In this study,composite films consisting of polylactic acid(PLA),ethyl cellulose(EC),and zein were prepared by solution casting method,and their performance and application in chilled fresh meat preservation were inve...In this study,composite films consisting of polylactic acid(PLA),ethyl cellulose(EC),and zein were prepared by solution casting method,and their performance and application in chilled fresh meat preservation were investigated.The results showed that the three materials had satisfactory compatibility in the composite film.Addition of EC and zein effectively improved the mechanical properties,thermodynamic properties,surface hydrophilicity,oxygen permeability,and degradation properties of PLA films.When the ratio of PLA to EC was 3:7,the tensile strength and elongation at break reached maximum values of 16.6 MPa and 30.5%,respectively.Moreover,under different conditions,the composite film exhibited better degradability than the PLA film.The composite film with a 3:7 ratio of PLA to EC had the best performance,with a degradation rate of 21.75%after 84 days.Chilled fresh meat wrapped with the composite film showed significantly improved antioxidant,antibacterial,and water-holding properties.展开更多
Polylactic acid(PLA),a biodegradable polymer,exhibits superior mechanical strength and processability.However,its broader adoption is hindered by inherent brittleness,low hydrophilicity,and sluggish crystallization ki...Polylactic acid(PLA),a biodegradable polymer,exhibits superior mechanical strength and processability.However,its broader adoption is hindered by inherent brittleness,low hydrophilicity,and sluggish crystallization kinetics.Chitosan(CS),a natural polysaccharide renowned for its biocompatibility and biodegradability,offers potential to address these limitations.While both materials have garnered significant attention in materials science,research on their integration via melt blending and the resulting performance enhancements for food-contact plastics remains understudied.This research comprehensively explores how different levels of CS content,from 0% to 10%,impact the characteristics of chitosan/polylactic acid(CS/PLA)composites.It specifically analyzes the influence of various CS concentrations on the mechanical attributes,crystallization behavior,thermomechanical properties,and rheological performance of these composites.The study concludes that a CS content of 4% in the CS/PLA composite results in the best overall properties.At this point,its elongation at break and impact strength reached theirmaximum values(16.16% and 20.63 kJ/m^(2)),representing increases of 23.9% and 15.7% compared to pure PLA.At this particular concentration,CS is evenly distributed throughout the PLA matrix,acting as a heterogeneous nucleating agent.It facilitates the crystallization of the composite material and offers effective reinforcement.This study presents a promising approach for developing environmentally friendly and sustainable alternatives to fossil-based plastics,highlighting significant research value and practical application potential.展开更多
An innovative microcrystalline cellulose(MCC)natural fibre powder-reinforced PLA biocomposite was investigated using the hand lay-up technique.The polymer matrix composite(PMC)samples were prepared by varying the weig...An innovative microcrystalline cellulose(MCC)natural fibre powder-reinforced PLA biocomposite was investigated using the hand lay-up technique.The polymer matrix composite(PMC)samples were prepared by varying the weight percentages(wt.%)of both PLA matrix and MCC reinforcement:pure PLA/100:0,90:10,80:20,70:30,60:40 and 50:50 wt.%,respectively.From the results obtained,MCC powder,with its impressive aspect ratio,proved to be an ideal reinforcement for the PLA,exhibiting exceptional mechanical properties.It was evident that the 80:20 wt.%biocomposite sample exhibited the maximum improvement in the tensile,flexural,notched impact,compressive strength and hardness by 28.85%,20.00%,91.66%,21.53%and 35.82%,respectively compared to the pure PLA sample.Similarly,during the thermogravimetric analysis(TGA),the same 80:20 wt.%biocomposite sample showed a minimum weight loss of 20%at 400℃,among others.The morphological study using Field Emission Scanning Electron Microscopy(FE-SEM)revealed that the uniform distribution of cellulose reinforcement in the PLA matrix actively improved the mechanical properties of the biocomposites,especially the optimal 80:20 wt.%sample.Importantly,it was evident that the optimal PLA/cellulose biocomposite sample could be a suitable and alternative sustainable,environmentally friendly and biodegradable material for semi/structural applications,replacing synthetic and traditional components.展开更多
Polylactic acid(PLA)is a potential polymer material used as a substitute for traditional plastics,and the accurate molecular weight distribution range of PLA is strictly required in practical applications.Therefore,ex...Polylactic acid(PLA)is a potential polymer material used as a substitute for traditional plastics,and the accurate molecular weight distribution range of PLA is strictly required in practical applications.Therefore,exploring the relationship between synthetic conditions and PLA molecular weight is crucially important.In this work,direct polycondensation combined with overlay sampling uniform design(OSUD)was applied to synthesize the low molecular weight PLA.Then a multiple regression model and two artificial neural network models on PLA molecular weight versus reaction temperature,reaction time,and catalyst dosage were developed for PLA molecular weight prediction.The characterization results indicated that the low molecular weight PLA was efficiently synthesized under this method.Meanwhile,the experimental dataset acquired from OSUD successfully established three predictive models for PLA molecular weight.Among them,both artificial neural network models had significantly better predictive performance than the regression model.Notably,the radial basis function neural network model had the best predictive accuracy with only 11.9%of mean relative error on the validation dataset,which improved by 67.7%compared with the traditional multiple regression model.This work successfully predicted PLA molecular weight in a direct polycondensation process using artificial neural network models combined with OSUD,which provided guidance for the future implementation of molecular weight-controlled polymer's synthesis.展开更多
The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by b...The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by braiding PLA filaments with 4 to 24 spindles on flax yarns.After curing at different temperatures(180℃and 190℃),the core/sheath structural flax/PLA composite yarns were manufactured.According to the results of the tensile test,the flax/PLA composite yarn with 4-spindle PLA yarns as a sheath layer and at a curing temperature of 180℃reached the maximum elastic modulus of about(5.79±0.65)GPa and the maximum tensile strength of about(162.17±18.18)MPa.This flax/PLA composite yarn with good mechanical properties would be suitable for green composites in the automobile manufacturing industry and building materials.展开更多
Flexible supercapacitors with high mechanical strength,excellent flexibility,and high performance are highly desired to meet the increasing demands of flexible electronics.However,the trade-offbetween mechanical and e...Flexible supercapacitors with high mechanical strength,excellent flexibility,and high performance are highly desired to meet the increasing demands of flexible electronics.However,the trade-offbetween mechanical and electrochemical properties remains challenging.In this context,an interface-engineered strategy approach was proposed to construct polylactic acid(PLA)/polyaniline(PANI)/MXene(PPM)film electrodes for flexible supercapacitor applications.In the PPM electrode,the porous PLA prepared from the nonsolvent-induced-phase-separation method served as an ideal flexible substrate,providing excel-lent flexibility and high mechanical strength,whereas PANI as the coupling agent,enhanced the interfa-cial strength between PLA and the electroactive MXene that was firmly anchored and deposited on PLA through a facile layer-by-layer dip coating method.The tensile strength at break,elongation at break,and toughness of PPM are 53.09 MPa,11.09%,and 4.12 MJ/m^(3),respectively,much higher than those of pure MXene(29.36 MPa,4.62%,and 0.75 MJ/m^(3)).At an optimum mass loading density of 3 mg cm−2 for MXene,the fabricated PPM3 film electrode achieved a high specific capacitance of 290.8 F g^(−1)at a cur-rent density of 1 A g^(−1)in the three-electrode setup,approximately 1.5 times that of 190.8 F g^(−1)for pure MXene.Meanwhile,the symmetric all-solid-state supercapacitor based on PPM3 film electrodes delivers a high specific capacitance of 193.7 F g^(−1)at a current density of 0.25 A g^(−1),with a corresponding high energy density of 9.3 Wh kg^(−1)at a power density of 291.3 W kg^(−1).The SC retains 86%of its original ca-pacitance even bent at 120°and also possesses an excellent fire-retardant ability,demonstrating its great potential for flexible and safe wearable electronics.展开更多
Aim Ciprofloxacin polylactic acid microspheres (CFX-PLA-MS) were preparedusing solvent evaporation method from a solid-in-oil-in-water emulsion system. Methods Orthogonalexperiment was used to optimize the method of C...Aim Ciprofloxacin polylactic acid microspheres (CFX-PLA-MS) were preparedusing solvent evaporation method from a solid-in-oil-in-water emulsion system. Methods Orthogonalexperiment was used to optimize the method of CFX-PLA-MS preparation. Microspheres werecharacterized in terms of morphology, size, encapsulation efficiency, drug loading and in vitro drugrelease. Results The physical state of CFX-PLA-MS was determined by scanning electron microscopy(SEM) and differential scanning calorimetry (DSC) . Microspheres formed were spherical with smoothsurfaces. Drug was enveloped in microspheres without mixing physically with PLA. The averageparticle size was 280.80 ± 0.15 μm, with over 90% of microspheres falling in the range of 250 -390 μm. The encapsulation efficiency was 65.8% ± 0.58% and the drug loading was 34.1% ± 0.51% .In vitro release study revealed a profile of sustained release of Ciprofloxacin from CFX-PLA-MS. Theaccumulated release percentage and half-life (T_(1/2) of Ciprofloxacin microspheres were 84.0% in53.2 h, and 31.9 h, respectively. Higuchi equation was Q= -0.0043 + 0.003 9 t^(1/2), r = 0.9941.Conclusion Ciprofloxacin microspheres have been successfully prepared and sustained release of CFXfrom microspheres is achieved.展开更多
The effects of adding poly （ethylene glycol） （PEG） into polylactic acid/thermoplastic starch blends （PLA/TPS） on the properties were investigated by DSC, SEM and mechanical property-testing. The blends of PLA/TP...The effects of adding poly （ethylene glycol） （PEG） into polylactic acid/thermoplastic starch blends （PLA/TPS） on the properties were investigated by DSC, SEM and mechanical property-testing. The blends of PLA/TPS blended with increasing content PEG exhibited lower temperature of glass transition （T） and lower temperature of melting （T） as well as higher melt flow index （MFI）, which indicates the plasticization and proeessability of the composites were dramatically improved. The tensile strength, flexural strength and izod impact strength of PLA/TPS （80/20） increased at first and then decreased with increasing content of PEG due to stronger interfacial adhesion. The optimized mechanical property can be obtained for the blend with 3 wt % PEG. The samples containing PEG after soil burial for 5 months showed quicker degradation being accompanied with large weight loss and mechanical properties loss.展开更多
Starch/polylactic acid(PLA) composites were prepared by melt extrusion, with corn starch and PLA as raw materials, glycerol as the plasticizer. Effects of starch/PLA ratio on the interdependence of two-phase and other...Starch/polylactic acid(PLA) composites were prepared by melt extrusion, with corn starch and PLA as raw materials, glycerol as the plasticizer. Effects of starch/PLA ratio on the interdependence of two-phase and other properties of the composites were studied. The combination of results of TGA with SEM indicated that the interdependence between starch and PLA was increased gradually as the starch/PLA ratio reduced. DSC results showed that the glass transition temperature(Tg), melting temperature(Tm) and degree of crystallinity of PLA in composites were increased gradually, whereas the cold crystallization temperature(Tc) was gradually decreased as the starch/PLA ratio reduced. The rheological properties of composites were closely related with the interdependence of two-phase, with reducing starch/PLA proportion, the interdependence was increased, and then the strain for storage modulus was firstl reduced and then gradually increased. Frequency scanning showed that the storage modulus and complex viscosity were decreased with reducing starch content. As the starch/PLA ratio reduced, the matrix phase PLA was increased, so that the strength of composites was increased gradually, whereas water absorption rate was decreased gradually.展开更多
Thermal decomposition of polylactic acid （PLA） was studied in the presence of pine wood sawdust （PS）, walnut shell （WS）, corncob （CC） in order to understand the pyrolytic behavior of these components occurring...Thermal decomposition of polylactic acid （PLA） was studied in the presence of pine wood sawdust （PS）, walnut shell （WS）, corncob （CC） in order to understand the pyrolytic behavior of these components occurring in waste. A thermogravimetric analyzer （TGA） was applied for monitoring the mass loss profiles under heating rate of 10℃·min^-1. Results obtained from this comprehensive investigation indicated that PLA was decomposed in the temperature range 300 -372℃, whereas the thermal degradation temperature of biomass is 183-462℃. The difference of mass loss （AW） between experimental and theoretical ones, calculated as algebraic sums of those from each separated component, is about 17%-46% at 300-400℃. These experimental results indicated a significant synergistic effect during PLA and biomass copyrolysis. Moreover, a kinetic analysis was performed to fit thermogravimetric data, the global processes being considered as one to two consecutive reactions. A reasonable fit to the experimental data was obtained for all materials and their blends.展开更多
High-performance liquid chromatography （HPLC） was employed to determine drug release rates based on emamectin benzoate concentrations in the medium. Release kinetics equations were used to fit the drug release behav...High-performance liquid chromatography （HPLC） was employed to determine drug release rates based on emamectin benzoate concentrations in the medium. Release kinetics equations were used to fit the drug release behavior. The effects of particle size and release medium pH on the release rate were also investigated. The indoor toxicity of emamectin benzoate-loaded polylactic acid microspheres on the diamondback moth larva （Plutella xylostella） was studied to explore drug sustained-release performance. In acidic and neutral media, the drug release behavior of the microspheres was in accord with the first-order kinetics equation. Increasing the spray dosage of emamectin benzoate-loaded polylactic acid microspheres initially resulted in an equivalent insecticidal efficacy with the conventional emamectin benzoate microemulsion. However, the drug persistence period was four-fold longer than that observed using the conventional formulation. The developed emamectin benzoate-loaded polylactic acid microspheres showed dramatic sustained-release performance. A treatment threshold of greater than 35 mg mL-1 was established for an efficient accumulated release concentration of emamectin benzoate-loaded microspheres.展开更多
Biodegradable polymers are highly attractive as potential alternatives to petroleum-based polymers in an attempt to achieve carbon neutrality whilst maintaining the mechanical properties of the structures.Among these ...Biodegradable polymers are highly attractive as potential alternatives to petroleum-based polymers in an attempt to achieve carbon neutrality whilst maintaining the mechanical properties of the structures.Among these polymers,polylactic acid(PLA)is particularly promising due to its good mechanical properties,biocompatibility and thermoplasticity.In this work,we aim to enhance the mechanical properties of PLA using mechanically-defibrated cellulose nanofibers(CNFs)that exhibit remarkable mechanical properties and biodegradability.We also employ fused deposition modeling(FDM),one of the three-dimensional printing methods for thermoplastic polymers,for the low-cost fabrication of the products.Mechanically-defibrated CNF-reinforced PLA matrix composites are fabricated by FDM.Their tensile properties are investigated in two printing directions(0°/90°and+45°/-45°).The discussion about the relationship between printing direction and tensile behavoir of mechanically-defibrated CNF-reinforced PLA matrix composite is the unique point of this study.We further discuss the microstructure and fracture surface of mechanically-defibrated CNF-reinforced PLA matrix composite by scanning electron microscope.展开更多
In this work, blank polylactic acid （PLA） nanoparticles with unstained surface were prepared by the nano-deposition method. On the basis of the preparation, the effect of surface modification on brain microvascular ...In this work, blank polylactic acid （PLA） nanoparticles with unstained surface were prepared by the nano-deposition method. On the basis of the preparation, the effect of surface modification on brain microvascular endothelial cells （BMECs） targeting was examined by in vivo experiments and fluorescence microscopy. The results showed that PLA nanoparticles are less toxic than PACA nanoparticles but their BMECs targeting is similar to PACA nanoparticles. The experiments suggest that drugs can he loaded onto the particles and become more stable through adsorption on the surface of PLA nanoparticles with high surface activity. The surface of PLA nanoparticles was obviously modified and the hydrophilicity was increased as well in the presence of non-ionic surfactants on PLA nanoparticles. As a targeting moiety, polysobate 80 （T-80） can facilitate BMECs targeting of PLA nanoparticles.展开更多
Esterified starch/polylactic acid（ES/PLA） blending composite was prepared by melting extrusion with maleic anhydride esterified starch and PLA as the raw materials. The composite was accelerated aging by using UV ag...Esterified starch/polylactic acid（ES/PLA） blending composite was prepared by melting extrusion with maleic anhydride esterified starch and PLA as the raw materials. The composite was accelerated aging by using UV aging box, and its properties were characterized by Fourier transform infrared spectroscopy（FT-IR）, scanning electron microscopy（SEM）, X-ray diffraction（XRD）, thermo gravimetric analysis（TGA） and mechanical testing machine. FT-IR and SEM results show that the infrared absorption peak intensities of C-O, C-H, and C=O in aged samples decrease gradually with increasing aging time. The damage degree of surface and internal of aged samples increases gradually. XRD analysis results show that after aging treatment, the crystalline diffraction peak of thermoplastic esterified starch at 2θ = 21° disappears and the diffraction peaks of PLA at 2θ = 16.5° appear, indicating that the hydrolysis rate of esterified starch is greater than that of PLA. The crystallinity of PLA in aged sample shows an increasing trend at first followed by a decreasing one along with the increasing time of aging treatment, suggesting that the hydrolysis of amorphous regions of PLA is more preferential than its crystalline regions. Because of the influence of crystal structure and the change of composition structure, the initial decomposition temperature of aging test specimen gradually increases with the extension of aging time. The maximum decomposition rate temperature and residual mass increases at first, and then decrease after the aging time extending to 1600 h. As the aging time increases, the damage degree of combination interface between esterification starch and PLA is exacerbated, resulting in the tensile strength and bending strength of aged specimen decreasing gradually.展开更多
Microfibrillated cellulose(MFC)is often added to polylactic acid(PLA)matrixes as a reinforcing filler to obtain fully-biodegradable composites with improved mechanical properties.However,the incompatibility between MF...Microfibrillated cellulose(MFC)is often added to polylactic acid(PLA)matrixes as a reinforcing filler to obtain fully-biodegradable composites with improved mechanical properties.However,the incompatibility between MFC and the PLA matrix limits the mechanical performance of MFC-reinforced PLA composites.In this paper,DL-lactic acid-grafted-MFC(MFC-g-DL)was used to improve the compatibility with PLA.Reinforced composites were prepared by melt extrusion and hot-cold pressing.The tensile strength of the PLA/MFC-g-DL composite increased by 22.1%compared with that of PLA after adding 1%MFC-g-DL.Scanning electron microscopy(SEM),differential scanning calorimetry(DSC),and dynamic thermomechanical analysis(DMA)were used to explore the enhancement mechanism.The energy dissipation in the MFC network and the improved compatibility between PLA and MFC-g-DL played important roles in the reinforcement.The SEM results showed that there was a closer combination between PLA and MFC-g-DL.The DSC results showed that the addition of cellulose changed the glass transition temperature,melting temperature,and crystallization temperature of PLA.The TG results showed that the initial and maximum decomposition temperature were lower than those of PLA.The ultraviolet spectra showed that the composite had good transparency at a low concentration of MFC-g-DL.展开更多
Polylactic acid(PLA)possesses good mechanical and biodegradability properties which make it a suitable material for polymer composites whereas brittleness and high costs limit its utilization in various applications.T...Polylactic acid(PLA)possesses good mechanical and biodegradability properties which make it a suitable material for polymer composites whereas brittleness and high costs limit its utilization in various applications.The reinforcement of natural fibres with biopolymers has been formed to be an efficient technique to develop composites having the ability to be fully biodegradable.This study concerns with the incorporation of various percentages of untreated and alkali-treated Coir Fibres(CF)and pineapple leaf fibres(PALF)in PLA biocomposites and characterizations of flexural,morphological and dynamic mechanical properties.Flexural properties showed that the treated C1P1 hybrid composites(C1P1A)displayed highest flexural strength(35.81 MPa)and modulus(5.28 GPa)among all hybrid biocomposites.Scanning Electron Microscopy(SEM)revealed a behaviour of fibre-matrix adhesion in untreated treated biocomposites.SEM observation revealed good dispersion of the fillers in PLA.Dynamic mechanical analysis revealed that C1P1A showed highest glass transition temperature(Tg)and storage modulus(E')while untreated C3P7 displayed the least Tg and E'.Overall findings showed that alkali-treated hybrid biocomposites(CF/PALF/PLA)especially C1P1A have improved flexural properties,dynamic and morphological properties over untreated biocomposites.Success of these findings will provide attracting consideration of these hybrid biocomposites for various lightweight uses in a broad selection of industrial applications such as biomedical sectors,automobile,construction,electronics equipment,and hardware tools.展开更多
Lanthanum(La)has tremendous potential in the treatment and prevention of bone diseases especially osteoporosis and metabolic disorders.However,controlling its distribution and keeping the release of La^(3+)ions sustai...Lanthanum(La)has tremendous potential in the treatment and prevention of bone diseases especially osteoporosis and metabolic disorders.However,controlling its distribution and keeping the release of La^(3+)ions sustained and steady in the body is still a big challenge.In this study,we prepared La-OCP powders via co-precipitation method,and further prepared La-OCP/PLA porous scaffolds by 3 D printing.La^(3+)was successfully introduced into the OCP crystal structure and substituted Ca^(2+)at the Ca-5 and Ca-8 sites.In particular,some La^(3+)ions were deposited on the crystal surface in the form of nanoparticles.Both octacalcium phosphate(OCP,Ca_(8)H_(2)(PO_(4))_6·5 H_(2)O)crystals and nanoparticles played as the carriers for La^(3+)ions.The La-OCP/PLA scaffolds displayed obvious mineralization effects and sustained release of La^(3+).The scaffolds contained a uniform structure with rough micro surface topography which acted as a suitable pathway for BMSCs cells to adhere,grow and proliferation.At a certain La^(3+)concentration,the extracts from La-OCP/PLA scaffolds increased the expression of osteogenesis-related genes,thus promoting the osteogenic differentiation of BMSCs.Moreover,the extracts regulated the immune responses.The experiment in vivo proved that La-OCP/PLA porous scaffolds were safe and could enhance bone defect regeneration in vivo.These findings suggest that 3 D printed La-OCP/PLA porous scaffolds have promising potentials in bone tissue engineering.展开更多
文摘In this study,composite films consisting of polylactic acid(PLA),ethyl cellulose(EC),and zein were prepared by solution casting method,and their performance and application in chilled fresh meat preservation were investigated.The results showed that the three materials had satisfactory compatibility in the composite film.Addition of EC and zein effectively improved the mechanical properties,thermodynamic properties,surface hydrophilicity,oxygen permeability,and degradation properties of PLA films.When the ratio of PLA to EC was 3:7,the tensile strength and elongation at break reached maximum values of 16.6 MPa and 30.5%,respectively.Moreover,under different conditions,the composite film exhibited better degradability than the PLA film.The composite film with a 3:7 ratio of PLA to EC had the best performance,with a degradation rate of 21.75%after 84 days.Chilled fresh meat wrapped with the composite film showed significantly improved antioxidant,antibacterial,and water-holding properties.
基金funded by National Natural Science Foundation of China(NSFC),grant number(No.U2341237).
文摘Polylactic acid(PLA),a biodegradable polymer,exhibits superior mechanical strength and processability.However,its broader adoption is hindered by inherent brittleness,low hydrophilicity,and sluggish crystallization kinetics.Chitosan(CS),a natural polysaccharide renowned for its biocompatibility and biodegradability,offers potential to address these limitations.While both materials have garnered significant attention in materials science,research on their integration via melt blending and the resulting performance enhancements for food-contact plastics remains understudied.This research comprehensively explores how different levels of CS content,from 0% to 10%,impact the characteristics of chitosan/polylactic acid(CS/PLA)composites.It specifically analyzes the influence of various CS concentrations on the mechanical attributes,crystallization behavior,thermomechanical properties,and rheological performance of these composites.The study concludes that a CS content of 4% in the CS/PLA composite results in the best overall properties.At this point,its elongation at break and impact strength reached theirmaximum values(16.16% and 20.63 kJ/m^(2)),representing increases of 23.9% and 15.7% compared to pure PLA.At this particular concentration,CS is evenly distributed throughout the PLA matrix,acting as a heterogeneous nucleating agent.It facilitates the crystallization of the composite material and offers effective reinforcement.This study presents a promising approach for developing environmentally friendly and sustainable alternatives to fossil-based plastics,highlighting significant research value and practical application potential.
基金funding from Researchers Supporting Project Number(RSP2024R355),King Saud University,Riyadh,Saudi Arabia.
文摘An innovative microcrystalline cellulose(MCC)natural fibre powder-reinforced PLA biocomposite was investigated using the hand lay-up technique.The polymer matrix composite(PMC)samples were prepared by varying the weight percentages(wt.%)of both PLA matrix and MCC reinforcement:pure PLA/100:0,90:10,80:20,70:30,60:40 and 50:50 wt.%,respectively.From the results obtained,MCC powder,with its impressive aspect ratio,proved to be an ideal reinforcement for the PLA,exhibiting exceptional mechanical properties.It was evident that the 80:20 wt.%biocomposite sample exhibited the maximum improvement in the tensile,flexural,notched impact,compressive strength and hardness by 28.85%,20.00%,91.66%,21.53%and 35.82%,respectively compared to the pure PLA sample.Similarly,during the thermogravimetric analysis(TGA),the same 80:20 wt.%biocomposite sample showed a minimum weight loss of 20%at 400℃,among others.The morphological study using Field Emission Scanning Electron Microscopy(FE-SEM)revealed that the uniform distribution of cellulose reinforcement in the PLA matrix actively improved the mechanical properties of the biocomposites,especially the optimal 80:20 wt.%sample.Importantly,it was evident that the optimal PLA/cellulose biocomposite sample could be a suitable and alternative sustainable,environmentally friendly and biodegradable material for semi/structural applications,replacing synthetic and traditional components.
基金funded by the Zhejiang Provincial Natural Science Foundation of China(LD21B060001)the National Natural Science Foundation of China(22078296,21576240).
文摘Polylactic acid(PLA)is a potential polymer material used as a substitute for traditional plastics,and the accurate molecular weight distribution range of PLA is strictly required in practical applications.Therefore,exploring the relationship between synthetic conditions and PLA molecular weight is crucially important.In this work,direct polycondensation combined with overlay sampling uniform design(OSUD)was applied to synthesize the low molecular weight PLA.Then a multiple regression model and two artificial neural network models on PLA molecular weight versus reaction temperature,reaction time,and catalyst dosage were developed for PLA molecular weight prediction.The characterization results indicated that the low molecular weight PLA was efficiently synthesized under this method.Meanwhile,the experimental dataset acquired from OSUD successfully established three predictive models for PLA molecular weight.Among them,both artificial neural network models had significantly better predictive performance than the regression model.Notably,the radial basis function neural network model had the best predictive accuracy with only 11.9%of mean relative error on the validation dataset,which improved by 67.7%compared with the traditional multiple regression model.This work successfully predicted PLA molecular weight in a direct polycondensation process using artificial neural network models combined with OSUD,which provided guidance for the future implementation of molecular weight-controlled polymer's synthesis.
基金National Natural Science Foundation of China(No.52273054)Shanghai Natural Science Foundation,China(No.20ZR1402200)。
文摘The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by braiding PLA filaments with 4 to 24 spindles on flax yarns.After curing at different temperatures(180℃and 190℃),the core/sheath structural flax/PLA composite yarns were manufactured.According to the results of the tensile test,the flax/PLA composite yarn with 4-spindle PLA yarns as a sheath layer and at a curing temperature of 180℃reached the maximum elastic modulus of about(5.79±0.65)GPa and the maximum tensile strength of about(162.17±18.18)MPa.This flax/PLA composite yarn with good mechanical properties would be suitable for green composites in the automobile manufacturing industry and building materials.
基金supported by the Young Elite Scien-tists Sponsorship Program by Tianjin(No.TJSQNTJ-2018-03)the Deanship of Scientific Re-search at Northern Border University,Arar,KSA for funding this re-search work through the project number NBU-FPEJ-2024-2605-01.
文摘Flexible supercapacitors with high mechanical strength,excellent flexibility,and high performance are highly desired to meet the increasing demands of flexible electronics.However,the trade-offbetween mechanical and electrochemical properties remains challenging.In this context,an interface-engineered strategy approach was proposed to construct polylactic acid(PLA)/polyaniline(PANI)/MXene(PPM)film electrodes for flexible supercapacitor applications.In the PPM electrode,the porous PLA prepared from the nonsolvent-induced-phase-separation method served as an ideal flexible substrate,providing excel-lent flexibility and high mechanical strength,whereas PANI as the coupling agent,enhanced the interfa-cial strength between PLA and the electroactive MXene that was firmly anchored and deposited on PLA through a facile layer-by-layer dip coating method.The tensile strength at break,elongation at break,and toughness of PPM are 53.09 MPa,11.09%,and 4.12 MJ/m^(3),respectively,much higher than those of pure MXene(29.36 MPa,4.62%,and 0.75 MJ/m^(3)).At an optimum mass loading density of 3 mg cm−2 for MXene,the fabricated PPM3 film electrode achieved a high specific capacitance of 290.8 F g^(−1)at a cur-rent density of 1 A g^(−1)in the three-electrode setup,approximately 1.5 times that of 190.8 F g^(−1)for pure MXene.Meanwhile,the symmetric all-solid-state supercapacitor based on PPM3 film electrodes delivers a high specific capacitance of 193.7 F g^(−1)at a current density of 0.25 A g^(−1),with a corresponding high energy density of 9.3 Wh kg^(−1)at a power density of 291.3 W kg^(−1).The SC retains 86%of its original ca-pacitance even bent at 120°and also possesses an excellent fire-retardant ability,demonstrating its great potential for flexible and safe wearable electronics.
基金National Natural Science Foundation of Guangdong Province (020885,980504).
文摘Aim Ciprofloxacin polylactic acid microspheres (CFX-PLA-MS) were preparedusing solvent evaporation method from a solid-in-oil-in-water emulsion system. Methods Orthogonalexperiment was used to optimize the method of CFX-PLA-MS preparation. Microspheres werecharacterized in terms of morphology, size, encapsulation efficiency, drug loading and in vitro drugrelease. Results The physical state of CFX-PLA-MS was determined by scanning electron microscopy(SEM) and differential scanning calorimetry (DSC) . Microspheres formed were spherical with smoothsurfaces. Drug was enveloped in microspheres without mixing physically with PLA. The averageparticle size was 280.80 ± 0.15 μm, with over 90% of microspheres falling in the range of 250 -390 μm. The encapsulation efficiency was 65.8% ± 0.58% and the drug loading was 34.1% ± 0.51% .In vitro release study revealed a profile of sustained release of Ciprofloxacin from CFX-PLA-MS. Theaccumulated release percentage and half-life (T_(1/2) of Ciprofloxacin microspheres were 84.0% in53.2 h, and 31.9 h, respectively. Higuchi equation was Q= -0.0043 + 0.003 9 t^(1/2), r = 0.9941.Conclusion Ciprofloxacin microspheres have been successfully prepared and sustained release of CFXfrom microspheres is achieved.
文摘The effects of adding poly （ethylene glycol） （PEG） into polylactic acid/thermoplastic starch blends （PLA/TPS） on the properties were investigated by DSC, SEM and mechanical property-testing. The blends of PLA/TPS blended with increasing content PEG exhibited lower temperature of glass transition （T） and lower temperature of melting （T） as well as higher melt flow index （MFI）, which indicates the plasticization and proeessability of the composites were dramatically improved. The tensile strength, flexural strength and izod impact strength of PLA/TPS （80/20） increased at first and then decreased with increasing content of PEG due to stronger interfacial adhesion. The optimized mechanical property can be obtained for the blend with 3 wt % PEG. The samples containing PEG after soil burial for 5 months showed quicker degradation being accompanied with large weight loss and mechanical properties loss.
基金Funded by the National Forestry Public Welfare Industry Major Projects of Scientific Research(No.201504502)National Natural Science Foundation of China(No.31200442)Supported by the Post Doctorate Research from the Ministry of Science and Technology of China(No.2014M550178)
文摘Starch/polylactic acid(PLA) composites were prepared by melt extrusion, with corn starch and PLA as raw materials, glycerol as the plasticizer. Effects of starch/PLA ratio on the interdependence of two-phase and other properties of the composites were studied. The combination of results of TGA with SEM indicated that the interdependence between starch and PLA was increased gradually as the starch/PLA ratio reduced. DSC results showed that the glass transition temperature(Tg), melting temperature(Tm) and degree of crystallinity of PLA in composites were increased gradually, whereas the cold crystallization temperature(Tc) was gradually decreased as the starch/PLA ratio reduced. The rheological properties of composites were closely related with the interdependence of two-phase, with reducing starch/PLA proportion, the interdependence was increased, and then the strain for storage modulus was firstl reduced and then gradually increased. Frequency scanning showed that the storage modulus and complex viscosity were decreased with reducing starch content. As the starch/PLA ratio reduced, the matrix phase PLA was increased, so that the strength of composites was increased gradually, whereas water absorption rate was decreased gradually.
文摘Thermal decomposition of polylactic acid （PLA） was studied in the presence of pine wood sawdust （PS）, walnut shell （WS）, corncob （CC） in order to understand the pyrolytic behavior of these components occurring in waste. A thermogravimetric analyzer （TGA） was applied for monitoring the mass loss profiles under heating rate of 10℃·min^-1. Results obtained from this comprehensive investigation indicated that PLA was decomposed in the temperature range 300 -372℃, whereas the thermal degradation temperature of biomass is 183-462℃. The difference of mass loss （AW） between experimental and theoretical ones, calculated as algebraic sums of those from each separated component, is about 17%-46% at 300-400℃. These experimental results indicated a significant synergistic effect during PLA and biomass copyrolysis. Moreover, a kinetic analysis was performed to fit thermogravimetric data, the global processes being considered as one to two consecutive reactions. A reasonable fit to the experimental data was obtained for all materials and their blends.
基金supported by the National Key Research and Development Program of China (2016YFD0200502, 2017YFD0200301)
文摘High-performance liquid chromatography （HPLC） was employed to determine drug release rates based on emamectin benzoate concentrations in the medium. Release kinetics equations were used to fit the drug release behavior. The effects of particle size and release medium pH on the release rate were also investigated. The indoor toxicity of emamectin benzoate-loaded polylactic acid microspheres on the diamondback moth larva （Plutella xylostella） was studied to explore drug sustained-release performance. In acidic and neutral media, the drug release behavior of the microspheres was in accord with the first-order kinetics equation. Increasing the spray dosage of emamectin benzoate-loaded polylactic acid microspheres initially resulted in an equivalent insecticidal efficacy with the conventional emamectin benzoate microemulsion. However, the drug persistence period was four-fold longer than that observed using the conventional formulation. The developed emamectin benzoate-loaded polylactic acid microspheres showed dramatic sustained-release performance. A treatment threshold of greater than 35 mg mL-1 was established for an efficient accumulated release concentration of emamectin benzoate-loaded microspheres.
基金supported by the Program for Creation of Interdisciplinary Research and Ensemble Program of Frontier Research Institute for Interdisciplinary Sciences,Tohoku University。
文摘Biodegradable polymers are highly attractive as potential alternatives to petroleum-based polymers in an attempt to achieve carbon neutrality whilst maintaining the mechanical properties of the structures.Among these polymers,polylactic acid(PLA)is particularly promising due to its good mechanical properties,biocompatibility and thermoplasticity.In this work,we aim to enhance the mechanical properties of PLA using mechanically-defibrated cellulose nanofibers(CNFs)that exhibit remarkable mechanical properties and biodegradability.We also employ fused deposition modeling(FDM),one of the three-dimensional printing methods for thermoplastic polymers,for the low-cost fabrication of the products.Mechanically-defibrated CNF-reinforced PLA matrix composites are fabricated by FDM.Their tensile properties are investigated in two printing directions(0°/90°and+45°/-45°).The discussion about the relationship between printing direction and tensile behavoir of mechanically-defibrated CNF-reinforced PLA matrix composite is the unique point of this study.We further discuss the microstructure and fracture surface of mechanically-defibrated CNF-reinforced PLA matrix composite by scanning electron microscope.
文摘In this work, blank polylactic acid （PLA） nanoparticles with unstained surface were prepared by the nano-deposition method. On the basis of the preparation, the effect of surface modification on brain microvascular endothelial cells （BMECs） targeting was examined by in vivo experiments and fluorescence microscopy. The results showed that PLA nanoparticles are less toxic than PACA nanoparticles but their BMECs targeting is similar to PACA nanoparticles. The experiments suggest that drugs can he loaded onto the particles and become more stable through adsorption on the surface of PLA nanoparticles with high surface activity. The surface of PLA nanoparticles was obviously modified and the hydrophilicity was increased as well in the presence of non-ionic surfactants on PLA nanoparticles. As a targeting moiety, polysobate 80 （T-80） can facilitate BMECs targeting of PLA nanoparticles.
基金Funded by the Key Laboratory of Bio-based Material Science&Technology(Northeast Forestry University)Ministry of Education(SWZCL2016-04)+1 种基金the Scientific Research Project of Hunan Provincial Education Department(15C1428)the State Bureau of Forestry 948 Project(2009-4-51)
文摘Esterified starch/polylactic acid（ES/PLA） blending composite was prepared by melting extrusion with maleic anhydride esterified starch and PLA as the raw materials. The composite was accelerated aging by using UV aging box, and its properties were characterized by Fourier transform infrared spectroscopy（FT-IR）, scanning electron microscopy（SEM）, X-ray diffraction（XRD）, thermo gravimetric analysis（TGA） and mechanical testing machine. FT-IR and SEM results show that the infrared absorption peak intensities of C-O, C-H, and C=O in aged samples decrease gradually with increasing aging time. The damage degree of surface and internal of aged samples increases gradually. XRD analysis results show that after aging treatment, the crystalline diffraction peak of thermoplastic esterified starch at 2θ = 21° disappears and the diffraction peaks of PLA at 2θ = 16.5° appear, indicating that the hydrolysis rate of esterified starch is greater than that of PLA. The crystallinity of PLA in aged sample shows an increasing trend at first followed by a decreasing one along with the increasing time of aging treatment, suggesting that the hydrolysis of amorphous regions of PLA is more preferential than its crystalline regions. Because of the influence of crystal structure and the change of composition structure, the initial decomposition temperature of aging test specimen gradually increases with the extension of aging time. The maximum decomposition rate temperature and residual mass increases at first, and then decrease after the aging time extending to 1600 h. As the aging time increases, the damage degree of combination interface between esterification starch and PLA is exacerbated, resulting in the tensile strength and bending strength of aged specimen decreasing gradually.
基金the Natural Science Foundation of China(No.32071704).
文摘Microfibrillated cellulose(MFC)is often added to polylactic acid(PLA)matrixes as a reinforcing filler to obtain fully-biodegradable composites with improved mechanical properties.However,the incompatibility between MFC and the PLA matrix limits the mechanical performance of MFC-reinforced PLA composites.In this paper,DL-lactic acid-grafted-MFC(MFC-g-DL)was used to improve the compatibility with PLA.Reinforced composites were prepared by melt extrusion and hot-cold pressing.The tensile strength of the PLA/MFC-g-DL composite increased by 22.1%compared with that of PLA after adding 1%MFC-g-DL.Scanning electron microscopy(SEM),differential scanning calorimetry(DSC),and dynamic thermomechanical analysis(DMA)were used to explore the enhancement mechanism.The energy dissipation in the MFC network and the improved compatibility between PLA and MFC-g-DL played important roles in the reinforcement.The SEM results showed that there was a closer combination between PLA and MFC-g-DL.The DSC results showed that the addition of cellulose changed the glass transition temperature,melting temperature,and crystallization temperature of PLA.The TG results showed that the initial and maximum decomposition temperature were lower than those of PLA.The ultraviolet spectra showed that the composite had good transparency at a low concentration of MFC-g-DL.
基金gratitude to Institute of Tropical Forestry and Forest Products(INTROP),Universiti Putra Malaysia for supporting the funding of research through Grant No:6369108funded by Researchers Supporting Project number(RSP-2021/117),King Saud University,Riyadh,Saudi Arabia.
文摘Polylactic acid(PLA)possesses good mechanical and biodegradability properties which make it a suitable material for polymer composites whereas brittleness and high costs limit its utilization in various applications.The reinforcement of natural fibres with biopolymers has been formed to be an efficient technique to develop composites having the ability to be fully biodegradable.This study concerns with the incorporation of various percentages of untreated and alkali-treated Coir Fibres(CF)and pineapple leaf fibres(PALF)in PLA biocomposites and characterizations of flexural,morphological and dynamic mechanical properties.Flexural properties showed that the treated C1P1 hybrid composites(C1P1A)displayed highest flexural strength(35.81 MPa)and modulus(5.28 GPa)among all hybrid biocomposites.Scanning Electron Microscopy(SEM)revealed a behaviour of fibre-matrix adhesion in untreated treated biocomposites.SEM observation revealed good dispersion of the fillers in PLA.Dynamic mechanical analysis revealed that C1P1A showed highest glass transition temperature(Tg)and storage modulus(E')while untreated C3P7 displayed the least Tg and E'.Overall findings showed that alkali-treated hybrid biocomposites(CF/PALF/PLA)especially C1P1A have improved flexural properties,dynamic and morphological properties over untreated biocomposites.Success of these findings will provide attracting consideration of these hybrid biocomposites for various lightweight uses in a broad selection of industrial applications such as biomedical sectors,automobile,construction,electronics equipment,and hardware tools.
基金financially supported by the National Natural Science Foundation of China(No.82072074)the National Natural Science Foundation of China(No.51801198)+2 种基金funds of Scientific and Technological Plan of Fujian Province(No.2020Y0083)the Natural and Science Foundation of Fujian Province(No.2019I0027)the Funds of Scientific and Technological Plan of Fujian Province(No.2020L3026)。
文摘Lanthanum(La)has tremendous potential in the treatment and prevention of bone diseases especially osteoporosis and metabolic disorders.However,controlling its distribution and keeping the release of La^(3+)ions sustained and steady in the body is still a big challenge.In this study,we prepared La-OCP powders via co-precipitation method,and further prepared La-OCP/PLA porous scaffolds by 3 D printing.La^(3+)was successfully introduced into the OCP crystal structure and substituted Ca^(2+)at the Ca-5 and Ca-8 sites.In particular,some La^(3+)ions were deposited on the crystal surface in the form of nanoparticles.Both octacalcium phosphate(OCP,Ca_(8)H_(2)(PO_(4))_6·5 H_(2)O)crystals and nanoparticles played as the carriers for La^(3+)ions.The La-OCP/PLA scaffolds displayed obvious mineralization effects and sustained release of La^(3+).The scaffolds contained a uniform structure with rough micro surface topography which acted as a suitable pathway for BMSCs cells to adhere,grow and proliferation.At a certain La^(3+)concentration,the extracts from La-OCP/PLA scaffolds increased the expression of osteogenesis-related genes,thus promoting the osteogenic differentiation of BMSCs.Moreover,the extracts regulated the immune responses.The experiment in vivo proved that La-OCP/PLA porous scaffolds were safe and could enhance bone defect regeneration in vivo.These findings suggest that 3 D printed La-OCP/PLA porous scaffolds have promising potentials in bone tissue engineering.
