PLA Blends Research Articles

Development of biopolymer/cellulose/silica nanostructured hybrid materials and their characterization by NMR relaxometry

The objective of this study was to investigate the preparation and properties of hybrid materials composed of poly(lactic acid) (PLA) and poly(lactic acid)/poly(lactic-co-glycolic acid) (PLA/PLGA) blends employing cellulose nanocrystals (CNCs) and/or organophilic silica (R972) as nanoparticles. The CNCs were obtained by acid hydrolysis of commercially available microcrystalline cellulose (MCC). The materials were produced in film form by solution casting. Organophilic silica was incorporated at a ratio of 3 wt.%, and CNCs were added at ratios of 3 wt.% and 5 wt.% in relation to the weight of the polymer matrix. Two series of films were obtained. The first was prepared using only PLA as the matrix, and the second was obtained using blends of PLA and PLGA. The properties of the films were evaluated by X-ray diffractometry, nuclear magnetic resonance, Fourier-transform infrared spectroscopy and measurement of mechanical properties. The results revealed that each nanoparticle, whether added individually or combined with the other type of nanoparticle, induced different final material properties. Cellulose nanocrystals can act as nucleating agents for the crystallization of PLA. There was an improvement in the mechanical performance of films with the addition of CNCs. Further, the incorporation of silica combined with CNCs resulted in the generation of films with the strongest mechanical properties. The results of this study indicate that silica decreases the surface tension between PLA-cellulose and PLA/PLGA-cellulose.

Synergistic reinforcing of poly(lactic acid)-based systems by polybutylene succinate and nano-calcium carbonate

Bio-based poly(lactic acid) (PLA) ternary systems were prepared by the solution blending of PLA, polybutylene succinate (PBS), and nano-CaCO3. The effects of PBS and nano-CaCO3 on the thermal stability, fracture toughness, mechanical properties, and morphology of PLA were investigated using several techniques. The morphology of the systems was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The fracture toughness and flexural strength of PLA were improved by the introduction of PBS and further enhanced by the addition of nano-CaCO3. The elastic modulus of PLA decreased with the addition of PBS alone, whereas the elastic modulus increased with the simultaneous addition of PBS and nano-CaCO3.

Analysis of Dynamic and Creep Behaviors of PLA Blends with Blending Ratio

Poly(lactic acid)/poly(butylene adipate-co-terephthalate)(PLA/PBAT) 블렌드의 경우 PLA에 블렌딩된 PBAT의 함량이 커질수록 열안정성이 증가하였으며 CaCOSUB3/SUB 첨가에 의한 storage modulus 값의 증가로 PLA/PBAT 블렌드의 강성이 향상되었음을 확인하였다. PLA/PBAT/CaCOSUB3/SUB 블렌드의 크리프 변형 결과로부터 CaCOSUB3/SUB가 증가할수록 더 낮은 온도에서 시편의 변형 저항성이 급격하게 감소하는 것을 확인하였다. 이로부터 60℃ 이상인 경우 PLA의 단독 사용보다 PLA/PBAT 블렌드를 사용하는 것이 변형에 대한 저항성이 클 것으로 생각된다.

Physical ageing and molecular mobility in PLA blends and composites

Poly(lactic acid) (PLA) blends and composites were prepared from thermoplastic starch, poly(butylene-adipate-co-terephtalate), polycarbonate, wood flour and CaSO4 in a wide range of compositions. The thermal transitions of PLA were studied by differential scanning calorimetry. The detailed analysis of the transitions of PLA/thermoplastic starch blends indicated that they all are determined by the molecular mobility of PLA chains. Blending changes molecular mobility, and thus it often decreases glass transition temperature and modifies the extent of enthalpy relaxation. All other transitions and characteristics, i.e. cold crystallization, melting and the corresponding enthalpies, change accordingly. Increased molecular mobility accelerates also the physical ageing of the polymer. The interaction between PLA and the various components used for modification changed in a wide range, but no direct correlation was found between the strength of interaction and molecular mobility.

Non-isothermal crystallization of P(3HB-co-4HB)/PLA blends

A series of P(3HB-co-4HB)/PLA blends with different mass ratios were prepared via solution blending. Non-isothermal crystallization kinetic, melting behavior and morphology of the blends at various cooling rates were investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy (POM). Mo’s theoretical model was applied to describe the process of non-isothermal crystallization. The results show that the blends form crystal structure of P(3HB-co-4HB) and PLA simultaneously, and Mo’s method could describe the non-isothermal crystallization of P(3HB-co-4HB)/PLA blends very well. The crystal morphologies of P(3HB-co-4HB)/PLA blends with different mass ratios by polarizing microscope (POM) clearly show that typical spherulite morphology with “Maltese Cross” extinction pattern can be found in all samples. Neat P(3HB-co-4HB) and P(3HB-co-4HB)/PLA at PLA mass ratio ≤20 % exhibit typical banded spherulites as PHB or PHBV. The blends with P(3HB-co-4HB) and PLA mass ratio 70–90 % form classic non-banded spherulites as neat PLA. The spherulitic morphologies of the blends are very complex when the mass ratios of P(3HB-co-4HB) and PLA are 70/30, 60/40, 50/50 and 40/60, respectively.

Poly(ethylene glycol) methyl ether methacrylate‐graft‐chitosan nanoparticles as a biobased nanofiller for a poly(lactic acid) blend: Radiation‐induced grafting and performance studies

ABSTRACTIn this study, we aimed to modify chitosan (CS) as a novel compatible bio‐based nanofiller for improving the compatibility including the thermal and mechanical properties of poly(lactic acid) (PLA). The modification of CS with poly(ethylene glycol) methyl ether methacrylate (PEGMA) was done by radiation‐induced graft copolymerization. The effects of the dose rate, irradiation dose, and PEGMA concentration on the degree of grating (DG) were investigated. The chemical structure, packing structure, thermal stability, particle morphology, and size of the PEGMA‐graft‐chitosan nanoparticles (PEGMA‐graft‐CSNPs) were characterized by fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, and transmission electron microscopy. The compatibility of the PEGMA‐graft‐CSNP/PLA blends was also assessed by field emission scanning electron microscopy. The PEGMA‐graft‐CSNPs exhibited a spherical shape with the DG and particle sizes in the ranges of 3–145% and 35–104 nm, respectively. The PEGMA‐graft‐CSNPs showed compatible with PLA because of the grafted PEGMA segment. A model case study of the PEGMA‐graft‐CSNP/PLA blend demonstrated the improvement not only the compatibility but also thermal stability flexibility, and ductility of PLA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42522.

Morphology and thermal degradation studies of melt-mixed poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) biodegradable polymer blend nanocomposites with TiO2 as filler

The morphology and thermal stability of melt-mixed poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blend nanocomposites with small amounts of TiO2 nanoparticles were investigated. The nanoparticles were mostly located in the PLA phase, with good dispersion of individual particles, although significant aggregation was also visible. The thermal stability and degradation behaviour of the different samples were studied using thermogravimetric analysis (TGA) and TGA-Fourier-transform infrared (FTIR) spectroscopy. Neat PCL showed better thermal stability than PLA, but the degradation kinetics revealed that PLA had a higher activation energy of degradation than PCL, indicating its degradation rate more strongly depends on temperature, probably because of a more complex degradation mechanism based on chain scission and re-formation. Blending of PLA and PCL reduced the thermal stabilities of both polymers, but the presence of TiO2 nanoparticles improved their thermal stability. The nanoparticles also influenced the volatilization of the degradation products from the blend, acted as degradation catalyst and/or retarded the escape of volatile degradation products.

Overcoming the Fundamental Challenges in Improving the Impact Strength and Crystallinity of PLA Biocomposites: Influence of Nucleating Agent and Mold Temperature.

Poly(lactic acid) (PLA), one of the widely studied renewable resource based biopolymers, has yet to gain a strong commercial standpoint because of certain property limitations. This work is a successful attempt in achieving PLA biocomposites that showed concurrent improvements in impact strength and heat deflection temperature (HDT). Biocomposites were fabricated from a super toughened ternary blend of PLA, poly(ether-b-amide) elastomeric copolymer and ethylene-methyl acrylate-glycidyl methacrylate and miscanthus fibers. The effects of varying the processing parameters and addition of various nucleating agents were investigated. Crystallinity was controlled by optimizing the mold temperature and cycle time of the injection process. With the addition of 1 wt % aromatic sulfonate derivative (Lak-301) as a nucleating agent at a mold temperature of 110 °C, PLA biocomposites exhibited dramatic reduction in crystallization half time to 1.3 min with crystallinity content of 42%. Mechanical and thermal properties assessment for these biocomposites revealed a 4-fold increase in impact strength compared to neat PLA. The HDT of PLA biocomposites increased to 85 °C from 55 °C compared to neat PLA. Crystallization behavior was studied in detail using differential scanning calorimetry and was supported with observations from wide-angle X-ray diffraction profiles and polarized optical microscopy. The presence of a nucleating agent did not alter the crystal structure of PLA; however, a significant difference in spherulite size, crystallization rate and content was observed. Fracture surface morphology and distribution of nucleating agent in the PLA biocomposites were investigated through scanning electron microscopy.

Microstructure and non-isothermal crystallization behavior of PP/PLA/clay hybrid nanocomposites

Various compositions of polypropylene (PP) and poly(lactic acid) (PLA) blends were prepared by one-step melt compounding in a twin-screw extruder. Two compositions were selected for investigation of effect of clay and n-butyl acrylate glycidyl methacrylate ethylene terpolymer (PTW) as compatibilizer on thermal properties and non-isothermal crystallization behavior of PP/PLA/clay nanocomposite systems, i.e., PP-rich one (75/25 composition) containing Cloisite 15A and PLA-rich one (25/75 composition) containing Cloisite 30B. The thermal behavior of the systems was investigated by means of differential scanning calorimetry (DSC) and correlated with their microstructures. The narrowing down of the peaks in the wide-angle X-ray scattering pattern of PP-rich blend was associated with an increase in size and/or perfection of the crystals. On the other hand, the broadening of the peaks in PLA-rich blend implied a decrease in the size of the crystals. The calculated interlayer distance, using Scherrer equation, in Cloisite 15A was slightly greater than that of Cloisite 30B. Moreover, an increase of 100 % in interlayer distance showed a greater level of intercalation in PP-rich system as compared to the PLA-rich system. Blending of PP and PLA led to significant changes in the crystallinity behavior of the blends compared to the neat components. Moreover, the incorporation of the both clays into the two systems led to a greater change in the crystallinity degree, comparing to that of unfilled blends.

Thermal, Mechanical and Morphological Properties of Binary and Ternary PLA Blends Containing a Poly(ether ester) Elastomer

Thermal, Mechanical and Morphological Properties of Binary and Ternary PLA Blends Containing a Poly(ether ester) Elastomer

Preparation and characterization of poly(lactic acid)/poly(methyl methacrylate) blend tablets for application in quantitative analysis by micro Raman spectroscopy

Poly(lactic acid) (PLA) is a biodegradable polymer that has a variety of applications, one of which is as biomaterial in surgery or as functional layers on implants, due to its compatibility with living tissue.This paper reports the possibilities of quantification of poly(lactic acid) (PLA) in a polymer matrix such as poly(methyl methacrylate) (PMMA) by micro Raman spectroscopy (MRS). Blends of amorphous poly(DL‐lactic acid) with poly(methyl methacrylate) were prepared by the procedure of dissolution/precipitation. Thermal properties of the blends such as the glass transition temperature (Tg) were characterized by differential scanning calorimetry (DSC). The PLA/PMMA blends exhibited only a single glass transition region, indicating that this system is miscible. The PLA/PMMA system obeys the Gordon–Taylor equation (Tg versus PLA content). Various concentration ratios of PLA blends were prepared to use as a basis for quantitative analysis by MRS. Intensities of the characteristic bands at 813 cm−1 (νCOC of PMMA) and 873 cm−1 (νC―COO of PLA) were used for the calculation. The calibration graph showed a good linear correlation with an R2 value of 0.9985. On the basis of the calibration curve obtained, the determined content of several PLA/PMMA blends was in good agreement when compared with nominal contents. The limit of detection (LOD) and quantification (LOQ) were calculated by the calibration data set as signal‐to‐noise method. The relative standard deviation of this method was lower than 10% and the accuracy better than 4%. This study demonstrated that Raman spectroscopy provides an alternative non destructive method for quantitative analysis of PLA in a PMMA matrix. Copyright © 2015 John Wiley & Sons, Ltd.

Characterization and biodegradation behavior of bio-based poly(lactic acid) and soy protein blends for sustainable horticultural applications

Blends of PLA and soy protein polymer (SP.A) fulfill the functional requirements of horticulture crop containers and provide a fertilizer effect. Blending SP.A with PLA strongly increases the rate of biodegradation compared to pure PLA.

Development and characterization of an electrospun mat from Eri silk fibroin and PLA blends for wound dressing application

Eri silk fibroin blend with poly-l-lactic acid polymer and tetracycline hydrochloride were electrospun as nanofibrous mat and evaluated for properties required for skin contact layer of multilayer wound dressing systems.

Compression molding and melt‐spinning of the blends of poly(lactic acid) and poly(butylene succinate‐co‐adipate)

ABSTRACTPoly(lactic acid) (PLA) is a biobased polymer made from biomass having high mechanical properties for engineering materials applications. However, PLA has certain limited properties such as its brittleness and low heat distortion temperature. Thus, the aim of this study is to improve toughness of PLA by blending with poly(butylene succinate‐co‐adipate) (PBSA), the biodegradable polymer having high toughness. Polymer blends of PLA and PBSA were prepared using a twin screw extruder. The melt rheology and the thermal property of the blends were examined. Further the blends were fabricated into compression molded parts and melt‐spun fiber and were subjected to tensile and impact tests. When the PBSA content was low, PBSA phase was finely dispersed in the PLA matrix. On the other hand, when the PBSA content was high, this minor phase dispersed as a large droplet. Mechanical properties of the compression molded parts were affected by the dispersion state of PBSA minor component in PLA matrix. Impact strength of the compression molded parts was also improved by the addition of soft PBSA. The improvement was pronounced when the PBSA phase was finely dispersed in PLA matrix. However, the mechanical property of the blend fibers was affected by the postdrawing condition as well as the PBSA content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41856.

Enhanced dispersion of cellulose nanocrystals in melt-processed polylactide-based nanocomposites

Dispersion and distribution of cellulose nanocrystals (CNC) in a thermoplastic matrix is one of the most important issues in the development of CNC-based high performance composites. During melt processing, agglomeration of CNC is prone to occur due to poor polymer wetting on the hydrophilic CNC surface and to strong particle–particle interactions. Because of the high temperature and intensive mixing involved in melt-processing, degradation of the CNC is also possible. To avoid these problems, solvent mixing followed by solvent casting is the main processing route used in the majority of studies on polymer–CNC composites. In this work, we have explored a novel two-step process where solvent-mixing and melt-mixing were carried out sequentially to improve the overall dispersion of the CNC. The first step consisted in forming a CNC suspension into a polyethylene oxide (PEO) aqueous solution. In the second step, water was removed by freeze-drying to form a water-free well dispersed PEO/CNC mixture. The final step consisted in melt-mixing the PEO/CNC mixture into PLA for the preparation of the composites. PEO and PLA are known to be miscible in certain molecular weight and composition ranges, thus leading to a composite where the CNC particles are well dispersed into a homogeneous mixture of PLA and PEO. Two different PEO molecular weights were investigated in this study, and several formulations were compared under the same processing conditions. Direct blending of CNC and molten PLA was also carried out for comparison purposes. CNC particles tended to agglomerate during blending but the agglomerates were smaller and their number was considerably decreased when the PEO content increased in the formulation. At the highest PEO/CNC ratio, no agglomerates were observed. Thermomechanical and rheological properties of the PLA-based nanocomposites were also investigated.

STUDIES ON MORPHOLOGY, MECHANICAL AND OPTICAL PROPERTIES OF PP/HDPE/EVA/ PLA BLEND MODIFIED WITH AL2O3 PARTICLES FOR CAST FILM

In this present work, study of mechanical and optical properties of PP/HDPE/EVA/PLA (80/20/5/4) blend reinforced with nano alumina (Al2O3) particles is investigated. In the production process co-rotating twin screw extruder are utilized. Reinforced films are produced with 0.5, 1, 1.5 and 2 phr Al2O3 contents .The screw speed of the extruder is maintained at 150 rpm. After post extrusion, cast films are prepared. Mechanical performance analysis are done in order to examine the change in tensile strength, burst strength, tear strength and kinetic coefficient of friction of the polymeric films. Optical properties are performed for obtaining the data of haze and transmittance. The morphology is studied by Scanning Electron Microscopy (SEM). These results are related to the Al2O3 dispersion, to the type of the different composite formulations with PP/HDPE/EVA/PLA polymer matrix. It has been found that at 0.5 Phr loading of Al2O3 in PP/HDPE/EVA/PLA (80/20/5/4) blend has shown the highest burst and tear strength. On the other hand, the tensile strength shows decreasing order on Al2O3 loading 0.5 to 2 phr. Optical properties such as maximum value of transmittance and haze are also observed as loading of 0.5 Phr of Al2O3 in PP/HDPE/EVA/PLA (80/20/5/4) blend.

Linear and four‐armed poly(l‐lactide)‐block‐poly(d‐lactide) copolymers and their stereocomplexation with poly(lactide)s

AbstractLinear and four‐armed poly(l‐lactide)‐block‐poly(d‐lactide) (PLLA‐b‐PDLA) block copolymers are synthesized by ring‐opening polymerization of d‐lactide on the end hydroxyl of linear and four‐armed PLLA prepolymers. DSC results indicate that the melting temperature and melting enthalpies of poly (lactide) stereocomplex in the copolymers are obviously lower than corresponding linear and four‐armed PLLA/PDLA blends. Compared with the four‐armed PLLA‐b‐PDLA copolymer, the similar linear PLLA‐b‐PDLA shows higher melting temperature (212.3 °C) and larger melting enthalpy (70.6 J g−1). After these copolymers blend with additional neat PLAs, DSC, and WAXD results show that the stereocomplex formation between free PLA molecular chain and enantiomeric PLA block is the major stereocomplex formation. In the linear copolymer/linear PLA blends, the stereocomplex crystallites (sc) as well as homochiral crystallites (hc) form in the copolymer/PLA cast films. However, in the four‐armed copolymer/linear PLA blends, both sc and hc develop in the four‐armed PLLA‐b‐PDLA/PDLA specimen, which means that the stereocomplexation mainly forms between free PDLA molecule and the inside PLLA block, and the outside PDLA block could form some microcrystallites. Although the melting enthalpies of stereocomplexes in the blends are smaller than that of neat copolymers, only two‐thirds of the molecular chains participate in the stereocomplex formation, and the crystallization efficiency strengthens. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1560–1567

Semi-interpenetrating polymer networks composed of poly(l-lactide) and diisocyanate-bridged 4-arm star-shaped ɛ-caprolactone oligomers

Semi-interpenetrating polymer networks (semi-IPNs) were prepared by reactions of methylenediphenyl 4,4’-diisocyanate (MDI) and hydroxy-terminated 4-arm star-shaped ε-caprolactone oligomers (H4CLOn's) with the degrees of polymerization per one arm, n = 3, 5 and 10 in the presence of poly(l-lactide) (PLA). Morphologies, thermal and mechanical properties of the MDI-bridged H4CLOn (MH4CLOn)/PLA semi-IPNs were evaluated by comparing with those of poly(ɛ-caprolactone) (PCL)/PLA blends. Two tan δ peaks related to MH4CLOn and PLA were observed in a dynamic mechanical curve of the semi-IPN. Although all the semi-IPNs and blends had micro-phase separated morphologies, the phase-separated droplets of MH4CLO5/PLA 50/50 were much finer than those of PCL/PLA 50/50. Differential scanning calorimetry (DSC) analyses revealed that MH4CLO3 and MH4CLO5 are substantially amorphous, while MH4CLO10 is semi-crystalline, and that cold crystallization of the PLA component of MH4CLOn/PLA is more strongly disturbed for the semi-IPN with a smaller n value and more MH4CLOn content. Tensile modulus, toughness and elongation at break of MH4CLO5/PLA 50/50 semi-IPN were much higher than those of PCL/PLA 50/50 blend.

Poly(lactic acid)/Biodegradable Polymer Blend for The Preparation of Flat-Sheet Membrane

Biodegradable polymers have been more attractive for membrane materials, especially poly(lactic acid) (PLA) because they degrade in natural environment after use. In this study, the membranes were developed from a polymer blend of PLA and other biodegradable polymers, such as poly(butylene succinate) (PBS), poly(butylene adipate-co-terphthalate) (PBAT) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The membranes were formed via nonsolvent induced phase separation process using n-methyl-2-pyrrolidone (NMP) as a solvent and water as a nonsolvent. The pure water flux and BSA rejection were tested to determine the filtration performance of membranes. The microstructures and tensile strength of membranes were characterized by field emission scanning electron microscope (FE-SEM) and universal testing machine (UTM), respectively. All of membranes appeared finger-like and sponge-like structures in cross-section, and porous structure on surface. PLA/PHBV blend membranes had pure water flux and BSA rejection as high as PLA/PBS and PLA/PBAT blend membranes. The pure water flux and BSA rejection of the blend ratio (PLA/PHBV/NMP) of 15:1:84 were 65 l/m2•h and 79%, respectively.

Thermal properties and miscibility of semi‐crystalline and amorphous PLA blends

ABSTRACTThe focus of this research is the study of the microstructures and miscibility at the interface between semi‐crystalline and amorphous PLAs [poly (l‐lactic acid)(PLLA) with poly (l,d‐lactic acid)(PDLLA), respectively]. The blends are prepared through thermal processing (extrusion and hot‐pressing). To increase the area of interface between PDLLA and PLLA, the fibers from PLLA and PDLLA are used. Thermal and microstructures of the blends were studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM), dynamic thermogravimetric analysis(DMA), small‐angle X‐ray diffraction(SAXS) and wide‐angle X‐ray diffraction (WAXD). The two PLAs are miscible in molten state. However, phase separation is detected after various thermal treatments, with PDLLA being excluded from the regions of interlamellar PLLA regions when PDLLA content is low, as determined from X‐ray diffraction studies. The compatibility between the two PLAs is not perfect in the molten state, since enthalpies of the various blends at Tg are lower than any pure PLA material. The semi‐crystalline PLLA fiber can recrystallize alone in the molten amorphous PDLLA, and a higher nuclei density is observed at the interface. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41205.