The present study aimed to understand the effect of dielectric barrier discharge cold plasma(DBD-CP)technology on the antimicrobial chitosan deposition and the properties enhancement of polylactic acid(PLA)films.The r...The present study aimed to understand the effect of dielectric barrier discharge cold plasma(DBD-CP)technology on the antimicrobial chitosan deposition and the properties enhancement of polylactic acid(PLA)films.The results indicated that DBD-CP was an effective method for improving the adhesion and surface hydrophilicity of PLA,facilitating the deposition of chitosan coating.This modification was attributed to the increased surface roughness,as well as the presence of polar functional groups observed through atomic force microscopy,surface free energy and Fourier transform infrared spectroscopy analysis.The study further revealed that both water resistance and mechanical properties were significantly improved after DBD-CP treatment,which was positively correlated with the amount of chitosan deposited on the PLA surfaces.Following comprehensive evaluation,the treatment at 75 W was determined as the optimal condition for enhancing the properties.Additionally,the modified film exhibited strong antimicrobial activity against Staphylococcus aureus.Consequently,the DBD-CP technology could be a promising tool for better utilization of PLA-based materials in the antibacterial food packaging industry.展开更多
At present,the clinical reconstruction of the auricle usually adopts the strategy of taking autologous costal cartilage.This method has great trauma to patients,poor plasticity and inaccurate shaping.Three-dimensional...At present,the clinical reconstruction of the auricle usually adopts the strategy of taking autologous costal cartilage.This method has great trauma to patients,poor plasticity and inaccurate shaping.Three-dimensional(3D)printing technology has made a great breakthrough in the clinical application of orthopedic implants.This study explored the combination of 3D printing and tissue engineering to precisely reconstruct the auricle.First,a polylactic acid(PLA)polymer scaffold with a precisely customized patient appearance was fabricated,and then auricle cartilage fragments were loaded into the 3D-printed porous PLA scaffold to promote auricle reconstruction.In vitro,gelatin methacrylamide(GelMA)hydrogels loaded with different sizes of rabbit ear cartilage fragments were studied to assess the regenerative activity of various autologous cartilage fragments.In vivo,rat ear cartilage fragments were placed in an accurately designed porous PLA polymer ear scaffold to promote auricle reconstruction.The results indicated that the chondrocytes in the cartilage fragments could maintain the morphological phenotype in vitro.After three months of implantation observation,it was conducive to promoting the subsequent regeneration of cartilage in vivo.The autologous cartilage fragments combined with 3D printing technology show promising potential in auricle reconstruction.展开更多
The main objective of this work was to study and develop composite materials by experiments with mixtures of synthetic(glass fiber, carbon fiber) and natural fiber(durian skin fiber) reinforcements on a polylactic aci...The main objective of this work was to study and develop composite materials by experiments with mixtures of synthetic(glass fiber, carbon fiber) and natural fiber(durian skin fiber) reinforcements on a polylactic acid(PLA) matrix composite, because of its excellent mechanical properties. Durian skin fiber(DSF) is a natural waste throughout Thailand, and an alternative to recycling is to realize its potential as a new reinforcement through mixing and the injection molding processes. The flexural strength(σ_(F)) and flexural modulus(E_(F)) of the composites from specimens showed a maximum value by content of durian skin fiber at 10 wt%, for good performance relative to particle dispersion between the matrix and the fiber, and showed a minimum value by content of durian skin fiber at 20 wt%, because the reinforcement material affects the mechanical properties in the experiments.展开更多
Petroleum-based materials,such as plastic,are characterized by adverse environmental pollution;as a result,researchers have sought alternative degradable plastics that are environmentally friendly,such as polylactic a...Petroleum-based materials,such as plastic,are characterized by adverse environmental pollution;as a result,researchers have sought alternative degradable plastics that are environmentally friendly,such as polylactic acid(PLA).PLA has shown great potential to replace petroleum-based plastics.In this study,seven different samples of unmodified Pueraria lobata root powder(PRP)with different contents(i.e.,0,5,10,15,20,25,and 30 wt%)and three different modified PRPs(i.e.,treated with NaOH,NaOH-KH-550,and Formic)were used to reinforce polylactic acid(PLA)via solution casting process.These prepared PRP/PLA composite films were characterized using SEM,FTIR,UV-visible spectra analysis,TG,DSC,weight loss measurement(wt%),and mechanical measurements.The results showed that the PRP modified with KH-550(PRPK)intensified the interaction in the interface region between the PRP and the PLA matrix,thus increasing the tensile strength(54.5 MPa),elongation at break(2.8%),and Young’s modulus(3310 MPa)of the PRPK/PLA biofilms.Contact angle measurement showed that the PRP treatments contributed to the hydrophobicity of films.The transparency of PRP-10/PLA film atλ_(800)was 11.09%,and its UVA and UVB transmittance were 3.28 and 1.16,respectively.After blending PLA with PRP,the PRP/PLA composite films exhibited excellent biodegradability.In summary,PRPK improved the mechanical properties of PLA and prevented the films from ultraviolet light,suggesting that PRPK-5/PLA film could be used as packaging materials.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
The effects of selected printing parameters on the fire properties of additively produced composites from neat polylactic acid(PLA)and wood/PLA filaments were investigated.The reaction to fire of the 3D-printed specim...The effects of selected printing parameters on the fire properties of additively produced composites from neat polylactic acid(PLA)and wood/PLA filaments were investigated.The reaction to fire of the 3D-printed specimens was tested according to the ISO 5660-1 cone calorimeter test method.The results showed that the properties of the specimens when exposed to fire were significantly affected by the incorporation of wood flour into the PLA filament.It was also interesting that PLA specimens had much better reactions to fire than the wood/PLA specimens.Time to ignition was found to be much longer in the 3D-printed PLA specimens.Although the maximal heat release rate was a little higher in the PLA than the wood/PLA specimens,the duration of HRR was longer for the wood/PLA specimens.The initial mass of the specimens was smaller in the wood/PLA composites,but during the radiant heat exposure the mass typically decreased slower than in the PLA specimens.展开更多
Polylactic acid(PLA)bioplastic is a common material used in Fused Deposition Modeling(FDM)3D printing.It is biodegradable and environmentally friendly biopolymer which made out of corn.However,it exhibits weak mechan...Polylactic acid(PLA)bioplastic is a common material used in Fused Deposition Modeling(FDM)3D printing.It is biodegradable and environmentally friendly biopolymer which made out of corn.However,it exhibits weak mechanical properties which reduced its usability as a functional prototype in a real-world application.In the present study,two PLA composites are created through coextruded with 3K carbon fibres and twisted Kevlar string(as core fibre)to form a fibre reinforced parts(FRP).The mechanical strength of printed parts was examined using ASTM D638 standard with a strain rate of 1 mm/min.It has been demonstrated that the FRPs coextruded with 3K carbon fibres had achieved significant improvement in Young’s modulus(+180.6%,9.205 GPa),ultimate tensile strength(+175.3%,103 MPa)and maximum tensile strain(+21.6%,1.833%).Although the Young’s modulus of Kevlar FRP was found to be similar to as compared to unreinforced PLA(~3.29 GPa),it has gained significant increment in terms of maximum tensile strain(+179.7%,104.64 MPa),and maximum tensile strain(+257%,5.384%).Thus,this study revealed two unique composite materials,in which the 3K carbon FRP can offer stiff and high strength structure while Kevlar FRP offers similar strength but at a higher elasticity.展开更多
In order to improve the thermal properties of polylactic acid(PLA) filament,nano-SiO_2 was applied to mix with PLA,then they were spun as composite filament by melt-spinning.The dispersion of nano SiO_2 and the frac...In order to improve the thermal properties of polylactic acid(PLA) filament,nano-SiO_2 was applied to mix with PLA,then they were spun as composite filament by melt-spinning.The dispersion of nano SiO_2 and the fracture surfaces of filaments were studied by scanning electron microscopy(SEM).The properties of composite filament,such as orientation degree,mechanical properties,and surface friction properties,were analyzed.The thermal performances of composite filament were analyzed by differential scanning calorimetry(DSC) and thermo gravimetric analysis(TGA).The results showed that the nano-SiO_2 modified by 5% KH-550 could disperse evenly and loosely in nano-scale,and 1 wt% and 3 wt% nano-SiO_2 dispersed throughout PLA evenly.As the quantity of nano-SiO_2 increased,the properties of composite filament,such as orientation degree,friction coefficient,thermal decomposition temperature,and glass transition temperature,increased more or less.The breaking tenacity increased when 1 wt% SiO_2 was added in PLA,but declined when 3 wt% SiO_2 was added.展开更多
In order to improve the thermal properties of polylactic acid( PLA) master batch,the nano-SiO2 was applied to mixing with PLA. The structure and thermal properties of the composite master batches were studied. The res...In order to improve the thermal properties of polylactic acid( PLA) master batch,the nano-SiO2 was applied to mixing with PLA. The structure and thermal properties of the composite master batches were studied. The results showed that the nano-SiO2 modified by 3% coupling agent KH-570 could be dispersed evenly in PLA in small scale. The thermal decomposition temperature of composite master batches increased by 6. 20-10. 80 ℃, the glass transition temperature increased by 0. 22-5. 16 ℃,and the heat enthalpy at the glass transition temperature increased by 0. 574-2. 437 J /g,compared with pure PLA. The composite master batch possessed superior thermal stability and heat resistance.展开更多
Seventeen disperse dyes including anthraquinone, azo, methine, nitro, and quinoline dyes were applied to dye the Polylactic Acid (PLA) yarns at different conditions, and the dyebath exhaustion was determined. The re...Seventeen disperse dyes including anthraquinone, azo, methine, nitro, and quinoline dyes were applied to dye the Polylactic Acid (PLA) yarns at different conditions, and the dyebath exhaustion was determined. The result shows that C.I. disperse red 167, C.I. disperse orange 30, and C.I. disperse blue 284 have dye-uptakes greater than 80%. Therefore, they can be used as the three principal dyes for PLA yams. The experiment discovered that the dyes, because of their Monoazo and ester group contents, have a higher dye-uptake for the PLA fiber. The research on the optimization of dyeing techniques suggests that PLA yarn can obtain a high level of dyeing effectiveness at the following conditions: pH 4- 5, dyeing temperture 110℃ for 30- 40 min. Color fastness to perspiration, and waterwashing fastness increased 1 - 1.5 by the addition of the abstergent FB during the reduction clearing.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
A novel magnetic nanocarrier was strategically designed and successfully prepared.Photosensitizer 2,7,12,18-tetramethyl-3,8-di-(1-propoxyethyl)-13,17-bis-(3-hydroxypropyl)porphyrin(PHPP)was encapsulated into polylacti...A novel magnetic nanocarrier was strategically designed and successfully prepared.Photosensitizer 2,7,12,18-tetramethyl-3,8-di-(1-propoxyethyl)-13,17-bis-(3-hydroxypropyl)porphyrin(PHPP)was encapsulated into polylactic acid(PLA)-coated Fe3O4 nanoparticles.The diameter of nanocarrier is 30-50 nm by transmission electron micrograph(TEM).The encapsulation efficiency of photosensitizer is 27.98% calculated from UV-vis absorption spectra.The nanocarrier shows obvious photocytotoxic activity to Hela299 tumor cells in vitro.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
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
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
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
基金This work was financially assisted by the National Natural Science Foundation of China(32101875)China Postdoctoral Science Foundation(2021M702458).
文摘The present study aimed to understand the effect of dielectric barrier discharge cold plasma(DBD-CP)technology on the antimicrobial chitosan deposition and the properties enhancement of polylactic acid(PLA)films.The results indicated that DBD-CP was an effective method for improving the adhesion and surface hydrophilicity of PLA,facilitating the deposition of chitosan coating.This modification was attributed to the increased surface roughness,as well as the presence of polar functional groups observed through atomic force microscopy,surface free energy and Fourier transform infrared spectroscopy analysis.The study further revealed that both water resistance and mechanical properties were significantly improved after DBD-CP treatment,which was positively correlated with the amount of chitosan deposited on the PLA surfaces.Following comprehensive evaluation,the treatment at 75 W was determined as the optimal condition for enhancing the properties.Additionally,the modified film exhibited strong antimicrobial activity against Staphylococcus aureus.Consequently,the DBD-CP technology could be a promising tool for better utilization of PLA-based materials in the antibacterial food packaging industry.
基金supported by the National Natural Science Foundation of China(No.81171731)the Project of Chengdu Science and Technology Bureau(Nos.2021-YF05-01619-SN and 2021-RC05-00022-CG)+2 种基金the Science and Technology Project of Tibet Autonomous Region(Nos.XZ202202YD0013C and XZ201901-GB-08)the Sichuan Science and Technology Program(No.2022YFG0066)the 1·3·5 Project for Disciplines of Excellence,West China Hospital,Sichuan University(Nos.ZYJC21026,ZYGD21001 and ZYJC21077).
文摘At present,the clinical reconstruction of the auricle usually adopts the strategy of taking autologous costal cartilage.This method has great trauma to patients,poor plasticity and inaccurate shaping.Three-dimensional(3D)printing technology has made a great breakthrough in the clinical application of orthopedic implants.This study explored the combination of 3D printing and tissue engineering to precisely reconstruct the auricle.First,a polylactic acid(PLA)polymer scaffold with a precisely customized patient appearance was fabricated,and then auricle cartilage fragments were loaded into the 3D-printed porous PLA scaffold to promote auricle reconstruction.In vitro,gelatin methacrylamide(GelMA)hydrogels loaded with different sizes of rabbit ear cartilage fragments were studied to assess the regenerative activity of various autologous cartilage fragments.In vivo,rat ear cartilage fragments were placed in an accurately designed porous PLA polymer ear scaffold to promote auricle reconstruction.The results indicated that the chondrocytes in the cartilage fragments could maintain the morphological phenotype in vitro.After three months of implantation observation,it was conducive to promoting the subsequent regeneration of cartilage in vivo.The autologous cartilage fragments combined with 3D printing technology show promising potential in auricle reconstruction.
文摘The main objective of this work was to study and develop composite materials by experiments with mixtures of synthetic(glass fiber, carbon fiber) and natural fiber(durian skin fiber) reinforcements on a polylactic acid(PLA) matrix composite, because of its excellent mechanical properties. Durian skin fiber(DSF) is a natural waste throughout Thailand, and an alternative to recycling is to realize its potential as a new reinforcement through mixing and the injection molding processes. The flexural strength(σ_(F)) and flexural modulus(E_(F)) of the composites from specimens showed a maximum value by content of durian skin fiber at 10 wt%, for good performance relative to particle dispersion between the matrix and the fiber, and showed a minimum value by content of durian skin fiber at 20 wt%, because the reinforcement material affects the mechanical properties in the experiments.
基金This research was funded by the Xiaohe Talent Project of Zhangjiajie City(No.2022xhrc01)the Research Foundation of Hunan Provincial Education Department(Nos.20A412+1 种基金19C1541)the Natural Science Research Project of Jishou University(No.Jd19005).
文摘Petroleum-based materials,such as plastic,are characterized by adverse environmental pollution;as a result,researchers have sought alternative degradable plastics that are environmentally friendly,such as polylactic acid(PLA).PLA has shown great potential to replace petroleum-based plastics.In this study,seven different samples of unmodified Pueraria lobata root powder(PRP)with different contents(i.e.,0,5,10,15,20,25,and 30 wt%)and three different modified PRPs(i.e.,treated with NaOH,NaOH-KH-550,and Formic)were used to reinforce polylactic acid(PLA)via solution casting process.These prepared PRP/PLA composite films were characterized using SEM,FTIR,UV-visible spectra analysis,TG,DSC,weight loss measurement(wt%),and mechanical measurements.The results showed that the PRP modified with KH-550(PRPK)intensified the interaction in the interface region between the PRP and the PLA matrix,thus increasing the tensile strength(54.5 MPa),elongation at break(2.8%),and Young’s modulus(3310 MPa)of the PRPK/PLA biofilms.Contact angle measurement showed that the PRP treatments contributed to the hydrophobicity of films.The transparency of PRP-10/PLA film atλ_(800)was 11.09%,and its UVA and UVB transmittance were 3.28 and 1.16,respectively.After blending PLA with PRP,the PRP/PLA composite films exhibited excellent biodegradability.In summary,PRPK improved the mechanical properties of PLA and prevented the films from ultraviolet light,suggesting that PRPK-5/PLA film could be used as packaging materials.
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would like to thank the Slovenian Research Agency for financial support within the scope of the program P4-0015,as well as BI-CN/18-20-016:Study on the functional properties and thermal safety performance of wood materials and adhesives for 3D printing technology.
文摘The effects of selected printing parameters on the fire properties of additively produced composites from neat polylactic acid(PLA)and wood/PLA filaments were investigated.The reaction to fire of the 3D-printed specimens was tested according to the ISO 5660-1 cone calorimeter test method.The results showed that the properties of the specimens when exposed to fire were significantly affected by the incorporation of wood flour into the PLA filament.It was also interesting that PLA specimens had much better reactions to fire than the wood/PLA specimens.Time to ignition was found to be much longer in the 3D-printed PLA specimens.Although the maximal heat release rate was a little higher in the PLA than the wood/PLA specimens,the duration of HRR was longer for the wood/PLA specimens.The initial mass of the specimens was smaller in the wood/PLA composites,but during the radiant heat exposure the mass typically decreased slower than in the PLA specimens.
基金This project is funded by Universiti Tunku Abdul Rahman through the grant number IPSR/RMC/UTARRF/2018-C2/T02.
文摘Polylactic acid(PLA)bioplastic is a common material used in Fused Deposition Modeling(FDM)3D printing.It is biodegradable and environmentally friendly biopolymer which made out of corn.However,it exhibits weak mechanical properties which reduced its usability as a functional prototype in a real-world application.In the present study,two PLA composites are created through coextruded with 3K carbon fibres and twisted Kevlar string(as core fibre)to form a fibre reinforced parts(FRP).The mechanical strength of printed parts was examined using ASTM D638 standard with a strain rate of 1 mm/min.It has been demonstrated that the FRPs coextruded with 3K carbon fibres had achieved significant improvement in Young’s modulus(+180.6%,9.205 GPa),ultimate tensile strength(+175.3%,103 MPa)and maximum tensile strain(+21.6%,1.833%).Although the Young’s modulus of Kevlar FRP was found to be similar to as compared to unreinforced PLA(~3.29 GPa),it has gained significant increment in terms of maximum tensile strain(+179.7%,104.64 MPa),and maximum tensile strain(+257%,5.384%).Thus,this study revealed two unique composite materials,in which the 3K carbon FRP can offer stiff and high strength structure while Kevlar FRP offers similar strength but at a higher elasticity.
基金Funded by the Shanxi Province Science Foundation for Youths of China[Nos.2014021020-2 and 2015021076]the Shanxi Province Higher School Science and Technology Innovation Project[No.2015125]+2 种基金the Project of Taiyuan University of Technology[Nos.2013T0202013T0212013T022]
文摘In order to improve the thermal properties of polylactic acid(PLA) filament,nano-SiO_2 was applied to mix with PLA,then they were spun as composite filament by melt-spinning.The dispersion of nano SiO_2 and the fracture surfaces of filaments were studied by scanning electron microscopy(SEM).The properties of composite filament,such as orientation degree,mechanical properties,and surface friction properties,were analyzed.The thermal performances of composite filament were analyzed by differential scanning calorimetry(DSC) and thermo gravimetric analysis(TGA).The results showed that the nano-SiO_2 modified by 5% KH-550 could disperse evenly and loosely in nano-scale,and 1 wt% and 3 wt% nano-SiO_2 dispersed throughout PLA evenly.As the quantity of nano-SiO_2 increased,the properties of composite filament,such as orientation degree,friction coefficient,thermal decomposition temperature,and glass transition temperature,increased more or less.The breaking tenacity increased when 1 wt% SiO_2 was added in PLA,but declined when 3 wt% SiO_2 was added.
基金Shanxi Province Science Foundation for Youths,China(No.2014021020-2)the Projects of Taiyuan University of Technology,China(Nos.2012L074,2013T020,2013T021,and 2013T022)Shanxi Province College Students Training Program,China(No.2013067)
文摘In order to improve the thermal properties of polylactic acid( PLA) master batch,the nano-SiO2 was applied to mixing with PLA. The structure and thermal properties of the composite master batches were studied. The results showed that the nano-SiO2 modified by 3% coupling agent KH-570 could be dispersed evenly in PLA in small scale. The thermal decomposition temperature of composite master batches increased by 6. 20-10. 80 ℃, the glass transition temperature increased by 0. 22-5. 16 ℃,and the heat enthalpy at the glass transition temperature increased by 0. 574-2. 437 J /g,compared with pure PLA. The composite master batch possessed superior thermal stability and heat resistance.
基金Supported by the General Administration of Quality Supervision,Inspection and Quarantine of P. R.C,(No.2005IK099)
文摘Seventeen disperse dyes including anthraquinone, azo, methine, nitro, and quinoline dyes were applied to dye the Polylactic Acid (PLA) yarns at different conditions, and the dyebath exhaustion was determined. The result shows that C.I. disperse red 167, C.I. disperse orange 30, and C.I. disperse blue 284 have dye-uptakes greater than 80%. Therefore, they can be used as the three principal dyes for PLA yams. The experiment discovered that the dyes, because of their Monoazo and ester group contents, have a higher dye-uptake for the PLA fiber. The research on the optimization of dyeing techniques suggests that PLA yarn can obtain a high level of dyeing effectiveness at the following conditions: pH 4- 5, dyeing temperture 110℃ for 30- 40 min. Color fastness to perspiration, and waterwashing fastness increased 1 - 1.5 by the addition of the abstergent FB during the reduction clearing.
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.
基金National Natural Science Foundations of China(No.30070862,No.30271534)Shanghai Municipal Natural Science Foundation,China(No.05ZR14002,No.06PJ14001,No.064319020,No.108146)the FundamentalResearch Funds for the Central Universities,China(No.10D10514)
文摘A novel magnetic nanocarrier was strategically designed and successfully prepared.Photosensitizer 2,7,12,18-tetramethyl-3,8-di-(1-propoxyethyl)-13,17-bis-(3-hydroxypropyl)porphyrin(PHPP)was encapsulated into polylactic acid(PLA)-coated Fe3O4 nanoparticles.The diameter of nanocarrier is 30-50 nm by transmission electron micrograph(TEM).The encapsulation efficiency of photosensitizer is 27.98% calculated from UV-vis absorption spectra.The nanocarrier shows obvious photocytotoxic activity to Hela299 tumor cells in vitro.
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.
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.