PLA Blends Research Articles

Mechanochemical Oleation of Lignin Through Ball Milling and Properties of its Blends with PLA

AbstractIn this work, mechanochemical modification of lignin and PLA blends with the modified lignin were studied. Oleated organosolv lignin (OL) was prepared by transesterification between OL and methyl oleate and the oleation reaction was conducted in ball milling process. PLA/lignin blends were successfully prepared through melt extrusion. The tensile, dynamic mechanical, rheological and morphological properties of the blends were investigated. Compared with the PLA/milled OL blends, the PLA/oleated OL blends exhibited finer dispersion of lignin in the blends, increased glass transition temperature and higher tensile properties.

Biodegradability of poly(lactic acid) (PLA)/lactic acid (LA) blends using anaerobic digester sludge

Poly(lactic acid) (PLA) has been highlighted for its excellent biodegradability and hydro-degradability. On the other hand, an estimation of the biodegradability of PLA generally requires lengthy measurements over several months because it is difficult for the terminal decomposer, a microorganism, to uptake and utilize the polymer material, making it difficult to analyze and compare the results quantitatively. In this study, it was hypothesized that the inclusion of mono lactic acid (LA) in a PLA blend improves the level of microbial attachment to the surface of the PLA blend, and increases the biodegradation rate. PLA blend films containing 1%, 2.5%, and 5% of LA were prepared, and their morphological changes to the surface and cross section of films were investigated. The biodegradation of a PLA/LA blend using digester sludge was estimated quantitatively from the specific gas production rate (SGPR) based on the surface area of the blend film. The physical and chemical properties before and after biodegradation were also compared. These results show that PLA/LA blends with a controlled degradation rate can be developed by incorporating readily degradable chemicals, and implemented as environmentally friendly plastics and polymers.

Grafting collagen on poly (lactic acid) by a simple route to produce electrospun scaffolds, and their cell adhesion evaluation.

Increasing bioactivity and mechanical properties of polymers to produce more suitable scaffold for tissue engineering is a recurrent goal in the development of new biomedical materials. In this study, collagen-functionalized poly (lactic acid), PLA, was obtained by means of a simple grafting route, and electrospun scaffolds were produced to grow cells in vitro; their bioactivity was compared with scaffolds made of physical blends of PLA and collagen. Grafting was verified via nuclear magnetic resonance, attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopy. The cell adhesion performance of the scaffolds was studied using macrophages. Elastic modulus (74.7 megapascals) and tensile strength (3.0 megapascals) of the scaffold made from PLA grafted with collagen were substantially higher than the scaffolds made from physical blends of collagen and PLA: 32 and 2.16 megapascals, respectively, implying a more resistant material because of the chemical bond of the polypeptide to PLA. Besides, the fibers had more uniform diameter without defects. Scaffolds made from PLA grafted with collagen presented four-fold increase in cell adhesion than those of PLA blended with collagen. Furthermore, cell spreading within the scaffolds occurred only when collagen-functionalized poly (lactic acid) was used. These results open a new option for the easy tailoring of nanofiber-based scaffolds in three dimensions for tissue engineering.

Biodegradable Blends with Potential Use in Packaging: A Comparison of PLA/Chitosan and PLA/Cellulose Acetate Films

Poly(lactic acid) (PLA) is a biodegradable polymer that exhibits high elastic modulus, high mechanical strength, and feasible processability. However, high cost and fragility hinder the application of PLA in food packaging. Therefore, this study aimed to develop flexible PLA/acetate and PLA/chitosan films with improved thermal and mechanical properties without the addition of a plasticizer and additive to yield extruder compositions with melt temperatures above those of acetate and chitosan. PLA blends with 10, 20, and 30 wt% of chitosan or cellulose acetate were processed in a twin-screw extruder, and grain pellets were then pressed to form films. PLA/acetate films showed an increase of 30 °C in initial degradation temperature and an increase of 3.9 % in elongation at break. On the other hand, PLA/chitosan films showed improvements in mechanical properties as an increase of 4.7 % in elongation at break. PLA/chitosan film which presented the greatest increase in elongation at break proved to be the best candidate for application in packaging.

Synthesis of multi-arm poly(l-lactide) and its modification on linear polylactide

Multi-arm poly(l-lactide)s (PLLAs) were prepared by using alcohols with different numbers of hydroxyl groups as initiator and Sn(Oct)2 as catalyst. The structure and composition was confirmed by NMR and GPC analysis. A series of blends of PLLA/multi-arm PLLA were prepared by melt-mixing. Several techniques were applied to investigate the effects of multi-arm PLLA on the melt rheology, crystallization, thermal stability, morphology and mechanical properties of the linear PLLA. Multi-arm PLLA enhanced crystallization rate of PLLA as a nucleating agent. Rheological analysis showed that the viscosity of PLLA at low frequencies increased after addition of multi-arm PLLA. In addition, the tensile strength was increased with the increase of multi-arm PLLA and can achieve a maximum. FE-SEM measurements revealed that the surface of blends was homogenous, indicating good compatibility between PLLA and multi-arm PLLA. The results had an important guiding role in PLA modification, which provided an opportunity for generating new PLA blending systems with enhanced properties.

The effect of the addition of poly(styrene‐co‐glycidyl methacrylate) copolymer on the properties of polylactide/poly(methyl methacrylate) blend

ABSTRACTThe effect of the addition of poly(styrene‐co‐glycidyl methacrylate) P(S‐co‐GMA) copolymer on the properties of melt blended polylactide/poly(methyl methacrylate) (PLA/PMMA) 80/20 (wt %) composition was studied. In the literature high ductility levels were achieved by melt blending PLA with different additives. However, the gained ductility was counter balanced with drastic drops in strength and modulus values. The novelty of this work was the preparation of PLA‐based blends with polylactide content higher than 75 wt % which showed an impact resistance value improvement of about 60% compared with the neat PLA and maintained similar tensile strength and modulus values as well as glass transition temperature to neat PLA. The addition of only 3 pph of copolymer to PLA/PMMA blend improved the impact resistance almost 100%. The chemical reaction between PLA/PMMA blend and P(S‐co‐GMA) copolymer were analyzed by FTIR, rotational rheometry, and GPC/SEC. Phase structure and morphology were studied by Differential Scanning Calorimetry and Scanning Electronic Microscopy. Tensile and impact properties as well as thermal stability were also studied. Results showed that as the amount of copolymer in the blend was increased then higher was average molecular weight and polydispersity index. After the addition of P(S‐co‐GMA) copolymer to the PLA/PMMA blend the impact resistance, elongation at break and thermal stability were improved while tensile strength and elastic modulus remained almost unaltered. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43935.

Biodegradation in Landfilled of Biodegradable Micro-braided Yarn

Biodegradable polymer yarns of polymer blends of poly(lactic acid) (PLA) and poly(butylene succinate-co-adipate) (PBSA) reinforced with natural fiber were prepared by a micro braiding technique. The biodegradation of the micro-braid yarn was studied by field tests. The yarn are prepared from polymer blends of PLA:PBSA with ratios of 100:0, 90:10, and 85:15 (wt%) by a single screw extruder. Braided samples were prepared using jute as a braided core fiber. The mechanical property analysis showed tensile strength of polymer yarn with jute fiber higher than polymer yarn without jute. Biodegradation of micro-braiding yarn with and without jute fiber was studied by buried under controlled conditions compared with cellulose. The field biodegradation test was carried out for 28 days with period of 7 days sampling. It was found that humidity and soil temperature affected the biodegradability of polymers. Analysis of samples confirmed that buried at low temperature position showed higher degradation than at high temperature. High humidity enhanced the degradability due to hydrolysis reaction. Micro-braided polymer yarns of PLA:PBSA (85:15) and PLA:PBSA (85:15)/jute showed similar biodegradability confirmed that the mechanism of biodegradation from surface of the yarn was priority.

Synthesis of poly(lactic acid) by heterogeneous acid catalysis from d,l-lactic acid

Poly(lactic acid) (PLA) is an important polymer because of its significant biocompatibility and biodegradability. Supported H3PW12O40 (H3PW) on activated carbon was utilized for the catalytic polymerization of D,L-lactic acid, resulting in blends of PLA. The stability of the polymer was monitored by thermogravimetry (TGA), and the decomposition temperature (Td) was used to determine the optimal production conditions (i.e., temperature of 180 °C for 15 h; 0.1 wt. % catalyst; 20 wt. % H3PW/carbon calcined at 400 °C). The best catalyst was reused three times with good activity and recovery (95 %) and was analyzed to confirm the consistency of its Keggin structure, dispersion, and acidity, which are important parameters that affect the catalyst’s activity. The obtained polymer was characterized by gel permeation chromatography (GPC), Fourier-transform infrared spectroscopy (FT-IR), 1H/13C nuclear magnetic resonance (NMR) spectroscopy, specific optical rotation ([α]D 25), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The average molar mass of the polymer was 17,400 g mol−1. Blends of poly(lactic acid) with 85 % poly(L-lactic acid) stereospecific isomer were obtained.

Toughening of polylactic acid using styrene ethylene butylene styrene: Mechanical, thermal, and morphological studies

Polylactic acid, PLA, derived from renewable resources has gained great attention nowadays owing to their sustainability, biodegradability, superior property, and transparency. However, intrinsic brittleness and low toughness severely limits its variety of applications. Blending of PLA with other polymers is more economical and more flexible technique for the property improvement of PLA. In this study, Styrene Ethylene Butylene Styrene (SEBS) and Maleic Anhydride grafted SEBS (MA-g-SEBS) are used as toughening agents to study their effect for its toughness, high strength and heat resistance on PLA. PLA/SEBS and PLA/Maleic Anhydride grafted SEBS blends were prepared under four different compositions by melt mixing technique using a corotating twin–screw extruder after optimizing the mixing conditions. The mechanical properties of the blends such as tensile, flexural, and impact strengths were investigated using specimens prepared by injection molding process. The percentage elongation and impact strength of PLA/MA-g-SEBS blends were found to be increased significantly by 540 and 135%, respectively in comparison with virgin PLA and PLA/SEBS blends. However, tensile strength and modulus of PLA/SEBS and PLA/MA-g-SEBS blends decreased compared with pristine PLA. SEM behaviour supported the higher impact property of PLA with the incorporation of modified SEBS via multiple crazing and cavitation mechanisms. DSC study also supported greater compatibility between maleated SEBS and PLA. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

Preparation, rheological properties and primary cytocompatibility of TPU/PLA blends as biomedical materials

A polymer blends containing thermoplastic polyurethane (TPU) and poly (lactic acid) (PLA) as a biomedical material were prepared by a process of modifying thermally induced phase separation (MTIPS) and melt blending. The influences of composition, shear frequency, and temperature on the rheological behaviors of the blends were investigated by small amplitude oscillatory shear rheology. The results revealed that the addition of TPU into PLA significantly decreased the non-Newtonian index of the blends, and increased the sensitivity of the blends on shear rate, suggesting that optimization of the shear rate and temperature could improve the flowability of the blend melts in the extrusion process. In addition, the results of SEM images revealed that TPU distributed well into PLA matrix and showed good compatibility between the TPU and PLA, which made the blends with good toughness. The primary cytocompatibility of the blends was evaluated using C2C12 cells. The results suggested that the TPU/PLA blends did not affect cell growth, showing no cytotoxicity. In short, the TPU/ PLA blends with excellent toughness had potential application as biomedical devices.

Preparation and Characterization of Poly(lactic Acid)-based Composite Reinforced with Oil Palm Empty Fruit Bunch Fiber and Nanosilica

The properties of poly(lactic acid) (PLA) bio-composite films reinforced with oil palm empty fruit bunch (OPEFB) fiber and nanosilica were studied in this work. The composite films were prepared via the solvent casting method. The composites were characterized via Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, field-emission scanning electron microscopy (FESEM), tensile testing, and X-ray diffraction (XRD). Ultraviolet visible spectroscopy results revealed that the PLA-based composites and neat PLA had similar light transmittances of approximately 89%. The FTIR and FESEM results showed that OPEFB fibers and nanosilica were embedded into the PLA matrix. The tensile strength of the composites with addition of nanosilica increased with an increasing fiber load content. The XRD analysis showed that the addition of organic or inorganic silica reduced the crystallinity of the composites. The water vapor permeability test results indicated that the inorganic silica decreased the diffusion rate of water molecules through the polymer film. The OPEFB-reinforced PLA blend with additional organic silica exhibited a higher thermal stability than the composites reinforced with inorganic silica.

A comparative study on different rubbery modifiers: Effect on morphologies, mechanical, and thermal properties of PLA blends

ABSTRACTTo improve the impact toughness of poly(lactic acid) (PLA), four kinds of rubbery modifiers, including ground tyre rubber (GTR), styrene‐butadiene‐styrene block copolymer (SBS), ethylene‐α‐octene copolymer (EOC) and glycidyl methacrylate grafted EOC (mEOC), were introduced for fabricating the PLA blends. The morphological structures, mechanical properties, thermal stability and thermal decomposition kinetics of pristine PLA and the blends were investigated. Results showed that representative droplet‐matrix structures were observed in the PLA blends, of which the PLA/SBS blend presented the smallest domains while PLA/EOC case had the largest elastomeric particle size. Accordingly, the highest impact toughness and elongation at break were achieved by PLA/SBS blend, whereas the tensile strength and elastic modulus for the blends were all lower than that of pristine PLA. Though the incorporation of rubbery modifiers barely altered the peak temperature of melting, the degrees of crystallinity for blends were declined sharply. The results of thermo gravimetric analysis indicated thermal degradation process of PLA phase was accelerated by rubbery modifiers and evidenced by the relative higher mass conversion at peak temperature. The reaction order of PLA phase for blends calculated by Carrasco method exhibited similar values when compared with control sample. However, the values of activation energy were rather lower than that of pure PLA. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43340.

Thienyl Difluoroboron β-Diketonates in Solution and Polylactide Media.

Difluoroboron β-diketonates have impressive optical properties in both solution and the solid state. In particular, both fluorescence and room-temperature phosphorescence are present when the dyes are confined to a rigid matrix, such as poly(lactic acid) (PLA). To expand current knowledge and color range capabilities of this unique type of multi-emitting chromophore, a series of thienyl-substituted BF2bdk complexes have been synthesized. The photophysical properties were investigated in methylene chloride solution and in the solid state as dye/PLA blends. By varying donor ability, i.e. methyl, phenyl, methoxyl, and thienyl substituents, and by changing the dye loading in the PLA media (0.1-10% dye loading) red-shifted emission was achieved, important for biological imaging applications. In dilute CH2Cl2 solution, complexes exhibited absorptions ranging from 350 - 420 nm, solid-state fluorescence in PLA ranging from 390 - 500 nm, and oxygen sensitive phosphorescence ranging from 540 - 585 nm in PLA blends. Promising candidates as dye/PLA blends serve as models for dyepolymer conjugates for application as biological oxygen nanoprobes.

Effect of PHB on the properties of biodegradable PLA blends

AbstractBlends of biodegradable polymers polylactic acid/thermoplastic starch/polyhydroxybutyrate (PLA/TPS/PHB) were prepared using a twin-screw extruder. The TPS content was constant (50 %) and the PHB content in the blends was gradually changed from 0 mass % to 20 mass %. TPS was prepared by melting, where a mixture of native starch, water and glycerol was fed into the twin-screw extruder. Average temperature of extrusion was 180 °C and the concentration of glycerol was 40 mass %. Influence of the PHB concentration in the blend and that of the processing technology on the mechanical and rheological properties of the PLA/PHB composition containing TPS were studied. Mechanical properties were measured 24 h after the film and monofilament preparation and also after the specific storage time to study the effect of storage on the properties. The results indicate that differences in morphology strongly influence the mechanical properties of the studied materials with identical material composition.

Synthesis and characterization of well‐defined random and block copolymers of ε‐caprolactone with l‐lactide as an additive for toughening polylactide: Influence of the molecular architecture

ABSTRACTWell‐defined multiarmed star random and block copolymers of ε‐caprolactone with l‐lactide with controlled molecular weights, low polydispersities, and precise numbers of arms were synthesized by the ring‐opening polymerization of respective cyclic ester monomers. The polymers were characterized by 1H‐NMR and 13C‐NMR to determine their chemical composition, molecular structure, degree of randomness, and proof of block copolymer formation. Gel permeation chromatography was used to establish the degree of branching. Star‐branched random copolymers exhibited lower glass‐transition temperatures (Tg's) compared to a linear random copolymer. When the star random copolymers were melt‐blended with poly(l‐lactic acid) (PLA), we observed that the elongation of the blend increased with the number of arms of the copolymer. Six‐armed block copolymers, which exhibited higher Tg's, caused the maximum improvement in elongation. In all cases, improvements in the elongation were achieved with no loss of stiffness in the PLA blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43267.

Influence of the Formulation Parameters on the Particle Size and Encapsulation Efficiency of Resveratrol in PLA and PLA-PEG Blend Nanoparticles: A Factorial Design.

Polymeric nanoparticles are colloidal systems that promote protection and modification of physicochemical characteristics of a drug and that also ensure controlled and extended drug release. This paper reports a 2(3) factorial design study to optimize poly(lactide) (PLA) and poly(lactide)-polyethylene glycol (PLA-PEG) blend nanoparticles containing resveratrol (RVT) for prolonged release. The independent variables analyzed were solvent composition, surfactant concentration and ratio of aqueous to organic phase (two levels each factor). Mean particle size and RVT encapsulation efficiency were set as the dependent variables. The selected optimized parameters were set as organic phase comprised of a mixture of dichloromethane and ethyl acetate, 1% of surfactant polyvinyl alcohol and a 3:1 ratio of aqueous to organic phase, for both PLA and PLA-PEG blend nanoparticles. This formulation originated nanoparticles with size of 228 ± 10 nm and 185 ± 70 nm and RVT encapsulation efficiency of 82 ± 10% and 76 ± 7% for PLA and PLA-PEG blend nanoparticles, respectively. The in vitro release study showed a biphasic pattern with prolonged RVT release and PEG did not influence the RVT release. The in vitro release data were in favor of Higuchi-diffusion kinetics for both nanoformulations and the Kossmeyer-Peppas coefficient indicated that anomalous transport was the main release mechanism of RVT. PLA and PLA-PEG blend nanoparticles produced with single emulsion-solvent evaporation technology were found to be a promising approach for the incorporation of RVT and promoted its controlled release. The factorial design is a tool of great value in choosing formulations with optimized parameters.

Effect of Processing Method on Thermal Behavior in PLA/PEG Melt Blending

The dispersion of PEG acts as plasticizer in PLA blends were investigated using thermal analysis. The comparisons were made between two melt processing method, twin screw extruder and two-roll mills to study how it will affect theTg,TcandTmof blends in DSC analysis. The TGA behavior was also studied for two-roll mills processing method to confirm the effect of PEG loading in PLA on degradation and amount of residue left after analysis. In DSC analysis, it can be seen clearly, the PEG loading decreased the glass transition temperature in all blends compares to neat PLA. For twin screw extruder blending, the crystallization peak existed for some blend. It was difference for two-roll mills blends where the crystallization peak absent in all blends with PEG loading. The presence of PEG gave no significant variation on melting temperature peak for both processing method.

Isosorbide dioctoate as a “green” plasticizer for poly(lactic acid)

Isosorbide dioctoate (SDO), a “green” plasticizer for poly(lactic acid) (PLA), was synthesized and evaluated as bio-based alternative to traditional phthalate plasticizers. The structure of SDO was confirmed by FTIR and 1H NMR. The miscibility, thermal properties, mechanical properties and transparency of the PLA/SDO blends were investigated in detail, and PLA plasticized with commercial dioctyl terephthalate (DOTP) was used for comparison. The calculated solubility parameter and SEM morphological analysis indicated that SDO exhibited better miscibility with PLA than that of DOTP. Results from DSC showed that SDO was more effective than DOTP in lowering the glass transition temperature of PLA. Moreover, the elongation at break of PLA/SDO blends was significantly improved with the increasing of SDO content. The effect of the concentration of SDO on transparency of PLA blends was negligible, while PLA plasticized with 20wt.% DOTP exhibited poor transparency. In conclusion, SDO showed attractive potential as alternative to phthalate plasticizers.

Effect of poly (lactic acid)‐graft‐glycidyl methacrylate as a compatibilizer on properties of poly (lactic acid)/banana fiber biocomposites

The main aim of this study was to synthesis of poly (lactic acid) (PLA)‐graft‐glycidyl methacrylate (GMA) as well as its influence on the properties of PLA/banana fiber biocomposites. PLA‐graft‐GMA graft copolymer (GC) was synthesized by melt blending PLA with GMA using benzoyl peroxide and dicumyl peroxide as initiators. Graft copolymerization was confirmed by FTIR and 1H‐NMR spectroscopic studies. PLA/silane treated banana fiber (SiB) biocomposites with various GC concentrations were prepared by melt blending followed by injection molding techniques. The influence of GC content on the mechanical, thermal and moisture resistance properties of the composite was investigated. The addition of 15 wt% GC content in the biocomposite provided optimum tensile and flexural strength, which is attributed to the greater compatibility between fiber and PLA matrix. The thermal properties of biocomposites have been evaluated using thermogravimetric analysis which provided evidence of improved interfacial adhesion between SiB and PLA by the addition of GC. Additionally, GC enhanced the moisture absorption resistance of biocomposites. These results indicated that GC is indeed a good candidate as a compatibilizing agent to improve the compatibility in PLA/fiber biocomposites. Copyright © 2015 John Wiley & Sons, Ltd.

Entanglement network formed in miscible PLA/PMMA blends and its role in rheological and thermo-mechanical properties of the blends

The miscible amorphous/semi-crystalline polymer blends with shape memory potential has received increasing interests in recent years. In this work, the shape memory mechanism of the miscible amorphous PMMA/semi-crystalline PLA blends was investigated using thermo-mechanical and rheological approaches. With the incorporation of PMMA into PLA, a broad glass transition and increased glass transition temperature Tg were observed by differential scanning calorimetry (DSC) measurements. The broadening of glass transition is attributed to the local nanoscale heterogeneities in the miscible blend system which is related to the self-concentration of the components. The degree of molecular entanglement of the blends was derived based on the oscillatory rheological measurements, showing that the dissimilar chains are more likely to entangle with each other than the similar ones, and the entanglement density ve is enhanced with increased PMMA content up to 50% where a 100% recovery of the initial shape is yielded. After that, ve is reduced with the addition of PMMA. The mechanism underlying the shape memory property is further validated by performing the shape memory test on the PLA/PMMA blend films at respective Tg. It is evident that for the semi-crystalline blends (PLA rich), PLA crystallites and molecular entanglement provide physical cross-links for shape recording, while a negative effect of crystallinity on the shape recovery ratio is obtained due to the strain-induced crystallization and chain slippage between the crystalline and amorphous chains. In contrast, for the amorphous blends (PMMA rich), the shape recovery ratio shows a strong positive linear dependence on ve, and the entanglement network is regard as the most important factor in the shape memory performance.