Flax/Polylactic Acid(PLA)Core/Sheath Structural Composite Yarn Fabricated by Spindle Braiding Technique

The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by braiding PLA filaments with 4 to 24 spindles on flax yarns.After curing at different temperatures(180℃and 190℃),the core/sheath structural flax/PLA composite yarns were manufactured.According to the results of the tensile test,the flax/PLA composite yarn with 4-spindle PLA yarns as a sheath layer and at a curing temperature of 180℃reached the maximum elastic modulus of about(5.79±0.65)GPa and the maximum tensile strength of about(162.17±18.18)MPa.This flax/PLA composite yarn with good mechanical properties would be suitable for green composites in the automobile manufacturing industry and building materials.

Isolation of Microcrystalline Cellulose from Wood and Fabrication of Polylactic Acid(PLA)Based Green Biocomposites

An innovative microcrystalline cellulose(MCC)natural fibre powder-reinforced PLA biocomposite was investigated using the hand lay-up technique.The polymer matrix composite(PMC)samples were prepared by varying the weight percentages(wt.%)of both PLA matrix and MCC reinforcement:pure PLA/100:0,90:10,80:20,70:30,60:40 and 50:50 wt.%,respectively.From the results obtained,MCC powder,with its impressive aspect ratio,proved to be an ideal reinforcement for the PLA,exhibiting exceptional mechanical properties.It was evident that the 80:20 wt.%biocomposite sample exhibited the maximum improvement in the tensile,flexural,notched impact,compressive strength and hardness by 28.85%,20.00%,91.66%,21.53%and 35.82%,respectively compared to the pure PLA sample.Similarly,during the thermogravimetric analysis(TGA),the same 80:20 wt.%biocomposite sample showed a minimum weight loss of 20%at 400℃,among others.The morphological study using Field Emission Scanning Electron Microscopy(FE-SEM)revealed that the uniform distribution of cellulose reinforcement in the PLA matrix actively improved the mechanical properties of the biocomposites,especially the optimal 80:20 wt.%sample.Importantly,it was evident that the optimal PLA/cellulose biocomposite sample could be a suitable and alternative sustainable,environmentally friendly and biodegradable material for semi/structural applications,replacing synthetic and traditional components.

Biodegradation and Mechanical Property of Polylactic Acid/Thermoplastic Starch Blends with Poly (ethylene glycol)

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.

Effects of Selected Printing Parameters on the Fire Properties of 3D-Printed Neat Polylactic Acid(PLA)and Wood/PLA Composites

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.

Radial basis function neural network and overlay sampling uniform design toward polylactic acid molecular weight prediction

Polylactic acid(PLA)is a potential polymer material used as a substitute for traditional plastics,and the accurate molecular weight distribution range of PLA is strictly required in practical applications.Therefore,exploring the relationship between synthetic conditions and PLA molecular weight is crucially important.In this work,direct polycondensation combined with overlay sampling uniform design(OSUD)was applied to synthesize the low molecular weight PLA.Then a multiple regression model and two artificial neural network models on PLA molecular weight versus reaction temperature,reaction time,and catalyst dosage were developed for PLA molecular weight prediction.The characterization results indicated that the low molecular weight PLA was efficiently synthesized under this method.Meanwhile,the experimental dataset acquired from OSUD successfully established three predictive models for PLA molecular weight.Among them,both artificial neural network models had significantly better predictive performance than the regression model.Notably,the radial basis function neural network model had the best predictive accuracy with only 11.9%of mean relative error on the validation dataset,which improved by 67.7%compared with the traditional multiple regression model.This work successfully predicted PLA molecular weight in a direct polycondensation process using artificial neural network models combined with OSUD,which provided guidance for the future implementation of molecular weight-controlled polymer's synthesis.

3D Printing of Polylactic Acid Bioplastic–Carbon Fibres and Twisted Kevlar Composites Through Coextrusion Using Fused Deposition Modeling

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.

Preparation and Properties of Heat Resistant Polylactic Acid(PLA)/Nano-SiO2 Composite Filament

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.

盐酸多巴胺处理对PLA非织造布油水分离性能的影响

为了研究盐酸多巴胺对PLA非织造布油水分离性能的影响,采用质量分数为0.5%~1.0%的盐酸多巴胺对PLA熔喷非织造布和PLA纺黏非织造布进行处理,并对处理后的样品进行性能测试。结果表明:随着盐酸多巴胺质量分数的增加,处理后的PLA非织造布纤维表面盐酸多巴胺黏附量增加,且非织造布由疏水性转变为超亲水性;PLA纺黏非织造布单位面积质量的变化对盐酸多巴胺的黏附量影响较小;PLA非织造布拉伸应力随着盐酸多巴胺溶液质量分数的增加呈现先下降后上升的趋势;PLA熔喷非织造布对CCl_(4)/水和正己烷/水混合溶液正常表现为水可快速通过,而油性溶剂被拦截;相反,材料经油性溶剂浸润,油性溶剂可快速通过,而水被拦截的自主选择性,且其油水分离通量为1671.123 L/(m^(2)·h)和1697.951 L/(m^(2)·h);PLA纺黏非织造布对CCl_(4)/水和正己烷/水混合溶液的油水分离通量达到3852.743 L/(m^(2)·h)和3922.961 L/(m^(2)·h);PLA非织造布对正己烷/水混合溶液重复分离10次后,分离通量降幅较小,油水分离循环性较好。

基于原位交联增容策略的增强PLA/NR共混物界面相容性和发泡性能研究

聚乳酸(PLA)是目前最具发展潜力的生物材料之一,但其韧性差,极大的限制了在塑料领域的发展与应用.已有研究发现天然橡胶(NR)的引入可以改善其韧性差的缺陷,但二者为不相容体系,发泡性能差.因此,本文基于原位交联增容原理,采用1,4-双(叔丁基过氧异丙基)苯(BIPB)增强PLA和NR的界面相容性,并以超临界二氧化碳(scCO_(2))发泡技术制备了PLA/NR复合发泡材料.探究了不同BIPB含量对复合材料界面相容性、韧性及复合材料发泡行为的影响.结果表明,BIPB的引入显著增强了PLA/NR复合材料的相容性、韧性及发泡性能.当BIPB含量为0.25 phr时,PLA/NR复合材料的断裂伸长率从原来的25.75%增加到35.24%,提升了1.37倍;表观密度从初始的0.565 g·cm^(-3)下降至0.373 g·cm^(-3);平均泡孔尺寸从7.5μm下降至5.0μm.

Preparation and Properties of Polylactic Acid( PLA) /Nano-SiO_2 Composite Master Batch with Good Thermal Properties

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.

Study on Dyeing of a Novel,Pro-environment Polylactic Acid (PLA) Fiber Yarn

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.

Properties enhancement of antimicrobial chitosan-deposited polylactic acid films via cold plasma treatment

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.

Preparation, Characterization and in Vitro Release of Ciprofloxacin Polylactic Acid Microspheres

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.

羟基化氮化硼改性PLA纳米纤维膜的制备及性能研究

为拓展生物基可降解PLA纳米纤维膜在空气过滤等医疗卫生领域的应用范围,通过机械剥离与功能化改性方法制备羟基化氮化硼(BNO)二维纳米片,并采用静电纺丝工艺制备羟基化氮化硼纳米片改性聚乳酸(PLA/BNO)纳米纤维膜。探讨BNO纳米片的引入对PLA纳米纤维膜的微观结构与形貌、导热性能、力学性能以及空气过滤性能的影响。结果表明:与纯PLA纳米纤维膜相比,PLA/BNO纳米纤维膜的拉伸力学性能以及导热性能显著提高。当纺丝液中BNO纳米片质量分数为0.7%时,风速为0.01 m/s时,PLA/BNO纳米纤维膜的过滤效率为99.97%,品质因子达到最大值0.262 Pa^(-1),阻力压降最小为31 Pa,PLA/BNO纳米纤维膜的拉伸断裂强度以及导热系数较纯PLA纳米纤维膜分别提高27.39%和26.62%。

Tensile Properties of Mechanically-Defibrated Cellulose Nanofiber-Reinforced Polylactic Acid Matrix Composites Fabricated by Fused Deposition Modeling

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.

Mechanical and Thermal Properties of Apocynum and Ramie Fiber Mat Reinforced Polylactic Acid Composites

With the increasing awareness of environmental protection and rational utilization of resources,natural fiber reinforced composites have shown broad development prospects.Apocynum fiber,known as the“king of wild fiber”,not only has moisture absorption,air permeability,and good mechanical properties but also has many health-related advantages such as antibacterial properties.In this study,four types of needle-punched Apocynum fiber and ramie fiber mat reinforced polylactic acid(PLA)composites were fabricated.Mechanical and thermal properties of the composites were tested and analyzed.The results showed that compared with those of the ramie fiber finish needle-punched mat reinforced composites,the tensile strength and the tensile modulus of Apocynum fiber finish needle-punched mat reinforced composites had increased by 15.3%and 60.1%,respectively.In comparison,the bending strength and the bending modulus were decreased by 21.8%and 7.6%,respectively.Moreover,compared with the Apocynum fiber finish needled-punched mat reinforced composites and the ramie fiber finish needle-punched mat reinforced composites,the Apocynum 50/ramie 50 finish needle-punched mat reinforced composites had the best tensile and bending properties.The after-fracture morphology was detected by a scanning electron microscope(SEM).The thermal properties of the composites were also characterized.It was found that the thermal properties of the four types of composites showed very similar behaviors.

3D printing of personalized polylactic acid scaffold laden with GelMA/autologous auricle cartilage to promote ear reconstruction

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.

PLA/天然废弃植物源提取物复合材料的制备与性能

针对废弃资源综合利用和通用塑料污染问题,采用超声波辅助提取法提取天然废弃植物源有效成分,并与聚乳酸(PLA)复合,探究石榴皮提取物(PGE)和洋葱皮提取物(OPE)对PLA性能的影响。结果表明:两种提取物的加入并没有改变PLA的晶型,但提高了成核密度,减小了球晶尺寸。复合材料的热稳定性有一定的下降,但由于提取物中羟基与PLA发生了氢键作用使其下降幅度不大,同时弥补了复合材料力学性能减小的趋势。植物源提取物的添加使复合材料中的—OH基团数量增多,水蒸汽透过率也随之增大,适用于地膜及食品果蔬保鲜材料中。两种提取物赋予了复合材料不同色泽,染色成分与PLA间的界面作用使复合材料耐摩擦色牢度得以保持,扩大了其应用范围。两种复合材料具有显著的抑菌作用,其中,PGE含量为9%时,其复合材料的抗菌率可达95%以上,可以作为抗菌材料应用。

Thermal Decomposition and Kinetics of Mixtures of Polylactic Acid and Biomass during Copyrolysis

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.

Effect of Starch/Polylactic Acid Ratio on the Interdependence of Two-Phase and the Properties of Composites

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.