Polylactic Acid Composite Films Research Articles

Reinforcement of ozone pre-treated and enzyme hydrolyzed longer jute micro crystals in poly lactic acid composite films

Abstract In present study, jute fibers were pre-treated with ozone gas to remove the lignin. The effect of ozone treatment on change in single fiber strength, fiber surface morphology, whiteness, moisture absorbency, etc was studied. For comparison purpose, chemical pre-treatment of jute fibers was also carried out. In subsequent step, untreated, chemical and ozone pre-treated jute fibers were hydrolyzed by cellulase enzymes for separation of longer jute micro crystals. The influence of non-cellulosic contents on the enzyme hydrolysis and morphology of obtained micro crystals was presented. Later, 3 wt% of these jute micro crystals were incorporated into poly (lactic acid) matrix to prepare composite films by solvent casting. The reinforcement behavior was evaluated from tensile tests, dynamic mechanical analysis, and differential scanning calorimetry.

The effect of nanofiller geometry and compounding method on polylactic acid nanocomposite films

The effect of the compounding method and of the nanofiller geometry on the thermo-mechanical properties and electrical behavior of polylactic acid (PLA) nanocomposite films was investigated. The films were fabricated using two methods: (i) melt compounding followed by melt fiber spinning or (ii) solution compounding followed by electrospinning. Both the melt and electrospun fibers were then compression molded. In the case of melt compounding, both exfoliated graphite nanoplatelets (GNP) and carbon nanotubes (CNT) were used as reinforcement, whereas only CNT were used in the case of solution compounding. The microstructure was examined using scanning electron microscopy and the crystallization behavior, thermo-mechanical behavior, and electrical response of the PLA composite films were investigated as a function of nanofiller content, geometry, and compounding method. It was concluded that the GNP/PLA films had the highest percolation at greater than 3wt% of GNP, while the CNT/PLA films had the lowest at less than 1wt% of CNT. In addition, the solution method and electrospun fibers resulted in a higher conductance compared to the CNT/PLA films of the same CNT content made by melt compounding due to a more heterogeneous distribution and dispersion of CNT throughout the matrix that facilitated the formation of interconnected conductive networks.

Preparation and Characterization of Composites Based on Polylactic Acid and Beeswax with Improved Water Vapor Barrier Properties.

Beeswax and a plasticizer (ATBC) were added to polylactic acid (PLA) films in order to enhance the water vapor barrier properties of the films. Beeswax improved the barrier properties; the water vapor permeability in the composite containing 1% beeswax was 58% lower than that of the neat PLA. Fourier transform infrared spectroscopy and X-ray diffraction analysis revealed that the incorporation of beeswax and ATBC had so little effect on the PLA structure. In addition, the structure of PLA did not vary substantially with the additions. The surfaces of the composites were examined by using field emission scanning electron microscopy. Differential scanning calorimetry results showed that the degree of crystallinity of the PLA films increased with the addition of beeswax and ATBC. However, the tensile strength and elongation at break of the composites containing beeswax were up to approximately 50% lower than those of the neat PLA. Although further study is needed to improve the mechanical properties, the aforementioned results showed that the PLA barrier properties can be improved by the incorporation of a small amount of beeswax and ATBC. The results of this study can be applied for the preparation of PLA composite films with improved barrier properties. Such biodegradable films are extremely useful for applications in the food packaging industry.

Polylactic Acid (PLA) Composite Films Reinforced with Wet Milled Jute Nanofibers

In the present study, waste jute fibers formed in textile industries were wet pulverized to nanoscale using high energy planetary ball milling. The rate of refinement of uncleaned jute fibers having noncellulosic contents was found slower than the cleaned jute fibers. This behavior is attributed to the strong holding of fiber bundles by noncellulosic contents which offered resistance to the defibrillation during wet milling. In addition, the pulverization of fibers in the presence of water prevents the increase in temperature of mill which subsequently avoided the sticking of material on the milling container. After three hours milling, the diameter of nanofibers was observed around 50 nm. In the further stage, obtained nanofibers were incorporated under 1 wt%, 5 wt%, and 10 wt% loading into polylactic acid composite films. The potentials of jute nanofibers were investigated for improvement in mechanical and barrier properties of films. The maximum improvement in mechanical properties was observed in case of 5 wt% composite film where Young’s modulus was increased to 3.3 GPa from 1.0 GPa as compared with neat PLA film.

Mechanical properties of poly lactic acid composite films reinforced with wet milled jute nanofibers

In the present study, waste jute fibers generated in textile industries, were wet pulverized to the scale of nanofibers of 50 nm diameter using high energy planetary ball milling for 3 h. The presence of water during wet pulverization found to reduce the rising temperature of mill, which prevented sticking of nanofibers on the mill wall and resulted in unimodal size distribution. In the subsequent stage, 1, 5, and 10 wt% of jute nanofibers were incorporated in poly(lactic acid) (PLA) matrix to prepare nanocomposite films by solvent casting. The reinforcement of nanofibers was investigated from the improvements in mechanical properties based on tensile tests, dynamic mechanical analysis, and differential scanning calorimetry. The maximum improvement was observed in case of 5 wt% nanocomposite film where initial modulus and tensile strength increased by 217.30% and 170.59%, respectively as compared to neat PLA film. These improvements are attributed to the increased interaction between nanofibers and matrix as well as to the increased crystallinity of PLA in composites. The improvements in load bearing capacity of nanocomposite films were significant at 60°C than 35°C, which showed ability of jute nanofibers to improve the softening temperature of PLA matrix. In the end, experimental results of Young's modulus were compared with predicted modulus of mechanical models. A good level of agreement was observed up to 5 wt% loading of jute nanofibers. POLYM. COMPOS., 34:2133–2141, 2013. © 2013 Society of Plastics Engineers

Wet Pulverization of Waste Jute Fibers as Reinforcement for Biodegradable Nanocomposite Films

In the present study, waste jute fibers formed in textile industries, were wet pulverized to nanoscale using high energy planetary ball milling. The rate of refinement of uncleaned jute fibers having non-cellulosic contents was found slower than the cleaned jute fibers. This behavior is attributed to the strong holding of fiber bundles by noncellulosic contents which offered resistance to the defibrillation during wet milling. In addition, the pulverization of fibers in the presence of water prevents the increase in temperature of mill which subsequently avoided sticking of material on the milling container. After three hours milling, the diameter of nanofibers was observed around 50 nm. In the further stage, obtained nanofibers were incorporated under 1 wt%, 5 wt% and 10 wt% loading into poly lactic acid composite films. The potentials of jute nanofibers were investigated for improvement in mechanical and barrier properties of films. The maximum improvement in mechanical properties was observed in case of 5 wt% composite film where Young’s modulus was increased to 3.3 GPa from 1.0 GPa as compared with neat PLA film.

Effect of Microcrystalline Cellulose from Banana Stem Fiber on Mechanical Properties and Crystallinity of PLA Composite Films

This work focused on the preparation of the biocomposite films of polylactic acid (PLA) reinforced with microcrystalline cellulose (MCC) prepared from agricultural waste, banana stem fiber, and commercial microcrystalline cellulose, Avicel PH 101. Banana stem microcrystalline cellulose (BS MCC) was prepared by three steps, delignification, bleaching, and acid hydrolysis. PLA and two types of MCC were processed using twin screw extruder and fabricated into film by a compression molding. The mechanical and crystalline behaviors of the biocomopsite films were investigated as a function of type and amount of MCC. The tensile strength and Young’s modulus of PLA composites were increased when concentration of MCC increased. Particularly, banana stem (BS MCC) can enhance tensile strength and Young’s modulus of PLA composites than the commercial MCC (Avicel PH 101) because BS MCC had better dispersion in PLA matrix than Avicel PH 101. This result was confirmed by SEM image of fractured surface of PLA composites. In addition, XRD patterns of BS MCC/PLA composites exhibited higher crystalline peak than that of Avicel PH 101/PLA composites

Antimicrobial activity of nisin incorporated in pectin and polylactic acid composite films against Listeria monocytogenes

SummaryAn extruded composite food packaging film containing pectin, polylactic acids (PLAs) and nisin was developed to inhibit Listeria monocytogenes. The mechanical properties and surface structure of the film were also examined. Cells of L. monocytogenes were reduced by 2.1, 4.5 and 3.7 log units mL−1 by the pectin plus PLA (pectin/PLA) film containing nisin (1000 IU mL−1 of tested liquid) in Brain Heart Infusion (BHI) broth, liquid egg white and orange juice, respectively, after 48 h at 24 °C. Pectin played an important roll in embedding nisin into the film. The pectin/PLA film had a similar stiffness but lower tensile strength, elongation and fracture energy than the pure PLA film. These data suggested that nisin incorporated into the pectin/PLA film was an effective approach to reducing L. monocytogenes in a typical growth medium (e.g. BHI broth) as well as in foods (e.g. orange juice and liquid egg).