Pure Polylactic Acid Film Research Articles

Evaluation of antimicrobial activity of Poly Lactic Acid (PLA) films containing cellulose nanoparticle and Bunium persicum and Mentha pepperita essential oils (EOs)

BACKGROUND: Packaging is one of the important aspect of food quality and safety. Unfortunately, most of food packaging materials are from oil resources that are limited resources and undegradable. OBJECTIVES: The aim of this study was reaching an environmentally friendly packaging with enhancement safety of food. METHODS: After obtaining Bunium persicum (BP) and Mentha pepperita (MP) essential oils (EOs) by steam distillation method, their chemical compositions were determined using GC-MS analysis. PLA films were prepared using solvent casting technique containing different concentrations of BP (0, 0.5 and1%v/v), MP (0, 0.5 and1%v/v) EOs and cellulose nanoparticle (CN) (0 and 1% w/v) and their antimicrobial effects against gram positive bacteria (Staphylococcus aureus ATCC 65138, Bacillus cereus ATCC 11778) and Gram negative bacteria (Vibrio parahaemolyticus ATCC 43996, Escherichia coli O157:H7 and Salmonella typhymurium ATCC 14028) were assessed by disk diffusion method. RESULTS: Major compounds of BP EO were Propanal 2-methyl-3-phenyl (34.08%), Cymene (18.23%) and Myrtenal (12.37%) and for MP EO were p-Menthan-3-ol (44.59%) and p-Menthan-3-onetrans (12.14%). The results of present study indicated that pure PLA film or PLA films containing CN showed no antimicrobial activity against any of the five tested bacteria but films containing EOs had significant antimicrobial activity and BP EO was more effective than MP EO and their combination (p<0.05). Besides, the inhibitory effect of films were concentration-dependent. In addition results of current study revealed, gram-positive bacteria were more sensitive than gram negative bacteria to PLA films containing EOs. CONCLUSIONS: The results of this study indicated that PLA films containing MP and BP EOs may be useful for packaging of foods in order to increase their shelf life and safety.

Effects of PLA Film Incorporated with ZnO Nanoparticle on the Quality Attributes of Fresh-Cut Apple.

A novel nanopackaging film was synthesized by incorporating ZnO nanoparticles into a poly-lactic acid (PLA) matrix, and its effect on the quality of fresh-cut apple during the period of preservation was investigated at 4 ± 1 °C for 14 days. Six wt % cinnamaldehyde was added into the nano-blend film. Scanning electron microscope (SEM) analysis showed a rougher cross-section of the nano-blend films and an X-ray diffraction (XRD) was carried out to determine the structure of the ZnO nanoparticles. Compared to the pure PLA film, the nano-blend film had a higher water vapor permeability (WVP) and lower oxygen permeability. With the increase of the nanoparticles (NPs) in the PLA, the elongation at break (ε) and elastic modulus (EM) increased, while tensile strength (TS) decreased. Thermogravimetric analysis (TGA) presented a relatively good thermostability. Most importantly, the physical and biochemical properties of the fresh-cut apple were also measured, such as weight loss, firmness, polyphenol oxidase (PPO), total phenolic content, browning index (BI), sensory quality, and microbiological level. The results indicated that nano-blend packaging films had the highest weight loss at the end of storage compared to the pure PLA film; however, nanopackaging provided a better retention of firmness, total phenolic countent, color, and sensory quality. It also had a remarkable inhibition on the growth of microorganisms. Therefore, Nano-ZnO active packaging could be used to improve the shelf-life of fresh-cut produce.

Preparation and characterization of PLA/NCC nanofibers

ABSTRACTBy electronspinning PLA/NCC nanofibers were prepared with polylactic acid (PLA) and nanocellulose whiskers (NCC) which obtained from microcrystalline cellulose (MCC) by sulfuric acid hydrolysis. The morphologies and physical states were investigated using scanning electron microscopy (SEM), thermogravimetric analysis (TG-DTG) and differential scanning calorimetry (DSC). When the mass fraction of NCC was 5%, scanning electron microscopy observations revealed that the diameter of PLA/NCC nanofibers was the smallest and the distribution was uniform and results from TG-DTG and DSC suggested that thermal decomposition temperature of composite films was approximately increased by 20°C than pure PLA film, at the same time mechanical and hydrolysis property of composite films were obviously improved.

Preparation and characterization of PLA/acetylated nanocellulose films

In order to improve the mechanical and barrier properties of polylactic acid( PLA) film,nanocellulose( NCC) was added into it.The microcrystalline cellulose( MCC) was used to prepare NCC with sulfuric acid method,and then the NCC was modified to gain the acetylated nanocellulose( ANCC). The composite films with different ratio of ANCC/PLA were prepared by solvent casting method. The microstructure and morphology of films were observed by TEM,FTIR and SEM. The tensile tester and oxygen transmission tester were applied to analyze the mechanical and gas barrier properties of films.The results showed that,the length of the single nanocellulose fiber was in the range of 100 to 200 nm,and the diameter was in the range of 10 to 20 nm.The Acetylation had little effect on the fiber micromorphology. Compared with pure PLA film,the tensile strength of the composite film with 1%ANCC increased by 29.09%,but the tensile strength was declined with the further increase of ANCC was content.The oxygen transmittance rate of the composite film with 0.5% ANCC was decreased by 42%. The addition of ANCC had no significant effect on the transparence and haze.

Improved thermal stability of polylactic acid (PLA) composite film via PLA–β-cyclodextrin-inclusion complex systems

The effects of the incorporation of PLA–β-cyclodextrin-inclusion complex (IC) and β-cyclodextrin (β-CD) on biopolyester PLA films were investigated. Thermal stability, surface morphology, barrier, and mechanical properties of the films were measured at varying IC (1, 3, 5, and 7%) and β-CD (1 and 5%) concentrations. The PLA-IC-composite films (IC-PLA-CFs) showed uniform morphological structure, while samples containing β-CD (β-CD–PLA-CFs) showed high agglomeration of β-CD due to poor interfacial interaction between β-CD and PLA moieties. According to the thermal property analysis, the 5% IC-PLA-CFs showed 6.6 times lower dimensional changes (6.5%) at the temperature range of 20–80°C than that of pure PLA film (43.0%). The increase of IC or β-CD content in the PLA-composite films shifted the glass transition and crystallization temperature to higher temperature regions. The crystallinity of both composite films improved by increasing IC or β-CD content. Both composite films had higher oxygen and water vapor permeability as IC or β-CD content increased in comparison to pure PLA film. All the composite films had less flexibility and lower tensile strength than the pure PLA film. In conclusion, this study shows that the IC technique is valuable to improve the thermal expansion stability of PLA-based films.

Degradation Behaviors of Different Blends of Polylactic Acid Buried in Soil

Polylactic acid (PLA), as the biodegradable polymer becomes more attention as a green material for industrial applications. Lipase-catalysed polymerization with Lecitase Ultra and Lipozyme TL IM were applied to synthesize PLA to decrease the chemical-catalysts utilization which having toxicity interferes in products. PLA products were characterized by end group/HPLC analyses for Mn/Mw determination. The results indicated that low molecular weight PLA could be successfully produced from commercial lactic acid by using the commercial lipases. With using Lipozyme TL IM as biocatalyst, obtainable Mn and Mw of PLA were 7,933Da and 194Da, respectively. For Lecitase Ultra used as biocatalyst obtainable Mn and Mw of PLA were 8,330Da and 216Da, respectively. Subsequently, the resulting PLA products from this method were prepared as PLA films blended with commercial PLA beads varying the blending ratios by casting on glass plate. Their degradable behaviors were studied under controlled soil burial laboratory conditions. The characteristics of PLA blend films were analyzed using visual observations, measuring weight loss, DSC and FTIR analysis. The results observed that the different blends ratios of PLA films showed more flexible than pure PLA film. Besides, the different blends of PLA films were disintegrated in soil within the short burial time.

Toughening mechanisms in poly(lactic) acid reinforced with TEMPO-oxidized cellulose

The mechanical properties of poly(lactic) acid (PLA) were modified by the addition of small amounts of cellulose, prepared from the mechanical disintegration of birch Kraft pulp following oxidation of the primary alcohol groups mediated by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO). The TEMPO-fibrillated cellulose (TOFC) was subsequently acetylated in acetic anhydride to degrees of substitution (DS) of 0.4 and 0.6 to enhance the compatibility between the polar cellulose and the non-polar polymer. The fracture behaviour of tensile specimens prepared from PLA film containing weight fractions of 1, 2 and 5 % of TOFC was considerably altered. The strain-to-failure of PLA modified by the incorporation of 1 wt% TOFC acetylated to a DS of 0.6 increased approximately 25-fold and the work of fracture by order of magnitude. The increase in the fracture properties were, nevertheless, accompanied by a reduction in Young’s modulus of around 60 % at both DS levels. At the higher TOFC addition levels, no toughening was observed, with the strains-to-failure and works of fracture both decreasing compared to pure PLA film. On the other hand, the Young’s modulus and tensile strength of films prepared from PLA incorporating TOFC esterified to a DS of 0.6 was found to be greater than that of pure PLA film. Possible mechanisms explaining the increase in toughness at 1 wt% are postulated.

Characterization of an antioxidant polylactic acid (PLA) film prepared with α-tocopherol, BHT and polyethylene glycol using film cast extruder

Polylactic acid (PLA) films were prepared with α-tocopherol, buthylated hydroxytoluene (BHT), and polyethylene glycol 400 (PEG 400) using a cast film extruder in an effort to create an antioxidant film. Film properties were characterized by radical scavenging activity and thermal, physical, and gas barrier properties. Final resin compounding and pelletization was achieved by a twin screw extruder and a pelletizator to permit the homogenization of all resin components prior to film casting. Three different PLA films were fabricated for this study: pure PLA film, PLA film with BHT and PEG 400 (BP-PLA film), PLA film with α-tocopherol, BHT, and PEG 400 (ABP-PLA film). The addition of PEG 400 into the pure PLA film decreased the glass transition temperature ( T g) of the film. The BP-PLA and ABP-PLA film had around 51 °C of T g while pure PLA film had 66 °C. Due to the decreased T g of both the BP-PLA and ABP-PLA film, both films had an increased elongation at break (%E). The addition of plasticizer into the pure PLA film also caused increased water vapor permeability (WVP) and decreased oxygen permeability (OP). The ABP-PLA film had highest DPPH radical scavenging activity, 90%, while pure PLA and BP-PLA film had only 0 and 14%, respectively.