An overview of the recent advances in polylactide‐based sustainable nanocomposites

Quantitative Analysis of Morphology and Surface Properties of Poly(lactic acid)/Poly(ε-caprolactone)/Hydrophilic Nano-Silica Blends

A quantitative analysis of the morphology, as well as an analysis of the distribution of components and surface/interfacial properties in poly(lactic acid)(PLA) InegoTM 3251D, poly(ε-caprolactone) (PCL) Capa 6800 and nano-silica (SiO2) Aerosil®200 blends, was conducted in this research. The study aimed to improve the understanding of how PLA, PCL, and nano-SiO2 interact, resulting in the specific morphology and surface properties of the blends. Samples were produced by varying the concentration of all three components. They were analyzed using SEM, EDS mapping, water contact angle measurements, surface free energy calculation, adhesion parameter measurements, and FTIR-ATR spectroscopy. The results showed that the addition of SiO2 nanoparticles led to an increase in the contact angle of water, making the surface more hydrophobic. SEM images of the blends showed that increasing the PCL content reduced the size of spherical PCL elements in the blends. FTIR-ATR analysis showed that SiO2 nanoparticles influenced the structure ordering of PLA in the blend with equal portions of PLA and PCL. In the samples with a higher PCL content, the spherical elements present in the samples with a higher PLA/PCL ratio have been reduced, indicating better interactions at the interface between PLA, PCL, and SiO2. SEM-EDS mapping of the PLA/PCL 100/0 blend surfaces revealed the presence of SiO2 clusters and the silicon (Si) concentration reaching up to ten times higher than the nominal concentration of SiO2. However, with the addition of 3% SiO2 to the blend containing PCL, the structure became more granular. Specifically, Si protrusions in the sample PLA/PCL 90/10 with 3% SiO2 displayed 29.25% of Si, and the sample PLA/PCL 70/30 with 3% SiO2 displayed an average of 10.61% of Si at the protrusion locations. The results confirmed the affinity of SiO2 to be encapsulated by PCL. A better understanding of the interactions between the materials in the presented blends and the quantitative analysis of their morphology could improve the understanding of their properties and allow the optimization of their application for different purposes.

Nanocellulose-stabilized nanocomposites for effective Hg(II) removal and detection: a comprehensive review

Mercury pollution, with India ranked as the world's second-largest emitter, poses a critical environmental and public health challenge and underscores the need for rigorous research and effective mitigation strategies. Nanocellulose is derived from cellulose, the most abundant natural polymer on earth, and stands out as an excellent choice for mercury ion remediation due to its remarkable adsorption capacity, which is attributed to its high specific surface area and abundant functional groups, enabling efficient Hg(II) ion removal from contaminated water sources. This review paper investigates the compelling potential of nanocellulose as a scavenging tool for Hg(II) ion contamination. The comprehensive examination encompasses the fundamental attributes of nanocellulose, its diverse fabrication techniques, and the innovative development methods of nanocellulose-based nanocomposites. The paper further delves into the mechanisms that underlie Hg removal using nanocellulose, as well as the integration of nanocellulose in Hg detection methodologies, and also acknowledges the substantial challenges that lie ahead. This review aims to pave the way for sustainable solutions in mitigating Hg contamination using nanocellulose-based nanocomposites to address the global context of this environmental concern.

Synergistic effect of stereo-complexation and interfacial compatibility in ammonium polyphosphate grafted polylactic acid fibers for simultaneously improved toughness and flame retardancy

Flammability and poor toughness of unmodified PLA limit its applications in various fields. Though ammonium polyphosphate (APP) is a green and effective flame retardant, it has poor compatibility with the matrix, leading to a decrease in mechanical properties. Stereo-complexation greatly improves the strength and heat resistance of traditional PLA. However, the effect of flame retardants on the formation of stereo-complexed crystals and the impact of stereo-complexation on flame retardancy have not been studied previously. In this research, PDLA chains were first in-situ reacted with APP particles for improved interfacial compatibility. By utilizing the characteristic of PLA enantiomers that can form stereo-complexed crystals, near-complete stereo-complexed PLA fibers with flame retardancy were produced via clean and continuous melt spinning. The compatibility between PDLA-g-APP and PLLA matrix was studied by SEM, rheological analyses and DSC. Strength and flexibility of the fibers were simultaneously enhanced compared to traditional PLA due to the synergistic effect of interfacial compatibility and stereo-complexation. Compared to traditional PLA, the peak heat release rate and total heat release in microcalorimetry test were reduced by 33 % and 22 %, respectively. The flame-retardant fibers achieved a V-0 rating in the UL-94 test, and an increase in LOI value from 19.4 % to 28.2 %.

Recent Advances and Outlook in 2D Nanomaterial-Based Flame-Retardant PLA Materials

Poly (lactic acid) or polylactide (PLA) has gained widespread use in many industries and has become a commodity polymer. Its potential as a perfect replacement for petrochemically made plastics has been constrained by its extreme flammability and propensity to flow in a fire. Traditional flame-retardants (FRs), such as organo-halogen chemicals, can be added to PLA without significantly affecting the material's mechanical properties. However, the restricted usage of these substances causes them to bioaccumulate and endanger plants and animals. Research on PLA flame-retardants has mostly concentrated on organic and inorganic substances for the past few years. Meanwhile, there has been a significant increase in renewed interest in creating environmentally acceptable flame-retardants for PLA to maintain the integrity of the polymer, which is the current trend. This article reviews recent advancements in novel FRs for PLA. The emphasis is on two-dimensional (2D) nanosystems and the composites made from them that have been used to develop PLA nanocomposite (NCP) systems that are flame retarding. The association between FR loadings and efficiency for different FR-PLA systems is also briefly discussed in the paper, as well as their influence on processing and other material attributes. It is unmistakably established from the literature that adding 2D nanoparticles to PLA matrix systems reduces their flammability by forming an intumescent char/carbonized surface layer. This creates a barrier effect that successfully blocks the filtration of volatiles and oxygen, heat and mass transfer, and the release of combustible gases produced during combustion.

Role of Rheology in Morphology Development and Advanced Processing of Thermoplastic Polymer Materials: A Review

This review presents fundamental knowledge and recent advances pertaining to research on the role of rheology in polymer processing, highlights the knowledge gap between the function of rheology in various processing operations and the importance of rheology in the development, characterization, and assessment of the morphologies of polymeric materials, and offers ideas for enhancing the processabilities of polymeric materials in advanced processing operations. Rheology plays a crucial role in the morphological evolution of polymer blends and composites, influencing the type of morphology in the case of blends and the quality of dispersion in the cases of both blends and composites. The rheological characteristics of multiphase polymeric materials provide valuable information on the morphologies of these materials, thereby rendering rheology an important tool for morphological assessment. Although rheology extensively affects the processabilities of polymeric materials in all processing operations, this review focuses on the roles of rheology in film blowing, electrospinning, centrifugal jet spinning, and the three-dimensional printing of polymeric materials, which are advanced processing operations that have gained significant research interest. This review offers a comprehensive overview of the fundamentals of morphology development and the aforementioned processing techniques; moreover, it covers all vital aspects related to the tailoring of the rheological characteristics of polymeric materials for achieving superior morphologies and high processabilities of these materials in advanced processing operations. Thus, this article provides a direction for future advancements in polymer processing. Furthermore, the superiority of elongational flow over shear flow in enhancing the quality of dispersion in multiphase polymeric materials and the role of extensional rheology in the advanced processing operations of these materials, which have rarely been discussed in previous reviews, have been critically analyzed in this review. In summary, this article offers new insights into the use of rheology in material and product development during advanced polymer-processing operations.

The 3D-Printed (FDM/FFF) Biocomposites Based on Polylactide and Carbonate Lake Sediments-Towards a Circular Economy

In this study, composites containing polylactide and carbonate lake sediment in concentrations of 2.5, 5, 10, and 15% by weight were prepared by a 3D printing method. The material for 3D printing was obtained by directly diluting the masterbatch on an injection moulder to the desired concentrations, and after granulation, it was extruded into a filament. The material prepared thusly was used to print standardised samples for mechanical testing. To compare the mechanical properties of the composites obtained by 3D printing and injection moulding, two sets of tests were performed, i.e., mechanical tests (tensile strength, flexural strength, and impact strength) and hydrophobic-hydrophilic surface character testing. The degree of composite waste in the 3D printing was also calculated. Mechanical and surface tests were performed for both systems conditioned at room temperature and after accelerated ageing in a weathering chamber. The study showed differences in the properties of composites obtained by 3D printing. Sedimentary fillers improved the hydrophobicity of the systems compared with pure PLA, but it was not a linear relationship. The PLA/CLS sedB composite had higher strength parameters, especially after ageing in a weathering chamber. This is due to its composition, in which, in addition to calcite and silica, there are also aluminosilicates, causing a strengthening of the PLA matrix.

Recent Advances in the Investigation of Poly(lactic acid) (PLA) Nanocomposites: Incorporation of Various Nanofillers and their Properties and Applications

Poly(lactic acid) (PLA) is considered the most promising biobased substitute for fossil-derived polymers due to its compostability, biocompatibility, renewability, and good thermomechanical properties. However, PLA suffers from several shortcomings, such as low heat distortion temperature, thermal resistance, and rate of crystallization, whereas some other specific properties, i.e., flame retardancy, anti-UV, antibacterial or barrier properties, antistatic to conductive electrical characteristics, etc., are required by different end-use sectors. The addition of different nanofillers represents an attractive way to develop and enhance the properties of neat PLA. Numerous nanofillers with different architectures and properties have been investigated, with satisfactory achievements, in the design of PLA nanocomposites. This review paper overviews the current advances in the synthetic routes of PLA nanocomposites, the imparted properties of each nano-additive, as well as the numerous applications of PLA nanocomposites in various industrial fields.

Effect of the Addition of Nano-Silica and Poly(ε-caprolactone) on the Mechanical and Thermal Properties of Poly(lactic acid) Blends and Possible Application in Embossing Process

In this study, the mechanical and thermal properties of poly(lactic acid) (PLA) blends with an addition of poly(ε-caprolactone) (PCL) and fumed silica (SiO₂) were evaluated to research the possibility of their use as relief printing plates for embossing processes. PCL and nano-silica were added to the PLA matrix at different concentrations. Morphological, thermal and mechanical analyses were performed to determine the properties and possible functional characteristics of the studied blends. SEM micrographs showed that unmodified PLA/PCL blends exhibit a morphology typical of incompatible blends with clearly visible spherical domains of dispersed PCL in PLA. In particular, the results of the hardness tests showed that the selected blends have the optimal hardness (between 65 SH D and 75 SH D) for use in the embossing process. The tensile tests showed that the addition of nano-silica to neat PLA and to the PLA/PCL blends 50/50 and 60/40 improved the mechanical properties of the blends, especially stiffness and toughness. The DMA results showed that the addition of smaller amounts of SiO₂ can contribute to an increase in storage modulus, which is due to good dispersion and distribution of SiO₂ in the matrix. DSC analysis showed that the addition of PCL to PLA polymer increased the thermal stability of PLA and that the addition of nano-silica increased the degree of crystallinity of PLA. The TGA results showed that the addition of nano-silica improved the thermal degradation behavior of the studied blends, especially for blends modified with 3 wt% nano-silica. The results show that it is possible to optimize the mechanical and thermal properties of the blends with the aim of using them in the embossing process.

Tailoring and Long-Term Preservation of the Properties of PLA Composites with "Green" Plasticizers

Concerning new polylactide (PLA) applications, the study investigates the toughening of PLA-CaSO₄ β-anhydrite II (AII) composites with bio-sourced tributyl citrate (TBC). The effects of 5-20 wt.% TBC were evaluated in terms of morphology, mechanical and thermal properties, focusing on the enhancement of PLA crystallization and modification of glass transition temperature (T_g). Due to the strong plasticizing effects of TBC (even at 10%), the plasticized composites are characterized by significant decrease of T_g and rigidity, increase of ductility and impact resistance. Correlated with the amounts of plasticizer, a dramatic drop in melt viscosity is also revealed. Therefore, for applications requiring increased viscosity and enhanced melt strength (extrusion, thermoforming), the reactive modification, with up to 1% epoxy functional styrene-acrylic oligomers, was explored to enhance their rheology. Moreover, larger quantities of products were obtained by reactive extrusion (REX) and characterized to evidence their lower stiffness, enhanced ductility, and toughness. In current prospects, selected samples were tested for the extrusion of tubes (straws) and films. The migration of plasticizer was not noted (at 10% TBC), whereas the mechanical and thermal characterizations of films after two years of aging evidenced a surprising preservation of properties.

Influence of Diatomaceous Earth Particle Size on Mechanical Properties of PLA/Diatomaceous Earth Composites

The fractionation of diatomaceous earth (DE) using sedimentation made it possible to obtain separate unbroken diatom fractions from broken or agglomerated bodies with a range of particle sizes. The produced filler was used to prepare polylactide (PLA)/diatomaceous earth biocomposite samples containing different particle sizes, which were subjected to mechanical testing (tensile strength, flexural strength, impact strength), colloidal testing (contact angle, color change test, SEM/EDS), and thermal testing (TGA, DSC, DMA). Modification of the PLA containing the smallest particle size with diatomaceous earth (Fraction 5) resulted in a higher impact strength compared to both the pure PLA and the PLA/DE composite that contained base diatomaceous earth. Furthermore, the melt flow rate was improved by more than 80 and 60% for the composite modified with fractionated diatomaceous earth (Fraction 4) compared to pure PLA and base diatomaceous earth, respectively. The elasticity of the composite was also improved from 3.3 GPa for pure polylactide to 4.4 GPa for the system containing the smallest diatomaceous earth particles (Fraction 5).

A Review of Polylactic Acid as a Replacement Material for Single-Use Laboratory Components

Every year, the EU emits 13.4 Mt of CO₂ solely from plastic production, with 99% of all plastics being produced from fossil fuel sources, while those that are produced from renewable sources use food products as feedstocks. In 2019, 29 Mt of plastic waste was collected in Europe. It is estimated that 32% was recycled, 43% was incinerated and 25% was sent to landfill. It has been estimated that life-sciences (biology, medicine, etc.) alone create plastic waste of approximately 5.5 Mt/yr, the majority being disposed of by incineration. The vast majority of this plastic waste is made from fossil fuel sources, though there is a growing interest in the possible use of bioplastics as a viable alternative for single-use lab consumables, such as petri dishes, pipette tips, etc. However, to-date only limited bioplastic replacement examples exist. In this review, common polymers used for labware are discussed, along with examining the possibility of replacing these materials with bioplastics, specifically polylactic acid (PLA). The material properties of PLA are described, along with possible functional improvements dure to additives. Finally, the standards and benchmarks needed for assessing bioplastics produced for labware components are reviewed.

Novel Biodegradable 3D-Printed Analgesics-Eluting-Nanofibers Incorporated Nuss Bars for Therapy of Pectus Excaratum

A novel hybrid biodegradable Nuss bar model was developed to surgically correct the pectus excavatum and reduce the associated pain during treatment. The scheme consisted of a three-dimensional (3D) printed biodegradable polylactide (PLA) Nuss bar as the surgical implant and electrospun polylactide–polyglycolide (PLGA) nanofibers loaded with lidocaine and ketorolac as the analgesic agents. The degradation rate and mechanical properties of the PLA Nuss bars were characterized after submersion in a buffered mixture for different time periods. In addition, the in vivo biocompatibility of the integrated PLA Nuss bars/analgesic-loaded PLGA nanofibers was assessed using a rabbit chest wall model. The outcomes of this work suggest that integration of PLA Nuss bar and PLGA/analgesic nanofibers could successfully enhance the results of pectus excavatum treatment in the animal model. The histological analysis also demonstrated good biocompatibility of the PLA Nuss bars with animal tissues. Eventually, the 3D printed biodegradable Nuss bars may have a potential role in pectus excavatum treatment in humans.

Evaluation of the Oil-Rich Waste Fillers' Influence on the Tribological Properties of Polylactide-Based Composites

In recent years, natural-based polymeric composites have gained the attention of researchers and the industry due to their low environmental impact and good applicational properties. A promising example of these materials is polylactide-based composites filled with linseed cake. Even though they can be characterized by reduced brittleness and enhanced crystallization rate, their applicational potential cannot be fully evaluated without knowing their tribological properties. This paper is aimed to analyze the influence of the oil contained by the filler on the mechanical and frictional properties of polylactide-based composites. Specimens of unfilled polylactide and its composites containing 10 wt % of linseed cake with different oil content were prepared by injection molding. Their microhardness was measured by the Vickers method. The softening temperature was determined by the Vicat method. The scratch resistance of the samples was tested with the loading of 10, 20 and 40 N. The coefficient of friction was evaluated by the pin-on-plate method, using CoCrMo alloy as the counter surface. It was found that the oil content in the filler does not directly influence the mechanical and tribological properties, but the composite samples present comparable hardness and lower coefficient of friction than the unfilled polymer, so they can be a good eco-friendly alternative to the unfilled polylactide when the frictional properties are an important factor.

Progresses in synthetic technology development for the production of L-lactide

L-Lactide is an intermediate for the industrial production of polylactic acid (PLA). The chemical and optical purities of lactide determine the quality of the prepared PLA. It is of great challenge to synthesize L-lactide efficiently with high chemical and optical purities under the conditions applicable for industrial production. With the national plastic reduction order issued, developing biodegradable materials such as PLA has gradually become a hot topic, and the production of upstream lactide is the key technique for the whole industrial chain. This mini-review aims to summarize typical works on the related synthetic technology development in recent years.

Poly(L-Lactic Acid) Composite with Surface-Modified Magnesium Hydroxide Nanoparticles by Biodegradable Oligomer for Augmented Mechanical and Biological Properties

Poly(L-lactic acid) (PLLA) has attracted a great deal of attention for its use in biomedical materials such as biodegradable vascular scaffolds due to its high biocompatibility. However, its inherent brittleness and inflammatory responses by acidic by-products of PLLA limit its application in biomedical materials. Magnesium hydroxide (MH) has drawn attention as a potential additive since it has a neutralizing effect. Despite the advantages of MH, the MH can be easily agglomerated, resulting in poor dispersion in the polymer matrix. To overcome this problem, oligo-L-lactide-ε-caprolactone (OLCL) as a flexible character was grafted onto the surface of MH nanoparticles due to its acid-neutralizing effect and was added to the PLLA to obtain PLLA/MH composites. The pH neutralization effect of MH was maintained after surface modification. In an in vitro cell experiment, the PLLA/MH composites including OLCL-grafted MH exhibited lower platelet adhesion, cytotoxicity, and inflammatory responses better than those of the control group. Taken together, these results prove that PLLA/MH composites including OLCL-grafted MH show excellent augmented mechanical and biological properties. This technology can be applied to biomedical materials for vascular devices such as biodegradable vascular scaffolds.

Pathways to Green Perspectives: Production and Characterization of Polylactide (PLA) Nanocomposites Filled with Superparamagnetic Magnetite Nanoparticles

In the category of biopolymers, polylactide or polylactic acid (PLA) is one of the most promising candidates considered for future developments, as it is not only biodegradable under industrial composting conditions, but it is produced from renewable natural resources. The modification of PLA through the addition of nanofillers is considered as a modern approach to improve its main characteristic features (mechanical, thermal, barrier, etc.) and to obtain specific end-use properties. Iron oxide nanoparticles (NPs) of low dimension (10–20 nm) such as magnetite (Fe₃O₄), exhibit strong magnetization in magnetic field, are biocompatible and show low toxicity, and can be considered in the production of polymer nanocomposites requiring superparamagnetic properties. Accordingly, PLA was mixed by melt-compounding with 4–16 wt.% magnetite NPs. Surface treatment of NPs with a reactive polymethylhydrogensiloxane (MHX) was investigated to render the nanofiller water repellent, less sensitive to moisture and to reduce the catalytic effects at high temperature of iron (from magnetite) on PLA macromolecular chains. The characterization of nanocomposites was focused on the differences of the rheology and morphology, modification, and improvements in the thermal properties using surface treated NPs, while the superparamagnetic behavior was confirmed by VSM (vibrating sample magnetometer) measurements. The PLA−magnetite nanocomposites had strong magnetization properties at low magnetic field (values close to 70% of M_max at H = 0.2 T), while the maximum magnetic signal (M_max) was mainly determined by the loading of the nanofiller, without any significant differences linked to the surface treatment of MNPs. These bionanocomposites showing superparamagnetic properties, close to zero magnetic remanence, and coercivity, can be further produced at a larger scale by melt-compounding and can be designed for special end-use applications, going from biomedical to technical areas.

Materials Based on Chitosan and Polylactide: From Biodegradable Plastics to Tissue Engineering Constructions

Abstract

The transition to green chemistry and biodegradable polymers is a logical stage in the development of modern chemical science and technology. In the framework of this review, the advantages, disadvantages, and potential of biodegradable polymers of synthetic and natural origin are compared using the example of polylactide and chitosan as traditional representatives of these classes of polymers, and the possibilities of their combination via obtaining composite materials or copolymers are assessed. The mechanochemical approach to the synthesis of graft copolymers of chitosan with oligolactides/polylactides is considered in more detail.

Synthetic Biopolymers and Their Composites: Advantages and Limitations-An Overview

Recently, polymer science and engineering research has shifted toward the development of environmentally benign polymers to reduce the impact of plastic leakage on the ecosystems. Stringent regulations and concerns regarding conventional polymers are the main driving forces for the development of renewable, biodegradable, sustainable, and environmentally benign materials. Although biopolymers can alleviate plastic-related pollution, several factors dictate the utilization of biopolymers. Herein, an overview of the potential and limitations of synthetic biopolymers and their composites in the context of environmentally benign materials for a sustainable future are presented. The synthetic biopolymer market, technical advancements for different applications, lifecycle analysis, and biodegradability are covered. The current trends, challenges, and opportunities for bioplastic recycling are also discussed. In summary, this review is expected to provide guidelines for future development related to synthetic biopolymer-based sustainable polymeric materials suitable for various applications.

Cold Crystallization Kinetics and Thermal Degradation of PLA Composites with Metal Oxide Nanofillers

Poly(lactic acid) (PLA) nanocomposites with antimicrobial fillers have been increasingly explored as food packaging materials that are made of a biobased matrix and can minimize food loss due to spoilage. Some of the most commonly studied fillers are zinc oxide (ZnO), titanium dioxide (TiO2), and silver nanoparticles (AgNPs). In this work, nanocomposites with 1 wt.% of each filler were prepared by melt mixing. An extensive study of thermally stimulated processes such as crystallization, nucleation, degradation, and their kinetics was carried out using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). In detail, non-isothermal cold crystallization studies were performed with DSC and polarized light microscopy (PLM), and kinetics were analyzed with multiple equations. The activation energy of the non-isothermal cold crystallization was calculated with the methods of Kissinger and Friedman. The latter was used to also determine the Hoffman–Lauritzen parameters (Kg and U*) by applying the Vyazovkin method. Additionally, effective activation energy and kinetic parameters of the thermal decomposition process were determined by applying the isoconversional differential method and multivariate non-linear regression method. According to TGA results, metal oxide nanofillers affected the thermal stability of PLA and caused a decrease in the activation energy values. Moreover, the fillers acted as heterogenous nucleating agents, accelerating the non-isothermal crystallization of PLA, thus reducing its activation energy. It can be concluded that metal oxide nanofillers catalytically affect the thermal degradation and crystallization of PLA samples.

Modification of Polylactide Nonwovens with Carbon Nanotubes and Ladder Poly(silsesquioxane)

Electrospun nonwovens of poly(L-lactide) (PLLA) modified with multiwall carbon nanotubes (MWCNT) and linear ladder-like poly(silsesquioxane) with methoxycarbonyl side groups (LPSQ-COOMe) were obtained. MWCNT and LPSQ-COOMe were added to the polymer solution before the electrospinning. In addition, nonwovens of PLLA grafted to modified MWCNT were electrospun. All modified nonwovens exhibited higher tensile strength than the neat PLA nonwoven. The addition of 10 wt.% of LPSQ-COOMe and 0.1 wt.% of MWCNT to PLLA increased the tensile strength of the nonwovens 2.4 times, improving also the elongation at the maximum stress.