A Review of the Synthesis and Applications of Polymer–Nanoclay Composites

Organoclay-assisted disperse dyeing of polypropylene nanocomposite fabrics in supercritical carbon dioxide

Dyeing using supercritical carbon dioxide (SC-CO2) is carried out on the polypropylene (PP) nanocomposite fabrics with model disperse dye compared with their regular fabric at various dyeing temperatures and pressures. The results are compared with those obtained in aqueous dyeing method. The PP nanocompsite fabrics dyed in SC-CO2 medium exhibited higher colour strength (K/S) values compared with their PP regular fabric. The PP nanocompsite fabrics and their regular fabric dyed in SC-CO2 medium have higher K/S values than those dyed in aqueous medium. The color coordinates of all PP fabrics dyed in SC-CO2 and aqueous medium were positive with respect to a* and b* coordinates depending on the disperse red dye uptake. The PP nanocomposite fabrics dyed in SC-CO2 and aqueous medium exhibited higher antibacterial properties than their regular fabrics. All PP fabrics dyed in SC-CO2 and aqueous medium present very good washing, perspiration and light fastness.

Clay-reinforced PVC composites and nanocomposites

Clay-reinforced polyvinyl chloride (PVC) composites and nanocomposites are one of the newest and most important compounds studied and used in various applications, including the biomedical, automotive industry, water treatment, packaging, fire retarding, and construction. The most important clays used in the synthesis of these composites are Bentonite, Montmorillonite, Kaolinite, and Illite. The addition of these nanoclays to the PVC matrix improves mechanical properties, thermal stability, and yellowness index properties. In this chapter, a detailed study of PVC and its properties, types of nanoclays and their properties, modification of nanoclays, production methods of composites, and nanocomposites of PVC/clay, their characterization, and applications have been performed. Herein, the types, properties, and applications of PVC/clay nanocomposites, as well as their challenges and future remarks, are reviewed.

The Effects of Incorporating Nanoclay in NVCL-NIPAm Hydrogels on Swelling Behaviours and Mechanical Properties

Following the formulation development from a previous study utilising N-vinylcaprolactam (NVCL) and N-isopropylacrylamide (NIPAm) as monomers, poly(ethylene glycol) dimethacrylate (PEGDMA) as a chemical crosslinker, and Irgacure 2959 as photoinitiator, nanoclay (NC) is now incorporated into the selected formulation for enhanced mechanical performance and swelling ability. In this research, two types of NC, hydrophilic bentonite nanoclay (NCB) and surface-modified nanoclay (NCSM) of several percentages, were included in the formulation. The prepared mixtures were photopolymerised, and the fabricated gels were characterised through Fourier transform infrared spectroscopy (FTIR), cloud-point measurements, ultraviolet (UV) spectroscopy, pulsatile swelling, rheological analysis, and scanning electron microscopy (SEM). Furthermore, the effect of swelling temperature, NC types, and NC concentration on the hydrogels' swelling ratio was studied through a full-factorial design of experiment (DOE). The successful photopolymerised NC-incorporated NVCL-NIPAm hydrogels retained the same lower critical solution temperature (LCST) as previously. Rheological analysis and SEM described the improved mechanical strength and polymer orientation of gels with any NCB percentage and low NCSM percentage. Finally, the temperature displayed the most significant effect on the hydrogels' swelling ability, followed by the NC types and NC concentration. Introducing NC to hydrogels could potentially make them suitable for applications that require good mechanical performance.

Combined Thermomechanical Effect of Graphene Oxide and Montmorillonite on Biobased Epoxy Network Formation for Coatings

Epoxy nanocomposites derived from linseed oil, reinforced with graphene oxide (GO) and montmorillonite (MMT) nanostructures, were synthesized. The nanohybrids were developed by enriching the structure of MMT and GO with primary amines through a common and simplified method, which implies physical interactions promoted by ultrasonic processing energy. The influence of the new nanoreinforcing agents along with neat ones on the overall properties of the biobased epoxy materials for coating applications was assessed. Interface formation through surface compatibility was contained by the lower values of activation energy calculated from differential scanning calorimetry (DSC) curves, along with a consistent 70% increase in the cross-linking density when amine-modified MMT was used. Thermomechanical characteristics of the biobased epoxy nanocomposites were explained through the interaction of the functional groups over the curing process of epoxidized linseed oil (ELO), giving a 15 °C higher Tg value increase. Furthermore, the low surface energy values suggested an intrinsic antibacterial activity, as proved by a significant decrease of CFU against Staphylococcus aureus bacterial strains on the 0.25% reinforced coatings.

Advancement in nanomaterials for environmental pollutants remediation: a systematic review on bibliometrics analysis, material types, synthesis pathways, and related mechanisms

Environmental pollution is a major issue that requires effective solutions. Nanomaterials (NMs) have emerged as promising candidates for pollution remediation due to their unique properties. This review paper provides a systematic analysis of the potential of NMs for environmental pollution remediation compared to conventional techniques. It elaborates on several aspects, including conventional and advanced techniques for removing pollutants, classification of NMs (organic, inorganic, and composite base). The efficiency of NMs in remediation of pollutants depends on their dispersion and retention, with each type of NM having different advantages and disadvantages. Various synthesis pathways for NMs, including traditional synthesis (chemical and physical) and biological synthesis pathways, mechanisms of reaction for pollutants removal using NMs, such as adsorption, filtration, disinfection, photocatalysis, and oxidation, also are evaluated. Additionally, this review presents suggestions for future investigation strategies to improve the efficacy of NMs in environmental remediation. The research so far provides strong evidence that NMs could effectively remove contaminants and may be valuable assets for various industrial purposes. However, further research and development are necessary to fully realize this potential, such as exploring new synthesis pathways and improving the dispersion and retention of NMs in the environment. Furthermore, there is a need to compare the efficacy of different types of NMs for remediating specific pollutants. Overall, this review highlights the immense potential of NMs for mitigating environmental pollutants and calls for more research in this direction.

Engineered Clay-Polymer Composite for Biomedical Drug Delivery and Future Challenges: A Survey

Clay materials are widely used in drug delivery systems due to their unique characteristics. Montmorillonite is a major component of bentonite and it has a large surface area, better swelling capacity, and high adsorption capacity. The modification of natural bentonite could improve its sorption ability for new emerging applications. Recent advancements in the polymer-silicate composite have novel biomedical applications in drug delivery, tissue regeneration, wound healing, cancer therapy, enzyme immobilization, diagnostic and therapeutic devices, etc. Perspective view of the montmorillonite- polymer composite as a pharmaceutical carrier in drug delivery systems has been discussed in this review. Different types of modification of montmorillonite for the development of pharmaceutical formulations have also been documented. Many challenges in clay nanocomposite systems of polymer of natural/synthetic origin are yet to be explored in improving antimicrobial properties, mechanical strength, stimuli responsiveness, resistance to hydrolysis, etc. Drug interaction and binding capability, swelling of clay may be carried out for finding possible applications in monitoring delivery systems. Pharmaceutical properties of active drugs in the formulation could also be improved along with dissolution rate, solubility, and adsorption. The clay-incorporated polymeric drug delivery systems may be examined for a possible increase in swelling capacity and residence time after mucosal administration.

Assessing the Adjuvant Effect of Layered Double Hydroxides (LDH) on BALB/c Mice

The discovery and validation of new adjuvants are critical areas for vaccinology. Mineral materials (e.g., alum microparticles) have been used for a long time as adjuvants in human vaccine formulations. Nonetheless, the use of nanosized materials is a promising approach to diversify the properties of adjuvants. Nanoclays are potential adjuvants proposed by some research groups. However, their adjuvant mechanisms and safety have not been fully elucidated. Herein, we aimed at expanding the knowledge on the potential adjuvanticity of layered double hydroxide (LDH) nanoparticles by reporting a detailed method for the synthesis and characterization of LDHs and the adsorption of a model antigen (bovine serum albumin, BSA). LDHs varying in diameter (from 56 to 88 nm) were obtained, and an in vitro evaluation revealed that the LDHs are not inherently toxic. BSA was passively adsorbed onto the LDHs, and the immunogenicity in mice of the conjugates obtained was compared to that of free BSA and BSA co-administered with alum (Alum-BSA). The LDH-BSA conjugates induced a higher humoral response that lasted for a longer period compared with that of free BSA and Alum-BSA, confirming that LDH exerts adjuvant effects. The 56 nm LDH particles were deemed as the more efficient carrier since they induced a higher and more balanced Th1/Th2 response than the 88 nm particles. This study is a contribution toward expanding the characterization and use of nanoclays in vaccinology and justifies further studies with pathogen-specific antigens.

Characteristics of Components and Density of Rigid Nanoclay-Filled Medium-Density Polyurethane Foams Produced in a Sealed Mould

The characteristics of rigid, nanoclay-filled, medium-density NEOpolyol-380 polyurethane foams components can be estimated when two conditions are met: (1) the foam blocks are produced in a sealed mould; and (2) the mass of the reacting mixture is kept constant. It was shown that, with an increase in filler concentration, the total mass of the filled polymeric network stays constant, but the total volume reduces; the higher the ratio of density of the exfoliated nanoclay platelets and polymer, the higher the volume reduction of the polymeric network. Experimental data of polyurethane foam block mass were acquired at concentrations η = 0%, 0.25%, 0.5%, 1%, 2%, 3% and 5% from the mass of a filled reacting mixture. Foam-density dependence in the uniform zone and in the side-sections of the produced blocks on the: (1) mass of the blocks; and (2) the concentration of the filler was analysed. The study demonstrated that the correlation of the specimens' density with the foam block mass is much higher than that of the filler concentration.

Investigation of the Effect of Hybrid Nanofiller on the Mechanical Performance and Surface Properties of Bio-Based Polylactic Acid/Polyolefin Elastomer (PLA/POE) Blend

Polylactic acid has stood out among bio-based polymers for its usage in the food packaging industry and biomedical fields. Through the melt mixing process, the toughened poly(lactic) acid (PLA) was prepared with polyolefin elastomer (POE), incorporated via various ratios of nanoclay and a fixed amount of nanosilver particles (AgNPs). The correlation between the compatibility and morphology, mechanical properties, and surface roughness of samples with nanoclay was studied. The calculated surface tension and melt rheology confirmed the interfacial interaction demonstrated by droplet size, impact strength, and elongation at break. Each blend sample exhibited matrix-dispersed droplets, and the size of POE droplets steadily dropped with increasing nanoclay content, corresponding to the enhanced thermodynamic affinity between PLA and POE. Scanning electron microscopy (SEM) acknowledged that the inclusion of nanoclay in the PLA/POE blend ameliorated the mechanical performance by preferable localization in the interface of used components. The optimum value of elongation at break was acquired at about 32.44%, where the incorporation of 1 wt.% nanoclay led, respectively, to 171.4% and 24% enhancement rather than the PLA/POE blend with the composition of 80/20 and the virgin PLA. Similarly, the impact strength reached 3.46 ± 0.18 kJ m^-1 as the highest obtained amount, showing the proximity of 23% progress to the unfilled PLA/POE blend. Surface analysis indicated that adding nanoclay caused the augment of surface roughness from 23.78 ± 5.80 µm in the unfilled PLA/POE blend to 57.65 ± 18.2 µm in PLA/POE contained 3 wt.% nanoclay. Rheological measurements implied that organoclay resulted in the strengthening of melt viscosity as well as the rheological parameters such as storage modulus and loss modulus. Han plot further showed that the storage modulus is always higher than the loss modulus in all prepared PLA/POE nanocomposite samples, corresponding to the restriction of polymer chains mobility induced by the formation of strong molecular interaction between nanofillers and polymer chains.

Anisotropy and Mechanical Properties of Nanoclay Filled, Medium-Density Rigid Polyurethane Foams Produced in a Sealed Mold, from Renewable Resources

Medium-density rigid polyurethane (PU) foams are often produced in sealed molds; therefore, the processes inside the mold and structure of the produced foam blocks need to be understood. The structural and mechanical anisotropy is shown to be the third variable along with (1) concentration of the nanoclay filler and (2) density, to determine the mechanical properties of the filled PU foam composites produced in a sealed mold. The varying anisotropy of the specimens hinders the accurate evaluation of the filling effect. The methodology for the estimation of the anisotropy characteristics of specimens from different locations within the nanoclay filled PU foam blocks is elaborated. A criterion, based on analysis of Poisson's ratios, is formulated for the selection of specimens with similar anisotropy characteristics. The shear and bulk moduli are estimated theoretically, dependent on the filler's concentration, using the experimentally determined constants.

Development of an Epoxy Matrix Hybrid Composite with Astrocaryum Aculeatum (Tucumã) Endocarp and Kaolin from the Amazonas State in Brazil

Composites with natural lignocellulosic fillers are being cited as a viable and sustainable alternative to conventional materials, as they combine lower costs with lower weight. In many tropical countries, such as Brazil, there is a considerable amount of lignocellulosic waste that is improperly discarded, which causes pollution of the environment. The Amazon region has huge deposits of clay silicate materials in the Negro River basin, such as kaolin, which can be used as fillers in polymeric composite materials. This work investigates a new composite material (ETK) made of epoxy resin (ER), powdered tucumã endocarp (PTE), and kaolin (K), without coupling agents, with the aim of producing a composite with lower environmental impact. The ETK samples, totaling 25 different compositions, were prepared by cold molding. Characterizations of the samples were performed using a scanning electron microscope (SEM) and a Fourier-transform infrared spectrometer (FTIR). In addition, the mechanical properties were determined via tensile, compressive, three-point flexural and impact tests. The FTIR and SEM results showed an interaction between ER, PTE, and K, and the incorporation of PTE and K reduced the mechanical properties of the ETK samples. Nonetheless, these composites can be considered potential materials to be used for sustainable engineering applications in which high mechanical strength is not a main requirement of the material.

Effect of Kaolinite and Cloisite Na+ on Storage Stability of Rubberized Binders

This study aimed to evaluate the impact of a two-step modification process involving kaolinite and cloisite Na+ on the storage stability of rubberized binders. The process involved the manual combination of virgin binder PG 64-22 with crumb rubber modifier (CRM), which was heated to condition it. The preconditioned rubberized binder was then modified for two hours at a high speed of 8000 rpm using wet mixing. The second stage modification was performed in two parts, with part 1 using only crumb rubber as the modifier and part 2 involving the use of kaolinite and montmorillonite nano clays at a replacement percentage of 3% to the original weight of the binder along with the crumb rubber modifier. The Superpave and multiple shear creep recovery (MSCR) test methods were used to calculate the performance characteristics and separation index % of each modified binder. The results showed that the viscosity properties of kaolinite and montmorillonite improved the performance class of the binder, with montmorillonite demonstrating greater viscosity values than kaolinite even at high temperatures. Additionally, kaolinite with rubberized binders showed higher resistance to rutting, and the % recovery value from multiple shear creep recovery testing indicated that kaolinite with rubberized binders was more effective than montmorillonite with rubberized binders, even at higher load cycles. The use of kaolinite and montmorillonite reduced phase separation between the asphaltene phase and rubber-rich phase at higher temperatures, but the performance of the rubber binder was affected by higher temperatures. Overall, kaolinite with the rubber binder generally demonstrated greater binder performance.

Fireproof Nanocomposite Polyurethane Foams: A Review

First introduced in 1954, polyurethane foams rapidly became popular because of light weight, high chemical stability, and outstanding sound and thermal insulation properties. Currently, polyurethane foam is widely applied in industrial and household products. Despite tremendous progress in the development of various formulations of versatile foams, their use is hindered due to high flammability. Fire retardant additives can be introduced into polyurethane foams to enhance their fireproof properties. Nanoscale materials employed as fire-retardant components of polyurethane foams have the potential to overcome this problem. Here, we review the recent (last 5 years) progress that has been made in polyurethane foam modification using nanomaterials to enhance its flame retardance. Different groups of nanomaterials and approaches for incorporating them into foam structures are covered. Special attention is given to the synergetic effects of nanomaterials with other flame-retardant additives.

Polyamide 11 Composites Reinforced with Diatomite Biofiller-Mechanical, Rheological and Crystallization Properties

Amorphic diatomaceous earth is derived from natural sources, and polyamide 11 (PA11) is produced from materials of natural origin. Both of these materials show a low harmfulness to the environment and a reduced carbon footprint. This is why the combination of these two constituents is beneficial not only to improve the physicochemical and mechanical properties of polyamide 11 but also to produce a biocomposite. For the purpose of this paper, the test biocomposite was produced by combining polyamide 11, as well as basic and pre-fractionated diatomaceous earth, which had been subjected to silanization. The produced composites were used to carry out rheological (melt flow rate-MFR), mechanical (tensile strength, bending strength, impact strength), crystallographic (X-ray Diffraction-XRD), thermal and thermo-mechanical (differential scanning calorimetry-DSC, dynamic mechanical thermal analysis-DMTA) analyses, as well as a study of hydrophobic-hydrophilic properties of the material surface (wetting angle) and imaging of the surface of the composites and the fractured specimens. The tests showed that the additive 3-aminopropyltriethoxysilane (APTES) acted as an agent that improved the elasticity of composites and the melt flow rate. In addition, the produced composites showed a hydrophilic surface profile compared to pure polylactide and polyamide 11.

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.

Influence of Surface-Modified Montmorillonite Clays on the Properties of Elastomeric Thin Layer Nanocomposites

In recent years, polyurethane nanocomposites have attracted more attention due to the massive demand for materials with increasingly exceptional mechanical, optical, electrical, and thermal properties. As nanofillers have a high surface area, the interaction between the nanofiller and the polymer matrix is an essential issue for these materials. The main aim of this study is to validate the impact of the montmorillonite nanofiller (MMT) surface structure on the properties of polyurethane thin-film nanocomposites. Despite the interest in polyurethane-montmorillonite clay nanocomposites, only a few studies have explored the impact of montmorillonite surface modification on polyurethane's material properties. For this reason, four types of polyurethane nanocomposites with up to 3% content of MMT were manufactured using the prepolymer method. The impact of montmorillonites on nanocomposites properties was tested by thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), contact angle measurement, X-ray diffraction (XRD), and optical coherence tomography (OCT). The results showed that chemical and physical interactions between the polymer matrix and functional groups on the montmorillonite surface have a considerable impact on the final properties of the materials. It was noticed that the addition of MMT changed the thermal decomposition process, increased T_2% by at least 14 °C, changed the hydrophilicity of the materials, and increased the glass transition temperature. These findings have underlined the importance of montmorillonite surface structure and interactions between nanocomposite phases for the final properties of nanocomposites.

A Review on Antimicrobial Packaging for Extending the Shelf Life of Food

Food packaging systems are continually impacted by the growing demand for minimally processed foods, changing eating habits, and food safety risks. Minimally processed foods are prone to the growth of harmful microbes, compromising quality and safety. As a result, the need for improved food shelf life and protection against foodborne diseases alongside consumer preference for minimally processed foods with no or lesser synthetic additives foster the development of innovative technologies such as antimicrobial packaging. It is a form of active packaging that can release antimicrobial substances to suppress the activities of specific microorganisms, thereby improving food quality and safety during long-term storage. However, antimicrobial packaging continues to be a very challenging technology. This study highlights antimicrobial packaging concepts, providing different antimicrobial substances used in food packaging. We review various types of antimicrobial systems. Emphasis is given to the effectiveness of antimicrobial packaging in various food applications, including fresh and minimally processed fruit and vegetables and meat and dairy products. For the development of antimicrobial packaging, several approaches have been used, including the use of antimicrobial sachets inside packaging, packaging films, and coatings incorporating active antimicrobial agents. Due to their antimicrobial activity and capacity to extend food shelf life, regulate or inhibit the growth of microorganisms and ultimately reduce the potential risk of health hazards, natural antimicrobial agents are gaining significant importance and attention in developing antimicrobial packaging systems. Selecting the best antimicrobial packaging system for a particular product depends on its nature, desired shelf life, storage requirements, and legal considerations. The current review is expected to contribute to research on the potential of antimicrobial packaging to extend the shelf life of food and also serves as a good reference for food innovation information.

Nanocomposite of CO2-Based Polycarbonate Polyol with Highly Exfoliated Nanoclay

Polypropylene carbonate (PPC) derived from carbon dioxide has been used as a precursor for the synthesis of polyurethane (PU). The high viscosity of the PPC is the key parameter hindering its processability during PU synthesis. Herein, a PPC nanocomposite with highly exfoliated nanoclay was prepared through a solution intercalation process. A wide range of nanoclay concentrations incorporated into the PPC were studied. The impacts of the nanoclay on the PPC were investigated in order to maintain the polymer structure while improving its physical properties. The characterizations of PPC nanocomposites showed that the highly exfoliated nanoclay contributed to a viscosity reduction, and a slight reduction in the molecular weight. The polymer degradation was indicated by the formation of cyclic propylene carbonate. The minimum or critical concentration of nanoclay was found to be between ∼0.5 and 2.0 wt %. Within this range, the polymer degradation is minimal. The PPC nanocomposites with a lower viscosity showed excellent precursors for making PU coating materials. The PU coating derived from the PPC nanocomposite has higher anticorrosive properties in comparison with the non-modified PU coating.

Nanoclays-containing bio-based packaging materials: properties, applications, safety, and regulatory issues

Food packaging is an important concept for consumer satisfaction and the increased shelf life of food products. The introduction of novel food packaging materials has become an emerging trend in recent years, which could be mainly due to environmental pollution caused by plastic packaging and to reduce food waste. Recently, numerous studies have been carried out on nanoclays or nanolayered silicate to be used in packaging material development as reinforcing filler composites. Different types of nanoclays have been used as food packaging materials, while montmorillonite (MMT), halloysite, bentonite (BT), Cloisite, and organically modified nanoclays have become of great interest. The incorporation of nanoclays into the packaging matrix improves the mechanical and barrier properties and at the same time prolongs the biodegradation of the packaging material. The purpose of this article is to examine the development of nanoclay-based food packaging materials. The review article highlights the current state of research on bio-based polymers with nanoclay for food packaging. In addition, the report analyses the mechanical, barrier, and antibacterial characteristics of nanoclay-based food packaging materials. Finally, it discusses the migration of nanoclays, toxicity levels, and the legislation associated with the application of nanoclays.

Graphical abstract

Gas permeameter for polymers and nanocomposites: a new equipment

Information on the gas transport coefficients in the permeation of homogeneous semipermeable materials such as semicrystalline polymers under extreme pressures and temperatures is rarely found in the literature. Therefore, the objective of this work is to showcase innovation regarding the accuracy and usability of the medium pressure and temperature gas permeameter suitable for polymeric and polymeric nanocomposite plates built by the authors, which was tested with nitrogen at 1 MPa and 69 °C (342.15 K) permeating pure high density polyethylene samples (HDPE) and HDPE samples with added nanoclay, redoing the tests published in a previous work on the subject. The results were compared against data obtained previously and information present in the literature, validating the permeameter presented in this work, which is capable of analyzing gas permeability under the described conditions with greater accuracy and ease of operation than the previous model for the values of the transport coefficients of nitrogen permeating HDPE, demonstrating that the implemented improvements and advances were adequate, allowing the measurement of the transport properties of gases permeating polymeric and nanocomposite plates, necessary information for the design of risers for the transportation of oil and natural gas, for example.

A critical review on biomass-based sustainable biorefineries using nanobiocatalysts: Opportunities, challenges, and future perspectives

Biocatalysts, including live microbial cells/enzymes, have been considered a predominant and advantageous tool for effectively transforming biomass into biofuels and valued biochemicals. However, high production costs, separation, and reusability limit its practical application. Immobilization of single and multi-enzymes by employing different nano-supports have gained massive attention because of its elevated exterior domain and high enzymatic performance. Application of nanobiocatalyst can overcome the drawbacks mainly, stability and reusability, thus reflecting the importance of biomass-based biorefinery to make it profitable and sustainable. This review provides an in-depth, comprehensive analysis of nanobiocatalysts systems concerning nano supports and biocatalytic performance characteristics. Furthermore, the effects of nanobiocatalyst on waste biomass to biofuel and valued bioproducts in the biorefinery approach and their critical assessment are discussed. Lastly, this review elaborates commercialization and market outlooks of the bioconversion process using nanobiocatalyst, followed by different strategies to overcome the limitations and future research directions on nanobiocatalytic-based industrial bioprocesses.

Environmental Properties and Applications of Biodegradable Starch-Based Nanocomposites

In recent years, the demand for environmental sustainability has caused a great interest in finding novel polymer materials from natural resources that are both biodegradable and eco-friendly. Natural biodegradable polymers can displace the usage of petroleum-based synthetic polymers due to their renewability, low toxicity, low costs, biocompatibility, and biodegradability. The development of novel starch-based bionanocomposites with improved properties has drawn specific attention recently in many applications, including food, agriculture, packaging, environmental remediation, textile, cosmetic, pharmaceutical, and biomedical fields. This paper discusses starch-based nanocomposites, mainly with nanocellulose, chitin nanoparticles, nanoclay, and carbon-based materials, and their applications in the agriculture, packaging, biomedical, and environment fields. This paper also focused on the lifecycle analysis and degradation of various starch-based nanocomposites.

Nano-Clays for Cancer Therapy: State-of-the Art and Future Perspectives

To date, cancer continues to be one of the deadliest diseases. Current therapies are often ineffective, leading to the urgency to develop new therapeutic strategies to improve treatments. Conventional chemotherapeutics are characterized by a reduced therapeutic efficacy, as well as them being responsible for important undesirable side effects linked to their non-specific toxicity. In this context, natural nanomaterials such as clayey mineral nanostructures of various shapes (flat, tubular, spherical and fibrous) with adjustable physico-chemical and morphological characteristics are emerging as systems with extraordinary potential for the delivery of different therapeutic agents to tumor sites. Thanks to their submicron size, high specific surface area, high adsorption capacity, chemical inertia and multilayer organization of 0.7 to 1 nm-thick sheets, they have aroused considerable interest among the scientific community as nano systems that are highly biocompatible in cancer therapy. In oncology, the nano-clays usually studied are halloysite, bentonite, laponite, kaolinite, montmorillonite and sepiolite. These are multilayered minerals that can act as nanocarriers (with a drug load generally between 1 and 10% by weight) for improved stabilization, efficient transport and the sustained and controlled release of a wide variety of anticancer agents. In particular, halloysite, montmorillonite and kaolinite are used to improve the dissolution of therapeutic agents and to delay and/or direct their release. In this review, we will examine and expose to the scientific community the extraordinary potential of nano-clays as unique crystalline systems in the treatment of cancer.

Nanoclays: Promising Materials for Vaccinology

Clay materials and nanoclays have gained recent popularity in the vaccinology field, with biocompatibility, simple functionalization, low toxicity, and low-cost as their main attributes. As elements of nanovaccines, halloysite nanotubes (natural), layered double hydroxides and hectorite (synthetic) are the nanoclays that have advanced into the vaccinology field. Until now, only physisorption has been used to modify the surface of nanoclays with antigens, adjuvants, and/or ligands to create nanovaccines. Protocols to covalently attach these molecules have not been developed with nanoclays, only procedures to develop adsorbents based on nanoclays that could be extended to develop nanovaccine conjugates. In this review, we describe the approaches evaluated on different nanovaccine candidates reported in articles, the immunological results obtained with them and the most advanced approaches in the preclinical field, while describing the nanomaterial itself. In addition, complex systems that use nanoclays were included and described. The safety of nanoclays as carriers is an important key fact to determine their true potential as nanovaccine candidates in humans. Here, we present the evaluations reported in this field. Finally, we point out the perspectives in the development of vaccine prototypes using nanoclays as antigen carriers.

Current synthesis and characterization techniques for clay-based polymer nano-composites and its biomedical applications: A review

Clays and its composites have received considerable attention recently due to their low cost, wide availability and low environmental impact. The development of various preparation processes and applications of innovative polymer-nanoclay composites has been aided by recent breakthroughs in material technologies. Novel polymer-nanoclay composites with better qualities have been effectively adopted in a variety of fields, including aerospace, car, construction, petroleum, biomedical, and wastewater treatment, owing to innovative production processes. Due to their superior qualities, such as increased density, strength, relatively large surface areas, high elastic modulus, flame retardancy, and thermomechanical/optoelectronic/magnetic capabilities, these composites are acknowledged as potential advanced materials. Hence the present paper reviews the advances in synthesis and preparation of clay-polymer nanocomposites. In addition, this study also focuses on the various techniques used for clay-polymer nanocomposites characterization e.g. scanning electron microscope (SEM), transmission electron microscope (TEM), thermo-gravimetric analysis (TGA) and differential colorimetric analysis (DSC), x-ray diffraction (XRD) analysis, Nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopic (FTIR) characterization. These advanced physico-mechanical and chemical characterization techniques would be effective in understanding the most appropriate application of clay polymer nanocomposites. In addition, the application of clay polymer nanocomposites in biomedical sector is also discussed in brief.

Covalent and Non-covalent Functionalized Nanomaterials for Environmental Restoration

Nanotechnology has emerged as an extraordinary and rapidly developing discipline of science. It has remolded the fate of the whole world by providing diverse horizons in different fields. Nanomaterials are appealing because of their incredibly small size and large surface area. Apart from the naturally occurring nanomaterials, synthetic nanomaterials are being prepared on large scales with different sizes and properties. Such nanomaterials are being utilized as an innovative and green approach in multiple fields. To expand the applications and enhance the properties of the nanomaterials, their functionalization and engineering are being performed on a massive scale. The functionalization helps to add to the existing useful properties of the nanomaterials, hence broadening the scope of their utilization. A large class of covalent and non-covalent functionalized nanomaterials (FNMs) including carbons, metal oxides, quantum dots, and composites of these materials with other organic or inorganic materials are being synthesized and used for environmental remediation applications including wastewater treatment. This review summarizes recent advances in the synthesis, reporting techniques, and applications of FNMs in adsorptive and photocatalytic removal of pollutants from wastewater. Future prospects are also examined, along with suggestions for attaining massive benefits in the areas of FNMs.

A Polypyrrole/Nanoclay Hybrid Film for Ultra-Sensitive Cardiac Troponin T Electrochemical Immunosensor

An electrochemical immunosensor based on a nanohybrid film of carboxylated polypyrrole and amine nanoclay was developed for label-free detection of the human cardiac troponin T (cTnT). The nanohybrid film was formed in situ on the surface of the glassy carbon electrode, followed by the covalent immobilization of anti-troponin T antibodies by glutaraldehyde. Morphological and chemical characterizations of the nanohybrid film were performed by scanning electron microscopy and Fourier-transform infrared spectroscopy. Under the optimized conditions, a calibration curve for cTnT in spiked serum was obtained by square wave voltammetry, and a low limit of detection and quantification was achieved (0.35 and 1.05 pg mL⁻¹, respectively). This was the first time that this type of nanohybrid film was used in the development of an immunosensor for cTnT that proved to be a simple and efficient strategy for the manufacture of a label-free electrochemical device that could be applied in the diagnosis of acute myocardial infarction.

Experimental and modeling studies of the effects of nanoclay on the oil behaviors in a water-sand system

When oil is released into the oceans, spilled oil may get to the shoreline driven by wind and wave. This study comprehensively explored the effects of bentonite nanoclay on the oil behaviors in a water-sand system from both experimental and modeling perspectives. Four factors including nanoclay concentration, temperature, salinity, and pH have been studied. The increasing nanoclay concentration resulted in the decrease in remaining oil on sand. Higher temperature and salinity were associated with less residual oil on sand in the presence of nanoclay. The lower residual oil on sand with coexisting nanoclay was found to be at pH 7. The factorial analysis results indicated that the nanoclay concentration showed the most significant impact among these factors. Miscibility modeling results showed an increasing temperature was favorable to the nanoclay miscibility. Moreover, the effect of nanoclay on oil behavior was further revealed through the dynamic simulation, in which it can be seen the nanoclay could penetrate into oil droplets and promote the oil detachment from solid substrate. The results of this study can help understand the role of fine particles in the fate and transport of oil on shoreline and support the risk assessment and response planning after oil spill.

Advances in Biologically Applicable Graphene-Based 2D Nanomaterials

Climate change and increasing contamination of the environment, due to anthropogenic activities, are accompanied with a growing negative impact on human life. Nowadays, humanity is threatened by the increasing incidence of difficult-to-treat cancer and various infectious diseases caused by resistant pathogens, but, on the other hand, ensuring sufficient safe food for balanced human nutrition is threatened by a growing infestation of agriculturally important plants, by various pathogens or by the deteriorating condition of agricultural land. One way to deal with all these undesirable facts is to try to develop technologies and sophisticated materials that could help overcome these negative effects/gloomy prospects. One possibility is to try to use nanotechnology and, within this broad field, to focus also on the study of two-dimensional carbon-based nanomaterials, which have excellent prospects to be used in various economic sectors. In this brief up-to-date overview, attention is paid to recent applications of graphene-based nanomaterials, i.e., graphene, graphene quantum dots, graphene oxide, graphene oxide quantum dots, and reduced graphene oxide. These materials and their various modifications and combinations with other compounds are discussed, regarding their biomedical and agro-ecological applications, i.e., as materials investigated for their antineoplastic and anti-invasive effects, for their effects against various plant pathogens, and as carriers of bioactive agents (drugs, pesticides, fertilizers) as well as materials suitable to be used in theranostics. The negative effects of graphene-based nanomaterials on living organisms, including their mode of action, are analyzed as well.

UV-LED Curable Acrylic Films Containing Phosphate Glass Powder: Effect of the Filler Loading on the Thermal, Optical, Mechanical and Flame Retardant Properties

In this work, we thoroughly investigate the effects of the incorporation of a phosphate glass micrometric powder on the morphology, as well as on the thermal, optical, mechanical and flame retardant properties of UV-LED curable acrylic films. To this aim, the filler loading was changed within 10 and 50 wt.%. UV-LED initiated curing was selected as a fast and reliable system, as the standard UV-curing process was not suitable because of the presence of the glass powder that decreased the quantum efficiency during the UV exposure, hence preventing the transformation of the liquid system into a solid network. The glass powder slightly increased the glass transition temperature of the acrylic network, hence showing a limited effect on the chain segments mobility; besides, increasing filler loadings were responsible for a progressive decrease of the transparency of films, irrespective of a marginal effect on their refractive index. Conversely, the presence of increasing amounts of phosphate glass improved the thermal and thermo-oxidative stability of the cured products. Besides, phosphate glass was capable of remarkably enhancing the flame retardance of the acrylic network at 50 wt.% loading, which achieved self-extinction in vertical flame spread tests (and was V-0 rated). This formulation, as assessed by forced-combustion tests, also displayed a remarkable decrease of peak of Heat Release Rate and Total Heat Release (by 44 and 33%, respectively) and of Total Smoke Release and Specific Extinction Area (by 53 and 56%, respectively). Further, the filler promoted an increase of the stiffness and surface hardness of the films, at the expense of a decrease in ductility. All these findings may justify the potential use of these composite films as flame retardant coatings for different flammable substrates.

A critical review on clay-based nanocomposite particles for application of wastewater treatment

Nanotechnology plays an important function in recent environmental aspects for the elimination of contaminants in the ecosystem. In recent times, nano-clay has initiated more concentration because of its distinctive physicochemical properties and characteristics. Recently, many types of research in clay-based nanocomposite were accomplished in the elimination of pollutants from water sources. Nanocomposite materials have advanced properties useful for contaminat removal such as higher surface area, thermal stability, selectivity to remove different contaminants, improved process ability, and fast decontamination. Thus, the development of clay-based composite materials is one of the upcoming directions to use effectively in water and wastewater treatment as adsorbent nanomaterials. This paper assesses the latest achievement in clay-based nanocomposite preparation, material property analysis and function for various pollutant removals. In particular, great consideration was paid to the recent progress in clay/metallic, clay-polymer, and clay-carbon composites presenting their application in the removal of different kinds of pollutants. Moreover, the mechanism of adsorption, the challenges and future perspective were also discussed to reach the optimum performance of the nanomaterials adsorbent. It is confirmed that clay-based nanocomposite materials are more cost-effective technology than conventional treatment methods.

Porous frameworks from Ecuadorian clays

This research provides a literature review on several topics as a foundation to comprehend porous materials, their structure, and behavior to explore how they can be derived from clays and nanoclays. In this case, considering the several minerals present in some Ecuadorian clays, which are a potential starting material for the synthesis of porous frameworks, they constitute a solid source of metal atoms such as Silicon or Aluminum. This research presents the evaluation and characterization via XRD and AAS of clay samples collected in the southeast of Ecuador in the provinces of Azuay, Morona Santiago and Zamora Chinchipe, which present diversified soil mineralogy with many chemical and crystallographic features for suitable precursors in nanomaterials design.

Enhancement of the Properties of Hybridizing Epoxy and Nanoclay for Mechanical, Industrial, and Biomedical Applications

The strong demand for plastic and polymeric materials continues to grow year after year, making these industries critical to address sustainability. By functioning as a filler in either a synthetic or natural starch matrix, nanoclay enables significant reductions in the impact of nonbiodegradable materials. The effect of treated nanoclay (NC) loading on the mechanical and morphological properties (EP) of epoxy is investigated in this research. The NC-EP nanocomposites were prepared via casting. The investigation begins with adding NC at concentrations of 1, 2, and 3 weight percent, followed by the effect of acid treatment on the same nanocomposites. The evaluation is focused on four mechanical tensile strength parameters: Young’s modulus, maximum load, and % elongation. The addition of NC improved the mechanical properties of the four components by 27.2%, 33.38%, 46.98%, and 43.58%, respectively. The acid treatment improved 35.9%, 42.8%, 51.1%, and 83.5%, respectively. These improvements were attributed to NC’s ability to alter the structural morphology as assessed by field emission scanning electron microscopy (FESEM), a tool for analysing the microstructure. FESEM images were used to visualise the interaction between the NC and EP nanocomposites. The dynamic mechanical properties of the hybrid nanocomposites were investigated using storage modulus, loss modulus, and tan(delta). The results have shown that the viscoelastic properties improved as the fraction of NC increased. The overall findings suggest that these nanocomposites could be used in various industrial and biomedical applications.

Capture and Release Mechanism of Ni and La Ions via Solid/Liquid Process: Use of Polymer-Modified Clay and Activated Carbons

This study is a starting point for the development of an efficient method for rare earths (REs) and transition metals (TMs) recovery from waste electrical and electronic equipment (WEEE) via a hydrometallurgical process. The capture and release capability of mineral clays (STx) and activated carbons (AC), pristine and modified (STx-L6 and AC-L6) with a linear penta-ethylene-hexamine (L6), towards solutions representative of the process, are assessed in the lab-scale. The solids were contacted with synthetic mono- and bi-ionic solutions containing Ni(II) and La(III) in a liquid/solid adsorption process. Contacting experiments were carried out at room temperature for 90 min by fixing a La concentration at 19 mM and varying the Ni one in the range of 19-100 mM. The four solids were able to capture Ni(II) and La(III), both in single- and bi-ionic solutions; however, the presence of the polyamine always results in a large improvement in the capture capability of the pristine sorbents. For all the four solids, capture behaviour is ascribable to an adsorption or ion-sorbent interaction process, because no formation of aquo- and hydroxy-Ni or La can be formed. The polyamine, able to capture Ni ions via coordination, allowed to differentiate ion capture behaviour, thus bypassing the direct competition between Ni and La ions for the capture sites found in the pristine solids. Release values in the 30-100% range were found upon one-step treatment with concentrated HNO₃ solution. However, also, in this case, different metals recovery was found depending on both the sorbent and the ions, suggesting a possible selective recovery.

Comparative Reinforcement Effect of Achatina fulica Snail Shell Nanoparticles, Montmorillonite, and Kaolinite Nanoclay on the Mechanical and Physical Properties of Greenpoxy Biocomposite

This study investigated the comparative reinforcement effect of Achatina fulica snail shell nanoparticles, montmorillonite, and kaolinite nanoclay on greenpoxy. Greenpoxy nanocomposites of snail shell nanoparticles, montmorillonite, and kaolinite nanoclay were developed separately, with the nanofiller content ranging from 1 to 3% by weight. Specimens of the nanocomposites with different percentage weights of the nanoparticles were prepared using the resin casting method. Mechanical properties, such as the tensile strength, stiffness, hardness, and impact strength, and water absorption properties of the specimens were evaluated experimentally. It was observed that the incorporation of nanoparticles improved the mechanical properties of pure greenpoxy irrespective of the percentage weight, source, and type of reinforcement. Significantly, the loading of 1 wt.% of snail shell nanoparticles offered superior properties in most cases. Protein fibers and high-concentration calcium carbonate in snail shell nanoparticles, uniform dispersion, and excellent matrix/snail shell nanoparticle adhesion provided a strong structure, resulting in the high strength, stiffness, and decreased water uptake of the composites. The superior properties observed in snail shell nanoparticle composites suggest that this naturally sourced nanofiller can be used as a potential substitute for montmorillonite and kaolinite clays.

Fast and Clean Synthesis of Nylon-6/Synthetic Saponite Nanocomposites

Nylon/saponite nanocomposites were synthesized and characterized. The nanocomposites were prepared by means of a fast, efficient, low cost, and environmentally friendly method. All of the tested preparations resulted in the pre-designed nanocomposites. To this end, delaminated saponites were directly synthesized to be used as a filler in a polymer matrix formed by nylon-6 by the in situ intercalation polymerisation of an ε-caprolactam monomer without the use of surfactants or other organic reagents to organophilise the clay, thus avoiding the drawbacks of contamination. The efficiency of the preparation method increased, and significant savings were achieved in terms of both energy reaction time, savings of 60% and 70%, respectively, by using microwave radiation as an energy source during the synthesis of the nanocomposites. In addition, given that the method that was followed avoids the use of contaminating organophilic agents, it is important to highlight the savings in reagents and the fact that there was zero environmental contamination.

Therapeutic Applications of Halloysite

In recent years, nanomaterials have attracted significant research interest for applications in biomedicine. Many kinds of engineered nanomaterials, such as lipid nanoparticles, polymeric nanoparticles, porous nanomaterials, silica, and clay nanoparticles, have been investigated for use in drug delivery systems, regenerative medicine, and scaffolds for tissue engineering. Some of the most attractive nanoparticles for biomedical applications are nanoclays. According to their mineralogical composition, approximately 30 different nanoclays exist, and the more commonly used clays are bentonite, halloysite, kaolinite, laponite, and montmorillonite. For millennia, clay minerals have been extensively investigated for use in antidiarrhea solutions, anti-inflammatory agents, blood purification, reducing infections, and healing of stomach ulcers. This widespread use is due to their high porosity, surface properties, large surface area, excellent biocompatibility, the potential for sustained drug release, thermal and chemical stability. We begin this review by discussing the major nanoclay types and their application in biomedicine, focusing on current research areas for halloysite in biomedicine. Finally, recent trends and future directions in HNT research for biomedical application are explored.

An Investigative Study on the Progress of Nanoclay-Reinforced Polymers: Preparation, Properties, and Applications: A Review

Nanoclay-reinforced polymers have attracted considerable universal attention in academic and industrial research due to their outstanding properties and their ever-expanding utilization in diversified applications. In that regard, in the present review, the structure of layered silicate clay, as well as procedures for clay material modification, are outlined. We also discuss the general characterization techniques, synthesis methods, and various properties of polymer-clay nanocomposites (PCNs), and some examples likewise are depicted from the scientific literature. The study's primary goal is to provide an up-to-date survey of polymer-clay nanocomposites and their specific applications in industries such as automotive, flame-retardant, and biomedical applications, coating, and packaging.

High-Density Polyethylene Waste (HDPE)-Waste-Modified Lube Oil Nanocomposites as Pour Point Depressants

Sustainability metrics have been established that cover the economic, social, and environmental aspects of human activities. Reduce, reuse, and recycle (3R) strategy targets solid waste management in the waste generation sectors. The purpose of this work is to study the possibility of using various plastic wastes containing high-density polyethylene (HDPE) and high-density polyethylene nanoclay (PMON) as polymer additives to modify lubricating oil. The structure of these additives was elucidated by Fourier transform infrared (FTIR) spectra, and the particle size of PMON was determined by dynamic light scattering (DLS). The thermal stability of HDPE and nanoclay HDPE (PMON) was studied, which showed higher thermal stability, and these additives completed degradation above 500 °C. The performance of HDPE and nanoclay HDPE (PMON) in lubricating oil was evaluated as pour point depressants by standard ASTM methods. The results showed that the efficiency of these additives increases with the decrease in the dose of these additives and lubricating oil treated with HDPE at 0.25% dosage lowers PPT to -30 °C, while lubricating oil treated with nanoclay HDPE (PMON7) at 0.25% dosage reduces PPT to -36 °C. Photomicrographic analysis was conducted to study accumulations and modifications in the wax crystal morphology in lube oil without and with HDPE and nanoclay HDPE (PMON7). Photomicrographs revealed that wax morphology changes due to effective pour point depressants on crystal growth.

Advances in Functional Biopolymer-Based Nanocomposites for Active Food Packaging Applications

Polymeric nanocomposites have received significant attention in both scientific and industrial research in recent years. The demand for new methods of food preservation to ensure high-quality, healthy foods with an extended shelf life has increased. Packaging, a crucial feature of the food industry, plays a vital role in satisfying this demand. Polymeric nanocomposites exhibit remarkably improved packaging properties, including barrier properties, oxygen impermeability, solvent resistance, moisture permeability, thermal stability, and antimicrobial characteristics. Bio-based polymers have drawn considerable interest to mitigate the influence and application of petroleum-derived polymeric materials and related environmental concerns. The integration of nanotechnology in food packaging systems has shown promise for enhancing the quality and shelf life of food. This article provides a general overview of bio-based polymeric nanocomposites comprising polymer matrices and inorganic nanoparticles, and describes their classification, fabrication, properties, and applications for active food packaging systems with future perspectives.