Enhanced thermal and electrical properties of poly (D,L-lactide)/ multi-walled carbon nanotubes composites by in-situ polymerization

Biodegradable poly （D,L-lactide） （PLA）/carboxyl-functionalized multi-walled carbon nanotubes （c-MWCNTs） composites were achieved via in-situ polymerization. These as-prepared composite materials were characterized with FT-IR, XRD, TG, DSC, SEM, and high insulation resistance meter. The results demonstrate that the multi-walled carbon nanotube was carboxyl functionalized, which improved the collection between c-MWCNTs and PLA, and further realized the graft copolymerization of c-MWCNTs and PLA. There is a higher glass transition temperature and a lower pyrolysis temperature of PLA/c-MWCNTs composites than pure PLA. The c-MWCNTs gave a better dispersion than unmodified MWCNTs in the PLA matrix, and an even coating of PLA on the surface of c-MWCNTs was obtained, which increased the interfacial interaction. High insulation resistance analysis showed that the addition of c-MWCNTs increased the electric conductivity, and c-MWCNTs performed against the large dielectric coefficient and electrostatic state of PLA. These results demonstrated that c-MWCNTs modified PLA composites were beneficial for potential application in the development of heat-resisting and conductivity plastic engineering.

Preparation and characterization of composite microspheres of nano zinc ferrite/poly(D,L-lactide-co-alanine)

Magnetic nano zinc ferrite fliuds were synthesized using an improved liquid phase chemical method, which would be used to replace tradditional iron oxides magnetic material. A novel copolymer （PLAA） with D, L-lactide （D, L-LA） and alanine was synthesized using stannous octoate as initiator. Magnetic polymer microspheres were fabricated with nano zinc ferrite fluid coated with alanine modified poly lactide. These as-prepared zinc ferrite fluids, modified poly lactide and magnetic composites, were characterized with X-ray diffraction diffractometer, FT-IR spectrometer, nuclear magnetic resonance spectrometer, scanning electron microscope, transmission electron microscope, vibrating sample magnetometer, and thermogravimetric analyzer. The results demonstrate that the as-prepared zinc ferrite is spinel type of ZnFe2O4 nano crystals with particle size of 20-45 nm and magnetization of 32×10^-3 A.m2. Alanine is copolymerized with lactide, and the prepared composite magnetic microsphere is coated with the modified polylactide, with mass fraction of 45.5% of PLA, particle size ranging from 80-300 nm, and magnetization of 10.6×10^-3 A·m^2, which suggests ZnFe2O4 enjoys a stable magnetization after being coated by polymer.

Flexible Polydimethylsiloxane Composite with Multi-Scale Conductive Network for Ultra-Strong Electromagnetic Interference Protection

Highly conductive polymer composites(CPCs) with excellent mechanical flexibility are ideal materials for designing excellent electromagnetic interference(EMI) shielding materials,which can be used for the electromagnetic interference protection of flexible electronic devices.It is extremely urgent to fabricate ultra-strong EMI shielding CPCs with efficient conductive networks.In this paper,a novel silver-plated polylactide short fiber(Ag@PL ASF,AAF) was fabricated and was integrated with carbon nanotubes(CNT) to construct a multi-scale conductive network in polydimethylsiloxane(PDMS) matrix.The multi-scale conductive network endowed the flexible PDMS/AAF/CNT composite with excellent electrical conductivity of 440 S m-1and ultra-strong EMI shielding effectiveness(EMI SE) of up to 113 dB,containing only 5.0 vol% of AAF and 3.0 vol% of CNT(11.1wt% conductive filler content).Due to its excellent flexibility,the composite still showed 94% and 90% retention rates of EMI SE even after subjected to a simulated aging strategy(60℃ for 7 days) and 10,000 bending-releasing cycles.This strategy provides an important guidance for designing excellent EMI shielding materials to protect the workspace,environment and sensitive circuits against radiation for flexible electronic devices.

Preparation and Characterization of Polylactide/Montmorillonite Nanocomposites

The montmorillonite, a form of layered silicate, was successfully intercalated into polylactide （PLA） matrix through solvent-casting technique. In addition, PLA/MMT nanocomposite films were produced, in which homogenous distribution of the silicate lamellae plays a key role in the mechanical properties of the films. A small amount（5wt%） of OMMT intercalated into the PLA matrix resulted in their flexibility enhancement, from 3.68%（pure PLA film） to 352.65%. The results of wide-angle X-ray diffraction （WAXD） patterns confirmed that the silicate interlayer distance increased from 3.044 nm （for OMMT） to 3.56nm （for 5wt%, maximum） with increasing OMMT contents, but decreased to 3.319 nm when OMMT content was over 8wt%. FT-IR also verified the molecular-level associations between PLA chains and OMMT lamellae by vibration variances of hydrogen bonding. DSC thermograms demonstrated that thermal stabilities of the nanocomposite films enhanced, due to the silicate lamellae dispersed into PLA matrix.

Dyes with high affinity for polylactide

Attempts were made to develop dyes with high affinity for polylactide as an alternative to the existent commercial disperse dyes. The dyes synthesized according to the affinity concept of dye to polylactide exhibited excellent dyeing properties on polylactide compared with the commercial disperse dyes.

Novel Bio-based Flame Retardant Systems Derived from Tannic Acid

In this study,tannic acid(TA)was investigated as flame retardant agent for PLA.Different strategies to modify its thermal degradation pathway have been explored in order to improve its charring effect.The first one consists in combining TA with organomodified montmorillonite(oMMT),and enables limiting the thermo-oxidative degradation of TA and promoting the formation of an effective char layer.Flame-retardant(FR)behavior of PLA-based composition has been found to be positively impacted by this combination since a reduction of the peak of Heat Release Rate(PHRR),more important than the value recorded when oMMT and tannic acid are used separately,has been obtained.The second strategy,in which tannic acid was associated with a biosourced phosphorousbased compounds,i.e.metallic phytate salt,evidenced another alternative allowing enhancing TA flame retardant effect at 30 wt%loading content.The third and last strategy explored aims to chemically modify TA via a chemical grafting of phosphoric acid groups.This phosphorylated TA was shown to present the most effective flame-retardant(FR)effect.However,an important reduction of PLA molecular weight was observed.

Preparation of monomer of degradable biomaterial poly(L-lactide)

L-lactide was prepared from L-lactic acid with stannous octoate as the catalyst. The effects of reaction temperature and pressure on the ingredient of crude lactide were investigated. The results show that the mass fraction of meso-lactide increases with the increasing reaction temperature. Crude lactide containing 85.4% L-lactide is obtained when the reaction temperature is 200 ℃. High purity of L-lactide with a yield of 40.6 % is obtained by synthetic purifying method. The properties of L-lactide are characterized by optical purity, infrared spectrum and gas chromatogram/mass spectrum. The L-lactide samples purified by recrystallization and synthetic purifying methods are polymerized with the catalyst of stannous octoate, and the corresponding viscosity average relative molecular masses of poly(L-lactide) are 2.85 × 105 and 5.05 × 105 , respectively. This indicates that the optical purity of Llactide has great influence on the relative molecular mass of poly(L-lactide).

Dyeability of Polylactide Fabric with Hydrophobic Anthraquinone Dyes

The dyeability of polylactide fabric has been investigated with the substituted aminoanthraquinone hydophobic dyes. Their application to the polylactide fabric led to good exhaustion values and good wash fastness between 4 and 3. MIcroscopic assessment ot cross-sections ot the dyed polylactlde fibres confirmed that these dyes could penetrate into the fibres. The nature of the substituted amino groups showed little influence on the wash fastness, but clearly influenced.the exhauslion and light fastness.

Improving Polylactide Toughness by Plasticizing with Low Molecular Weight Polylactide-Poly(Butylene Succinate)Copolymer

A low-molecular-weight polylactide-poly(butylene succinate)(PLA-PBS)copolymer was synthesized and incorporated into polylactide(PLA)as a novel toughening agent by solvent casting.The copolymer had the same chemical structure and function as PLA and it was used as a plasticizer to PLA.The copolymer was blended with PLA at a weight ratio from 2 to 10 wt%.Phase separation between PLA and PLA-PBS was not observed from their scanning electron microscopy(SEM)images and the crystal structure of PLA almost remained unchanged based on the X-ray diffraction(XRD)measurement.The melt flow index(MFI)of the blends was higher as the amount of PLA-PBS increased,indicating that the block copolymer did improve the mobility of the PLA chains.Moreover,tensile tests revealed that PLA with greater PLA-PBS copolymer exhibited higher elongation at break and it reached the maximum at 8 wt%of PLA-PBS in PLA,which was around 6 times higher than that of pure PLA.Furthermore,the glass transition temperature,measured by differential scanning calorimetry(DSC),markedly decreased with an increasing amount of the copolymer as it decreased from 61.2℃ for pure PLA to 41.3℃when it was blended with 10 wt%PLA-PBS copolymer.Therefore,the PLA-PBS copolymer was shown to be a promising plasticizer for fully biobased and toughened PLA.

Preparation and Characterization of Biological Non-toxic Hybrid Nanoparticles Based on Lactide and Poly(ethylene glycol) Loading Docetaxel for Anticancer Drug Delivery

Hybrid nanoparticles based on lactide and poly(ethylene glycol) were composed of a copolymer, poly(2-amino,1,3-propanediol carbonic ester-co-lactide) [P(LA-co-CA)], and a graft copolymer, poly(2-amino,1,3-propanediol carbonic ester-co-L-lactide)-g-methoxy-poly(ethylene glycol) [P(LA-co-CA)-m PEG]. The hybrid nanoparticles were prepared using emulsion solvent diffusion method. The copolymer of poly(2-benzyloxy amide,1,3-propanediol carbonic ester-co-lactide) was prepared using ring-opening polymerization with diethylzinc(Zn Et2) as a catalyst, and then took off benzyl oxygen group to obtain P(LA-co-CA). P(LA-co-CA)-m PEG by grafting methoxy-PEG-propionaldehyde(m PEG-ALD) on P(LA-co-CA). With docetaxel as a model drug, the morphology of nanoparticles was characterized by scanning electron microscopy(SEM) and the size and size distribution were determined by dynamic light scattering(DLS). The size of DTX-loaded particle was approximately 110 nm. The size scale prevents them from uptake by the reticulo-endothelial system and accumulation at the target site through the enhanced permeability and retention effect. In MTT assay, the results showed that the polymers are non-cytotoxic. The study points to the potential application of the composite nanoparticles in biomedical applications, including tissue engineering and controlled drug delivery.

Suitability of Blends from Virgin and Reprocessed Polylactide: Performance and Energy Valorization Kinet

A blending strategy of virgin and reprocessed polylactide may be postulated as an alternative to reduce the material cost at industrial level,and as a valorization route to plastic waste management of production scraps.The performance of blends prepared from virgin polylactide and polylactide mechanically reprocessed up to two cycles(PLA-V/R)was assessed in terms of thermo-oxidative stability,morphology,viscoelasticity and thermal kinetics for energetic valorization.PLA-V/R blends showed appropriate thermo-oxidative stability.The amorphous nature of polylactide was preserved after blending.The viscoelastic properties showed an increment of the mechanical blend effectiveness,which suggested the feasibility of using PLA-V/R blends under similar mechanical conditions to those of virgin PLA goods.Finally,it was shown that the energetic valorization of PLA-V/R blends would result in a more feasible process,due to the lower required activation energy,thus highlighting the advantages of the energetic demand for the process.In conclusion,PLA-V/R blends showed similar processability,service performance and valorization routes as virgin PLA and therefore could be relevant in the sustainable circular industry of bioplastics.

Effect of Mixing Strategy on the Structure-Properties of the PLA/PBAT Blends Incorporated with CNC

Polylactide(PLA)/poly(butylene adipate-co-terephthalate)(PBAT)blend nanocomposites including 3 wt%of cel-lulose nanocrystals(CNCs)were prepared by melt compounding method in a twin-screw extruder and an inter-nal mixer.Blend nanocomposites were formulated by diluting three different masterbatches prepared by solution casting method that contained 7 wt%of CNC.These masterbatches were:(m1)PLA/PBAT/CNC masterbatch;(m2)PLA/CNC masterbatch;and(m3)PBAT/CNC masterbatch.These were to explore how different prepara-tion methods affect the dispersion and localization of CNC and hence the properties of PLA/PBAT/CNC blend nanocomposites.Scanning electron microscopy(SEM)was used to study the structural changes of the blends.Rheological properties of PLA/PBAT blends and PLA/PBAT/CNC blend nanocomposites were also investigated.In the samples prepared by internal mixer,the rheological behavior of blend nanocomposite prepared through premixing of CNC particles with PLA showed a transition from liquid-like to a gel-like behavior.According to the rheological results and differential scanning calorimetry(DSC)analysis,it was found that the CNC overall enhanced the viscoelastic properties of blends and improved the PLA crystallization,respectively.Dynamic mechanical analysis(DMA)illustrated that the incorporation of CNC also enhanced the elastic modulus of PLA/PBAT blends specifically above the glass transition temperature of PLA.The expected improvements in mechanical properties did not occur due to the possible existence of residual solvent in the blends.

Preparation of Hydroxyapatite/Polylactide Bicomposites by Absorption Process in Liquid Phase

The hydroxyapatite/polylactide biocomposites were prepared by absorption process in liquid phase. The method avoided many disadvantages, such as inaterfusion of chemical impurity substances, nonuniformity dispersal of HA in PLA, low molecular weight of PLA . HA particles were uniformly dispersed in PLA matrix, and showed well ndhesion with PLA matrix. The biocomposites have the higher mechanical properties and suitable decomposable capability.

Study on the Properties of Esterified Corn Starch/Polylactide Biodegradable Blends

Fully bio-based and biodegradable starch/polylactic acid blends have received increasing attentions for their biodegradability and potential to offset the use of unsustainable fossil resources,specifically,their application in packaging.Herein,corn starch was first esterified with maleic anhydride and then compounded with polylactide(PLA)to prepare esterified corn starch/polylactic acid blends with starch content up to 35 wt%.The structures,morphologies,thermal and mechanical properties of starch or blends were investigated.The results showed that corn starch was successfully grafted with maleic anhydride,which showed increased crystallinity and particle size than native starch.Esterified corn starch/polylactic acid blends showed good surficial compatibility and good thermal stability with main decomposition temperature in the range of 300℃to 400℃.Additionally,incorporation of corn starch increased the hydrophilicity and water uptake of composites.However,the tensile and flexural strengths of blends decreased with increasing esterified starch amount.

Amorphous Polylactide Bead Foam–Effect of Talc and Chain Extension on Foaming Behavior and Compression Properties

Polylactide(PLA)bead foams show a high potential regarding their applicability in packaging or consumer products.Concerning the comparable properties of PLA to Polystyrene(PS)and the good CO_(2) footprint it represents a potential alternative to petroleum-based polymer foams.However,foaming of PLA is challenging,due to its low melt strength,therefore chemical modifiers are often used.Concerning the bead foam technology regarding PLA,the available literature is limited so far.Within this study,the bead foaming behavior of neat and modified amorphous PLA was investigated.The material was modified by talc and an epoxy-based chain extender.These compounds have been investigated regarding their sorption behavior in CO_(2) atmosphere and their foaming behavior.Foaming was conducted by using the batch foaming method based on a rapid temperature increase after saturation with CO_(2).In order to achieve welded bead foams,a one-step processing for foaming and welding has been established.Finally,the compression properties of the PLA bead foams have been investigated.Densities below 50 kg/m^(3) for single bead foams and 80 kg/m^(3) for molded foams were achieved,respectively.

HOMOPOLYMERS AND COPOLYMERS OF GLYCOLIDE AND LACTIDE

The homopolymerization and copolymerization of glycolide (GA) and lactide (LA) are des-cribed. The resulting polymers are characterized by differential scanning calorimetry (DSC),thermogravimetric analysis (TGA), 300 MHz proton nuclear magnetic resonance spectroscopy(NMR), infrared spectroscopy, and X-ray diffraction. The rheological properties of PGA andPGLA 910 are evaluated by shear experiments. The biodegradation has been studied in vivo. Theresults show that the polyesters can be absorbed by the muscles of rabbits after 60 days.

The Influence of Poly(Vinyl Alcohol)on Oil Release Behavior of Polylactide-Based Composites Filled with Linseed Cake

In order to limit the negative impact of industry on natural environment,ecological alternatives to conventional polymers are being proposed.One of the most popular“green”polymers is polylactide,which can also be successfully applied as a matrix of composites.The application of ground linseed cake as a filler for polylactide-based composites is in line with the idea of Circular Economy,and moreover it provides a modifying effect on the polymer by increasing its crystallinity and reducing its brittleness.This effect is caused by the presence of linseed oil which can be released to the polymeric matrix in a non-controlled way.In order to control the miscibility of the oil and the polymer,we modified the filler particles with poly(vinyl alcohol)before introducing it to the polylactide.We concluded that poly(vinyl alcohol),which does not mix with oil,encapsulated the active ingredients inside the filler particles.We evaluated the mechanical properties of the composites containing 5,10,20 and 30 wt%of the filler in a static tensile stress and by means of dynamic mechanical thermal analysis.Crystallinity and thermal properties were tested using differential scanning calorimetry as well as thermogravimetric analysis.Composites’microstructure was evaluated by Scanning Electron Microscopy.It was found that modifying the oil-rich filler with poly(vinyl alcohol)helps to reduce its release to the matrix and thus limits the plasticizing effect of linseed cake.This result was in accordance with our hypothesis.

Research on the Sizing Performance of Starch Grafted Poly-hydroxy Alkyl-acid Esters

Starch grafted poly-hydroxy alkyl-acid esters were prepared via graft polymerization.Different characteristics of grafted starches were tested such as viscosity,viscosity stability,adhesion as well as properties of sized yarns.Sizing performance was analyzed from the aspect of physical and chemical reactions between polymer molecules.It shows that starch grafted poly-hydroxy alkyl-acid esters have excellent sizing performance and could absolutely be used as sizes for polyester-cotton yarns.

Synthetic Absorbable Surgical Sutures

This paper reviewed all types of the polymer - based synthetic absorbable surgical sutures that have been commercially produced. The chemical component, biological and mechanical properties, and using effect of these sutures were discussed. The recent development and the possible coming research orientation in these areas were also presented.