The increasing deployment of electronics in everyday life has generated great concerns regarding the effective disposal of waste from these components.Here,we focused on a facile sustainable and economical strategy to...The increasing deployment of electronics in everyday life has generated great concerns regarding the effective disposal of waste from these components.Here,we focused on a facile sustainable and economical strategy to provide ideas for this issue.This strategy relied on using appropriate mechanical treatment and sodium lignosulfonate coating to improve the dispersion and interfacial compatibility of bamboo fibers in poly(lactic acid).By optimising the particle size and concentration of sodium lignosulphonate,high value-added and green composites were prepared using sectional pressurization with a venting procedure.The treated composite displayed an ultra-smooth surface(roughness of 0.592 nm),impressive transient properties(disintegration and degradation behaviour after 30 d),and outstanding ultraviolet(UV)shielding properties(100%).These properties hold the promise of being an excellent substrate for electronic devices,especially for high-precision processing,transient electronics,and UV damage prevention.The satisfactory interfacial compatibility of the composites was confirmed by detailed characterisation regarding the related physicochemical properties.This investigation offers a sustainable approach for producing high value-added green composites from biomass and biomass-derived materials.展开更多
This article provided a preparation protocol for poly(lactic acid)(PLA)/modified epoxidized soybean oil(ECP)/nano-magnesium oxide(n-MgO)ternary composites and studied their mechanical and antibacterial properties.By m...This article provided a preparation protocol for poly(lactic acid)(PLA)/modified epoxidized soybean oil(ECP)/nano-magnesium oxide(n-MgO)ternary composites and studied their mechanical and antibacterial properties.By means of an organic synthesis technique,epoxidized soybean oil(ESO)is chemically grafted to PLA to synthesize ESO chemically plastically modified PLA,abbreviated ECP.To fabricate PLA/ECP/n-MgO composite materials,ECP acts as a plasticizer and a compatibilizer simultaneously,and n-MgO acts as an enhancer.Then scanning electron microscopy,X-ray diffraction,differential scanning calorimetry,universal tester,and antibacterial research were exploited to characterize the morphology,thermal resistance,mechanical properties,and antibacterial performance of PLA/ECP/n-MgO composites.The experimental results show that ECP acts as a plasticizer by causing heterogeneous nucleation,which increases PLA's crystallinity.Evenly distributed n-MgO can greatly improve PLA's antibacterial qualities.Furthermore,ECP and n-MgO work together to improve the positive aspects of PLA/ECP/n-MgO composites,with PLA/ECP/n-MgO 100/1/0.5 composites having the best overall properties.While improving the mechanical performance and toughness of PLA,this work offers a prospective approach and foundational database for the creation of multifunctional biodegradable composites.展开更多
Poly(lactic acid)(PLA),a bio-based polymer,is considered to be a sustainable alternative to conventional petroleum-based plastics.However,owing to its widespread use and relatively slow degradation rate in water,PLA s...Poly(lactic acid)(PLA),a bio-based polymer,is considered to be a sustainable alternative to conventional petroleum-based plastics.However,owing to its widespread use and relatively slow degradation rate in water,PLA still poses potential environmental pollution risks after being discarded.The efficient chemical recycling of PLA represents an attractive approach to addressing both resource reuse and environmental pollution challenges caused by its waste.Hydrolysis is the predominant method of industrial recycling.However,because PLA is insoluble in water,efficient heterogeneous hydrolysis requires high-temperature and high-pressure conditions.In this study,an efficient homogenous hydrolysis method capable of simultaneously dissolving PLA and calcium hydroxide(Ca(OH)_(2))was developed.Suitable solvents for this method were screened,and it was found that PLA hydrolysis using dioxane and 1,4,7,10,13-Pen-taoxacyclopentadecane as solvents achieved conversion rates of 93%and 90%,respectively,within 2 h at room temperature.Notably,the hydrolysis product,calcium lactate,precipitated as a solid from the solvent and therefore self-separated from the reaction solution.The solvent,acid/base conditions,water content,and depolymerization kinetics were investigated.Compared with previously reported hydrolysis methods,the enhanced efficiency observed in this study can be attributed to the concurrent solvation of PLA and Ca(OH)_(2),which maintains homogeneity throughout the reaction process.Additionally,this method facilitates closed-loop recycling of PLA and is compatible with the highly selective recovery of PLA from various types of PLA products.展开更多
To retain its inherent biodegradability,simultaneously improving the strength and toughness of poly(lactic acid)(PLA)is a significant challenge.In this study,we propose an innovative multiple dynamic pressure(MDP)proc...To retain its inherent biodegradability,simultaneously improving the strength and toughness of poly(lactic acid)(PLA)is a significant challenge.In this study,we propose an innovative multiple dynamic pressure(MDP)process that can produce pure PLA with excellent mechanical properties.The MDP process generates a dynamic stretching effect by regulating the application and release of pressure,prompting disordered molecular chains to be arranged regularly along the direction of the dynamic force field.This promoted the formation of more ordered crystal forms(α-form)and strengthened the connection between the crystalline and amorphous regions.Results show that after MDP treatment,the tensile strength and strain at break of MDP-PLA are significantly improved,reaching 91.6 MPa and 80.1%respectively,which are 49.4%higher and 10 times higher than those of the samples before treatment.The mechanical properties of MDP-PLA can be regulated as needed by adjusting the cycle times and peak pressure.In addition,through a systematic study of the structural evolution of MDP-PLA,the performance regulation mechanism of the MDP process was thoroughly investigated,and the internal relationship among the process-structure-performance was clarified.This research not only opens a new technical path for the preparation of high-performance pure PLA but also provides important guidance for the high-performance modification of other semi-crystalline polymers,thus possessing significant scientific and engineering value.展开更多
AIM:To develop a 5-fluorouracil(5-FU)mesoporous poly(lactic)acid(PLA)delivery system for glaucoma filtration surgery suitable for a single subconjunctival implantation.METHODS:The 5-FU was infiltration-loaded into mes...AIM:To develop a 5-fluorouracil(5-FU)mesoporous poly(lactic)acid(PLA)delivery system for glaucoma filtration surgery suitable for a single subconjunctival implantation.METHODS:The 5-FU was infiltration-loaded into mesoporous PLA.In vitro and in vivo release experiments and ocular toxicology evaluation of the formulation were performed.The antiproliferative effect of this 5-FU-PLA tablet after glaucoma filtration surgery in rabbits was evaluated.Pathology,immunohistochemistry,and Western blot were used to further validate the inhibitory effect of this sustained release system.RESULTS:Various drug formulations were tested,and two 5-FU-PLA tablets,namely 1.5P15(5-FU 1.5 mg+PLA 15000 Da)and 2.5P15(5-FU 2.5 mg+PLA 15000 Da),had the most suitable release profiles in vitro.Further in vivo studies confirmed the safety and sustained-release profiles of both drugs.Both 5-FU-PLA tablets,relative to the free drugs,significantly inhibited tissue proliferation after glaucoma filtration and improved surgical success.Western blot showed that transforming growth factor-β(TGF-β)and connective tissue growth factor(CTGF)were inhibited by 5-FU after filtration surgery,with the effects of the 5-FU-PLA tablets being more lasting.CONCLUSION:The tested 5-FU-PLA tablets provide a sustained release of 5-FU,which may be used for a single subconjunctival implantation to inhibit proliferation after filtration surgery.展开更多
The continuous improvement in patient care and recovery is driving the development of innovative materials for medical applications.Medical sutures,essential for securing implants and closing deep wounds,have evolved ...The continuous improvement in patient care and recovery is driving the development of innovative materials for medical applications.Medical sutures,essential for securing implants and closing deep wounds,have evolved to incorporate smart materials capable of responding to various stimuli.This study explores the potential of thermoresponsive sutures,made from shape memory materials,that contract upon heating to bring loose stitches closer together,promoting optimal wound closure.We developed nanocomposites based on a blend of poly(lactic acid)(PLA)and thermoplastic polyurethane(TPU)—biopolymers that inherently exhibit shape memory—enhanced with carbon nanotubes(CNT)and graphene nanoplatelets(GN)to improve mechanical performance.PLA/TPU(50/50)nanocomposites were prepared with 1 and 2 wt%GN,as well as hybrid formulations combining 1 wt%CNT with 1 or 2 wt%GN,using a twin-screw extrusion process to form filaments.These filaments were characterized through differential scanning calorimetry(DSC),field emission gun scanning electron microscopy(FEG-SEM),tensile testing,and shape memory assessments.While the PLA/TPU blend is immiscible,TPU enhances the crystallinity(X_(c))of the PLA phase,further increased by the addition of CNT and GN.FEG-SEM images indicate CNTs primarily in the PLA phase and GN in the TPU phase.PLA/TPU with 1 or 2 wt%GN showed the highest potential for suture applications,with a high elastic modulus(~1000 MPa),significant strain at break(~10%),and effective shape recovery(~20%at 55℃ for 30 min).These findings suggest that these nanocomposites can enhance suture performance with controlled shape recovery that is suitable for medical use.展开更多
Imidazolium-based elastomeric ionomers （i-BIIR） were facilely synthesized by ionically modified brominated poly（isobutylene-co-isoprene） （BIIR） with different alkyl chain imidazole and thoroughly explored as nov...Imidazolium-based elastomeric ionomers （i-BIIR） were facilely synthesized by ionically modified brominated poly（isobutylene-co-isoprene） （BIIR） with different alkyl chain imidazole and thoroughly explored as novel toughening agents for poly（lactic acid） （PLA）. The miscibility, thermal behavior, phase morphology and mechanical property of ionomers and blends were investigated through dynamic mechanical analyses （DMA）, differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, tensile and impact testing. DMA and SEM results showed that better compatibility between the PLA and i-BIIR was achieved compared to the PLA/unmodified BIIR elastomer. A remarkable improvement in ductility with an optimum elongation at break up to 235% was achieved for the PLA/i-BIIR blends with 1-dodecylimidazole alkyl chain （i-BIIR-12）, more than 10 times higher than that of pure PLA. The impact strengths of PLA were enhanced from 1.9 kJ/m2 to 4.1 k J/m2 for the PLA/10 wt% i-BIIR-12 blend. Toughening mechanism had been established by systematical analysis of the compatibility, intermolecular interaction and phase structures of the blends. Interracial cavitations initiated massive shear yielding of the PLA matrix owing to a suitable interfacial adhesion which played a key role in the enormous toughening effect in these blends. We believed that introducing imidazolium group into the BIIR elastomer was vital for the formation of a suitable interfacial adhesion.展开更多
Poly（lactic acid） （PLA） composites with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide （DOPO） and DOPO- containing polyhedral oligomeric silsesquioxane （DOPO-POSS） were prepared via melting extrusion and i...Poly（lactic acid） （PLA） composites with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide （DOPO） and DOPO- containing polyhedral oligomeric silsesquioxane （DOPO-POSS） were prepared via melting extrusion and injection molding. The crystallization, mechanical, and flame-retardant properties of PLA/DOPO and PLA/DOPO-POSS were investigated by differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, tensile testing, thermogravimetric analysis （TGA）, limiting oxygen index （LOI）, and cone calorimeter test. The DSC results showed that the DOPO added could act as a plasticizer as reflected by lower glass transition temperature and inhibited crystallization of part of the PLA; the DOPO-POSS acted like a filler in the PLA matrix and slightly improved the crystallinity of the PLA matrix. The XRD and DSC analyses indicated that the PLA composites by cold molding injection were amorphous, and the PLA composites following a heat treatment in an oven at 120 ℃for 30 min achieved crystallinity. All the PLA and its composites after heat treatment had improved mechanical properties. The thermogravimetric analysis （TGA） tests showed that the PLA, DOPO and DOPO-POSS decomposed separately in the PLA/DOPO and PLA/DOPO-POSS, respectively. The cone calorimeter tests offered clear evidence that addition of the DOPO-POSS resulted in an evident reduction of 25% for the peak of heat release rate （p-HRR）. It was also confirmed that the crystalline flame-retardant PLA composites after heat treatment had better flame retardant properties than the amorphous PLA composites prepared by the cold molding.展开更多
The natural fiber/poly(lactic acid) (PLA) composites were prepared with ramie and jute short fiber as reinforcement and PLA as matrix. The mechanical and thermal properties of the composites were investigated. The res...The natural fiber/poly(lactic acid) (PLA) composites were prepared with ramie and jute short fiber as reinforcement and PLA as matrix. The mechanical and thermal properties of the composites were investigated. The results show that the properties of the composites are better than those of plain PLA. When the content of the fiber is 30%, the composites can get the best mechanical properties. The dynamic mechanical analysis results show that the storage moduli of the PLA/ramie and PLA/jute composites increase with respect to the plain PLA. The Vicat softening temperature of the composites is greatly higher than that of PLA. The results of thermogravimetric analysis show that adding fiber to the PLA matrix can improve the degradation temperature of PLA.展开更多
A novel poly（d, /-lactic acid） （PDLLA） based biomimetic polymer was synthesized by grafting maleic anhydride, butanediamine and arg-gly-asp-ser （RGDS） peptides onto the backbone of PDLLA, aiming to overcome the ...A novel poly（d, /-lactic acid） （PDLLA） based biomimetic polymer was synthesized by grafting maleic anhydride, butanediamine and arg-gly-asp-ser （RGDS） peptides onto the backbone of PDLLA, aiming to overcome the acidity and auto-accelerating degradation of PDLLA during degradation and to improve its biospecificity and biocompatibility. The synthetic copolymer was characterized by FTIR, ^13C NMR and amino acid analyzer （AAA）.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
PLLA/CA mixtures of different compositions were successfully electrospun to obtain composite nanofibrous membranes. The microstructures of the membrances changed from homogeneous to heterogeneous with the addition of ...PLLA/CA mixtures of different compositions were successfully electrospun to obtain composite nanofibrous membranes. The microstructures of the membrances changed from homogeneous to heterogeneous with the addition of CA, which was observed by FE-ESEM. The PLLA/CA fabric membranes were characterized by mechanical testing, DSC and contact angle measurements. The tensile stress of the composite fibrous membranes increased obviously with the increase of CA content. DSC results indicated that the CA component was the main factor for the changes of enthalpies in the composite fibers. Contact angle measurements showed the hydrophilicity of the electrospun nanofiber membranes was improved with the addition of CA.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
One-step reaction compatibilized microfibrillar reinforced iPP/PET blends （CMRB） were successfully prepared through a ＂slit extrusion-hot stretching-quenching＂ process. Crystallization behavior and morphology of C...One-step reaction compatibilized microfibrillar reinforced iPP/PET blends （CMRB） were successfully prepared through a ＂slit extrusion-hot stretching-quenching＂ process. Crystallization behavior and morphology of CMRB were systematically investigated. Scanning electronic microscopy （SEM） observations showed blurry interface of compatibilized common blend （CCB）. The crystallization behavior of neat iPP, CCB, microfibrillar reinforced iPP/PET blend （MRB） and CMRB was investigated by differential scanning calorimetry （DSC） and polarized optical microscopy （POM）. The increase of crystallization temperature and crystallization rate during nonisothermal crystallization process indicated both PET particles and mierofibrils could serve as nucleating agents and PET microfibrils exhibited higher heterogeneous nucleation ability, which were also vividly revealed by results of POM. Compared with MRB sample, CMRB sample has lower crystallization temperature due to existence of PET microfibrils with smaller aspect ratio and wider distribution. In addition, since in situ compatibilizer tends to stay in the interphase, it could also hinder the diffusion ofiPP molecules to the surface of PET phase, leading to decrease of crystallization rate. Two-dimensional wide-angle X-ray diffi：action （2D-WAXD） was preformed to characterize the crystalline structure of the samples by injection molding, and it was found that well-developed PET microfibrils contained in MRB sample promoted formation of t-phase of/PP.展开更多
Diphenyl （4-hydroxyphenyl） hexadecyl phosphonium bromide （POH） -modified montmorillonite （POHMMT） was used to prepare a novel TiC14/MgC12/POHMMT compound catalyst and exfoliated iPP/POHMMT nanocomposites were pr...Diphenyl （4-hydroxyphenyl） hexadecyl phosphonium bromide （POH） -modified montmorillonite （POHMMT） was used to prepare a novel TiC14/MgC12/POHMMT compound catalyst and exfoliated iPP/POHMMT nanocomposites were prepared by the in situ intercalative polymerization of propylene with the TiC14/MgC12/POHMMT compound catalyst. The POH surfactants don＇t change the catalytic characteristic of the Z-N catalyst and the obtained PP presents high isotacticity, normal molecular weight and molecular weight distribution. The WAXD, SAXS and TEM results demonstrate the highly exfoliated iPP/POHMMT nanocomposites were produced by the in situ polymerization with this novel catalyst, while the intercalated iPP/Na＋MMT nanocomposites were produced with the TiC14/MgC12/Na＋MMT compound catalyst. Through this approach, in situ propylene polymerization can actually take place between the silicate layers and lead not only to PP with high isotacticity and molecular weight, but also to highly exfoliated PP nanocomposites.展开更多
Micro-encapsulated phase-change materials(micro PCMs) with Na_2 HPO_4·12 H_2 O encapsulated in poly(lactic acid)(PLA) shell were prepared by a solvent evaporation–precipitation method that involves the use of a ...Micro-encapsulated phase-change materials(micro PCMs) with Na_2 HPO_4·12 H_2 O encapsulated in poly(lactic acid)(PLA) shell were prepared by a solvent evaporation–precipitation method that involves the use of a coaxial needle. The effects of PLA concentration, stirring speed, injection rate of core and shell solutions, and polyvinyl alcohol(PVA) concentration on phase change properties were investigated. The thermal properties of microP CMs were characterized by differential scanning calorimetry(DSC). The capsules prepared under the optimal conditions are about 2 mm in diameter and show a latent heat of up to 122.2 J·g^(-1).展开更多
Blends of poly（lactic acid）（PLA） and thermoplastic acetylated starch（ATPS） were prepared by means of the melt mixing method. The results show that PLA and ATPS were partially miscible, which was confirmed with t...Blends of poly（lactic acid）（PLA） and thermoplastic acetylated starch（ATPS） were prepared by means of the melt mixing method. The results show that PLA and ATPS were partially miscible, which was confirmed with the measurement of Tg by dynamic mechanical analysis（DMA） and differrential scanning calorimetry（DSC）. The mechanical and thermal properties of the blends were improved. With increasing the ATPS content, the elongation at break and impact strength were increased. The elongation at break increased from 5% of neat PLA to 25% of the blend PLA/ATPS40. It was found that the cold crystallization behavior of PLA changed evidently by addition of ATPS. The cold crystallization temperature（Tcc） of each of PLA/ATPS blends was found to shift to a lower temperature and the width of exothermic peak became narrow compared with that of neat PLA. The thermogravimetry analysis（TGA） results showed that the peak of derivative weight for ATPS moved to higher temperature with increasing PLA content in PLA/ATPS blends. It can be concluded that PLA could increase the thermal stability of ATPS. The rheological measurement reveals the melt elasticity and viscosity of the blends decreased with the increased concentration of ATPS, which was favorable to the processing properties of PLA.展开更多
Biodegradable chitosan-g-poly (D, L-lactic acid) copolymers were prepared via two methods. (1) The lactide was grafted onto hydroxyl groups of chitosan by using macromolecular initiator sodium of trimethylsilyl-chit...Biodegradable chitosan-g-poly (D, L-lactic acid) copolymers were prepared via two methods. (1) The lactide was grafted onto hydroxyl groups of chitosan by using macromolecular initiator sodium of trimethylsilyl-chitosan, (2) poly (D,L-lactic acid)(PLA) with low molecular weight can be linked to the amino group by coupling activated PLA to trimethylsilyl-chitosan. Two graft copolymers had hydrophilic-hydrophobic character and can be applied as carriers for drug delivery.展开更多
Aggregation process of isotactic poly（methyl methacrylate） （i-PMMA） has been studied extensively for many years, and considerable progress has been made in both experimental and theoretical studies. They are, howe...Aggregation process of isotactic poly（methyl methacrylate） （i-PMMA） has been studied extensively for many years, and considerable progress has been made in both experimental and theoretical studies. They are, however, seldom sustained by real-space observations of the underlying morphology. In this paper, the aggregation process of i-PMMA in concentrated acetone solutions and the fractal structure of the resulting three-dimensional clusters were characterized on the basis of real-space AFM observations of their two-dimensional projection. It was found that spherical multiple-chain particles formed upon collapse and aggregation of the involving chains as a whole during quenching the solution to room temperature. By keeping the solution at room temperature, the initially formed particles stick together upon contact to form larger particles through reassembling very slowly. The succeeding collision of the enlarged spherical particles leads to the formation of small clusters. These newly formed small clusters grow when they meet with other clusters or single Brownian particles. This leads to the formation of large clusters with fractal dimension of 1.95 ± 0.05, which suggest a reaction-limited cluster aggregation of i-PMMA in a concentrated acetone solution. This is in accordance with the conclusion obtained by light scattering measurements.展开更多
基金supported by the National Natural Science Foundation of China(Nos.31971741 and 31760195)the Yunnan Fundamental Research Projects(Nos.2018FB066 and 202001AT070141)the Yunnan Agricultural Basic Research Special Projects(No.202101BD070001-086).
文摘The increasing deployment of electronics in everyday life has generated great concerns regarding the effective disposal of waste from these components.Here,we focused on a facile sustainable and economical strategy to provide ideas for this issue.This strategy relied on using appropriate mechanical treatment and sodium lignosulfonate coating to improve the dispersion and interfacial compatibility of bamboo fibers in poly(lactic acid).By optimising the particle size and concentration of sodium lignosulphonate,high value-added and green composites were prepared using sectional pressurization with a venting procedure.The treated composite displayed an ultra-smooth surface(roughness of 0.592 nm),impressive transient properties(disintegration and degradation behaviour after 30 d),and outstanding ultraviolet(UV)shielding properties(100%).These properties hold the promise of being an excellent substrate for electronic devices,especially for high-precision processing,transient electronics,and UV damage prevention.The satisfactory interfacial compatibility of the composites was confirmed by detailed characterisation regarding the related physicochemical properties.This investigation offers a sustainable approach for producing high value-added green composites from biomass and biomass-derived materials.
基金Funded by the National Natural Science Foundation of China(No.21104031)the Education Department of Hunan province in 2020(No.20C1589)。
文摘This article provided a preparation protocol for poly(lactic acid)(PLA)/modified epoxidized soybean oil(ECP)/nano-magnesium oxide(n-MgO)ternary composites and studied their mechanical and antibacterial properties.By means of an organic synthesis technique,epoxidized soybean oil(ESO)is chemically grafted to PLA to synthesize ESO chemically plastically modified PLA,abbreviated ECP.To fabricate PLA/ECP/n-MgO composite materials,ECP acts as a plasticizer and a compatibilizer simultaneously,and n-MgO acts as an enhancer.Then scanning electron microscopy,X-ray diffraction,differential scanning calorimetry,universal tester,and antibacterial research were exploited to characterize the morphology,thermal resistance,mechanical properties,and antibacterial performance of PLA/ECP/n-MgO composites.The experimental results show that ECP acts as a plasticizer by causing heterogeneous nucleation,which increases PLA's crystallinity.Evenly distributed n-MgO can greatly improve PLA's antibacterial qualities.Furthermore,ECP and n-MgO work together to improve the positive aspects of PLA/ECP/n-MgO composites,with PLA/ECP/n-MgO 100/1/0.5 composites having the best overall properties.While improving the mechanical performance and toughness of PLA,this work offers a prospective approach and foundational database for the creation of multifunctional biodegradable composites.
基金financially supported by the National Key R&D Program of China(No.2021YFB3801901)the National Natural Science Foundation of China(No.22075188 and U19A2095)supported by State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology。
文摘Poly(lactic acid)(PLA),a bio-based polymer,is considered to be a sustainable alternative to conventional petroleum-based plastics.However,owing to its widespread use and relatively slow degradation rate in water,PLA still poses potential environmental pollution risks after being discarded.The efficient chemical recycling of PLA represents an attractive approach to addressing both resource reuse and environmental pollution challenges caused by its waste.Hydrolysis is the predominant method of industrial recycling.However,because PLA is insoluble in water,efficient heterogeneous hydrolysis requires high-temperature and high-pressure conditions.In this study,an efficient homogenous hydrolysis method capable of simultaneously dissolving PLA and calcium hydroxide(Ca(OH)_(2))was developed.Suitable solvents for this method were screened,and it was found that PLA hydrolysis using dioxane and 1,4,7,10,13-Pen-taoxacyclopentadecane as solvents achieved conversion rates of 93%and 90%,respectively,within 2 h at room temperature.Notably,the hydrolysis product,calcium lactate,precipitated as a solid from the solvent and therefore self-separated from the reaction solution.The solvent,acid/base conditions,water content,and depolymerization kinetics were investigated.Compared with previously reported hydrolysis methods,the enhanced efficiency observed in this study can be attributed to the concurrent solvation of PLA and Ca(OH)_(2),which maintains homogeneity throughout the reaction process.Additionally,this method facilitates closed-loop recycling of PLA and is compatible with the highly selective recovery of PLA from various types of PLA products.
基金supported by the National Key Research and Development Program of China(No.2023YFC3904604)the Fundamental Research Funds for the Central Universities(No.2024ZYGXZR080)+1 种基金Science and Technology Project of Guangzhou(No.2025A04J3914)Research and Development Program of Jiangmen(No.2023780200030009506).
文摘To retain its inherent biodegradability,simultaneously improving the strength and toughness of poly(lactic acid)(PLA)is a significant challenge.In this study,we propose an innovative multiple dynamic pressure(MDP)process that can produce pure PLA with excellent mechanical properties.The MDP process generates a dynamic stretching effect by regulating the application and release of pressure,prompting disordered molecular chains to be arranged regularly along the direction of the dynamic force field.This promoted the formation of more ordered crystal forms(α-form)and strengthened the connection between the crystalline and amorphous regions.Results show that after MDP treatment,the tensile strength and strain at break of MDP-PLA are significantly improved,reaching 91.6 MPa and 80.1%respectively,which are 49.4%higher and 10 times higher than those of the samples before treatment.The mechanical properties of MDP-PLA can be regulated as needed by adjusting the cycle times and peak pressure.In addition,through a systematic study of the structural evolution of MDP-PLA,the performance regulation mechanism of the MDP process was thoroughly investigated,and the internal relationship among the process-structure-performance was clarified.This research not only opens a new technical path for the preparation of high-performance pure PLA but also provides important guidance for the high-performance modification of other semi-crystalline polymers,thus possessing significant scientific and engineering value.
基金Supported by the National Natural Science Foundation of China(No.82301211)Beijing Natural Science Foundation(No.J230028).
文摘AIM:To develop a 5-fluorouracil(5-FU)mesoporous poly(lactic)acid(PLA)delivery system for glaucoma filtration surgery suitable for a single subconjunctival implantation.METHODS:The 5-FU was infiltration-loaded into mesoporous PLA.In vitro and in vivo release experiments and ocular toxicology evaluation of the formulation were performed.The antiproliferative effect of this 5-FU-PLA tablet after glaucoma filtration surgery in rabbits was evaluated.Pathology,immunohistochemistry,and Western blot were used to further validate the inhibitory effect of this sustained release system.RESULTS:Various drug formulations were tested,and two 5-FU-PLA tablets,namely 1.5P15(5-FU 1.5 mg+PLA 15000 Da)and 2.5P15(5-FU 2.5 mg+PLA 15000 Da),had the most suitable release profiles in vitro.Further in vivo studies confirmed the safety and sustained-release profiles of both drugs.Both 5-FU-PLA tablets,relative to the free drugs,significantly inhibited tissue proliferation after glaucoma filtration and improved surgical success.Western blot showed that transforming growth factor-β(TGF-β)and connective tissue growth factor(CTGF)were inhibited by 5-FU after filtration surgery,with the effects of the 5-FU-PLA tablets being more lasting.CONCLUSION:The tested 5-FU-PLA tablets provide a sustained release of 5-FU,which may be used for a single subconjunctival implantation to inhibit proliferation after filtration surgery.
基金This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoalde Nível Superior-Brasil(CAPES)-Finance Code 001.
文摘The continuous improvement in patient care and recovery is driving the development of innovative materials for medical applications.Medical sutures,essential for securing implants and closing deep wounds,have evolved to incorporate smart materials capable of responding to various stimuli.This study explores the potential of thermoresponsive sutures,made from shape memory materials,that contract upon heating to bring loose stitches closer together,promoting optimal wound closure.We developed nanocomposites based on a blend of poly(lactic acid)(PLA)and thermoplastic polyurethane(TPU)—biopolymers that inherently exhibit shape memory—enhanced with carbon nanotubes(CNT)and graphene nanoplatelets(GN)to improve mechanical performance.PLA/TPU(50/50)nanocomposites were prepared with 1 and 2 wt%GN,as well as hybrid formulations combining 1 wt%CNT with 1 or 2 wt%GN,using a twin-screw extrusion process to form filaments.These filaments were characterized through differential scanning calorimetry(DSC),field emission gun scanning electron microscopy(FEG-SEM),tensile testing,and shape memory assessments.While the PLA/TPU blend is immiscible,TPU enhances the crystallinity(X_(c))of the PLA phase,further increased by the addition of CNT and GN.FEG-SEM images indicate CNTs primarily in the PLA phase and GN in the TPU phase.PLA/TPU with 1 or 2 wt%GN showed the highest potential for suture applications,with a high elastic modulus(~1000 MPa),significant strain at break(~10%),and effective shape recovery(~20%at 55℃ for 30 min).These findings suggest that these nanocomposites can enhance suture performance with controlled shape recovery that is suitable for medical use.
基金financially support by the National Natural Science Foundation of China (No. 51573130)
文摘Imidazolium-based elastomeric ionomers （i-BIIR） were facilely synthesized by ionically modified brominated poly（isobutylene-co-isoprene） （BIIR） with different alkyl chain imidazole and thoroughly explored as novel toughening agents for poly（lactic acid） （PLA）. The miscibility, thermal behavior, phase morphology and mechanical property of ionomers and blends were investigated through dynamic mechanical analyses （DMA）, differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, tensile and impact testing. DMA and SEM results showed that better compatibility between the PLA and i-BIIR was achieved compared to the PLA/unmodified BIIR elastomer. A remarkable improvement in ductility with an optimum elongation at break up to 235% was achieved for the PLA/i-BIIR blends with 1-dodecylimidazole alkyl chain （i-BIIR-12）, more than 10 times higher than that of pure PLA. The impact strengths of PLA were enhanced from 1.9 kJ/m2 to 4.1 k J/m2 for the PLA/10 wt% i-BIIR-12 blend. Toughening mechanism had been established by systematical analysis of the compatibility, intermolecular interaction and phase structures of the blends. Interracial cavitations initiated massive shear yielding of the PLA matrix owing to a suitable interfacial adhesion which played a key role in the enormous toughening effect in these blends. We believed that introducing imidazolium group into the BIIR elastomer was vital for the formation of a suitable interfacial adhesion.
文摘Poly（lactic acid） （PLA） composites with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide （DOPO） and DOPO- containing polyhedral oligomeric silsesquioxane （DOPO-POSS） were prepared via melting extrusion and injection molding. The crystallization, mechanical, and flame-retardant properties of PLA/DOPO and PLA/DOPO-POSS were investigated by differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, tensile testing, thermogravimetric analysis （TGA）, limiting oxygen index （LOI）, and cone calorimeter test. The DSC results showed that the DOPO added could act as a plasticizer as reflected by lower glass transition temperature and inhibited crystallization of part of the PLA; the DOPO-POSS acted like a filler in the PLA matrix and slightly improved the crystallinity of the PLA matrix. The XRD and DSC analyses indicated that the PLA composites by cold molding injection were amorphous, and the PLA composites following a heat treatment in an oven at 120 ℃for 30 min achieved crystallinity. All the PLA and its composites after heat treatment had improved mechanical properties. The thermogravimetric analysis （TGA） tests showed that the PLA, DOPO and DOPO-POSS decomposed separately in the PLA/DOPO and PLA/DOPO-POSS, respectively. The cone calorimeter tests offered clear evidence that addition of the DOPO-POSS resulted in an evident reduction of 25% for the peak of heat release rate （p-HRR）. It was also confirmed that the crystalline flame-retardant PLA composites after heat treatment had better flame retardant properties than the amorphous PLA composites prepared by the cold molding.
基金Project(07XD14029) supported by the Program of Shanghai Subject Chief ScientistProject(075207046) supported by the Fund of Shanghai International Co-operation of Science and Technology+1 种基金Project(075211015) supported by the Key Science and Technologies Research and Development Program of Shanghai, ChinaProject(NCET-07-0620) supported by the Program for New Century Excellent Talents in University, China
文摘The natural fiber/poly(lactic acid) (PLA) composites were prepared with ramie and jute short fiber as reinforcement and PLA as matrix. The mechanical and thermal properties of the composites were investigated. The results show that the properties of the composites are better than those of plain PLA. When the content of the fiber is 30%, the composites can get the best mechanical properties. The dynamic mechanical analysis results show that the storage moduli of the PLA/ramie and PLA/jute composites increase with respect to the plain PLA. The Vicat softening temperature of the composites is greatly higher than that of PLA. The results of thermogravimetric analysis show that adding fiber to the PLA matrix can improve the degradation temperature of PLA.
基金This study was supported by the National Natural Science Foundation of China(No.30270395 and 30300084)the National"863"Project(No.2003AA32X210).
文摘A novel poly（d, /-lactic acid） （PDLLA） based biomimetic polymer was synthesized by grafting maleic anhydride, butanediamine and arg-gly-asp-ser （RGDS） peptides onto the backbone of PDLLA, aiming to overcome the acidity and auto-accelerating degradation of PDLLA during degradation and to improve its biospecificity and biocompatibility. The synthetic copolymer was characterized by FTIR, ^13C NMR and amino acid analyzer （AAA）.
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 National Natural Science Foundation of China(No.51103058)the Youth Foundation of Jilin Province(No.201101059)Open Foundation of Key Laboratory of Automobile Materials(Jilin University),Ministry of Education(No.10-450060326014)
文摘PLLA/CA mixtures of different compositions were successfully electrospun to obtain composite nanofibrous membranes. The microstructures of the membrances changed from homogeneous to heterogeneous with the addition of CA, which was observed by FE-ESEM. The PLLA/CA fabric membranes were characterized by mechanical testing, DSC and contact angle measurements. The tensile stress of the composite fibrous membranes increased obviously with the increase of CA content. DSC results indicated that the CA component was the main factor for the changes of enthalpies in the composite fibers. Contact angle measurements showed the hydrophilicity of the electrospun nanofiber membranes was improved with the addition of CA.
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.
基金financially supported by National Natural Science Foundation of China(No.20776087)National Programs for High Technology Research and Development of China(No.2008AA03Z510)
文摘One-step reaction compatibilized microfibrillar reinforced iPP/PET blends （CMRB） were successfully prepared through a ＂slit extrusion-hot stretching-quenching＂ process. Crystallization behavior and morphology of CMRB were systematically investigated. Scanning electronic microscopy （SEM） observations showed blurry interface of compatibilized common blend （CCB）. The crystallization behavior of neat iPP, CCB, microfibrillar reinforced iPP/PET blend （MRB） and CMRB was investigated by differential scanning calorimetry （DSC） and polarized optical microscopy （POM）. The increase of crystallization temperature and crystallization rate during nonisothermal crystallization process indicated both PET particles and mierofibrils could serve as nucleating agents and PET microfibrils exhibited higher heterogeneous nucleation ability, which were also vividly revealed by results of POM. Compared with MRB sample, CMRB sample has lower crystallization temperature due to existence of PET microfibrils with smaller aspect ratio and wider distribution. In addition, since in situ compatibilizer tends to stay in the interphase, it could also hinder the diffusion ofiPP molecules to the surface of PET phase, leading to decrease of crystallization rate. Two-dimensional wide-angle X-ray diffi：action （2D-WAXD） was preformed to characterize the crystalline structure of the samples by injection molding, and it was found that well-developed PET microfibrils contained in MRB sample promoted formation of t-phase of/PP.
基金financially supported by the National Natural Science Foundation of China(Nos.20774098,21174074 and 51003050)the National Key Technology R&D Program of China(No.2011BAE26B05)Shandong Province Natural Science Fund for Distinguished Young Scholars(No.JQ201213)
文摘Diphenyl （4-hydroxyphenyl） hexadecyl phosphonium bromide （POH） -modified montmorillonite （POHMMT） was used to prepare a novel TiC14/MgC12/POHMMT compound catalyst and exfoliated iPP/POHMMT nanocomposites were prepared by the in situ intercalative polymerization of propylene with the TiC14/MgC12/POHMMT compound catalyst. The POH surfactants don＇t change the catalytic characteristic of the Z-N catalyst and the obtained PP presents high isotacticity, normal molecular weight and molecular weight distribution. The WAXD, SAXS and TEM results demonstrate the highly exfoliated iPP/POHMMT nanocomposites were produced by the in situ polymerization with this novel catalyst, while the intercalated iPP/Na＋MMT nanocomposites were produced with the TiC14/MgC12/Na＋MMT compound catalyst. Through this approach, in situ propylene polymerization can actually take place between the silicate layers and lead not only to PP with high isotacticity and molecular weight, but also to highly exfoliated PP nanocomposites.
基金Supported by the National Natural Science Foundation of China(21476065)the China National Tobacco Corporation
文摘Micro-encapsulated phase-change materials(micro PCMs) with Na_2 HPO_4·12 H_2 O encapsulated in poly(lactic acid)(PLA) shell were prepared by a solvent evaporation–precipitation method that involves the use of a coaxial needle. The effects of PLA concentration, stirring speed, injection rate of core and shell solutions, and polyvinyl alcohol(PVA) concentration on phase change properties were investigated. The thermal properties of microP CMs were characterized by differential scanning calorimetry(DSC). The capsules prepared under the optimal conditions are about 2 mm in diameter and show a latent heat of up to 122.2 J·g^(-1).
基金Supported by the Chinese Academy of Sciences Direction Project(No.KTCX-YW-208)
文摘Blends of poly（lactic acid）（PLA） and thermoplastic acetylated starch（ATPS） were prepared by means of the melt mixing method. The results show that PLA and ATPS were partially miscible, which was confirmed with the measurement of Tg by dynamic mechanical analysis（DMA） and differrential scanning calorimetry（DSC）. The mechanical and thermal properties of the blends were improved. With increasing the ATPS content, the elongation at break and impact strength were increased. The elongation at break increased from 5% of neat PLA to 25% of the blend PLA/ATPS40. It was found that the cold crystallization behavior of PLA changed evidently by addition of ATPS. The cold crystallization temperature（Tcc） of each of PLA/ATPS blends was found to shift to a lower temperature and the width of exothermic peak became narrow compared with that of neat PLA. The thermogravimetry analysis（TGA） results showed that the peak of derivative weight for ATPS moved to higher temperature with increasing PLA content in PLA/ATPS blends. It can be concluded that PLA could increase the thermal stability of ATPS. The rheological measurement reveals the melt elasticity and viscosity of the blends decreased with the increased concentration of ATPS, which was favorable to the processing properties of PLA.
文摘Biodegradable chitosan-g-poly (D, L-lactic acid) copolymers were prepared via two methods. (1) The lactide was grafted onto hydroxyl groups of chitosan by using macromolecular initiator sodium of trimethylsilyl-chitosan, (2) poly (D,L-lactic acid)(PLA) with low molecular weight can be linked to the amino group by coupling activated PLA to trimethylsilyl-chitosan. Two graft copolymers had hydrophilic-hydrophobic character and can be applied as carriers for drug delivery.
基金This work was supported by the National Natural Science Foundations of China.
文摘Aggregation process of isotactic poly（methyl methacrylate） （i-PMMA） has been studied extensively for many years, and considerable progress has been made in both experimental and theoretical studies. They are, however, seldom sustained by real-space observations of the underlying morphology. In this paper, the aggregation process of i-PMMA in concentrated acetone solutions and the fractal structure of the resulting three-dimensional clusters were characterized on the basis of real-space AFM observations of their two-dimensional projection. It was found that spherical multiple-chain particles formed upon collapse and aggregation of the involving chains as a whole during quenching the solution to room temperature. By keeping the solution at room temperature, the initially formed particles stick together upon contact to form larger particles through reassembling very slowly. The succeeding collision of the enlarged spherical particles leads to the formation of small clusters. These newly formed small clusters grow when they meet with other clusters or single Brownian particles. This leads to the formation of large clusters with fractal dimension of 1.95 ± 0.05, which suggest a reaction-limited cluster aggregation of i-PMMA in a concentrated acetone solution. This is in accordance with the conclusion obtained by light scattering measurements.
