Elongational rheology of biodegradable poly(lactic acid)/poly[(butylene succinate)‐co‐adipate] binary blends and poly(lactic acid)/poly[(butylene succinate)‐co‐adipate]/clay ternary nanocomposites

A series of blends based on poly(lactic acid) (PLA) and poly[(butylene succinate)‐co‐adipate] (PBSA) as well as their nanocomposites with nanoclay (PLA/PBSA/Clay ternary nanocomposites) were prepared using the twin‐screw extruder. The blends were prepared for PBSA contents ranging from 25 to 75 wt % and their corresponding nanocomposites were prepared at a single‐clay concentration. The morphology and structure of the blends and the nanocomposites were examined using field emission scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. Rheological properties (dynamic oscillatory shear measurements and elongational viscosities) of the blends, nanocomposites, and pure components were studied in detail. The strain hardening intensity of different blends and nanocomposites was compared with the behavior of the pure components. Strong strain hardening behavior was observed for blends composed of 50 wt % and higher PBSA content. However, the effect of PBSA content on the elongational viscosity was less pronounced in PLA/PBSA/Clay ternary nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Tapioca starch‐poly(lactic acid)‐Cloisite 30B nanocomposite foams

Tapioca starch (TS), poly(lactic acid) (PLA), and Cloisite 30B nanocomposite foams, with four clay contents of 1, 3, 5, 7 wt%, were prepared by a melt‐intercalation method. Selected structural, thermal, physical, and mechanical properties were characterized using X‐ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine, respectively. XRD results indicated that intercalation of TS/PLA into the nanoclay layers occurred in all four nanocomposite foams. At the same time, tactoid structures were observed in all nanocomposite foams but to a lesser extend with 1 and 3 wt% clay contents. Effect of clay content on melting temperature (T_m), onset degradation temperature, radial expansion ratio, unit density, bulk compressibility and bulk spring index of the nanocomposites were investigated. Among the four nanocomposites, 3 wt% clay content produced significantly different (p < 0.05) properties. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Synergistic reinforcing of poly(lactic acid) by poly(butylene adipate-co-terephthalate) and alumina nanoparticles

Biodegradable poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blends and PLA/PBAT/Al₂O₃ nanocomposites were fabricated via solution blending. The influence of PBAT and Al₂O₃ content on the thermal stability, flexural properties, impact strength, and morphology of both the PLA/PBAT blends and the PLA/PBAT/Al₂O₃ nanocomposites were investigated. The impact strength of the PLA/PBAT/Al₂O₃ nanocomposites containing 5 wt% PBAT increased from 4.3 to 5.2 kJ/m² when the Al₂O₃ content increased from 0 to 1 wt%. This represents a 62% increase compared to the impact strength of pristine PLA and a 20% increase compared to the impact strength of PLA/PBAT blends containing 5 wt% PBAT. Scanning electron microscopy imaging revealed that the Al₂O₃ nanoparticles in the PLA/PBAT/Al₂O₃ nanocomposites function as a compatibilizer to improve the interfacial interaction between the PBAT and the PLA matrix.     

Morphology,thermal, mechanical,and barrier properties of graphene oxide/poly(lactic acid) nanocomposite films

To improve the physical and gas barrier properties of biodegradable poly(lactic acid) (PLA) film, two graphene nanosheets of highly functionalized graphene oxide (0.3 wt% to 0.7 wt%) and low-functionalized graphene oxide (0.5 wt%) were incorporated into PLA resin via solution blending method. Subsequently, we investigated the effects of material parameters such as loading level and degree of functionalization for the graphene nanosheets on the morphology and properties of the resultant nanocomposites. The highly functionalized graphene oxide (GO) caused more exfoliation and homogeneous dispersion in PLA matrix as well as more sustainable suspensions in THF, compared to low-functionalized graphene oxide (LFGO). When loaded with GO from 0.3 wt% to 0.7 wt%, the glass transition temperature, degree of crystallinity, tensile strength and modulus increased steadily. The GO gave rise to more pronounced effect in the thermal and mechanical reinforcement, relative to LFGO. In addition, the preparation of fairly transparent PLA-based nanocomposite film with noticeably improved barrier performance achieved only when incorporated with GO up to 0.7wt%. As a result, GO may be more compatible with hydrophilic PLA resin, compared to LFGO, resulting in more prominent enhancement of nanocomposites properties.     

Hydrolytic degradation of nanocomposites based on poly(l‐lactic acid) and layered double hydroxides modified with a model drug

Hydrolytic degradation of a nanocomposite of poly(L‐lactic acid), PLA, and a layered double hydroxide (LDH) modified with the drug 4‐biphenyl acetic acid (Bph) has been studied. PLA/LDH‐Bph nanocomposite was prepared by solvent casting with 5 wt % of drug modified LDH and the hydrolytic degradation was carried out in a PBS solution at pH 7.2 and 37 °C. Neat PLA with 5 wt % 4‐biphenyl acetic acid was studied as reference material (PLA/Bph). The materials were studied by WAXS, TEM, TGA, DSC, SEM, FTIR, SEC and contact angle measurements. For PLA/Bph, an acid catalytic effect, caused by the drug, accelerates PLA mass loss. However, for PLA/LDH‐Bph, the presence of LDH produces a barrier effect that initially reduces the diffusion of the oligomers produced during hydrolytic degradation. DSC results demonstrate that Bph induces faster PLA crystallization and this effect is reduced in PLA/LDH‐Bph nanocomposites because of their lower drug content. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43648.     

Enhanced dyeability of poly(ethylene terephthalate)/organoclay nanocomposite filaments

This study deals with the generation of poly(ethylene terephthalate)/organoclay nanocomposite filaments by the melt‐spinning method and with the investigation of their morphological and dyeing properties. Different montmorillonite types of clay (Resadiye and Rockwood) were modified using different intercalating agents, and poly(ethylene terephthalate) nanocomposite filaments containing 0.5 and 1 wt% organoclays were prepared. Afterwards, the filaments were dyed with two disperse dyes (Setapers Red P2G and Setapers Blue TFBL‐NEW) at different temperatures (100, 110, and 120 °C) in the absence/presence of a carrier. Organoclays and poly(ethylene terephthalate)/organoclay nanocomposites showed an increased d‐spacing between clay layers. Irrespective of clay and surfactant type, poly(ethylene terephthalate)/organoclay nanocomposite filaments dyed at 120 °C in the presence of only a very small amount of carrier showed appreciable dyeability in comparison with neat poly(ethylene terephthalate). The dyeability of the organoclay‐containing poly(ethylene terephthalate) samples was found to be better in spite of having increased degrees of crystallinity. Moreover, the colour fastness properties of the clay‐containing samples were not affected adversely.     

Nanoindentation analysis of 3D printed poly(lactic acid)-based composites reinforced with graphene and multiwall carbon nanotubes

Influences of different nanocomposite loadings in poly(lactic acid) (PLA) matrix on resulting hardness and elasticity were examined in nanoindentation experiments. The following study was focused on the nanomechanical properties of PLA reinforced with graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (MWCNTs) by using Berkovich type pyramidal nanoindenter. A masterbatch strategy was developed to disperse GNP and MWCNT into PLA by melt blending. Young's modulus and nanohardness of as-prepared nanocomposites were characterized as a function of the graphene and carbon nanotubes loading. The nanoindentation analysis reveals that these carbon nanofillers improve the mechanical stability of the nanocomposites GNP/PLA, MWCNT/PLA, and GNP/MWCNT/PLA. That improvement of mechanical properties strongly depends on the fillers content. It was found that the best mechanical performance was achieved for the compound having 6 wt % graphene and 6 wt % MWCNTs in the PLA matrix. The received values for nanohardness and Young's modulus are among the highest reported for PLA-based nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47260.     

Structural evaluation and thermal properties of poly(lactic acid) and different synthetic micas nanocomposites

Two types of organophilic synthetic micas were used to prepare poly(lactic acid) (PLA) nanocomposites. The effect of both micas at different concentrations were evaluated and correlated to the nanocomposite structure and thermal properties. Nanocomposites containing 3, 5, and 7 wt% of mica were obtained by mixing the components in the melt state at different conditions of temperature, rotor speed, and contacting time. The mica Somasif MAE showed the higher affinity with PLA and caused a slight variation in the thermal properties. Nevertheless, the nanocomposite presented a lower‐degradation temperature than the Somasif MPE alone. Despite no evidence of complete exfoliation, intercalation was noted in the composites obtained from the mica MAE. The organophilic mica Somasif MPE, which contains a high amount of intercalant, had a more significant influence on the composite properties, decreasing the T_g, and the crystallization temperature on heating, due to the plasticizing effect of the intercalant. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers     

Structure and properties of poly(lactic acid)/poly(ε‐caprolactone) nanocomposites with kinetically induced nanoclay location

Poly(lactic acid)/poly(ε‐caprolactone)/organically modified montmorillonite (PLA/PCL/OMMT) nanocomposites were melt‐processed in a twin‐screw extruder under high shear conditions. As a result of the processing conditions employed, the OMMT layers located in the less compatible PCL phase in all the ternary nanocomposites. The morphology of the PLA/PCL blend evolved from “sea‐island” to co‐continuous upon the addition of OMMT. Both the X‐ray diffraction (XRD) and viscoelastic characterization suggested similar OMMT dispersion in the reference PLA binary and in the PLA/PCL ternary nanocomposites, regardless of its location in the PLA and PCL phase, respectively. The reinforcing effect of the organoclay was also similar. The addition of OMMT to the PLA/PCL blend fully compensated the loss in stiffness and oxygen barrier performance produced by PCL in PLA; the nanocomposite with 3% OMMT showed the same modulus and permeability values as those of pure PLA. Moreover, the ductile behavior (elongation at break > 80%) of the PLA/PCL blend remained constant even in the nanocomposite containing 5% OMMT. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43815.     

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

Poly(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.     

Synergetic association of grafted PLA and functionalized graphene on the properties of the designed nanocomposites

The synergetic association of poly(lactic acid) grafted with maleic anhydride (MA-g-PLA) containing 0.44 wt% of maleic anhydride and epoxy-functionalized graphene (GFe) on the properties of the designed nanocomposites was studied. Rheological, mechanical and barrier properties of PLA nanocomposites were studied using different content of epoxy-functionalized graphene and MA-g-PLA compatibilizer. The PLA/MA-g-PLA/GFe nanocomposites prepared by melt blending, containing 5 wt% of MA-g-PLA, yield a maximum in storage modulus G′ and a rheological plateau at low frequencies, with a content of epoxy-functionalized graphene comprised between 4 and 7 wt%. This phenomenon was ascribed to a pseudo-solid behavior resulting from the high degree of epoxy-functionalized graphene exfoliation due to strong interfacial interactions with PLA and epoxy-functionalized graphene. The better mechanical and barrier performances were obtained with PLA/GFe containing 10 wt% of epoxy-functionalized graphene and 5 wt% of MA-g-PLA compatibilizer. The variation of the percentage of compatibilizer showed that 5 wt% of maleated PLA was sufficient to improve the thermal, rheological, mechanical and barrier properties of the PLA nanocomposite containing 7 wt% of epoxy-functionalized graphene.     

Preparation of PET/LDH composite materials and their mechanical properties and permeability for O2

The terephthalate‐intercalated LDHs (TA‐LDHs) are used to improve the barrier properties of poly(ethylene terephthalate) (PET) for their application in liquid food packaging. First, TA‐LDHs were synthesized from freshly prepared metal hydroxides. PET/LDH nanocomposites were then prepared by a masterbatch process. The structures and morphologies of TA‐LDHs and PET/LDH nanocomposites were characterized using X‐ray diffractometer, transmission electronic microscopy, and scanning electron microscope. The mechanical performances and the oxygen permeability of the PET/LDH composites were measured using a precision universal tester and differential pressure gas permeameter, respectively. The influence of TA‐LDH content on their structures and properties was studied. PET/LDH nanocomposites with 1 and 2 wt% of TA‐LDHs are partially exfoliated nanocomposites, while PET/LDH with 5 wt% of TA‐LDHs is an intercalated nanocomposite. The PET/LDH nanocomposites prepared by a masterbatch process show better mechanical properties and gas barrier properties. PET/LDHs‐m2 with 2 wt% of TA‐LDHs could offer up to a 29.4% improvement in tensile strength over PET and the Young's modulus is increased by 38.9%. The O₂ permeation of PET/LDHs‐m2 with 2 wt% of TA‐LDHs is decreased by 46.2%. POLYM. ENG. SCI., 59:E366–E371, 2019. © 2019 Society of Plastics Engineers     

Synthesis of poly(butyl acrylate)—laponite nanocomposite nanoparticles for improving the impact strength of poly(lactic acid)

This work aims at preparing and characterizing poly(butyl acrylate) (PBA)—laponite (LRD) nanocomposite nanoparticles and nanocomposite core (PBA‐LRD)‐shell poly(methyl methacrylate) (PMMA) nanoparticles, on the one hand, and the morphology and properties of poly(lactic acid) (PLA)‐based blends containing PBA‐LRD nanocomposite nanoparticles or (PBA‐LRD)/PMMA core–shell nanoparticles as the dispersed phase, on the other hand. The PBA and (PBA‐LRD)/PMMA nanoparticles were synthesized by miniemulsion or emulsion polymerization using LRD platelets modified by 3‐methacryloxypropyltrimethoxysilane (MPTMS). The grafting of MPTMS onto the LRD surfaces was characterized qualitatively using FTIR and quantitatively using thermogravimetric analysis (TGA). The amounts of LRD in the PBA‐LRD nanocomposites were characterized by TGA. The PBA/PMMA core–shell particles were analyzed by ¹H‐NMR. Their morphology was confirmed by SEM and TEM. Mechanical properties of (PBA‐LRD)/PLA blends and (PBA‐LRD)/PMMA/PLA ones were tested and compared with those of the pure PLA, showing that core–shell particles allowed increasing impact strength of the PLA while minimizing loss in Young modulus and tensile strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The influence of surface modification on the structure and properties of a zinc oxide‐filled poly(ethylene terephthalate)

Hydrophobic zinc oxide (ZnO) nanoparticles were successfully prepared by a one‐step precipitation reaction in an aqueous solution of zinc sulfate and sodium hydroxide with stearic acid as the modifying agent. Poly(ethylene terephthalate) (PET)/ZnO nanocomposites were prepared by further in situ polymerization of purified terephthalic acid, ethylene glycol and the ZnO nanoparticles. The surface modification of ZnO and the microstructure and properties of the nanocomposites were investigated using relative contact angle measurements, Fourier transform infrared spectroscopy, X‐ray diffraction, transmission and scanning electron microscopies, thermogravimetric analysis and differential scanning calorimetry. Measurements of relative contact angle indicated that the surface‐treated ZnO was hydrophobic. Compared to the nanocomposite filled with unmodified ZnO, a significant improvement in thermal stability and crystallinity was observed with the addition of 2 wt% surface‐treated ZnO. The experimental results also suggested that the properties of the nanocomposites were correlated with the dispersion of ZnO in PET and the interfacial interactions between ZnO and PET matrix. © 2012 Society of Chemical Industry     

Effectiveness of the preparation of maleic anhydride grafted poly (lactic acid) by reactive processing for poly (lactic acid)/carbon nanotubes nanocomposites

An effective strategy to increase the properties of poly (lactic acid) (PLA) is the addition of carbon nanotubes (CNT). In this work, aiming to improve the surface adhesion of PLA and CNT a new compatibilizer agent was prepared by reactive processing, PLA grafted maleic anhydride (PLA-g-MA) using benzoyl peroxide and maleic anhydride. The effectiveness of the PLA-g-MA as a compatibilizer agent was verified for PLA/PLA-g-MA/CNT nanocomposites. PLA and PLA-g-MA samples were characterized by Fourier transform infrared spectroscopy (FT-IR) to confirm the grafting reaction of maleic anhydride on PLA chains and by rheological analysis to prove the changes in the matrix PLA after the graphitization reaction. Thermal (differential scanning calorimetry and thermogravimetric analysis), mechanical tests (Izod impact strength and tensile test), and morphological characterization were used to verify the effect of the compatibilizer agent. The preparation of PLA-g-MA by reactive extrusion processing proved satisfactory and the nanocomposites presented good thermal and mechanical properties. The addition of the PLA-g-MA also contributed to the greater distribution of CNT and can be used as an alternative for the production of PLA/CNT nanocomposites.     

Preparation and characterization of poly(lactic acid)/poly(ethylene oxide) blend film: effects of poly(ethylene oxide) and poly(ethylene glycol) on the properties

Poly(lactic acid) (PLA) film plasticized with poly(ethylene oxide) (PEO) at various weight percentages (1–5 wt%) was prepared to improve the elongation, thus overcoming the inherent brittleness of the material. After optimization of the amount of PEO (4 wt%) through mechanical analysis, poly(ethylene glycol) (PEG), a well‐established plasticizer of PLA, was added (0.5–1.5 wt%) without hampering the transparency and tensile strength much, and again its amount was optimized (1 wt%). Neat PLA and PLA with the other components were solvent‐cast in the form of films using chloroform as a solvent. Improvement in elongation at break and reduction in tensile strength suggested a plasticizing effect of both PEO and PEG on PLA. Thermal and infrared data revealed that the addition of PEO induced β crystals in PLA. Scanning electron micrographs indicated a porous surface morphology of the blends. PEO alone in PLA exhibited the best optical clarity with higher percentage crystallinity, while PEG incorporation in PLA/PEO resulted in superior barrier properties. Also, the stability of the blends under a wide range of pH means prospective implementation of the films in packaging of food and non‐food‐grade products. © 2018 Society of Chemical Industry     

Influence of montmorillonite layered silicate on plasticized poly(l-lactide) blown films

Plasticized poly(l-lactide) (PLA) montmorillonite layered silicate (MLS) nanocomposites were compounded and blown-film processed using a co-rotating twin screw extruder. PLA was mixed with 10 wt% acetyltriethyl citrate ester plasticizer and 5 wt% of an organically modified montmorillonite at various screw speeds. Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) determined that the compounded pellets and the blown film PLA/MLS nanocomposites were intercalated. The effect of processing screw speeds on the barrier, thermal, mechanical, and biodegradation properties of the nanocomposites were analyzed and compared to the neat polymer. Nanocomposite films show a 48% improvement in oxygen barrier and a 50% improvement in water vapor barrier in comparison to the neat PLA. The thermogravimetric analysis (TGA) showed an overall 9 °C increase in the decomposition temperature for all of the nanocomposites. Differential scanning calorimetry (DSC) has determined that the glass transition, cold crystallization and melting point temperatures were not significantly influenced by the presence of MLS. Mechanical properties of the nanocomposites showed that the Young's modulus increased by 20% and the ultimate elongation of the nanocomposites were not sacrificed in comparison to the neat samples. Biodegradation rates in soil were slightly greater for the PLA/MLS nanocomposite than the pure PLA. However, none of the PLA pure and nanocomposites achieved significant biodegradation levels after 180 days.     

Fabrication and characterization of biodegradable poly(lactic acid)/layered silicate nanocomposites

In this study biocompatible/biodegradable poly(lactic acid) (PLA)/layered silicate nanocomposites (PLSNs) were successfully prepared by the intercalation of PLA polymer into organically modified layered silicate through the solution mixing process. Both X‐ray diffraction data and transmission electron microscopy images of PLSNs indicate most of the swellable silicate layers were disorderedly intercalated into the PLA matrix. Mechanical properties of the 0.1 wt% silicate‐containing fabricated nanocomposites performed by dynamic mechanical analysis have significant improvements in the storage modulus when compared to that of neat PLA matrix. Adding more layered silicates into PLA matrix induced a decrease in the mechanical properties of PLSNs, probably due to the presence of a large dimension of porosity in the fabricated nanocomposites. POLYM. ENG. SCI., 45:1615–1621, 2005. © 2005 Society of Plastics Engineers     

Synthesis,characterization and surface properties of poly(lactic acid)–perfluoropolyether block copolymers

Laboratory‐scale synthesis and morphological and surface energy characterization of triblock A–B–A copolymers based on poly(lactic acid) (PLA; A segment) containing various block lengths of perfluoropolyether (PFPE; B segment) at 5 wt% PFPE content are reported. Incorporation of PFPE segments in PLA lowers significantly both the polar and dispersive components of total surface energy. Total surface energy is lowered from ca 35 to ca 17 mN m^?1 on copolymerization of PLA with 5 wt% PFPE. Thermal analysis data reveal that lower molecular weight PFPE segments lower significantly the glass transition, crystallization and melting temperatures of the PLA matrix. Although block length variation of the PFPE segment does not affect surface energies of copolymer films, smaller PFPE segments increase significantly the low‐temperature modulus as observed from dynamic mechanical analysis. Copyright © 2010 Society of Chemical Industry     

Biodegradable composites of poly(butylene succinate‐co‐butylene adipate) reinforced by poly(lactic acid) fibers

Biodegradable composites of poly(butylene succinate‐co‐butylene adipate) (PBSA) reinforced by poly(lactic acid) (PLA) fibers were developed by hot compression and characterized by Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analyzer, and tensile testing. The results show that PBSA and PLA are immiscible, but their interface can be improved by processing conditions. In particular, their interface and the resulting mechanical properties strongly depend on processing temperature. When the temperature is below 120 °C, the bound between PBSA and PLA fiber is weak, which results in lower tensile modulus and strength. When the processing temperature is higher (greater than 160 °C), the relaxation of polymer chain destroyed the molecular orientation microstructure of the PLA fiber, which results in weakening mechanical properties of the fiber then weakening reinforcement function. Both tensile modulus and strength of the composites increased significantly, in particular for the materials reinforced by long fiber. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43530.