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Results for “LACTIC ACID”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Micro/nanofabrication of poly({sub L}-lactic acid) using focused ion beam direct etching

Micro/nanofabrication of biocompatible and biodegradable poly({sub L}-lactic acid) (PLLA) using focused Ga ion beam direct etching was evaluated for future bio-device applications. The fabrication performance was determined with different ion fluences and fluxes (beam currents), and it was found that the etching speed and fabrication accuracy were affected by irradiation-induced heat. Focused ion beam (FIB)-irradiated surfaces were analyzed using micro-area X-ray photoelectron spectroscopy. Owing to reactions such as the physical sputtering of atoms and radiation-induced decomposition, PLLA was gradually carbonized with increasing C=C bonds. Controlled micro/nanostructures of PLLA were fabricated with C=C bond-rich surfaces expected to have good cell attachment properties.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Performance of Cow Dung Reinforced Biodegradable Poly(Lactic Acid) Biocomposites for Structural Applications

In this work, performance of cow dung (CD) reinforced poly(lactic acid) (PLA) biocomposites was investigated for the potential use in load bearing application. CD of average 4 mm size was blended with PLA at different CD ratios (0–50 wt%) and their effects on the biocomposite properties were studied. The results showed an improvement in the flexural properties, while the tensile and impact strength dropped by 20 and 28% with the addition of 50% CD. The decline in the tensile and impact strength was due to micro-cracking and voids formation at higher CD content. Also, the incorporation of CD slightly decreased the thermal stability of the biocomposite. However, dynamic mechanical properties of the biocomposites generally improved. SEM analysis of tensile and impact fractured surfaces indicated that the CD had a reasonable adhesion with matrix. Moreover, the SEM micrographs of soil burial studies showed an accelerated degradation of higher CD wt% biocomposites.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Hydrothermal Aging on Injection Molded Short Jute Fiber Reinforced Poly(Lactic Acid) (PLA) Composites

This work focused on the durability of short jute fiber reinforced poly(lactic acid) (PLA) composites in distilled water at different temperatures (23, 37.8 and 60 °C). Morphological, thermal and mechanical properties (tensile, flexural, and impact) of jute/PLA composites were investigated before and after aging. Different from traditional synthetic fiber reinforced polymer composites, the stability of jute/PLA composites in water was significantly influenced by hydrothermal temperature. The mechanical properties of the composites and molecular weight of PLA matrix declined quickly at 60 °C, however, this process was quite slower at temperatures of 23 and 37.8 °C. Impact properties of the composites were hardly decreased, but the tensile and flexural properties suffered a drop though to various degrees with three degradation stages at 23 and 37.8 °C. The poor interface of composites and the degradation of PLA matrix were the main damage mechanism induced by hydrothermal aging. Furthermore, considering the hydrolysis of PLA matrix, the cleavage of PLA molecular chain in different aging time was quantitatively investigated for the first time to illustrate hydrolysis degree of PLA matrix at different aging time.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Polymer-Grafted Cellulose Nanofibrils with Enhanced Interfacial Compatibility for Stronger Poly(lactic acid) Composites

Cellulose nanofibrils (CNFs) are a promising reinforcement for biodegradable composite matrices such as poly(lactic acid) (PLA), but they require commercially scalable drying methods that preserve their fibrillar morphology along with improved interfacial interactions with polymer matrices. In this work, a water-based grafting-through polymerization scheme to modify CNFs improved spray drying behavior and reinforcement capacity in PLA composites. All polymer modifications yielded CNFs with a more fibrillar morphology after spray drying, increasing specific surface area by up to 490% compared to unmodified CNFs, values similar to conventional freeze drying. Polymer-grafted CNFs in PLA composites improved the tensile strength by 16% at 20 wt % loading and stiffness by 22% at a 10 wt % loading with two different graft-polymer chemistries compared to unmodified CNF composites. Surface energy heterogeneity measurements of the reinforcements and PLA matrix were employed to understand the improvements in composite properties. Polymer modifications lowered the total surface energy of the CNFs, and calculated ratios of work of adhesion to work of cohesion suggested improved interfacial compatibility for four of the modified CNFs with PLA. Rheological oscillatory shear studies of the composites correlated solid-like melt behavior, as demonstrated by storage moduli dominance, with higher tensile strength. Thermal analysis of the composites revealed that excessive plasticization by the poly(oligoethylene glycol methyl ether methacrylate)-grafted sample potentially offset mechanical property improvements imparted by the more fibrillar morphology. This work provides an opportunity for large-scale manufacturing of CNF/PLA composites via an entirely aqueous modification scheme and industrially relevant spray drying process.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Life Cycle Analysis of Extruded Films Based on Poly(lactic acid)/Cellulose Nanocrystal/Limonene: A Comparative Study with ATBC Plasticized PLA/OMMT Systems

Life cycle analysis (LCA) of limonene plasticized poly(lactic acid) (PLA) films containing cellulose nanocrystals (CNC) extracted, by acid hydrolysis, from Phormium tenax leaf fibres, was assessed and compared with the results of acetyl tributyl citrate (ATBC) plasticized PLA films, having equivalent mechanical properties, containing organo-modified montmorillonite (OMMT). Eco-Indicator 99 tool has been adopted as the main method for life cycle assessment. Results indicated that, despite CNC are biobased fillers obtained by natural sources, the related chemical extraction leads to a large environmental footprint and a relatively relevant energy expense. LCA characterization of these films demonstrated that the environmental impact of PLA/limonene film reinforced with 1% in weight of CNC (PLA/CNC/limonene) is comparable to the environmental impact of polylactic acid films reinforced with OMMT and plasticized with a petroleum based plasticizer (ATBC) (PLA/OMTT/ATBC). A “cradle to gate” approach has been considered for both the film typologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Engineering of thermotolerant Bacillus coagulans for production of D(-)-lactic acid

Genetically modified microorganisms having the ability to produce D(-)-lactic acid at temperatures between 30.degree. C. and 55.degree. C. are provided. In various embodiments, the microorganisms may have the chromosomal lactate dehydrogenase (ldh) gene and/or the chromosomal acetolactate synthase (alsS) gene inactivated. Exemplary microorganisms for use in the disclosed methods are Bacillus spp., such as Bacillus coagulans.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Preparation and characterization of reactive blends of poly(lactic acid), poly(ethylene-co-vinyl alcohol), and poly(ethylene-co-glycidyl methacrylate)

The ternary blends of poly(lactic acid) (PLA), poly(ethylene-co-vinyl alcohol) (EVOH), and poly(ethylene-co-glycidyl methacrylate) (EGMA) were prepared. The role of EGMA as a compatibilizer was evaluated. The weight ratio of PLA:EVOH was 80:20 and the EGMA loadings were varied from 5-20 phr. The blends were characterized as follows: thermal properties by differential scanning calorimetry, morphology by scanning electron microscopy, and mechanical properties by pendulum impact tester, and universal testing machine. The glass transition temperature of PLA blends did not change much when compared with that of PLA. The blends of PLA/EGMA and EVOH/EGMA showed EGMA dispersed droplets where the latter led to poor impact properties. However, the tensile elongation at break and tensile toughness substantially increased upon addition of EGMA to blends of PLA and EVOH. It was noted in tensile test samples that both PLA and EVOH domains fibrillated significantly to produce toughness.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Preparation and characterization of composites based on poly(lactic acid) and CaCO{sub 3} nanofiller

In recent years, extensive studies have been conducted on the study of the poly(lactic acid) (PLA) properties, because of its being a typical biobased and biodegradable polymer, with good mechanical properties. However, its toughness and gas barrier properties are not satisfactory and can be improved by the addition of nanofillers, such as calcium carbonate (n-CaCO{sub 3}). The present work PLA composites with nano-sized precipitated calcium carbonate (n-NPCC) were prepared by melt extrusion. Thermal, mechanical and flow properties of the composites were evaluated by using a factorial design.The results showed that the addition of the nanofiller in the PLA matrix didn’t improve thethermal and mechanical properties of the matrix significantly. This behavior is probably due to the presence of the stearic acid that is coating on the n-NPCC particles, resulting in a weak polymer-particle interaction. Beyond this, it was also observed a decrease in MFI of the composites when nanofiller was added and at a higher screw speed.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Draft Genome Sequence of Bacillus coagulans MA-13, a Thermophilic Lactic Acid Producer from Lignocellulose

Bacillus coagulans MA-13 is an efficient lactic acid producer which withstands high concentrations of the growth inhibitors formed during the pretreatment of lignocellulosic feedstock. This draft genome sequence is expected to pave the way toward the understanding of mechanisms responsible for the robustness of MA-13 during simultaneous saccharification and fermentation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Effect of Talc on Mechanical Characteristics and Fracture Toughness of Poly(lactic acid)/Poly(butylene succinate) Blend

This research investigates the effect of talc additive on physical and mechanical characteristics of poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) polymer blend. In the study, the talc content is varied between 0, 5, 10, and 20 parts per hundred resin (phr) and the PLA/PBS ratio is 80/20 w/w. The results reveal that talc enhances the mechanical properties of PLA/PBS blend. Specifically, tensile strength, Young’s modulus, and impact strength of PLA/PBS/talc composite increase as talc content rises. In addition, fracture toughness increases substantially as talc quantity is raised. The enhanced fracture toughness is attributable to nucleation of talc which promotes crystallization of PLA while hindering PBS crystal growth. Moreover, morphology analysis shows efficient distribution of talc in the polymer matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Amino-Modified Halloysite Nanotubes to Reduce Polymer Degradation and Improve the Performance of Mechanically Recycled Poly(lactic acid)

From an environmental point of view, mechanical recycling is, in general, a good end-of-life option for poly(lactic acid) (PLA), one of the most important biobased polymers. However, the degradation of PLA during the service life and, especially, during the mechanical recycling process, leads to a decrease in the properties of PLA, thus reducing the applications of the recycled plastic. The main aim of this work was to study the addition of small amounts of halloysite nanotubes, during the recycling step, as the basis of a cost-effective method for improving the properties of the recycled PLA. Raw halloysite was modified with an aminosilane, and 2% by weight of both raw and modified halloysite were melt compounded with PLA previously subjected to accelerated ageing. The addition of the nanotubes led to recycled materials with improved properties because halloysite reduces the degradation of PLA by blocking the carboxyl groups, generated during the ageing and washing steps, which catalyze the degradation during the recycling process. This effect was more intense in the silanized nanotubes, because the carboxyl groups were effectively blocked by acid–base interactions with the amino groups of the chemical modification. The properties of the recycled plastic with only 2 wt% of silanized halloysite were very close to those of the virgin plastic.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Contribution of Catalytic Transesterification Reactions to the Compatibilization of Poly(lactic acid)/Polycarbonate Blends: Thermal, Morphological and Viscoelastic Characterization

Samarium acetylacetonate (Sm-Acac) was added to catalyze interchange reactions between poly(lactic acid) (PLA) and polycarbonate (PC) in order to promote compatibilization and enhance the performances of the PLA/PC blend. The effects of the composition and catalyzed transesterification reactions were investigated using differential scanning calorimetry (DSC), thermogravimetry (TG), dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). DMTA and DSC analysis revealed the immiscibility of the uncatalyzed PLA/PC blends for the studied compositions because the glass transition temperatures of PC and PLA were unchanged after blending. In the PLA glassy region, PLA/PC blends exhibited lower storage moduli which increased upon heating due to the cold crystallization process. During melt mixing with Sm-Acac catalyst, PLA/PC blends were submitted to two competing processes. In one hand, Sm-Acac acted as a plasticizer and contributed in decreasing significantly the glass transition, crystallization and melting temperatures of PLA phase. In the other hand, Sm-Acac proved its efficiency in catalyzing the transesterification reactions that were evidenced by the decrease of the PLA aptitude to crystallization due to the hindering effect of the PC units inserted into the PLA chains. PLA/PC blends melt mixed with 0.25% of Sm-Acac showed a significant strengthening effect, corresponding to an increase in the storage modulus in the temperature range comprised between 70 and 90 °C. This indicated the formation of a copolymer at the interface and the promotion of adhesion as it is confirmed from the decrease in the height of the PLA Tan δ peak. At 0.5% of Sm-Acac, (90/10) PLA/PC blend revealed a new peak assigned to the glass transition of the PLA-PC copolymer, whereas the (50/50) PLA/PC blend was converted into a new random copolymer. TG analysis proved the presence of a copolymer structure presenting an intermediate thermal stability in both the catalyzed and uncatalyzed blends.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microcellular Foaming Behaviors of Poly (Lactic Acid)/Low-Density Polyethylene Blends Induced by Compatibilization Effect

A facile methodology for improving the crystallization ability, rheological properties and microcellular foaming behaviors of poly (lactic acid)/low-density polyethylene (PLA/LDPE) blends through compatibilization was proposed. Poly (ethylene octene) grafted with glycidyl methacrylate (GPOE) as reactive compatibilizer was introduced into PLA/LDPE blends and the resultant PLA/LDPE/GPOE blends were foamed by supercritical CO{sub 2}. Torque curves and Fourier transformation infrared spectroscopy results confirmed that GPOE reacted with PLA successfully. The crystallization ability and rheological properties of PLA was promoted obviously by the addition of LDPE and GPOE. The size of LDPE dispersion phase in PLA/LDPE blends decreased from 4.4 ± 0.1 to 1.2 ± 0.1 µm, owing to the compatibility effect. When the content of GPOE reach 8 phr, microcellular structure appeared in the PLA/LDPE/GPOE blending foam. An interesting flower-like cellular structure was observed in PLA/LDPE/GPOE blending foams, with the foaming temperature at 85 and 90 °C. Finally, the microcellular foaming mechanism for various PLA foams was proposed and clarified using schematic diagram.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Study on Mechanical and Thermal Properties of Poly(Lactic acid)/Poly(Butylene adipate-co-terephthalate)/Office Wastepaper Fiber Biodegradable Composites

Office wastepaper fibers(OWF)/poly(butylene adipate-co-terephthalate) (PBAT)/poly(lactic acid) (PLA) biodegradable composites with different mass ratio were made by melt blending and injection moulding process. At the same time, the use of MAPLA and KH560 was studied as a potential approach for improving interfacial adhesion between OWF, PBAT and PLA. The results revealed that with the increasing of PBAT, the notched impact strength of PLA/PBAT/OWF composites can be first increased and then decreased. When the content of PBAT was 20 wt%, the notch impact strength of PLA/PBAT/OWF composite was the highest, increased by 291% compared with pure PLA. TGA results revealed that the onset degradation temperature of the composites can be increased and its thermal decomposition step can be changed. According to the crystallization and melting performance table, OWF can act as nucleating agent to promote the crystallization properties of composites, while PBAT can prevent the crystallization and the higher the content is, the more obvious it is. It can be seen from the SEM figures that the addition of MAPLA and KH560 simultaneously makes the composites interface bond closer, thus improving the interface performance of PLA/20PBAT/OWF composite. Among the three kinds of modified composites, PLA/20PBAT/OWF/MK composite has the lowest water absorption and the best comprehensive performance.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Rheology, Mechanical Properties and Morphology of Poly(lactic acid)/Ethylene Vinyl Acetate Blends

In this work, the effect of ethylene vinyl acetate (EVA) content on the rheology, mechanical properties, and morphology of poly (lactic acid) (PLA)/EVA blends was investigated. Differential Scanning Calorimetry (DSC) showed that the addition of EVA to PLA decreased the degree of crystallinity of PLA. Dynamic Mechanical Thermal Analysis (DMTA) results showed that the presence of EVA copolymer increased the cold crystallization temperature (T{sub cc}) of PLA. The addition of 10% of EVA to PLA substantially increased the impact strength. Morphology analysis by Scanning Electron Microscopy (SEM) indicated the immiscibility between PLA and EVA phases and an in increase the EVA average dispersed phase domains size with the increase in EVA content. Rheological measurements under oscillatory shear flow showed that storage modulus (G′) increased with the increase in the EVA content at low frequencies and is related to the increase in the EVA dispersed phase domains size, as also observed by relaxation spectrum analysis. Cole–Cole plots of imaginary viscosity (η″) versus real viscosity (η′) and Han plots of storage modulus (G′) versus loss modulus (G″) indicated that PLA and EVA phases are immiscible, as also observed by SEM.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Enhancing the Melt Strength of Poly(Lactic Acid) via Micro-Crosslinking and Blending with Poly(Butylene Adipate-co-Butylene Terephthalate)for the Preparation of Foams

The melt strength of poly(lactic acid) (PLA) is an important factor in preparing foams and blowing films. Aiming to endow PLA with a suitable melt strength via a slight crosslink, a superficial micro-crosslinking method was introduced in which the PLA feed was mixed with benzoyl peroxide (BPO) and crosslinked in a 100 °C oven for 1 h. Additionally, poly(butyleneadipate-co-terephthalate) (PBAT) was blended with the crosslinked PLA (C-PLA) to further improve melt strength and viscosity. The blend foams were prepared using a single-screw extruder and azodicarbonamide as a foaming agent. The properties were characterized by gel fraction, melt flow rate (MFR), rheometry, DSC and SEM. The rheological results showed that the complex viscosity and storage modulus of C-PLA and C-PLA/PBAT blends increased, attributed to the micro-crosslinking and addition of PBAT and indicating an improvement in melt strength. Furthermore, the crystallization of modified PLA was also enhanced. Compared with pure PLA foams, the C-PLA/PBAT blend foams showed larger cells with more uniform shapes and homogenous distribution. This approach to improve the melt strength of polymers with micro-crosslinking and blending with PBAT represents an attractive method for preparing foams with regular cells.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Rheological Properties of Poly(lactic acid) Solutions Added with Metal Oxide Nanoparticles for Electrospinning

Nanocomposites based on poly(lactic acid) (PLA) with antibacterial properties are of great potential interest as food packaging biomaterials. The investigations carried out in this study include the rheological properties of PLA/ZnO nanoparticles solutions used in the electrospinning of nanofibrous mats and the morphological evaluation of the mats. A detailed rheological analysis of the solutions used for electrospinning was carried out to understand the achieved morphology and structure of nanofibers (NFs). The effect of ZnO nanoparticles (ZnO-NPs) was investigated for various PLA solutions and solvents. The polymer solutions were prepared at various loading levels of ZnO: 0.4, 0.8, 1, 3 and 5 wt% relative to the polymer. Two solvent systems were used: 2,2,2-trifluoroethanol (TFE) and a mixture of dichloromethane/trifluoroethanol (DCM/TFE) (50:50 v/v). PLA with a low loading level of ZnO-NPs showed higher viscosity than neat PLA solutions. They also showed a maximum value of viscosity at 3 wt% content. Solutions containing more than 3 wt% ZnO exhibited a notable decrease in viscosity, which was attributed to PLA degradation. Other nanoparticles (NPs) such as SiO{sub 2} and TiO{sub 2} showed no decrease in the solution viscosity for all concentrations. The morphological characterization of the electrospun nanofibers was performed using scanning electron microscopy (SEM). The SEM images showed a network of smooth, randomly oriented, PLA nanofibers (PLA-NFs) and ZnO agglomeration was observed on the surface of the NFs. In the case of the PLA mats produced from PLA/TFE/ZnO suspensions with decreased viscosity, the SEM results confirmed the generation of beaded-fibers.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Nanocomposites Based on Poly(lactic acid) and Bacterial Cellulose Acetylated by an α-Hydroxyacid Catalyzed Route

Poly(lactic acid) (PLA) nanocomposite films reinforced with acetylated bacterial cellulose nanoribbons were prepared by solvent casting. Acetylation of bacterial cellulose (BC) was performed by an innovative and sustainable direct solvent-free route catalyzed by citric acid. The effect of derivatization and its extent on the morphological, optical, thermal and mechanical properties of the nanocomposites was analyzed. Data collected from the above studies showed that acetylation of BC nanoribbons clearly improved the nanofibers dispersion in the PLA matrix with respect to unmodified BC, which in turn resulted in increased transparency and mechanical properties of the nanocomposites produced.

77 NANOSCIENCE AND NANOTECHNOLOGY↗