniE. Saino L. Visai L.A. BerglundJ.M. Kenny 《Carbohydrate polymers》2012,87(2):1596-1605
Nanocomposite films were prepared by the addition of cellulose nanocrystals (CNCs) eventually surfactant modified (s-CNC) and silver (Ag) nanoparticles in the polylactic acid (PLA) matrix using melt extrusion followed by a film formation process. Multifunctional composite materials were investigated in terms of morphological, mechanical, thermal and antibacterial response. The nanocomposite films maintained the transparency properties of the PLA matrix. Thermal analysis showed increased values of crystallinity in the nanocomposites, more evident in the s-CNC based formulations that had the highest tensile Young modulus. The presence of surfactant favoured the dispersion of cellulose nanocrystals in the polymer matrix and the nucleation effect was remarkably enhanced. Moreover, an antibacterial activity against Staphylococcus aureus and Escherichia coli cells was detected for ternary systems, suggesting that these novel nanocomposites may offer good perspectives for food packaging applications which require an antibacterial effect constant over time. 相似文献
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From lactic acid to poly(lactic acid) (PLA): characterization and analysis of PLA and its precursors 总被引:5,自引:0,他引:5
The quality of the monomers lactic acid and lactide as well as the chemical changes induced during polymerization and processing are crucial parameters for controlling the properties of the resulting poly(lactic acid) (PLA) products. This review presents the most important analysis and characterization methods for quality assessment of PLA and its precursors. The impurities typically present in lactic acid or lactide monomers and their possible origins and effects on resulting PLA products are discussed. The significance of the analyses for the different polymer production stages is considered, and special applications of the methods for studying features specific for PLA-based materials are highlighted. 相似文献
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Rafaela Magalhães Brandão Maria das Graças Cardoso Luís Roberto Batista Alex Rodrigues Silva Caetano Ana Carolina Cortez Lemos Maria Alice Martins David Lee Nelson Juliano Elvis De Oliveira 《Letters in applied microbiology》2022,74(5):765-776
Poly(lactic acid) (PLA) nanofibres containing different proportions of the essential oils from Ocimum basilicum L. and Ocimum gratissimum L. were prepared by solution blow spinning method. The essential oils were extracted by hydrodistillation and characterized by gas chromatography. MEV, contact angle, DSC and FTIR were used to characterize the nanofibres. The effect of bioative nanofibres on the growth of the fungus and on the production of ochratoxin A were evaluated using the fumigation test. Linalool, 1·8-cineole and camphor were the principal components of the essential oil from O. basilicum, and eugenol was the principal constituent in the oil from O. gratissimum. An increase in the average diameter of the nanofibres was observed with the addition of the essential oils. The essential oils acted as a plasticizer, resulting in a reduction in the crystallinity of the PLA. The encapsulation of essential oils in PLA nanofibres was verified by FTIR. An effective antifungal and antimicotoxygenic activity against Aspergillus ochraceus and Aspergillus westerdjikiae was observed for the bioative nanofibres. These results confirm the potential of PLA nanofibres containing the essential oils for the control of toxigenic fungi that cause the deterioration of food and are harmful to human health. 相似文献
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Laboratory composting of extruded poly(lactic acid) sheets 总被引:4,自引:0,他引:4
Composting of extruded poly(lactic acid) (PLA) in combination with pre-composted yard waste in a laboratory composting system was studied. Yard waste and PLA mixtures containing 0%, 10%, or 30% PLA (dry weight basis) were placed in composting vessels for four weeks. Exhaust gases were analyzed for carbon dioxide concentration twice per week. After the first week, significantly greater (P < 0.05) amounts of carbon dioxide were generated in vessels with 10% or 30% PLA than in control (0% PLA) vessels. Data indicated that microbial degradation of PLA occurred. There was no significant difference (P > 0.05) in carbon dioxide emission between 10% and 30% PLA mixtures. Compost pH dropped (from 6.0 to 4.0) after 4 weeks of composting for 30% PLA, but remained unchanged (6.3) for 0% or 10% PLA. Most likely, in the case of 30% PLA, substantial chemical hydrolysis and lactic acid generation lowered the compost pH. The lowered pH likely suppressed microbial activity, thus explaining the lack of difference in carbon dioxide emissions between 10% and 30% PLA mixtures. Gel permeation chromatography showed a notable decrease in PLA molecular weight as a result of composting. It was demonstrated that PLA can be efficiently composted when added in small amounts (<30% by weight) to pre-composted yard waste. 相似文献
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Stereocomplex formation between enantiomeric poly(lactic acid)s. 12. spherulite growth of low-molecular-weight poly(lactic acid)s from the melt 总被引:2,自引:0,他引:2
The spherulite growth of stereocomplex crystallites in the blend from low-molecular-weight poly(L-lactide) [i.e., poly(L-lactic acid) (PLLA)] and poly(D-lactide) [i.e., poly(D-lactic acid) (PDLA)] from the melt, together with that of the homocrystallites in pure PLLA and PDLA films, was investigated using polarization optical miscroscopy. The spherulite growth of stereocomplex crystallites occurred at a wider temperature range (=190 degrees C) compared with that of homocrystallites (=140 degrees C). At 140 degrees C, the spherulite radius growth rate (G) for the stereocomplex crystallites (136.4 microm min(-1)) was an order of magnitude higher than those for the homocrystallites of PLLA (11.8 microm min(-1)) and PDLA (15.7 microm min(-1)), whereas the induction period was shorter for the spherulties of stereocomplex crystallites (0.0 min) than for the spherulties of homocrystallites of PLLA (2.6 min) and PDLA (0.7 min). In addition to these two factors, the higher spherulite density of stereocomplex crystallites compared with those of the homocrystallites of PLLA and PDLA resulted in rapid completion of overall crystallization of stereocomplex. The front factor (G(0)) and nucleation constant (K(g)) for the stereocomplex crystallites in the temperature range of 140-190 degrees C were estimated to be 3.56 x 10(12) microm min(-1) and 8.42 x 10(5) K(2), respectively. The G(0) value for stereocomplex crystallites was 1 and 2 orders of magnitude higher than those for the homocrystallites of PLLA (9.69 x 10(11) microm min(-1)) and PDLA (8.79 x 10(10) microm min(-1)), whereas the K(g) value for stereocomplex crystallites was twice those for the homocrystallites of PLLA (4.95 x 10(5) K(2)) and PDLA (4.20 x 10(5) K(2)). 相似文献
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Poly(lactic acid) (PLA) and poly(acrylic acid) (PAA) biomaterials with luminescent ruthenium tris(bipyridine) centers couple drug delivery and imaging functions. Hydrophobic [Ru(bpyPLA2)3](PF6)2 (1) was generated from [Ru[bpy(CH2OH)2]3](PF6)2 in bulk monomer using 4-(dimethylamino)pyridine as the catalyst. The bromoesters, [Ru[bpy(CH2OR)2]3](PF6)2, [Ru[bpy(C13H27)2][bpy(CH2OR]2](PF6)2 (4), and [Ru[bpy(PLAOR)2]3]2+ (9) (R=COCBr(CH3)2), served as initiators for tert-butyl acrylate (tBA) polymerization. Conversion of PtBA to PAA via hydrolysis affords water soluble materials, [Ru(bpyPAA2)3]2+ (7) and [Ru[bpy(C13H27)2](bpyPAA2)2]2+ (8) and the amphiphilic star polymer [Ru[bpy(PLA-PAA)2]3)](PF6)2 (11), which is soluble in a H2O/CH3CN (1:1) mixture. Luminescence excitation and emission spectra of the Ru polymers were in agreement with the parent [Ru(bpy)3]2+ chromophore (lambdaex=468, lambdaem=621 nm). Lifetimes of tau approximately 700 ns in both air and nitrogen atmospheres are typical for most materials; however, the amphiphilic star block copolymer 11 is quenched by oxygen to some degree. Thermal analysis shows the expected glass transitions for the polymeric ruthenium complex materials. 相似文献
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Biocatalyzed approach for the surface functionalization of poly(L‐lactic acid) films using hydrolytic enzymes 下载免费PDF全文
Alessandro Pellis Enrique Herrero Acero Hansjoerg Weber Michael Obersriebnig Rolf Breinbauer Ewald Srebotnik Georg M. Guebitz 《Biotechnology journal》2015,10(11):1739-1749
Poly(lactic acid) as a biodegradable thermoplastic polyester has received increasing attention. This renewable polyester has found applications in a wide range of products such as food packaging, textiles and biomedical devices. Its major drawbacks are poor toughness, slow degradation rate and lack of reactive side‐chain groups. An enzymatic process for the grafting of carboxylic acids onto the surface of poly(L‐lactic acid) (PLLA) films was developed using Candida antarctica lipase B as a catalyst. Enzymatic hydrolysis of the PLLA film using Humicola insolens cutinase in order to increase the number of hydroxyl and carboxylic groups on the outer polymer chains for grafting was also assessed and showed a change of water contact angle from 74.6 to 33.1° while the roughness and waviness were an order of magnitude higher in comparison to the blank. Surface functionalization was demonstrated using two different techniques, 14C‐radiochemical analysis and X‐ray photoelectron spectroscopy (XPS) using 14C‐butyric acid sodium salt and 4,4,4‐trifluorobutyric acid as model molecules, respectively. XPS analysis showed that 4,4,4‐trifluorobutyric acid was enzymatically coupled based on an increase of the fluor content from 0.19 to 0.40%. The presented 14C‐radiochemical analyses are consistent with the XPS data indicating the potential of enzymatic functionalization in different reaction conditions. 相似文献
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Mechanical properties of poly(lactic acid)/starch composites compatibilized by maleic anhydride 总被引:3,自引:0,他引:3
Blending poly(lactic acid) (PLA) with wheat starch compatibized by maleic anhydride (MA) was performed with a lab-scale co-extruder. An initiator, 2,5-bis(tert-butylperoxy)-2,5 dimethylhexane (L101), was used to improve compatability among PLA, starch and MA. Interfacial adhesion between PLA and starch was significantly improved. Mechanical properties increased markedly compared to the virgin composites of PLA/starch. The PLA/starch composites at a constant ratio of 55/45 compatibilized by 1% MA and initiated by 10% L101 (MA basis) resulted in the highest tensile strength and elongation. 相似文献
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Poly 2'0-ethylcytidylic acid (poly (Ce)) was prepared by polymerization of 2'-0-ethylcytidine-5'-pyrophosphate with Escherichia coli polynucleotide phosphorylase in the presence of Mn++, and its properties compared with those of poly (rC), poly (Cm) and poly (dC). The neutral form of pOLY (Ce) exhibits properties similar to those of poly (rC) and poly (Cm). It also forms an acid twin-stranded helix with a transition pH of 5.9 in 0.1 M NaCl. The neutral form readily forms a double-stranded helical complex with poly (rI). Relative to poly (Cm), replacement of the 2'-0-methyl by 2-0-ethyl leads to increased enhancement of the thermal stabilities of both the acid helical form of poly (Ce) and its complex with poly (rI). 相似文献
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Synthesis and properties of poly(2-methylthioinosinic acid) 总被引:3,自引:0,他引:3