Polylactic Acid Biocomposites Research Articles

Mechanical and tribological behaviour of three-dimensional printed almond shell particles reinforced polylactic acid bio-composites

Recently, composite filament development for three-dimensional printing has emerged and is used for numerous applications. The present research work develops neat polylactic acid and Almond Shell Particles reinforced polylactic acid bio-composites for three-dimensional printing and investigates the effects of printing orientation, including 0°, 45° and 90° orientation, on the tribological and mechanical behaviours of three-dimensional printed materials. The novel almond shell particles reinforced polylactic acid filaments are extruded by the filament extrusion method with the presence of 10% almond shell particles in the polylactic acid matrix, and the samples are three-dimensional printed by the fused filament fabrication technique. Mechanical characteristics such as tensile, flexural, compressive strength, and shore hardness are evaluated with respect to various three-dimensional printing orientations. The surface quality of the three-dimensional printed polylactic acid composite samples is analysed with respect to length and diameter deviation. Length accuracy of the 90° oriented polylactic acid and almond shell particles reinforced polylactic acid bio-composite samples exploits a better accuracy of 99.12% and 98.81%, respectively. It is shown that adding almond shell particles to the polylactic acid matrix decreases the flexural and tensile strength. Among the printing orientations, 0° flat samples result in the maximum tensile strength of 36 and 28 MPa for the neat polylactic acid and almond shell particles reinforced polylactic acid composites, respectively. The lowest contact angle of 54° is observed on the almond shell particles reinforced polylactic acid bio-composites three-dimensional printed with a 90° orientation. The highest contact angle value of 94° is observed on the neat polylactic acid three-dimensional printed with a 0° printing orientation. A tribological study is carried out under dry conditions on the pin-on-disc tribometer by varying the sliding speed (1, 2, and 3 m/s) and load (10, 20, and 30 N). The result shows that the lowest coefficient of friction of 0.22 is achieved for the almond shell particles reinforced polylactic acid bio-composite samples with a 0° printing orientation under a sliding load of 10 N. These kinds of newly developed compostable materials can be used for developing disposable orthotic foot appliances.

Preparation and characterization of hybrid PLA biocomposites reinforced by wood and silane treated basalt fibers or compatibilized by maleic anhydride‐grafted polypropylene (MAPP)

AbstractIn this study, basalt and/or beech wood fibers were treated with vinyltrimethoxysilane or compatibilized by maleic anhydride‐ grafted polypropylene (MAPP) to produce hybrid polylactic acid (PLA) biocomposites. Twin‐screw extruder was used to produce biocomposites, following by a hot press to form samples. Physical and mechanical properties of composites that were produced from both treated and untreated fibers were compared. Chemical, morphological, and thermal analysis of biocomposites were analyzed with TGA, FTIR and SEM, respectively. The results showed that silane treated basalt/wood fiber reinforced PLA (PBWS) and silane treated basalt reinforced PLA (PBS) have significantly better flexural strength than neat PLA. Besides, basalt reinforced bio‐composites except PBW3 and PBWM variations have significantly superior impact strength than neat PLA. Utilization of compatibilizers also reduced thickness swelling and water uptake features of biocomposites. All the above experimental data showed that the utilization of silane compatibilizer has better impact on properties than MAPP for such wood/basalt hybrid composite.Highlights Hybrid biocomposites with wood and basalt fibers by using coupling agents were prepared for the first time. Hybridization of organic and inorganic fibers gave promising results. Silane and maleic anhydride compatibilization improves physical properties. Vinyltrimethoxy silane grafted basalt fiber improves flexural strength significantly. Silanization of wood or basalt fibers enhances significantly the impact strength.

Development and Characterization of a PLA Biocomposite reinforced with Date Palm Fibers

Despite the promising potential of bio-composites derived from plant fibers due to their ecological and economic benefits, challenges persist in their preparation, restricting their commercial applications. These challenges are primarily associated with developing suitable methods, acquiring appropriate equipment for treating plant fibers, and addressing the time constraints in preparation. This study aims to contribute to the development and characterization of a new biocomposite and biodegradable material based on natural fibers produced through hot compression. The newly developed biocomposite comprises commercial biodegradable poly-lactic acid (PLA) as a matrix and untreated fiber fabric extracted from date palms as reinforcement. The use of untreated fiber fabric has successfully overcome the preparation difficulties. Experimental results on the new biocomposite reveal the strong adhesion between its fibers and the matrix, emphasizing the significant impact of choosing the right manufacturing conditions on the developed mechanical properties.

Characterization of Polylactic Acid Biocomposites Filled with Native Starch Granules from Dioscorea remotiflora Tubers.

Biocomposites were fabricated utilizing polylactic acid (PLA) combined with native starch sourced from mountain's yam (Dioscorea remotiflora Knuth), an underexplored tuber variety. Different starch compositions (7.5, 15.0, 22.5, and 30.0 wt.%) were blended with PLA in a batch mixer at 160 °C to produce PLA/starch biocomposites. The biocomposites were characterized by analyzing their morphology, particle size distribution, thermal, X-ray diffraction (XDR), mechanical, and dynamic mechanical (DMA) properties, water absorption behavior, and color. The results showed that the amylose content of Dioscorea remotiflora starch was 48.43 ± 1.4%, which corresponds to a high-amylose starch (>30% of amylose). Particle size analysis showed large z-average particle diameters (Dz0) of the starch granules (30.59 ± 3.44 μm). Scanning electron microscopy (SEM) images showed oval-shaped granules evenly distributed throughout the structure of the biocomposite, without observable agglomeration or damage to its structure. XDR and DMA analyses revealed an increase in the crystallinity of the biocomposites as the proportion of the starch increased. The tensile modulus (E) underwent a reduction, whereas the flexural modulus (Eflex) increased with the amount of starch incorporated. The biocomposites with the highest Eflex were those with a starch content of 22.5 wt.%, which increased by 8.7% compared to the neat PLA. The water absorption of the biocomposites demonstrated a higher uptake capacity as the starch content increased. The rate of water absorption in the biocomposites followed the principles of Fick's Law. The novelty of this work lies in its offering an alternative for the use of high-amylose mountain's yam starch to produce low-cost bioplastics for different applications.

Avocado seed starch utilized in eco-friendly, UV-blocking, and high-barrier polylactic acid (PLA) biocomposites for active food packaging applications

Efficient and effective use of biopolymers, such as starch, has increasingly prompted interest due to the current environmental challenges. However, starch-based composites still show poor ductility along with water and oxygen permeability, which may not meet the requirements for food packaging standards. In this study, modified starch (m-St), isolated from the avocado seed and synthesized with tert-butyl acetoacetate (t-BAA), was embedded into polylactic acid (PLA) to design new eco-friendly composites. The developed biocomposites were found to exhibit high performance with outstanding mechanical properties in conjunction with remarkable light, water vapor, and oxygen blocking features for food packaging applications. PLA/m-St(1:6) 20 wt% composites showed a dramatic increase in elongation at break (EB%) from 3.35 to 27.80 % (about 730 % enhancement) and exhibited remarkable UV-blocking performance from 16.21 to 83.86 % for UVB, relative to pure PLA. Equally importantly, these biocomposites revealed significant improvement in oxygen and water vapor barrier performance by reducing their values from 1331 to 32.9 cc m−2 day−1 (indicating a remarkable reduction of 97.53 %) and 61.9 to 28 g m−2 day−1, respectively. This study can show the great potential of extracting starch from biowaste resources and transforming it into sustainable bio-based composites as a promising solution for food packaging applications.

Ecofriendly quince peel powder incorporated Polylactic acid biocomposite film

This study aims to develop sustainable, renewable and biodegradable biocomposite films from environmentally friendly materials. For this purpose, completely biodegradable polymer composites were prepared by mixing polylactic acid (PLA) with a new source, quince peel (QP), by solvent casting method, and their structural, mechanical and thermal properties were examined. The tensile strengths of the composites prepared using QP in proportions varying between 5% (P5Q) and 30% (P30Q) by weight vary between 21.13 ± 0.80 and 12.01 ± 0.10 MPa, and their elongations at break vary between 11.33 ± 0.38 and 4.08 ± 1.06 %. As the QP contribution increased, the tensile strength and breaking elongation of these composites generally decreased, while the elastic modulus also increased. Among these composites, whose elastic modulus varies between 1040.00 ± 140.01 and 811.33 ± 13.31 MPa, it was determined that the elastic modulus (1040.00 ± 140.01 MPa) of the 20% QP added composite (P20Q) was higher than the others. When the thermal analysis of PLA/QP films were examined, it was observed that the glass transition temperatures (Tg) were between 58.54 and 51.45°C and the melting temperatures (Tm) were between 167.71 and 164.28°C, and these temperatures generally decreased with increasing QP doping. When the T50 values, which represent the temperature at which 50% of the composite materials decompose, were examined, it was found that the QP-added ones were higher than the pure composites. While this value was 317.96°C in pure PLA composite, T50 values varied between 327.92 and 340.80°C depending on the varying QP ratios. According to the XRD results performed to evaluate the crystalline properties of PLA composites containing quince bark, the crystallinity of pure PLA was determined as 19.5% and the crystallinity of composites containing 5, 10, 20 and 30 wt % QP additives was determined as 19.3, 18.3, 16.4 and 14.6%, respectively.

Effect of Hygrothermal Conditioning on the Machining Behavior of Biocomposites

Abstract This work aims to study the cutting behavior of biocomposites under different controlled hygrothermal conditions. This investigation choice is motivated by the fact that natural plant fibers such as flax are characterized by their hydrophilicity which makes them able to absorb water from a humid environment. This absorption ability is intensified by increasing the conditioning temperature. The moisture diffusion process affects considerably the mechanical properties of the resulting composite, which causes many issues during the machining operations. In this paper, moisture diffusion, chip form, cutting and thrust forces, and scanning electron microscope (SEM) observations are considered to explore the cutting behavior of flax fiber-reinforced polylactic acid (PLA) depending on the hygrothermal conditioning time. Results reveal that moisture content in the biocomposite is significantly influenced by the conditioning temperature and the fiber orientation. Moisture content and fiber orientation affect both the curling behavior of the removed chip as well as the tool/chip interaction in terms of friction. The machinability of flax fiber-reinforced PLA biocomposites depending on hygrothermal conditioning time is then investigated using SEM analysis in addition to analytical modeling. An analysis of variance is used finally to quantify the observed results.

A study of the mechanical, thermal and rheological properties of sisal fiber-reinforced polylactic acid bio-composites with tributyl 2-acetylcitrate as a plasticizer

In this study, bio-composites were developed using polylactic acid (PLA) as the matrix and sisal fibers (SFs) derived from agave sisalana leaves as the reinforcement. The bio-composites were prepared through injection molding with the addition of tributyl 2-acetylcitrate (ATBC) plasticizer. The mechanical, thermal, and rheological properties of these bio-composites were investigated to understand the effects of fiber and plasticizer contents. The results showed that the addition of SFs improved the tensile and flexural moduli of the bio-composites but led to a decrease in tensile strength compared to neat PLA. The flexural strength initially decreased with low fiber content but recovered to the level of neat PLA as the fiber content increased. The impact strength increased with the incorporation of SFs and ATBC. However, the presence of ATBC had a negative impact on the tensile and flexural properties of the bio-composites. The thermal conductivity of the materials was influenced by the fiber content and processing temperature, increasing with SFs inclusion but decreasing with temperature. Differential scanning calorimetry analysis revealed increased crystallinity of PLA with the presence of SFs and ATBC. The specific heat capacity increased with ATBC but decreased with increasing SFs. Dynamic mechanical property testing showed variations in storage and loss moduli of the bio-composites at different temperatures. The storage modulus increased with higher fiber content and abruptly dropped around glass transition temperature. Rheological characterization demonstrated effective interactions between the fibers and matrix with good fiber dispersion, resulting in uniform shear viscosity versus shear rate for different capillary dimensions. The shear viscosity of the SFs/PLA mixture increased with increasing fiber content but decreased with the addition of plasticizer. Furthermore, the compounding and molding processes had a notable impact on the microstructure of the fibers, specifically resulting in fiber breakage and fiber separation during processing.

Degradation of Mechanical Properties of Flax/PLA Composites in Hygrothermal Aging Conditions.

The main advantage of green composites is their biodegradability, but this biodegradability can also be considered a drawback if the degradation appears during the service life of the component. Therefore, the study of the mechanical behavior of green composites after hygrothermal aging tests is necessary to analyze their degradation process. This study aims to comprehensively analyze the hygrothermal aging behavior and aging mechanism of flax-fiber-reinforced polylactic acid (PLA) biocomposites. The fully biodegradable composites are manufactured by compression molding. In addition, the influence of atmospheric-pressure plasma treatment on the mechanical properties of the biocomposite is studied. Specimens are exposed to water vapor and 40 °C environmental conditions in a stove for up to 42 days. Several specimens of each type are taken out at regular intervals and tested to examine the water absorption, mechanical properties, and thermal characterization. The results show that the stiffness was significantly reduced after 24 h due to matrix degradation, while the strength was reduced only after three weeks.

Utilizing the Potential of Waste Hemp Reinforcement: Investigating Mechanical and Thermal Properties of Polypropylene and Polylactic Acid Biocomposites.

Hemp has gained significant popularity for its diverse applications; however, this study explores the untapped potential of waste hemp (wH) as a cost-effective and sustainable bioadditive for the development of high-performance biocomposites. wH offers advantages such as low cost, easy availability, and suitability for extrusion. Polypropylene (PP) and poly(lactic acid) (PLA) served as polymer matrices for this investigation. In order to enhance the interaction between the wH and polymer matrices, alkaline and silane pretreatments were applied to the wHs of both matrices. At the same time, the MA-g-PP additive was used exclusively for the PP matrix. The resulting PP biocomposite demonstrated Young's modulus (2986 MPa) and flexural modulus (2490 MPa), surpassing those of neat PP by 109 and 77%, respectively. Similarly, wH40-PLA-A showed enhancements in the PLA biocomposite, with Young's modulus (6214 MPa) and flexural modulus (5970 MPa) representing an increase of 81 and 56% over that of neat PLA, respectively. The thermal properties and behaviors of the resulting biocomposites were minimally affected by the inclusion of wH as a bioadditive. This study contributes to the advancement of sustainable materials and provides valuable insights into the utilization of wH as a valuable resource for the development of high-performance biocomposites.

Effect of steam explosion and silanization of hemp fibers on polylactic acid biocomposites; analysis of mechanical-thermal properties and fungal biodegradation

Alkaline pretreated hemp fibers were modified by steam explosion and/or silanization before being compounded with polylactic acid (PLA). The fungal biodegradation of the PLA/hemp fibers composite was investigated using Aspergillus niger TISTR 3153 in an aqueous medium for 28 days, following the ISO 846: 1997 standard method. The influence of the different physicochemical modifications of hemp fibers on the fungal biodegradation of the composite was evaluated in terms of molecular weight, chemical structure, mechanical properties, thermal properties, and hygroscopic properties. The results showed that the modulus of all composites were averagely increased by 109%, compared to neat PLA. All the PLA/hemp fiber composites better retained their properties after fungal biodegradation than neat PLA. Therefore, the physicochemical treatments of fibers after alkaline pretreatment promoted the resistance of the composite to fungal biodegradation. The treatment of hemp fibers in the present work was alkalization followed by silanization, which resulted in a PLA-based composite that was suitable for outdoor applications.

Tensile and Flexural Properties of Kenaf Reinforced Polylactic Acid under Heat Effect

iocomposite is a combination of natural reinforcement and natural matrix material consisting of kenaf reinforced with polylactic acid (PLA), where its mechanical properties will be affected when exposed to heat. This research investigates the effect of exposure of biocomposites to different temperatures on the mechanical properties of biocomposites, consisting of tensile and flexural properties. Before producing the sample, kenaf in the form of one-way yarn is conditioned with 40% RH humidity, and then the sample is produced using hot compression molding techniques by combining kenaf with PLA. Tensile and bending tests carried out in a heating chamber with the heat were studied using a Universal Testing Machine (UTM). The choice of heat temperature depends on the glass transition temperature of polylactic acid, where the study temperature ranges from 25 <sup>o</sup>C to 65 <sup>o</sup>C. From the results of the study, it was found that the maximum bending strength and modulus (117 MPa, 5.8 GPa) and the maximum tensile strength and modulus (59 MPa, 3.2 GPa) were both obtained at low temperatures (25 <sup>o</sup>C). While the modulus value decreases significantly at 55 <sup>o</sup>C, the tensile and flexural properties both show a steady decrease with increasing temperature. Therefore, the presence of temperature has a significant effect on the tensile and flexural properties of kenaf-reinforced PLA biocomposites. When it is exposed to high temperatures, the mechanical quality deteriorates, and the risk of failure increases. Failure is caused by poor reinforcement and matrix bonding caused by the degradation of natural fiber properties of kenaf and the level of PLA plastic deformation.

Mechanical Recycling of Waste PLA Generated From 3D Printing Activities: Filament Production and Thermomechanical Analysis

AbstractThere is a growing need to address waste generated from Fused Filament Fabrication (FFF) 3D printing activities. This study explores the mechanical recycling of waste polylactic acid (PLA) accumulated from failed 3D printing operations and PLA biocomposite filaments containing nanocellulose fibres. FFF 3D printable filaments were produced via melt mixing and extrusion of virgin PLA containing varying amounts of waste PLA. The chemical, thermal and thermomechanical characterisation of each specimen was evaluated using Fourier‐transform infrared spectroscopy (FTIR), simultaneous thermal analysis (SDT), dynamic mechanical analysis (DMA), and uniaxial tensile analysis (UTA). A desktop FFF 3D printer was used to fabricate UTA and DMA test specimens. The thermal stability of the filament specimens containing waste derived from the failed 3D prints were comparable with that of the commercial filaments. However, a 11% decrease in the onset of thermal degradation is observed for the filament containing waste biocomposites. The specimens containing waste PLA exhibited higher crystallinity and storage modulus. UTA results revealed similar tensile strength and % elongation, except for the specimen containing 50% waste PLA which exhibited a 29% decrease in tensile strength. This work successfully demonstrates mechanical recycling as a viable waste management strategy for waste materials generated during FFF 3D printing.

Characterization of tool-ply friction behavior for treated jute/PLA biocomposite prepregs in thermoforming

This paper investigates the tool-ply friction behavior of woven jute fabric reinforced poly-lactic acid (jute/PLA) biocomposite in thermoforming. A home-made pull-through friction testing device was developed to characterize the tool-ply friction behavior of the jute/PLA prepreg at elevated temperature. The effects of alkali treatment, fiber orientation, normal force and slipping velocity were studied. The results suggested a strong relationship between the tool-ply friction behavior and the woven and fiber structures. In addition, a quantitative definition of the tool-ply friction behavior was achieved by introducing the characteristic stress and friction coefficient. These findings indicated a hydrodynamic lubrication of tool-ply friction. This work provides a beneficial complement to the understanding of the thermoforming process of jute/PLA biocomposites.

Biodegradation behavior of acetylated lignin added polylactic acid under thermophilic composting conditions

Acetylated lignin (AL) can improve compatibility with commercial plastic polymers compared to existing lignin and can be used as an effective additive for eco-friendly biocomposites. For this reason, AL can be effectively incorporated into polylactic acid (PLA)-based biocomposites, but its biodegradation properties have not been investigated. In this study, biodegradation experiments were performed under mesophilic and thermophilic conditions to determine the effect of AL addition on the biodegradation characteristics of PLA-based biocomposites. As a result, the PLA-based biocomposite showed a faster biodegradation rate in a thermophilic composting environment, which is higher than the glass transition temperature of PLA, compared to a mesophilic environment. 16S rDNA sequencing results showed that differences in microbial communities depending on mesophilic and thermophilic environments strongly affected the biodegradation rate of lignin/PLA biocomposites. Importantly, the addition of AL can effectively delay the thermophilic biodegradation of PLA biocomposites. As a result of tracking the changes in physicochemical properties according to the biodegradation period in a thermophilic composting environment, the main biodegradation mechanism of AL/PLA biocomposite hydrolysis. It proceeded with cleavage of the PLA molecular chain, preferential biodegradation of the amorphous region, and additional biodegradation of the crystalline region. Above all, adding AL can be proposed as an effective additive because it can minimize the decline in the mechanical properties of PLA and delay the biodegradation rate more effectively compared to existing kraft lignin (KL).

Novel okra woven fabric reinforced polylactic acid composites: Mechanical, morphological, and thermal properties

AbstractContemporary researchers are directing attention towards enhancing the structural integrity of biodegradable matrices, such as polylactic acid (PLA), through the incorporation of plant fibers. The utilization of novel fibers is becoming more prevalent to achieve the specific demands of composite applications, particularly in the automotive and packaging fields. Woven fabrics are commonly favored for reinforcing composites due to their elevated specific strength and dimensional stability. In pursuit of this context, we have developed a unique woven fabric using 100% okra fiber and utilized it in the production of PLA biocomposites. This approach was made due to the unexplored potential of okra woven fabric in the field of composite manufacturing. To optimize the performance of the composites, three distinct weight proportions of okra woven fabric (OWF) were chosen, including 20%, 30%, and 40%. The obtained composites were mechanically, morphologically, and thermally characterized. The manufactured composite's maximum tensile and thermal property was attained by adding 20% OWF to the PLA. Scanning electron microscopy analysis revealed that 20% OWF composite possessed superior fiber‐matrix adhesion, improving all properties' efficacy. The overall findings reveal that the OWF/PLA composites are promising as a green material for applications in the automotive and packaging industries.Highlights A novel class of composite has been created using 100% okra woven fabric. The composite with 20% fabric content showed the best mechanical properties. Thermal properties of composites are also optimized using 20% fabric content. SEM confirms the strong fiber‐matrix bonding of 20% OWF/PLA composites. The composites are suitable for automotive and packaging applications.

Effect of Olive Pit Reinforcement in Polylactic Acid Biocomposites on Environmental Degradation.

Polylactic acid (PLA) is a biomaterial widely used as an alternative to petroleum-based polymeric matrices in plastic components. PLA-based biocomposites reinforced with lignocellulosic waste are currently receiving special attention owing to their mechanical properties, low toxicity, recyclability, and biodegradability. The influence of the percentage of waste on their properties and resistance to degradation are some of the points of great relevance. Therefore, a series of PLA-based biocomposites containing different percentages of olive pits (5, 15, 25 and 40% wt.) were manufactured and characterized both (a) immediately after manufacture and (b) after one year of storage under environmental conditions. The results obtained were analyzed to evaluate the influence of the incorporation of olive pits on the resistance to degradation (measured through Carbonyl Indices, CI), mechanical properties (tensile, flexural and impact strength), structure (Fourier Transform Infrared Spectroscopy, FT-IR; and, X-ray Diffraction, XRD), morphology (Scanning Electron Microscopy, SEM) and water absorption capacity of the manufactured materials. PLA degradation, corroborated by Differential Scanning Calorimetry (DSC), FT-IR, and XRD, resulted in a decrease in tensile and flexural strengths and an increase in the tensile and flexural moduli. This trend was maintained for the biocomposites, confirming that reinforcement promoted the PLA degradation.

Effects of different preparation methods (solvent casting and melt blending) on properties of chitosan-filled polylactic acid biocomposite films

Biocomposite films based on chitosan (CS) and polylactic acid (PLA) were prepared using two different methods; (1) solvent casting and (2) melt blending followed by hot-press methods. Polyethylene glycol (PEG) and polyvinyl alcohol (PVOH) were respectively incorporated as compatibilizer and processing aid. Thermal stability of solvent casted and hot-press composites were comparable and slightly lower than PLA, whereas the presence of PEG and PVOH lowered the thermal stability of the composites in N2 and in air. The secant modulus and ultimate stress of the hot-press films were clearly higher (about 80%–90%) whereas elongation was much lower than those of the solvent-casted films. XRD results revealed that the solvent-casted films exhibited semi-crystalline characteristics whereas the amorphous property was mostly observed for the hot-press films. The sharper XRD peaks of the casted and hot-press samples clearly observed with chitosan loading. Coarse surface after fracture was observed for the casted composite films whereas relatively smooth surface with a number of dispersed chitosan droplets was seen for the hot-press films. The presence of PEG and PVOH improved the dispersion of chitosan and slightly increased the water adsorption of the composites. The higher water adsorption capacity was observed for the casted composite films. The obtained results indicated that solvent casting and melt blending methods significantly affected the final properties of the material products, especially tensile and crystallinity characteristics of the chitosan-filled PLA biocomposite films.

Multifunctional polylactic acid biocomposite film for active food packaging with UV resistance, antioxidant and antibacterial properties

Antibacterial packaging used to control the growth of microorganisms in food is of great value for prolonging the shelf life of food. In this study, a bio-based antibacterial agent PDI based on zwitterionic and stereochemical synergistic antibacterial was designed and synthesized, and it was simultaneously introduced into polylactic acid (PLA) matrix with antioxidant o-vanillin (oVL) and plasticizer glycerol (GL). A series of PLA/oVL/PDI composite membranes with antibacterial, antioxidant and anti-ultraviolet properties were prepared by solution casting method. The results showed that the mechanical properties of the composite film were significantly improved compared with pure PLA (tensile strength increased by 37 %, elongation at break increased by 209 %), which was mainly attributed to the microphase separation structure induced by synthetic bio-based antibacterial agent, which improved the mechanical strength of PLA matrix, and the hydrogen bond formed by glycerol, o-vanillin and carbonyl group in PLA molecules plasticized PLA matrix. At the same time, the antibacterial rate of PLA/oVL/PDI composite membrane against Escherichia coli and Staphylococcus aureus can reach >95 %. Packaging experiments showed that PLA/oVL/PDI series composite films could effectively extend the shelf life of fresh bananas and apples for 5 days, and had great application prospects in preservative food packaging.

A novel 3D-printed graphite/polylactic acid sensor for the electrochemical determination of 2,4,6-trinitrotoluene residues in environmental waters

Here, lab-made graphite and polylactic acid (Gpt-PLA) biocomposite materials were used to additively manufacture electrodes via the fused deposition modeling (FDM) technique for subsequent determination of the explosive 2,4,6-trinitrotoluene (TNT, considered a persistent organic pollutant). The surface of the 3D-printed material was characterized by SEM and Raman, which revealed high roughness and the presence of defects in the graphite structure, which enhanced the electrochemical response of TNT. The 3D-printed Gpt-PLA electrode coupled to square wave voltammetry (SWV) showed suitable performance for fastly determining the explosive residues (around 7 s). Two reduction processes at around −0.22 V and −0.36 V were selected for TNT detection, with linear ranges between 1.0 and 10.0 μM. Moreover, detection limits of 0.52 and 0.66 μM were achieved for both reduction steps. The proposed method was applied to determine TNT in different environmental water samples (tap water, river water, and seawater) without a dilution step (direct analysis). Recovery values between 98 and 106% confirmed the accuracy of the analyses. Additionally, adequate selectivity was achieved even in the presence of other explosives commonly used by military agencies, metallic ions commonly found in water, and also some electroactive camouflage species. Such results indicate that the proposed device is promising to quantify TNT residues in environmental samples, a viable on-site analysis strategy.