A Zn-AI layered double hydroxide （ZnAI-LDH） coating consisted of uniform hexagonal nano-plates was firstly synthesized by co-precipitation and hydrothermal treatment on the AZ31 alloy, and then a poly（lactic acid）...A Zn-AI layered double hydroxide （ZnAI-LDH） coating consisted of uniform hexagonal nano-plates was firstly synthesized by co-precipitation and hydrothermal treatment on the AZ31 alloy, and then a poly（lactic acid） （PLA） coating was sealed on the top layer of the ZnAI-LDH coating using vacuum freeze-drying. The characteristics of the ZnAI-LDH/PLA composite coatings were investigated by means of XRD, SEM, FTIR and EDS. The corrosion resistance of the coatings was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy （EIS）. The results showed that the ZnAI-LDH coating contained a compact inner layer and a porous outer layer, and the PLA coating with a strong adhesion to the porous outer layer can prolong the service life of the ZnAI-LDH coating. The excellent corrosion resistance of this composite coating can be attributable to its barrier function, ion-exchange and self-healing ability.展开更多
Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable ...Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable biomaterials completely at present. Particularly, the alkalinity in the microenvironment surrounding the degradation, implants, resulting from the arises a major concern. Micro arc oxidation （MAO） and poly（lactic acid） （PLA） composite （MAO/PLA）coating on biomedical Mg- 1.21Li-1.12Ca-1.0Y alloy was prepared to manipulate pH variation in an appropriate range. Surface morphologies were discerned using SEM EMPA. AM corrosion resistance was evaluated via electrochemical Polarization and impedance and hydrogen volumetric method. The results demonstrated that the MAO coating predomlnantly consisted of MgO, Mg2SiO4 and YzO3. The composite coating markedly improved the corrosion resistance of the alloy. The rise in solution pH for the MAO/PLA coating was tailored to a favorable range of 7.5-7.8 The neutrallzation caused by the alkalinity of MAO and Mg substrate and acidification of PLA was probed. The reSult designates that MAOI PLA composite coating on Mg-1.21Li-1.12Ca-1.0Y alloys may be a promising biomedical coating.展开更多
Scrap leather fibers(SLFs) modified with active silane containing epoxide groups were incorporated into poly(lactic acid)(PLA) modified by vinyl trimethoxysilane,i.e.,the PLA/SLF composites were prepared for bio-compo...Scrap leather fibers(SLFs) modified with active silane containing epoxide groups were incorporated into poly(lactic acid)(PLA) modified by vinyl trimethoxysilane,i.e.,the PLA/SLF composites were prepared for bio-composites by solvent compounding technology in this article.The effects of silane coupling agents on the structures of PLA and SLF molecules were examined,and the mechanical properties and thermal stability of PLA/SLF composites were also measured.The results of Fourier-transform infrared spectroscopy(FTIR) had proved that silane had been incorporated successfully to PLA and SLF molecules by means of the solvent technology.Scanning electric microscopy(SEM) was used to investigate both the changes in shapes between the pristine SLFs and the treated SLFs and the microscopic structures of composites.According to SEM results,it was shown that there were some significant differences between the untreated and treated SLFs,and a double continuous phase structure had occurred in PLA/SLF composites due to the excellent dispersion of SLFs in matrix.The addition of the treated SLFs into PLA resulted in a distinct improvement of the impact and tensile strengths.When the mass fraction of the treated SLFs was 15%,the notched impact strength and tensile strength of PLA/SLF bio-composites were improved by 34.4%and 21.2%compared with the pristine PLA,respectively. Additionally,with the increase of the modified SLFs content,the thermal stability of PLA/SLF bi-composites was apparently improved.The macroscopic properties of bio-composites were found to be strongly dependent on their components,concentration,dispersion and resulted morphological structures.展开更多
This study investigated that epoxidized soybean oil （ESO） was blended as plasticizer with poly （lactic acid） （PLA） and its effects on the melt rheological properties, such as melt flow index, apparent shear visc...This study investigated that epoxidized soybean oil （ESO） was blended as plasticizer with poly （lactic acid） （PLA） and its effects on the melt rheological properties, such as melt flow index, apparent shear viscosity, and melt strength of the blends. PLA was blended by the twin-screw plastic extruder at five mass fractions： 3%, 6%, 9%, 12%, and 15% （based on PLA mass）. Melt flow index （MFI） was examined with a melt flow indexer. The results indicate that the blends of PLA/ESO had higher MFI than pure PLA, except for MFI at 9% reaching to the lowest point, even lower than that of pure PLA. Melt rheological properties were studied by a capillary rheometer in a temperature range of 160-180℃. The blends exhibited shear-thinning behavior and the apparent shear viscosity was well described by the power law in this shear rate region. The melt strength of PLA plasticized with 6% ESO reached the maximums. ESO was more effective in increasing the melt strength at the mass fractions less than 6%, which could toughen the blends to some extent. Therefore, the authors suggested the optimum addition level of 6%-9% ESO will get good melt rheological performance balance.展开更多
Composite nanofiber membranes based on biodegradable poly(lactic acid)(PLA) and cellulose nanofibrils(CNF) were produced via electrospinning. The influence of CNF content on the morphology, thermal properties, and mec...Composite nanofiber membranes based on biodegradable poly(lactic acid)(PLA) and cellulose nanofibrils(CNF) were produced via electrospinning. The influence of CNF content on the morphology, thermal properties, and mechanical properties of PLA/CNF composite nanofiber membranes were characterized by field scanning electron microscopy(FE-SEM), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), and dynamic mechanical analysis(DMA), respectively. The results show that the PLA/CNF composite nanofibers with smooth, free-bead surface can be successfully fabricated with various CNF contents. The introduction of CNF is an effective approach to improve the crystalline ability, thermal stability and mechanical properties for PLA/CNF composite fibers. The Young's moduli and tensile strength of the PLA/CNF composite nanofiber reach 106.6 MPa and 2.7 MPa when the CNF content is 3%, respectively, which are one times higher and 1.5 times than those of pure PLA nanofiber. Additionally, the water contact angle of PLA/CNF composite nanofiber membranes decreases with the increase of the CNF loading, resulting in the enhancement of their hydrophilicity.展开更多
The curcumin loaded chitosanlpoly （lactic acid） （PLA） nanoflbers were produced using electrospinning. Box-Behnken experimental design was used for the optimization of variables （-1, 0, ＋ 1 coded level） like chi...The curcumin loaded chitosanlpoly （lactic acid） （PLA） nanoflbers were produced using electrospinning. Box-Behnken experimental design was used for the optimization of variables （-1, 0, ＋ 1 coded level） like chitosan/PLA strength （% w/v）, curcumin strength （% w/v） and applied voltage （kV） to obtain uniform fiber diameter. The morphology of nanofibers was shown by SEM. Molecular interactions and the presence of each chemical compound of curcumin loaded chitosanlPLA fibers were characterized by FTIR and EDX analysis. Antioxidant, drug release and in vitro cytotoxicity tests were performed to evaluate the suitability of nanofibers that would be used for wound healing. In vivo wound healing studies on excision and incision wounds created on rat model showed significant reduction of wound area when compared to untreated. The better healing efficiency can be attributed to the presence of curcumin and chitosan.展开更多
Poly(lactic acid)(PLA) was blended with various polycaprolactone(PCL) components through the melt blending process for toughening modification on PLA.The tensile testing,scanning electron microscope(SEM) and different...Poly(lactic acid)(PLA) was blended with various polycaprolactone(PCL) components through the melt blending process for toughening modification on PLA.The tensile testing,scanning electron microscope(SEM) and differential scanning calorimetry(DSC) were implemented to analyze mechanical properties,disperse morphology,thermal properties and compatibility of composite materials,respectively.The shape memory performance of PCL/PLA composites was also investigated.The results showed that the elongation at break of composites increased by 10 and 15 times than pure PLA with adding 20% and30% by weight of PCL,and the yield strength retention rates were77% and 67%,respectively.The SEM showed that PCL/PLA composite was a semi-compatible system.PCL particles could be evenly dispersed in the PLA at 20% or 30% by weight PCL content,and the particle size was very small.DSC results showed a decline in Tg and Tm whereas an increase in Td with the addition of PCL.The addition of PCL could improve the shape memory performance of PLA.The shape memory performance was enhanced with the PCL content increase,but decreased with the tensile strain increase.The best temperature for shape recovery was between 60 and 70 ℃,and the shape memory performance remained 80% after 5 times recycle.展开更多
文摘A Zn-AI layered double hydroxide （ZnAI-LDH） coating consisted of uniform hexagonal nano-plates was firstly synthesized by co-precipitation and hydrothermal treatment on the AZ31 alloy, and then a poly（lactic acid） （PLA） coating was sealed on the top layer of the ZnAI-LDH coating using vacuum freeze-drying. The characteristics of the ZnAI-LDH/PLA composite coatings were investigated by means of XRD, SEM, FTIR and EDS. The corrosion resistance of the coatings was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy （EIS）. The results showed that the ZnAI-LDH coating contained a compact inner layer and a porous outer layer, and the PLA coating with a strong adhesion to the porous outer layer can prolong the service life of the ZnAI-LDH coating. The excellent corrosion resistance of this composite coating can be attributable to its barrier function, ion-exchange and self-healing ability.
基金This research was financially supported by the National Natural Science Foundation of China （Grant No. 51241001）, Shandong Provincial Natural Science Foundation, China （ZR2011E MM004）, SDUST Research Fund （2014TDJH 104）, Joint innovative Center for Safe and Effective Mining Technology and Equipment of Coal Resources, and Shandong Province as well as Taishan Scholarship Project of Shandong Province （TS20110828）. Thanks go to Prof. Rong-Shi Chen and the members of his group at Institute of Metals Research, Chinese Academy of Sciences for the preparation of the ingots.
文摘Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable biomaterials completely at present. Particularly, the alkalinity in the microenvironment surrounding the degradation, implants, resulting from the arises a major concern. Micro arc oxidation （MAO） and poly（lactic acid） （PLA） composite （MAO/PLA）coating on biomedical Mg- 1.21Li-1.12Ca-1.0Y alloy was prepared to manipulate pH variation in an appropriate range. Surface morphologies were discerned using SEM EMPA. AM corrosion resistance was evaluated via electrochemical Polarization and impedance and hydrogen volumetric method. The results demonstrated that the MAO coating predomlnantly consisted of MgO, Mg2SiO4 and YzO3. The composite coating markedly improved the corrosion resistance of the alloy. The rise in solution pH for the MAO/PLA coating was tailored to a favorable range of 7.5-7.8 The neutrallzation caused by the alkalinity of MAO and Mg substrate and acidification of PLA was probed. The reSult designates that MAOI PLA composite coating on Mg-1.21Li-1.12Ca-1.0Y alloys may be a promising biomedical coating.
基金the China Postdoctoral Science Foundation (No.20100470755)the Financial Supports of Department of Education of Zhejiang Province (No.Z20119661)
文摘Scrap leather fibers(SLFs) modified with active silane containing epoxide groups were incorporated into poly(lactic acid)(PLA) modified by vinyl trimethoxysilane,i.e.,the PLA/SLF composites were prepared for bio-composites by solvent compounding technology in this article.The effects of silane coupling agents on the structures of PLA and SLF molecules were examined,and the mechanical properties and thermal stability of PLA/SLF composites were also measured.The results of Fourier-transform infrared spectroscopy(FTIR) had proved that silane had been incorporated successfully to PLA and SLF molecules by means of the solvent technology.Scanning electric microscopy(SEM) was used to investigate both the changes in shapes between the pristine SLFs and the treated SLFs and the microscopic structures of composites.According to SEM results,it was shown that there were some significant differences between the untreated and treated SLFs,and a double continuous phase structure had occurred in PLA/SLF composites due to the excellent dispersion of SLFs in matrix.The addition of the treated SLFs into PLA resulted in a distinct improvement of the impact and tensile strengths.When the mass fraction of the treated SLFs was 15%,the notched impact strength and tensile strength of PLA/SLF bio-composites were improved by 34.4%and 21.2%compared with the pristine PLA,respectively. Additionally,with the increase of the modified SLFs content,the thermal stability of PLA/SLF bi-composites was apparently improved.The macroscopic properties of bio-composites were found to be strongly dependent on their components,concentration,dispersion and resulted morphological structures.
基金Supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (20030561014)
文摘This study investigated that epoxidized soybean oil （ESO） was blended as plasticizer with poly （lactic acid） （PLA） and its effects on the melt rheological properties, such as melt flow index, apparent shear viscosity, and melt strength of the blends. PLA was blended by the twin-screw plastic extruder at five mass fractions： 3%, 6%, 9%, 12%, and 15% （based on PLA mass）. Melt flow index （MFI） was examined with a melt flow indexer. The results indicate that the blends of PLA/ESO had higher MFI than pure PLA, except for MFI at 9% reaching to the lowest point, even lower than that of pure PLA. Melt rheological properties were studied by a capillary rheometer in a temperature range of 160-180℃. The blends exhibited shear-thinning behavior and the apparent shear viscosity was well described by the power law in this shear rate region. The melt strength of PLA plasticized with 6% ESO reached the maximums. ESO was more effective in increasing the melt strength at the mass fractions less than 6%, which could toughen the blends to some extent. Therefore, the authors suggested the optimum addition level of 6%-9% ESO will get good melt rheological performance balance.
基金Funded by the Outstanding Young Scientific Research Personnel Training Plan in Colleges and Universities of Fujian Province(No.GY-Z160146)the Research Fund of Fujian University of Technology(Nos.GY-Z15091,GY-Z160121)+2 种基金the External Cooperative Projects of Fujian Province(No.2018I0001)the Young Teachers Education Research Project(No.JAT170377)Fujian Province Undergraduate Training Program for Innovation and Entrepreneurship(No.201810388048)
文摘Composite nanofiber membranes based on biodegradable poly(lactic acid)(PLA) and cellulose nanofibrils(CNF) were produced via electrospinning. The influence of CNF content on the morphology, thermal properties, and mechanical properties of PLA/CNF composite nanofiber membranes were characterized by field scanning electron microscopy(FE-SEM), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), and dynamic mechanical analysis(DMA), respectively. The results show that the PLA/CNF composite nanofibers with smooth, free-bead surface can be successfully fabricated with various CNF contents. The introduction of CNF is an effective approach to improve the crystalline ability, thermal stability and mechanical properties for PLA/CNF composite fibers. The Young's moduli and tensile strength of the PLA/CNF composite nanofiber reach 106.6 MPa and 2.7 MPa when the CNF content is 3%, respectively, which are one times higher and 1.5 times than those of pure PLA nanofiber. Additionally, the water contact angle of PLA/CNF composite nanofiber membranes decreases with the increase of the CNF loading, resulting in the enhancement of their hydrophilicity.
文摘The curcumin loaded chitosanlpoly （lactic acid） （PLA） nanoflbers were produced using electrospinning. Box-Behnken experimental design was used for the optimization of variables （-1, 0, ＋ 1 coded level） like chitosan/PLA strength （% w/v）, curcumin strength （% w/v） and applied voltage （kV） to obtain uniform fiber diameter. The morphology of nanofibers was shown by SEM. Molecular interactions and the presence of each chemical compound of curcumin loaded chitosanlPLA fibers were characterized by FTIR and EDX analysis. Antioxidant, drug release and in vitro cytotoxicity tests were performed to evaluate the suitability of nanofibers that would be used for wound healing. In vivo wound healing studies on excision and incision wounds created on rat model showed significant reduction of wound area when compared to untreated. The better healing efficiency can be attributed to the presence of curcumin and chitosan.
基金National Natural Science Foundation of China(No.51303085)Prospective Joint Research Project of Jiangsu Province,China(No.BY2015047-14)
文摘Poly(lactic acid)(PLA) was blended with various polycaprolactone(PCL) components through the melt blending process for toughening modification on PLA.The tensile testing,scanning electron microscope(SEM) and differential scanning calorimetry(DSC) were implemented to analyze mechanical properties,disperse morphology,thermal properties and compatibility of composite materials,respectively.The shape memory performance of PCL/PLA composites was also investigated.The results showed that the elongation at break of composites increased by 10 and 15 times than pure PLA with adding 20% and30% by weight of PCL,and the yield strength retention rates were77% and 67%,respectively.The SEM showed that PCL/PLA composite was a semi-compatible system.PCL particles could be evenly dispersed in the PLA at 20% or 30% by weight PCL content,and the particle size was very small.DSC results showed a decline in Tg and Tm whereas an increase in Td with the addition of PCL.The addition of PCL could improve the shape memory performance of PLA.The shape memory performance was enhanced with the PCL content increase,but decreased with the tensile strain increase.The best temperature for shape recovery was between 60 and 70 ℃,and the shape memory performance remained 80% after 5 times recycle.
