Effect of nanosilver on the photodegradation of poly(lactic acid)

The poly(lactic acid), PLA, mixed with nanosilver in solution easily forms nanocomposite in solid state (after solvent evaporation), which was proved by UV–Vis spectroscopy. This work focuses on photodegradation occurring in PLA films doped with nanosilver. The changes in chemical structure of photodegraded PLA has been determined using FTIR spectroscopy. Differential scanning calorimetry of UV‐irradiated PLA samples provided information on polymer glass transition and crystallization/melting processes. It was found that PLA alone is more sensitive to photodegradation than PLA/silver nanocomposites. The mechanism of nanocomposite photodegradation and effect of nanosilver was discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40144.     

Borassus powder-reinforced poly(lactic acid) composites with improved crystallization and mechanical properties

This article reports on the development of biocomposites based on polylactic acid (PLA) and borassus powder. Borassus powder was treated with alkali to remove hemicelluloses and lignin. The treated borassus improved the homogeneous mixing with PLA and increased the crystallinity of PLA. Dispersibility of the borassus was studied by scanning electron microscopy (SEM) and X-ray MicroCT. PLA/borassus composites were prepared by melt mixing of PLA with 5, 10, and 15 wt % treated/untreated borassus. Composites were examined for mechanical properties and crystallization. Composites showed enhanced tensile strength compared to neat PLA. The PLA/treated borassus powder composites displayed higher crystallinity than PLA. The isothermal cold crystallization study showed increase in the crystallization rate of PLA in the presence of treated borassus. The spherulitic growth was studied using polarized optical microscopy. The enhanced performance of the PLA-borassus composites was observed in the presence of borassus. This study demonstrates that the PLA-borassus composites show great promise for bioplastics applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47440.     

Fabrication and characterization of sucrose palmitate reinforced poly(lactic acid) bionanocomposite films

Environmental issues concerning petroleum‐based polymers have begun a growing emphasis to utilize sustainable poly(lactic acid) (PLA) based packaging. However, PLA has its own limitations such as brittleness, high gas permeabilities and slow crystallization rate. With the aim to alleviate these limitations, we made a maiden effort to use a food additive, sucrose palmitate (SP) as eco‐friendly filler for fabrication of PLA based bionanocomposites. FTIR analysis elucidated the presence of hydrogen bonding and intermolecular interaction between PLA and reinforcement. Ordered orientation of the SP in the PLA matrix visualized by TEM analysis revealed uniform dispersion of SP filler into PLA matrix. DSC and XRD results confirmed that the incorporated bio‐filler acted as a nucleating agent and thus partially contributed towards the crystallinity of PLA‐SP bionanocomposites. Enhancement in the tensile strength and elongation at break up to 83 and 56% respectively is obtained. The best positive influence for the oxygen barrier was confirmed for the PLA‐SP bionanocomposite film where the reduction in oxygen permeability by 69% is achieved in comparison to pure PLA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41320.     

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.     

Study on flax fiber toughened poly (lactic acid) composites

Poly (lactic acid) (PLA) is a renewable and biodegradable polymer with high modulus, high strength but low toughness. Blending PLA with plant fiber has been believed an available strategy to improve the toughness of PLA. PLA/Flax composites were fabricated by extrusion and injection molding processes. The flax fiber surfaces were modified before blending to improve the compatibility, and the chemical structures of both untreated and treated fiber were characterized by Fourier transform infrared spectroscopy. Results of mechanical test showed that the impact strength and elongation at break of PLA/Flax composites were remarkably higher than PLA. The impact fractures of PLA/Flax composites were also observed by scanning electron microscope. The results showed uniform dispersion of fibers in PLA matrix and good compatibility between treated fibers and PLA matrix. Moreover, it can be observed that crazing propagation was hindered by fibers and transcrystalline developed along fibers by polarized optical microscope. Differential scanning calorimetry analysis was carried out to study the crystallinity of PLA and it was found that incorporation of fiber improved the crystallinity of PLA. The toughening mechanism of PLA/Flax composites was discussed according to the results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42573.     

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     

Statistical design of sustainable composites from poly(lactic acid) and grape pomace

Biocomposites from poly(lactic acid) (PLA) and grape pomace (GP) were created via injection molding to examine the effects of GP in a PLA matrix. To optimize the mechanical performance the biocomposites were compatibilized with maleic anhydride grafted PLA (MA-g-PLA). The objective of this work was to create a model that could accurately predict the mechanical properties of GP/PLA biocomposites. A region of feasibility for the biocomposites was determined using a statistical design of experiments. Linear regression was used to model the mechanical performance and predicted results with an error of 10% for both tensile and flexural strength and 16% for impact strength. The model was verified with a biocomposite of PLA/GP/MA-g-PLA with a ratio of 62/36/2. This biocomposite had a tensile strength, flexural modulus, and impact strength of 25.8 MPa, 40.0 MPa, and 18.4 J/m, respectively. It was found that a linear model can accurately predict the mechanical properties of PLA/GP/MA-g-PLA biocomposites.     

Epoxidized soybean oil‐plasticized poly(lactic acid) films performance as impacted by storage

This study examined the effect of storage time at room temperature on the melt viscosity, thermal, and tensile properties of epoxidized soybean oil plasticized poly(lactic acid) (PLA) films manufactured through a cast extrusion process. Infrared results indicate that plasticizer migration to the surface of the film occurred after only 30 days of storage, which significantly affected the performance of plasticized films. While the melt viscosity, glass transition temperature, degree of crystallinity, tensile strength, and modulus increased, the elongation at break and energy to break decreased with storage time up to 30 days and all properties remained constant thereafter. However, the ability of stored plasticized film to cold crystallize remained unaffected since both the cold crystallization temperature and melting temperature were not affected during storage. Although plasticized film lost some flexibility after only 30 days of storage due to plasticizer migration to the surface of the film, sufficient plasticization performance still remained in plasticized PLA films for flexible packaging application even after a long storage period at ambient conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43201.     

Mesomorphic phase formation of plasticized poly(l‐lactic acid)

The effects of the crystallization temperature, T_c, on the crystal structure as well as its thermal behavior of plasticized poly(l ‐lactic acid) were investigated by means of wide‐angle X‐ray diffraction (WAXD), Fourier‐transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). PLLA blended with succinic acid‐bis[2‐[2‐(2‐methoxyethoxy)ethoxy]ethyl] ester (SAE) showed clear difference in T_c dependence of crystalline form compared to PLLA homopolymer. PLLA with 26 wt % SAE crystallized into orthorhombic α form for T_c above 80°C, while a peculiar disordered structure (mesophase) was obtained for T_c at 40°C. A detailed FTIR analysis of the mesophase of PLLA, focusing on the intra‐ and inter‐chain interaction in the structure, indicated that mesophase had a large degree of disorder in 10/3 helical conformation as well as its packing manner of disordered 10/3 helical chain. Upon heating, mesophase showed a steep exothermic peak at 80°C in DSC thermogram, indicating the phase transformation from mesophase to a form crystal. FTIR results showed that the degree of interchain interaction of C=O in PLLA started to decrease above 60°C, followed by steep increase at 80°C due to the recrystallization into a form. Melt‐recrystallization process in mesophase‐α transformation was clarified. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39762.     

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.     

Halochromic poly (lactic acid) film for acid base sensor

A novel strategy to engineer biodegradable halochromic film based on poly (lactic acid) (PLA) for pH sensorial substances was presented. The effect of polyethylene glycol (PEG) compositions and dye amount on the efficiency of halochromic pH film was observed. The interactions between PLA, PEG, and dye was evidence by Fourier transform infrared. UV–VIS results indicated the sensitivity of the halochromic film through color changes. Mechanical performance was investigated by tensile testing to assess the potential of the halochromic film. It was found that the halochromic pH film has a clear color response from yellow to purple at pH 3–11 with a rapid response time within a minute. The results also revealed that varying content of PEG showed a significant effect on response time compared with varying dye compositions. PLA/PEG film and dye formed new interactions where PEG increased the free volume of PLA and made it possible for the PEG and the dye to diffuse and entrap between PLA chain. In term of the film strength, the addition of PEG and dye improved the flexibility of PLA film, which enables great potential in many applications such as medical, textile, and packaging.     

Effect of the molecular weight on the plasticization properties of poly(hexane succinate) in poly(vinyl chloride) blends

Blends of poly(vinyl chloride) (PVC) and poly(hexane succinate) (PHS) with various molecular weights were analyzed with respect to their mechanical properties, durability, and thermal stability. We found that the molecular weight of PHS played an important role in the plasticizing process, and the single glass-transition temperature (T _g) of the PVC blends measured by dynamic mechanical analysis supported the complete miscibility between PHS and PVC. The plasticizing efficiency of PHS increased as the molecular weight increased; this reflected the gradually increasing elongation at break and the decreased T _g of the PVC blend. Meanwhile, the higher molecular weight of PHS also improved the resistance of migration and thermal stability but decreased the biodegradability of the PVC blends; this was due to the strong intermolecular interactions between PHS and PVC. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47081.     

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.     

Efficient preparation of poly(lactic acid) nanofibers by melt differential electrospinning with addition of acetyl tributyl citrate

Poly(lactic acid) (PLA) nanofibers, as a biodegradable and environmentally friendly material, have potential applications such as biological medicine, efficient filter material, and so on. PLA nanofibers are usually prepared by solution electrospinning method with toxic solvents, such as chloroform, chloromethane, and N,N‐dimethyl formamide. In this work, PLA nanofibers were fabricated with a self‐designed melt differential electrospinning device, assisted by addition of nontoxic acetyl tributyl citrate (ATBC) and by airflow. Molecular dynamics simulations were performed to understand the experimental results. The results revealed that the fiber diameter decreased with increasing airflow velocity, and fibers with a diameter as small as 236 nm were obtained at the highest airflow velocity of 25 m/s (with 6 wt % of ATBC). Furthermore, a significantly accelerated falling speed of the jets of about 347 times of that without airflow was achieved at a flow rate of 25 m/s. These results demonstrated that the combination of adding ATBC and airflow assistance was a good strategy to achieve finer fibers with improved stability and efficiency, making it a promising way for mass green production of PLA nanofibers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46554.     

Improvement of melt stability and degradation efficiency of poly (lactic acid) by using phosphite

Concurrent improvement of melt processing stability and degradation efficiency of poly(lactic acid) (PLA) is still a challenge for the industry. This article presents the use of phosphites: tris(nonylphenyl) phosphite (TNPP) and tris (2,4-di-tert-butylphenyl) phosphite (TDBP), to control the thermal stabilization, mechanical performance, and hydrolytic degradation ability of the compressed PLA films. The hydrolysis process is followed as a function of time at 45, 60, and 75°C. During melt extrusion, both phosphites function as a processing aid, besides acting as a chain extender stabilizing the PLA molecular weight. The phosphite structure plays a crucial role over crystallinity and water absorption, in controlling the hydrolytic degradation of PLA. The application of TNPP significantly catalyzes the hydrolysis of PLA, which is the initial step of the biodegradation process. The optimum amount of TNPP for best hydrolytic degradation efficiency and thermal stabilization of PLA is 0.5 wt%. The excessive TNPP loadings cause a drastic drop in PLA molecular weight and, as a consequence, a reduction of flexural strength. The reactions between PLA and phosphite molecules are discussed.     

Biopolymer foams from Novatein thermoplastic protein and poly(lactic acid)

A batch processing method is used to fabricate foams comprising of a blend of poly(lactic acid) (PLA) and Novatein, a protein‐based thermoplastic. Various compositions of Novatein/PLA are prepared with and without a compatibilizer, PLA grafted with itaconic anhydride (PLA‐g‐IA). Pure Novatein cannot form a cellular structure at a foaming temperature of 80 °C, however, in a blend with 50 wt % of PLA, microcells form with smaller cell sizes (3.36 µm) and higher cell density (8.44 × 10²¹ cells cm^?3) compared to pure PLA and blends with higher amounts of PLA. The incorporation of 50 wt % of semicrystalline Novatein stiffens the amorphous PLA phase, which restrains cell coalescence and cell collapse in the blends. At a foaming temperature of 140 °C, NTP₃₀–PLA₇₀ shows a unique interconnected porous morphology which can be attributed to the CO₂‐induced plasticization effect. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45561.     

Preparation of poly(lactic acid) and pectin composite films intended for applications in antimicrobial packaging

A pectin and poly(lactic acid) (PLA) composite was compounded by extrusion. A model antimicrobial polypeptide, nisin, was loaded into the composite by diffusion. The incorporation of pectin into PLA resulted in a heterogeneous biphasic structure, as revealed by scanning electronic microscopy, confocal laser microscopy, and fracture–acoustic emission. The incorporation of pectin also created a rough and cragged surface, which was hydrophilic and facilitated the access and absorption of nisin. The nisin‐loaded composite suppressed Lactobacillus plantarum growth, as indicated by agar diffusion and liquid‐phase culture tests. The incorporation of pectin at the concentration of ～ 20% of the total mass did not alter the Young's modulus of the film from that of the pure PLA. The composite materials were able to retain their tensile strength, flexibility, and toughness to an extent that satisfied the requirements for packaging materials. Results from this research indicate the potential of pectin/PLA composites for applications in antimicrobial packaging. © 2007 Wiley Periodicals, Inc.? J Appl Polym Sci 2007     

Structural characterization of polypropylene/poly(lactic acid) bicomponent meltblown

The bicomponent meltblown process offers to associate two polymers in the same fiber generating fibrous media with new properties. In this study, we associate polypropylene (PP) and poly(lactic acid) (PLA), from renewable sources, polymers. The influence of primary air flow rate and the structural properties of the PP/PLA bicomponent meltblown are compared to PP and PLA monocomponent meltblown. The structural properties include fiber morphology and diameter, packing density, permeability, thermal shrinkage and crystallization. The results relate that the PP/PLA bicomponent meltblown fiber diameters are thinner than those of PLA monocomponent. Moreover, it has higher resistance to thermal shrinkage compared to PP monocomponent meltblown. The packing density and permeability are not affected by the association of PP and PLA due to low crimp effect. Two different filament formations of PP/PLA bicomponent meltblown at low and high primary air flow rate have also been observed. Lastly, this study illustrates that PP and PLA association is viable, showing the production of PP/PLA bicomponent microfiber and limited thermal shrinkage at high temperature. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44540.     

Effect of Tween 80 on morphology and performance of poly(L‐lactic acid) ultrafiltration membranes

Poly(L‐lactic acid) (PLLA) ultrafiltration (UF) membrane was fabricated by immersion precipitation method using Tween 80 as an additive. Membrane structure was characterized by scanning electron microscopy (SEM), porosity and pore size measurement, and atomic force microscopy (AFM). Membrane performance was evaluated by pure water flux, molecular weight cut‐off, and tensile test. It was found that the addition of Tween 80 into the casting solution significantly increased the permeability and molecular weight cut‐off of membrane. Tensile test confirmed that the as‐prepared PLLA membranes exhibited acceptable mechanical properties for ultrafiltration. Further, the role of Tween 80 in the process of membrane formation was analyzed and proposed. The addition of Tween 80 favored the formation of larger pores by interrupting the polymer chain entanglement and improving the miscibility between solvent and coagulant. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44428.     

Toughness improvement of poly(lactic acid) with poly(vinyl propionate)-grafted natural rubber

Natural rubber (NR) grafted with poly(vinyl propionate) (NR-g-PVP) was prepared by emulsion polymerization. The monomer content was set at 5, 10, 20, and 30 wt%. The chemical structure of NR-g-PVP was confirmed by ¹H-NMR and FTIR techniques. The grafting parameters of purified NR-g-PVP were evaluated. Binary (PLA/NR and PLA/NR-g-PVP) and ternary (PLA/NR/NR-g-PVP) blends were prepared by melt blending using a twin-screw extruder. The percentage of grafted PVP on NR affected morphology, thermal and mechanical properties of the blends. In binary blends, 5% grafting showed the greatest improvement of toughness and ductility with PLA, whereas there was no improvement in the mechanical properties of PLA/NR blend from using NR-g-PVP as a compatibilizer. The mechanical properties of the blends are related to mutual compatibility of the components. Good interfacial adhesion and proper particle size of NR were the key factors contributing to mechanical properties.