Effect of nanoparticles on the hydrolytic degradation of PLA-nanocomposites by water-ethanol solutions

Tuning polylactic acid performance using green citrate plasticizers of varying chain lengths

The addition of these plasticizers increases the chain mobility of PLA, enhancing its deformability while reducing both tensile strength and elastic modulus. Mechanical testing identified TEC at 20 wt% as the most effective formulation, achieving an elongation of 307 % and a reduction in tensile strength from 70.6 MPa (PLA) to 25.2 MPa. Formulations containing 10 wt% exhibited anti-plasticization effects, with a slight reduction in elongation from 3.4 % to 3.2 %. Thermal and thermomechanical analyses corroborated the plasticizing effect, demonstrating a decrease in glass transition temperature from 59.6 °C to 19.3 °C, which indicates sufficient chain mobility to attain a rubber-like state at room temperature. Enhanced mobility also promoted crystallization by modifying nucleation behavior, altering crystal growth dimensionality, and reducing the activation energy required. Shape memory characterization revealed a rapid initial recovery in plasticized samples; however, total recovery diminished at higher plasticizer contents near 20 %, while lower concentrations exhibited recovery rates close to 90 %. Due to their low molecular weight of the plasticizers, migration is anticipated, resulting in measurable weight loss when exposed to food simulants. This migration phenomenon is associated with an increase in free volume, which also contributes to the improved ductile properties observed in plasticized PLA.

Decoding the complex interplay of biological and chemical factors in Polylactic acid biodegradation: A systematic review

Polylactic Acid is a sustainable, compostable bioplastic that requires specific geoenvironmental conditions for degradation. The complexity of managing the PLA waste has limited the scope of its seamless application. There have been a significant number of studies exploring PLA degradation. Majorly they have explored degradability as a material property with limited discussions on the fundamental factors affecting degradation. The knowledge of the influence of biotic and abiotic factors and their complex interplay is critical for enhancing PLA degradation research, specifically accelerated degradation. This understanding is necessary for PLA waste upcycling and generating industrial-scale value-added products. Using the PRISMA framework, a database of articles on PLA degradation (1974-2023) has been created with each entry being annotated with 11 critical parameters depending on the scale and scope of the research. Abiotic hydrolysis, biotic hydrolysis and assimilation of PLA were discussed in detail with information on experiment design analytical techniques and background mechanisms to achieve systematic recommendations. Enzymes responsible for PLA degradation have been categorised and catalogued. The review highlights the need for future research related to PLA degradation in terms of molecular mechanisms of enzymatic degradation, bioengineering enzymes for accelerating degradation, and mathematical models for predicting degradation kinetics in complex environmental conditions.

Biodegradable plastics: mechanisms of degradation and generated bio microplastic impact on soil health

Conventional petroleum-derived polymers are valued for their versatility and are widely used, owing to their characteristics such as cost-effectiveness, diverse physical and chemical qualities, lower molecular weight, and easy processability for large-scale production. However, the extensive accumulation of such plastics leads to serious environmental issues. To combat this existing situation, an alternative lies in the production of bioplastics from natural and renewable sources such as plants, animals, microbes, etc. Bioplastics obtained from renewable sources are compostable and susceptible to degradation caused by microbes hydrolyzing to CO2, CH4, and biomass. Also, certain additives are reinforced into the bioplastic films to improve their physicochemical properties and degradation rate. However, on degradation, the bio-microplastic (BM) produced could have positive as well as negative impact on the soil health. This article thus focuses on the degradation of various fossil based as well as bio based biodegradable plastics such as polyhydroxyalkanoates (PHA), polyhydroxy butyrate (PHB), polylactic acid (PLA), polybutylene succinate (PBS), polycaprolactone (PCL), and polysaccharide derived bioplastics by mechanical, thermal, photodegradation and microbial approaches. The degradation mechanism of each approach has been discussed in detailed for different bioplastics. How the incorporation or reinforcement of various additives in the biodegradable plastics effects their degradation rates has also been discussed. In addition to that, the impact of generated bio-microplastic on physicochemical properties of soil such as pH, bulk density, carbon, nitrogen content etc. and biological properties such as on genome of native soil microbes and on plant nutritional health have been discussed in detailed.

Hydrolytic degradation and biodegradation of polylactic acid electrospun fibers

Increased use of bioplastics, such as polylactic acid (PLA), helps in reducing greenhouse gas emissions, decreases energy consumption and lowers pollution, but its degradation efficiency has much room for improvement. The degradation rate of electrospun PLA fibers of varying diameters ranging from 0.15 to 1.33 μm is measured during hydrolytic degradation under different pH from 5.5 to 10, and during aerobic biodegradation in seawater supplemented with activated sewage sludge. In hydrolytic conditions, varying PLA fiber diameter had significant influence over percentage weight loss (W%L), where faster degradation was achieved for PLA fibers with smaller diameter. W%L was greatest for PLA-5 > PLA-12 > PLA-16 > PLA-20, with average W%L at 30.7%, 27.8%, 17.2% and 14.3% respectively. While different pH environment does not have a significant influence on PLA degradation, with W%L only slightly higher for basic environments. Similarly biodegradation displayed faster degradation for small diameter fibers with PLA-5 attaining the highest degree of biodegradation at 22.8% after 90 days. Hydrolytic degradation resulted in no significant structural change, while biodegradation resulted in significant hydroxyl end capping products on the PLA surface. Scanning electron microscopy (SEM) imaging of degraded PLA fibers showed a deteriorated morphology of PLA-5 and PLA-12 fibers with increased adhesion structures and irregularly shaped fibers, while a largely unmodified morphology for PLA-16 and PLA-20.

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.

Fabrication of PLA-Based Electrospun Nanofibers Reinforced with ZnO Nanoparticles and In Vitro Degradation Study

In this work, electrospun nanofibers based on polylactic acid, PLA, reinforced with ZnO nanoparticles have been studied, considering the growing importance of electrospun mats based on biopolymers for their applications in different fields. Specifically, electrospun nanofibers based on PLA have been prepared by adding ZnO nanoparticles at different concentrations, such as 0.5, 1, 3, 5, 10 and 20 wt%, with respect to the polymer matrix. The materials have been characterized in terms of their morphological, mechanical, and thermal properties, finding 3 wt% as the best concentration to produce PLA nanofibers reinforced with ZnO nanoparticles. In addition, hydrolytic degradation in phosphate buffer solution (PBS) was carried out to study the effect of ZnO nanoparticles on the degradation behavior of PLA-based electrospun nanofiber mats, obtaining an acceleration in the degradation of the PLA electrospun mat.

Effect of birch tar embedded in polylactide on its biodegradation

The plasticized film was made of polylactide and birch tar, which was used in a concentration of 1, 5 and 10 % by weight. Tar was added to the polymer to obtain materials with antimicrobial properties. The main purpose of this work is to characterize and biodegradation of this film after the end of its use. Therefore, the following analyzes were performed: enzymatic activity of microorganisms in the presence of polylactide (PLA) film containing birch tar (BT), biodegradation process in compost, barrier changes and structural properties of the film before and after biodegradation and bioaugmentation. Biological oxygen demand BOD21, water vapor permeability (Pv), oxygen permeability (Po), scanning electron microscopy (SEM) and enzymatic activity of microorganisms were assessed. Microorganism strains Bacillus toyonensis AK2 and Bacillus albus AK3 were isolated and identified, which constituted an effective consortium increasing the susceptibility of polylactide polymer material with tar to biodegradation in compost. Analyses with the use of the above-mentioned strains had an impact on the change of physicochemical properties, e.g. the presence of biofilm on the surface of the analyzed films and the reduction of the barrier properties of the film, which translates into the recorded susceptibility to biodegradation of these materials. The analyzed films can be used in the packaging industry, and after use, subjected to intentional biodegradation processes, including bioaugmentation.

Polylactic Acid Cellulose Nanocomposite Films Comprised of Wood and Tunicate CNCs Modified with Tannic Acid and Octadecylamine

Herein, a one-pot strategy was used to prepare hydrophobic cellulose nanocrystals (CNCs) surface-modified with tannic acid and octadecylamine. By this strategy, CNCs derived from wood (W-CNC) and tunicates (T-CNC) were modified in situ and incorporated into a polylactic acid (PLA) matrix using two methods, without first drying the CNCs. Films of PLA-CNC nanocomposites were prepared both by solution casting and by wet compounding in a thermo-kinetic mixer, followed by melt extrusion. Various properties of these PLA nanocomposites were evaluated herein, along with an assessment of how these properties vary with the type of CNC reinforcement. Cast films with a hybrid mixture of wood and tunicate CNCs displayed improved mechanical properties compared to either wood or tunicate CNCs, but extruded films did not show this hybrid effect. The water vapor permeability of the extruded nanocomposite films with 1% CNCs was reduced by as much as 60% compared to the PLA films. The composite films also showed enhanced biodegradation compared to neat PLA films. These results demonstrate that wet compounded PLA composites produced with wood or tunicate CNCs modified using a one-pot, water-based route have improved barrier and biodegradation properties, indicating a potential for packaging applications without having to dry the CNCs.

Chemical Recycling of PET in the Presence of the Bio-Based Polymers, PLA, PHB and PEF: A Review

The great increase in the production and consumption of plastics has resulted in large amounts of plastic wastes, creating a serious problem in terms of their environmentally friendly disposal. The need for the production of more environmentally friendly polymers gave birth to the production of biodegradable, and more recently, biobased polymers, used in the production of biodegradable or biobased plastics. Although the percentage of currently produced bioplastics is rather small, almost 1% compared to petrochemical-based plastics, inevitably is going to significantly increase in the near future due to strict legislation recently posed by the European Union and other countries’ Governments. Thus, recycling strategies that have been developed could be disturbed and the economic balance of this sector could be destabilized. In the present review, the recycling of the polymer mainly used in food plastic packaging, i.e., poly(ethylene terephthalate), PET is examined together with its counterparts from the biobased polymers, i.e., poly(lactic acid), PLA (already replacing PET in several applications), poly(3-hydroxybutyrate), PHB and poly(ethylene furanoate), PEF. Methods for the chemical recycling of these materials together with the chemical products obtained are critically reviewed. Specifically, hydrolysis, alcoholysis and glycolysis. Hydrolysis (i.e., the reaction with water) under different environments (alkaline, acidic, neutral), experimental conditions and catalysts results directly in the production of the corresponding monomers, which however, should be separated in order to be re-used for the re-production of the respective polymer. Reaction conditions need to be optimized with a view to depolymerize only a specific polymer, while the others remain intact. Alcoholysis (i.e., the reaction with some alcohol, methanol or ethanol) results in methyl or ethyl esters or diesters that again could be used for the re-production of the specific polymer or as a source for producing other materials. Glycolysis (reaction with some glycol, such as ethylene, or diethylene glycol) is much studied for PET, whereas less studied for the biopolymers and seems to be a very promising technique. Oligomers having two terminal hydroxyl groups are produced that can be further utilized as starting materials for other value-added products, such as unsaturated polyester resins, methacrylated crosslinked resins, biodegradable polyurethanes, etc. These diols derived from both PET and the bio-based polymers can be used simultaneously without the need for an additional separation step, in the synthesis of final products incorporating biodegradable units in their chemical structure.

Comprehensive exploration of natural degradation of poly(lactic acid) blends in various degradation media: A review

Poly(lactic acid) (PLA), a bio-based polyester, has been extensively investigated in the recent past owing to its excellent mechanical properties. Several studies have been conducted on PLA blends, with a focus on improving the brittleness of PLA to ensure its suitability for various applications. However, the increasing use of PLA has increased the contamination of PLA-based products in the environment because PLA remains intact even after three years at sea or in soil. This review focuses on analyzing studies that have worked on improving the degradation properties of PLA blends and studies how other additives affect degradation by considering different degradation media. Factors affecting the degradation properties, such as surface morphology, water uptake, and crystallinity of PLA blends, are highlighted. In natural, biotic, and abiotic media, water uptake plays a crucial role in determining biodegradation rates. Immiscible blends of PLA with other polymer matrices cause phase separation, increasing the water absorption. The susceptibility of PLA to hydrolytic and enzymatic degradation is high in the amorphous region because it can be easily penetrated by water. It is essential to study the morphology, water absorption, and structural properties of PLA blends to predict the biodegradation properties of PLA in the blends.

Effect of Yerba Mate and Silk Fibroin Nanoparticles on the Migration Properties in Ethanolic Food Simulants and Composting Disintegrability of Recycled PLA Nanocomposites

The main objective of the present research is to study the effect of the incorporation of low amounts of silk fibroin nanoparticles (SFNs) and yerba mate nanoparticles (YMNs) on the migration phenomenon into ethanolic food simulants as well as on the disintegrability under composting conditions of mechanically recycled polylactic acid (PLA). Recycled PLA was obtained under simulated recycling conditions by melt processing virgin PLA into films and further subjecting them to an accelerated aging process, which involved photochemical, thermal, and hydrothermal aging steps followed by an intense washing step. SFNs were extracted from Bombyx mori cocoons and YMNs from yerba mate waste. Then, recycled PLA was melted, reprocessed, and reinforced with either 1%wt. of SFNs or YMNs, by melt extrusion, and further processed into films by compression molding. The obtained nanocomposites were exposed to ethanolic food simulants (ethanol 10% v/v, simulant A and ethanol 50% v/v, simulant D1) and the structural, thermal, and mechanical properties were studied before and after the exposure to the food simulants. The migration levels in both food simulants were below the overall migration limits required for food contact materials. The materials were disintegrated under simulated composting conditions at the laboratory scale level and it was observed that the nanoparticles delayed the disintegration rate of the recycled PLA matrix, but nanocomposites were fully disintegrated in less than one month.

Potential Chemicals from Plastic Wastes

Plastic is referred to as a “material of every application”. From the packaging and automotive industries to the medical apparatus and computer electronics sectors, plastic materials are fulfilling demands efficiently. These plastics usually end up in landfills and incinerators, creating plastic waste pollution. According to the Environmental Protection Agency (EPA), in 2015, 9.1% of the plastic materials generated in the U.S. municipal solid waste stream was recycled, 15.5% was combusted for energy, and 75.4% was sent to landfills. If we can produce high-value chemicals from plastic wastes, a range of various product portfolios can be created. This will help to transform chemical industries, especially the petrochemical and plastic sectors. In turn, we can manage plastic waste pollution, reduce the consumption of virgin petroleum, and protect human health and the environment. This review provides a description of chemicals that can be produced from different plastic wastes and the research challenges involved in plastic waste to chemical production. This review also provides a brief overview of the state-of-the-art processes to help future system designers in the plastic waste to chemicals area.

Migration kinetic of silver from polylactic acid nanocomposite film into acidic food simulant after different high-pressure food processing

The migration study of nano-Ag migration from polylactic acid (PLA) films was studied. Samples treated by high-pressure food processing (0, 100, 200, 300, and 400 MPa pressure) were soaked in acetic acid solution and incubated at 20 °C for 90 days. At the end of storage, nano-Ag particles (AgNPs) migration from the PLA/AgNPs composite film treated under 200 MPa high pressure was the lowest. However, AgNPs migration was accelerated under 400 MPa high pressure. High-pressure processing (200 MPa) could cause denser structure and higher crystallinity degree in films than other treatments. Lower amount of AgNPs induced a decline in the intensity of specific characteristic peaks. The diffraction peak intensity of α-crystal for the film sample treated with 400 MPa was the lowest on day 60. The crystallization index of the PLA matrix changed with different high-pressure processing. The result indicated that appropriate high-pressure food processing could effectively suppress AgNPs migration from PLA-based film while contacting with acidic acid food simulant. PRACTICAL APPLICATION: The release of nanoparticles from food packaging material is a very important matter when the migration is concerned with regulatory and toxicity issues. The study described the migration kinetic of AgNPs from PLA nanocomposite film into acidic food simulant after different high-pressure food processing. The results indicated that the PLA/AgNPs nanocomposite film was safe for acidic food after high-pressure treatment.

Polymer based nanoparticles for biomedical applications by microfluidic techniques: from design to biological evaluation

The development of microfluidic technologies represents a new strategy to produce and test drug delivery systems.

Effects of Rutile-TiO2 Nanoparticles on Accelerated Weathering Degradation of Poly(Lactic Acid)

The effect of accelerated weathering on poly(lactic acid) (PLA) and a PLA nanocomposite with rutile titanium (IV) dioxide (rutile–TiO₂) was investigated. The accelerated weathering test applied consecutive steps of ultraviolet (UV) (at 340 nm and 0.76 W m⁻² irradiance) and moisture at 50 °C for 2000 h, following the ASTM D4329 standard. The morphology, chemical structure, molecular weight, crystallization, as well as mechanical and thermal properties were thoroughly studied. Samples were characterized after 500 h, 1000 h and 2000 h exposure. Different degradation mechanisms were proposed to happen during the weathering exposure and confirmed based on the experimental data. The PLA and PLA/TiO₂ surfaces presented holes and increasing roughness over the exposure time. The molecular weight of the weathered samples decreased due to chain scission during the degradation processes. Thermal stability decreased in the presence of TiO₂ and a double melting peak was observed for the PLA/TiO₂ nanocomposite. A general improvement in the mechanical properties of the PLA/TiO₂ nanocomposite was observed over time during the accelerated weathering analysis up to 1000 h of exposure time. After 2000 h of weathering exposure, the PLA and PLA/TiO₂ became extremely brittle and lost their ductile properties. This was ascribed to a significant increase in the degree of crystallinity upon weathering, which was accelerated in the presence of TiO₂. Atomic force microscopy (AFM) using amplitude modulation–frequency modulation (AM–FM) tool confirmed the mechanical changes in the surface area of the PLA samples after accelerated weathering exposure. The stiffness and Young’s modulus achieved higher values than the unweathered ones up to 1000 h of exposure time. The changes in the physical and chemical properties of PLA/TiO₂ over the ageing time confirm the photocatalytic activity of rutile–TiO₂.

Preparation and Characterization of Bio-Based PLA/PBAT and Cinnamon Essential Oil Polymer Fibers and Life-Cycle Assessment from Hydrolytic Degradation

Nowadays, the need to reduce the dependence on fuel products and to achieve a sustainable development is of special importance due to environmental concerns. Therefore, new alternatives must be sought. In this work, extruded fibers from poly (lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT) added with cinnamon essential oil (CEO) were prepared and characterized, and the hydrolytic degradation was assessed. A two-phase system was observed with spherical particles of PBAT embedded in the PLA matrix. The thermal analysis showed partial miscibility between PLA and PBAT. Mechanically, Young's modulus decreased and the elongation at break increased with the incorporation of PBAT and CEO into the blends. The variation in weight loss for the fibers was below 5% during the period of hydrolytic degradation studied with the most important changes at 37 °C and pH 8.50. From microscopy, the formation of cracks in the fiber surface was evidenced, especially for PLA fibers in alkaline medium at 37 °C. This study shows the importance of the variables that influence the performance of polyester-cinnamon essential oil-based fibers in agro-industrial applications for horticultural product preservation.

Polyhedral Oligomeric Silsesquioxane (POSS) Surface Grafting: A Novel Method to Enhance Polylactide Hydrolysis Resistance

This work considers the development of an easy and scalable approach to change the features of poly(l-lactide) (PLLA) films, which is based on the application of a surface treatment with an amino-functionalized polyhedral oligomeric silsesquioxane (POSS). Indeed, the developed approach is based on the potential reactivity of POSS amino group towards the polymer functionalities to produce an aminolysis reaction, which should promote the direct grafting of the silsesquioxane molecules on the polymer surface. Neat and treated films were studied by infrared spectroscopy and X-ray photoelectron spectroscopy, which proved the effectiveness of POSS grafting. Moreover, scanning electron microscopy measurements demonstrated the homogeneous distribution of Si on the film surface treated with the silsesquioxane. The influence of the film treatment on the surface wettability was evidenced by contact angle measurements. These findings demonstrated a relevant enhancement of the surface hydrophobicity, which increase turned out to depend on the conditions applied, as it increased by increasing the reaction temperature and the contact time. Finally, in order to evaluate the stability of neat and of the treated PLLA films the surface morphology of the samples treated with pH 7.4 buffer at 50 °C was studied.

Cosmetic Packaging to Save the Environment: Future Perspectives

Consumer awareness about the damages that plastic packaging waste cause to the environment, coupled with bio-economy and circular economy policies, are pushing plastic packaging versus the use of bio-based and biodegradable materials. In this contest, even cosmetic packaging is looking for sustainable solutions, and research is focusing on modifying bio-based and biodegradable polymers to meet the challenging requirements for cosmetic preservation, while maintaining sustainability and biodegradability. Several bio-based and biodegradable polymers such as poly(lactic acid), polyhydroxyalkanoates, polysaccharides, etc., are available, and some first solutions for both rigid and flexible packaging are already present on the market, while many others are under study and optimization. A fruitful cooperation among researchers and industries will drive the cosmetic sector toward being more ecological and contributing to save our environment.