Plasticized Poly Lactic Acid Research Articles

Polyethylene glycol enhanced antibacterial activity of EDTA and ethyl maltol blended PLA against Staphylococcus aureus for biodegradable active packaging

Poly (lactic acid) (PLA) has limited promise as a bio-based antimicrobial packaging material due to its lack of plasticization, which limits antimicrobial agent release and antimicrobial efficiency. PLA were plasticized with polyethylene glycol (PEG) and blended with ethyl maltol or ethylenediaminetetraacetic acid (EDTA) as antibacterial agents by melt extrusion. The effects of combining PEG, EDTA, and ethyl maltol on sheet properties and antibacterial activity were investigated. Incorporation of ethyl maltol created a dense and smooth homogeneous surface, while EDTA addition caused large pores in the PLA sheet microstructure impacting swelling degree, water solubility and surface hydrophilicity. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) showed that both ethyl maltol and EDTA addition modified the amorphous and crystalline phases of plasticized PLA. FTIR results suggested interaction between the functional groups of PLA chains, PEG, ethyl maltol or EDTA which affected the glass transition temperature (Tg), degree of crystallinity, and thermal stability of PLA. Adding PEG into PLA-EDTA enhanced antibacterial activity against Gram-positive Staphylococcus aureus (reduction of 1.35 log CFU/mL from the initial inoculum). The higher water solubility of sheets corresponded to a suitable release rate and sufficient amounts of antimicrobial compounds against Staphylococcus aureus. In vitro antifungal testing, PLA-PEG-EDTA sheets did not exhibit a clear zone of inhibition but delayed Penicillium sp. spore formation until day 5 of incubation. PEG plasticized PLA sheets functionalized with ethyl maltol and EDTA showed potential as active biomaterials against food-borne pathogen bacteria Staphylococcus aureus.

Additive Manufacturing of Halochromic Polylactic Acid (PLA)

With increasing concerns regarding plastic waste and pollution, researchers have been looking to develop advanced materials from biodegradable plastics. This study features a halochromic biodegradable polymer produced using additive manufacturing. The purpose of this research is to fabricate halochromic polylactic acid (PLA) filaments and assess its halochromic behaviour, mechanical and chemical properties of the 3D printed PLA specimens. PLA/polyethylene glycol (PEG)/bromocresol purple (BCP) compound was prepared and added in extrusion to produce a 3D printing filament. Dumbbell-shaped and rectangular specimens were fabricated from the filament through 3D printing. The halochromic responsiveness and colour reversibility were tested by exposing the samples to liquid and vaporized hydrochloric acid (strong acid), acetic acid (weak acid) and ammonia (strong alkali). The tensile properties, fracture surface morphology and chemical species of the specimens were tested and analyzed through tensile test, scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy. The halochromic responsiveness shows obvious colour changes from yellow to blue when exposed to strong alkali. The tensile strength and modulus were found to be higher in comparison to plasticized PLA but the elongation at break was lower. SEM morphology show brittle fracture characteristics in the printed specimens. Overall, the 3D printed halochromic PLA specimens show promising results and have proven their functionality as pH sensors which offers wide applications in many industries such as medical, environmental and packaging.

Design of sustainable 3D printable polylactic acid composites with high lignin content

In this study, we report the development of a sustainable polymer system with 50 wt% lignin content, suitable for additive manufacturing and high value-added utilization of lignin. The plasticized polylactic acid (PLA) was incorporated with lignin to develop the bendable and malleable green composites with excellent 3D printing adaptability. The biocomposites exhibit increases of 765.54 % and 125.27 % in both elongation and toughness, respectively. The plasticizer enhances the dispersion of lignin and the molecular mobility of the PLA chains. The good dispersion of lignin particles within the structure and the reduction of chemical cross-linking promote the local relaxation of the polymer chains. The good local relaxation of the polymer chains and the high flexibility allow to obtain a better integration between the printed layers with good printability. This research demonstrates the promising potential of this composite system for sustainable manufacturing and provides insights into novel material design for high-value applications of lignin.

The Influence of Plasticizers and Accelerated Ageing on Biodegradation of PLA under Controlled Composting Conditions

The overall performance of plasticizers on common mechanical and physical properties, as well as on the processability of polylactic acid (PLA) films, is well-explored. However, the influence of plasticizers on biodegradation is still in its infancy. In this study, the influence of natural-based dicarboxylic acid-based ester plasticizers (MC2178 and MC2192), acetyl tributyl citrate (ATBC Citroflex A4), and polyethylene glycol (PEG 400) on the biodegradation of extruded PLA films was evaluated. Furthermore, the influence of accelerated ageing on the performance properties and biodegradation of films was further investigated. The biodegradation of films was determined under controlled thermophilic composting conditions (ISO 14855-1). Apart from respirometry, an evaluation of the degree of disintegration, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) of film surfaces was conducted. The influence of melt-processing with plasticizers has a significant effect on structural changes. Especially, the degree of crystallinity has been found to be a major factor which affects the biodegradation rate. The lowest biodegradation rates have been evaluated for films plasticized with PEG 400. These lower molecular weight plasticizers enhanced the crystallinity degrees of the PLA phase due to an increase in chain mobility. On the contrary, the highest biodegradation rate was found for films plasticized with MC2192, which has a higher molecular weight and evoked minimal structural changes of the PLA. From the evaluated results, it could also be stated that migration of plasticizers, physical ageing, and chain scission of films prompted by ageing significantly influenced both the mechanical and thermal properties, as well as the biodegradation rate. Therefore, the ageing of parts has to be taken into consideration for the proper evolution of the biodegradation of plasticized PLA and their applications.

Lignin-containing cellulose fibrils as reinforcement of plasticized PLA biocomposites produced by melt processing using PEG as a carrier

The present work shows the feasibility of incorporating lignocellulosic nanofibers (LCNFs) from date palm waste, with diameters in the range of 10 and 30 nm, into polyethylene glycol (PEG)-plasticized polylactic acid (PLA). PLA/PEG/LCNF nanocomposites, with nanocellulose contents ranging from 2 to 10 wt%. were successfully prepared by one-step melt processing using PEG as a carrier to prevent the aggregation of LCNFs. The effect of the LCNFs content on the mechanical properties was assessed by tensile tests and dynamic mechanical analysis (DMA), pointing an enhancement in the tensile strength and Young’s modulus by about 250% and 1100%, respectively, at 8% LCNFs content while maintaining a high toughness (around 16 MJ/m3). In addition, the proper dispersion in the form of a 3D-structured network and the good compatibility of LCNFs with the PLA/PEG matrix were confirmed by DMA and melt rheology measurements, as the stiffness in the rubbery state and the storage modulus increased with the content of LCNFs, respectively. The homogenous dispersion of LCNFs within PLA/PEG matrix was further confirmed by scanning electron microscopy (SEM) observation. Finally, from the disintegration tests in composting conditions, both PEG and LCNFs were found to positively contribute to the disintegration of PLA, mainly due to their affinity with water. Given the better sustainability of LCNFs owing to the absence of any chemical to isolate cellulose, along with their dispersibility within PLA matrix, the use of PEG as a carrier to produce PLA-LCNFs composites via melt processing may contribute to further highlight the merits of LCNFs as reinforcement in a biobased polymer matrix to produce composites with enhanced mechanical properties.

Preparation and characterization of the plasticized polylactic acid films produced by the solvent‐casting method for food packaging applications

A strategy to overcome the brittleness and rigidity of polylactic acid (PLA)-based materials for food packaging applications is adding a proper plasticizer in the right amount. Here, triacetin (TA) and polyethylene glycol (PEG) were used as plasticizers in different amounts (10, 20, and 30 wt%) to produce the plasticized PLA films by the solvent-casting method. Tensile properties, water vapor permeability (WVP), moisture content (MC), optical properties, Fourier transform infrared absorption (FTIR), and thermogravimetric analysis (TGA) are reported. The results showed that both TA and PEG cause increasing elongation at break (Eab) and decreasing tensile strength (TS), where the plasticized PLA films containing 10 and 30 wt% of TA showed the highest TS (26.6 MPa) and Eab (81.1%), respectively. Light transmission of PLA was decreased by introducing the plasticizers, while WVP, MC, and opacity of the plasticized films were increased compared to the neat PLA. Among the plasticized films, the sample with 10 wt% of TA and PEG showed the lowest WVP (4.9 × 10−10 g/m s−1 Pa−1) and MC (5.5%), respectively. Based on the TGA, an improvement in the thermal stability of TA and PEG plasticized films compared to the neat PLA was obvious. The sample containing 10 wt% of TA (PLA-TA10) showed the best performance for food packaging applications. Practical applications Food product packaging provides retarding deterioration, reducing microbial contamination, preserving safety, protecting quality, and extending the shelf life of packaged foods during transmission, storage, and consumption. Petroleum-based plastic and synthetic polymers have been mainly used in food packaging due to their cheap cost and good mechanical and barrier properties. However, increasing the use of these nonbiodegradable polymers causes serious environmental and health problems. The biopolymers which are extracted from biodegradable and renewable sources are considered as suitable alternatives for petroleum-based plastic materials. However, application of biopolymers as packaging materials has been limited due to their low mechanical properties and thermal stability. Many studies have been conducted to modify the properties of PLA-based packaging materials to create a favorable product for the food industry. Moreover, introducing plasticizer to PLA helps to develop biocomposite materials with unique characteristics for food packaging. This article shows an improvement in the properties of the PLA-based composites for food packaging applications.

Processing of Super Tough Plasticized PLA by Rotational Molding

This work is aimed at studying the suitability of polylactic acid (PLA) plasticized by two cardanol derivatives, i.e., cardanol and epoxidized cardanol acetate, in rotational molding, for the production of hollow items. For this purpose, plasticized PLA samples were obtained by melt mixing and then processed by a lab-scale rotational molding equipment. For comparison, poly(ethylene glycole), PEG, and plasticized PLA samples were also produced. Despite the very low cooling rates attained in rotational molding, completely amorphous samples were obtained with neat PLA and PLA plasticized by cardanol derivatives. In contrast, PEG plasticized PLA showed a very high degree of crystallinity, as highlighted by DSC and XRD analysis, which made the extraction of the rotomolded box-shaped specimens impossible. The plasticizing effectiveness of cardanol derivatives was proven by tensile testing of rotational molded prototypes, which highlighted the reduced modulus and strength and improved strain to break, compared to neat PLA. Therefore, efficient toughening of PLA can be attained by the use of the two cardanol derived plasticizers, which involves a significant reduction of the polymer glass transition, as well as a reduced increase of the crystallization kinetic. On the other hand, the reduction of the glass transition temperature due to the addition of plasticizer is responsible for significant crystallization effects even during ageing at room temperature, which involves significant embrittlement of the material.

Thermomechanical properties of alumina-filled plasticized polylactic acid: Effect of alumina loading percentage

Polylactic acid (PLA) is one of the most widely studied renewable and biodegradable polyesters and is expected to replace petrochemical-based synthetic polymers. In this study, we investigated the effect of the alumina volume fraction on the thermal and mechanical properties of polyethylene glycol (PEG)-plasticized PLA. The alumina particles were treated with maleic acid to improve their interaction with the PLA matrix. The field-emission scanning electron microscopy results revealed that the addition of alumina eliminated voids, leading to improved interfacial interactions between the PLA and alumina particles. The thermal conductivity of the neat PLA increased from 0.278 to 0.66 wm−1 k−1 with the addition of 30% alumina, which accounts for 137% increase. The tensile strength and Young's modulus of the neat PLA dropped by 52% and 56%, respectively, on the addition of 15% PEG plasticizer. However, the elongation at break increased from 5.4% to 207%, which was associated with a drop on the glass transition temperature values. The dynamic mechanical analysis results showed a drop in the storage modulus and height of the tan δ peak, revealing the increased flexibility of the composite after the inclusion of the plasticizer. The addition of 30% alumina exhibited a 41.6% increase on the stiffness of the PEG-blended PLA.

Effects of multi-walled carbon nanotubes (MWCNTs) on the degradation behavior of plasticized PLA nanocomposites

Polymer blend nanocomposites based on polylactic acid (PLA) were prepared via simple melt blending and investigated for its biodegradation behavior. The CNTs were surface-modified using acid treatment, and characterizations of composites were done using FTIR. FTIR spectra confirmed the surface modification of CNTs. The water uptake and weight loss behavior in hydrolytic analysis of CNT and m-CNT nanocomposites at different temperatures (25 and 45 °C) were studied. It was found that the water absorption and weight loss of nanocomposites increase by incorporation of CNTs and m-CNTs up to 2% for all samples, with and without PEG loading. In sample PLA/CNTs, 2% CNTs loading shows 1.18% water uptake at 25 °C and increases to 1.95% at 45 °C water immersion, whereas, in PLA/m-CNT nanocomposites, the water uptake reduces at 1.16% at 25 °C and 1.50% at 45 °C of analysis. In the meanwhile, the weight loss of 2% CNTs loading in PLA shows 2.88% at 25 °C and 6.28% at 45 °C, and for m-CNTs loading, the weight loss exhibits 2.09% at 25 °C and 5.29% at 45 °C. This proved the modified CNTs be able to retard the ability of nanocomposites degradation. The effect of plasticizer addition in nanocomposites was studied by loading 5 and 10% PEG. As expected, the inclusion of PEG enhanced the rate of degradation in both hydrolytic and soil burial studies. For the same amount of 2% CNTs inclusions and 10% PEG, at 45 C, the water uptake shows 5.56% as compared with 5% PEG loading, only 3.1% water uptake is shown. In soil burial test, the weight loss also increases with the addition of nanofiller. PLA/m-CNTs show lower weight loss which is only 4.50% and around 7.02% for PLA/CNTs nanocomposite. In the other hand, 10% PEG loading shows an increase in the weight loss in both CNT and m-CNT nanocomposites. Results from this study demonstrate that the inclusion of CNTs and m-CNTs into polymer matrix could increase the environmental persistence of polymers in lakes, landfills and surface waters.

PLA/ESO/MWCNT nanocomposite: a study on mechanical, thermal and electroactive shape memory properties

In the present study, solvent casted bio-based blends of polylactic acid (PLA) and epoxidized soybean oil (ESO) were prepared at varied composition of PLA: ESO of 95:5, 90:10, 85:15, 80:20 and 75:25 wt%. The shape memory polymer (SMP) nanocomposite films of optimized PLA/ESO blend (80:20) were prepared using same solvent casting method at three different loadings (1, 3 and 5 wt%) of acid functionalized multiwalled carbon nanotubes (COOH-MWCNT). The FTIR spectra confirmed acid functionalization of MWCNT and the molecular interactions by intermolecular hydrogen bonding between PLA and ESO. Mechanical properties of the PLA, plasticized PLA with 20 wt% of ESO and its nanocomposites were investigated by tensile measurements. Thermal properties such as Tm, Tc, Tg, Xc, degradation temperature of PLA and its modified forms were studied using DSC and TGA. SEM was used to observe surface morphology of plasticized PLA. Among all, PLA + 20wt%ESO + 3wt%COOH-MWCNT shows optimum mechanical and thermal performance, which was taken to perform electroactive shape recovery test. Finally, the electroactive shape recovery of the resulting nanocomposite with 3 wt% COOH-MWCNT was investigated by a fold deploy “U”-shape bending test.

Synergistic effect of chitin nanocrystals and orientations induced by solid-state drawing on PLA-based nanocomposite tapes

Uniaxial solid-state drawing was used to orientate plasticized polylactic acid (PLA) and its nanocomposite tapes with 1 and 5 wt% chitin nanocrystals (ChNC). Microscopy studies confirmed the orientation and formation of a ‘shish-kebab’ morphology in the drawn tapes. The mechanical properties demonstrated that the drawing led to stronger and tougher nanocomposites compared to plasticized PLA. The tensile strength increased from 41 MPa to 71 MPa, and the elongation at break increased from 5% to 60% for the nanocomposite with 5 wt% ChNC and a draw ratio of 3. The ChNC had a positive effect on the thermomechanical properties; the tan delta peak shifted to a higher temperature with an increasing ChNC content. These improvements in the mechanical and thermal properties are expected synergistic effects of both the ChNC in the nanocomposite and the alignment of the ChNC together with the polymer chains induced by the solid-state drawing.

Aligned plasticized polylactic acid cellulose nanocomposite tapes: Effect of drawing conditions

Aligned nanocomposite tapes based on plasticized polylactic acid (PLA) and 1 wt% cellulose nanofibers (CNF) were prepared using uniaxial solid-state drawing, and the effects of drawing conditions including temperature, speed and draw ratio on the material were studied. Microscopy studies confirmed alignment and the formation of ‘shish-kebab’ morphology in the drawn tape. Mechanical properties demonstrate that the solid-state drawing is a very effective way to produce stronger and tougher PLA nanocomposites, and the toughness can be improved 60 times compared to the undrawn tape. Additionally, the thermal properties, i.e. storage modulus, glass transition temperature and degree of crystallinity were improved. These improvements are expected due to the synergistic effect of CNF in the nanocomposite and orientations induced by the solid-state drawing.

INVESTIGATION OF THE EFFECTS OF CARBONIC AGENT AND NANOCLAY ON THE PROPERTIES OF THE POLYLACTIC ACID BASED NANOCOMPOSITES

The objective of this study is an investigation of the effects of carbonic agent and nanoclay loading level on the properties of the added flame retardant and plasticized polylactic acid (PLA) composites. Pentaerythritol (PER) was used as a carbonic agent in the composites. The flammability behaviour of these composites was investigated with the increasing nanoclay loading level. Flame retardant properties of plasticized PLA composites which are consisting of PER and nanoclay as a synergistic agent were evaluated. While the nanoclay loading levels were changed between 1-5 wt% of these samples, PER loading levels were fixed at 2 wt%. Besides, effects of increased PER loading level were also investigated with 3 wt% clay loading. Samples were produced by using extrusion and injection molding techniques. The morphological, thermal and mechanical properties were studied. The flammability was evaluated by using limiting oxygen index (LOI) and vertical burning test (UL-94). The results showed increased PER level didn’t significantly change LOI values of the PLA based nanocomposites. In addition, the highest LOI value was observed as 32 for 1 wt% nanoclay including sample. While adding PER to the PLA/PEG/TPP increased the elongation at break value, adding of the nanoclay decreased this value for nanocomposites.

Effects of the Nanoclay and Intumescent System on the Properties of the Plasticized Polylactic Acid

Effects of the Nanoclay and Intumescent System on the Properties of the Plasticized Polylactic Acid

Effects of the Nanoclay and Intumescent System on the Properties of the Plasticized Polylactic Acid

Effects of the Nanoclay and Intumescent System on the Properties of the Plasticized Polylactic Acid

Tensile Properties of Durian Skin Fibre Reinforced Plasticized Polylactic Acid Biocomposites

This research investigates the effects of plasticizer and durian skin fibre (DSF) loading on tensile and morphological properties of polylactic acid (PLA) biocomposites. Epoxidized palm oil (EPO) was added as a plasticizer in this project. The effect of EPO content 0–10 wt% was investigated over the tensile properties of PLA. EPO at 5 wt% was found to provide the highest tensile properties on PLA biocomposite. The plasticized PLA was then investigated for the effect of DSF content by varying the DSF at 1, 3 and 5 wt%. The tensile properties improved by about 7% with 3 wt% DSF. Scanning electron micrograph revealed that a ductile failure was induced in PLA composite with 5 wt% EPO and 3 wt% DSF.

Mechanical, structural and thermal properties of Ag–Cu and ZnO reinforced polylactide nanocomposite films

Plasticized polylactic acid (PLA) based nanocomposite films were prepared by incorporating polyethylene glycol (PEG) and two selected nanoparticles (NPs) [silver–copper (Ag–Cu) alloy (<100nm) and zinc oxide (ZnO) (<50 and <100nm)] through solvent casting method. Incorporation of Ag–Cu alloy into the PLA/PEG matrix increased the glass transition temperature (Tg) significantly. The crystallinity of the nanocomposites (NCs) was significantly influenced by NP incorporation as evidenced from differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. The PLA nanocomposite reinforced with NPs exhibited much higher tensile strength than that of PLA/PEG blend. Melt rheology of NCs exhibited a shear-thinning behavior. The mechanical property drastically reduced with a loading of NPs, which is associated with degradation of PLA. SEM micrographs exhibited that both Ag–Cu alloy and ZnO NPs were dispersed well in the PLA film matrix.

Evaluation of some eco‐friendly plasticizers forPLAfilms processing

ABSTRACTThis study was conducted as a first step in order to obtain green materials for food packaging by using an eco‐friendly bioplastic, polylactic acid (PLA), and nontoxic plasticizers. Different types of nontoxic biocompatible plasticizers/lubricants, both obtained in the laboratory, as well as commercial ones, were employed to modulate physical and mechanical properties of PLA. Melt compounding by means of a Brabender mixer led to obtaining of homogeneous materials. The incorporation of PLA oligomer,l‐lactide, poly(ethylene glycol), and epoxidized soybean oil (USE) improved the melt flow and processability, increasing the hydrophilicity of the resulted plasticized PLA systems. USE significantly increased the elongation at break, reduced the glass transition temperature, and increased the PLA chain mobility. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 43223.

Plasticized polylactic acid/cellulose nanocomposites prepared using melt-extrusion and liquid feeding: Mechanical, thermal and optical properties

Plasticized polylactic acid (PLA) and its nanocomposite based on cellulose nanofibers (CNF) and glycerol triacetate (GTA) were prepared using a co-rotating twin-screw extruder. GTA was used as a pl ...

Grafted d/l-lactide to cellulose acetate by reactive melt processing: Its role as CA/PLA blend compatibilizer

Cellulose acetate (CA) with a degree of substitution (DS) of 2.5 and polylactic acid (PLLA) were plasticized by melt extrusion using triacetin. Blends of resulting thermoplastic materials were then prepared and characterized by their tensile strength and differential scanning calorimetry (DSC). Thermal analysis revealed the invariability of the PLLA glass transition temperature in all blends, indicating that the compounds were immiscible. Grafted d/l lactide to CA copolymers were prepared by reactive melt processing using CA with different degree of substitution i.e. 2.1 and 2.5 and evaluated as CA/PLLA blend compatibilizer. The compatibility of the blends was investigated by scanning electron microscopy (SEM). Results showed that blend compatibility was improved evidencing the best performance of grafted copolymers with long grafted chains as blend compatibilizer of CA/PLLA blends. Finally, compatibilized blends compositions with enhanced ultimate elongation were achieved by using plasticized PLLA instead of neat PLLA.