Sustainable Nanocomposites Research Articles

Sustainable microwave synthesis of biodegradable active packaging films based on polycaprolactone and layered ZnO nanoparticles

Sustainable nanocomposites based on biodegradable polycaprolactone (PCL) matrix and ZnO nanoparticles (ZnONPs) functionalized with ionic liquid (IL) were prepared via bulk in-situ ring opening polymerization of ε-caprolactone (εCL). PCL-ZnONPs nanocomposite films were examined in terms of mechanical, thermal and barrier properties. The influence of ZnONPs on the potential antimicrobial effect and biodegradation of PCL-ZnONPs films was investigated. Introduction of IL-ZnONPs NPs (3.0 wt%) into PCL matrix resulted in significant decrease of water vapor permeation (46%), induced bactericidal effect against food-born pathogenic bacterium E.coli and enhanced biodegradation rate of the prepared nanocomposite film. Therefore, these materials present high application potential as active bio-packaging films, e.g. for food storage.

Catalyst-Free Mechanochemical Recycling of Biobased Epoxy with Cellulose Nanocrystals.

Mechanochemical vitrimerization, as a method to recycle cross-linked thermosets by converting the permanent network into a recyclable and reprocessable vitrimer network, inevitably requires a catalyst to accelerate the bond exchange reactions. Here, we demonstrate a catalyst-free approach to achieve the recycling of a cross-linked biobased epoxy into high-performance nanocomposites with cellulose nanocrystals (CNCs). CNCs provide abundant free hydroxyl groups to promote the transesterification exchange reactions while also acting as reinforcing fillers for the resultant nanocomposites. This technique introduces an effective way to fabricate high-performance thermoset nanocomposites based on recycled polymers in an ecofriendly way, promoting the recycle and reuse of thermosets as sustainable nanocomposites for different applications.

Performance Evaluation of Cellulose Nanofiber with Residual Hemicellulose as a Nanofiller in Polypropylene-Based Nanocomposite.

Residual hemicellulose could enhance cellulose nanofiber (CNF) processing as it impedes the agglomeration of the nanocellulose fibrils and contributes to complete nanofibrillation within a shorter period of time. Its effect on CNF performance as a reinforcement material is unclear, and hence this study seeks to evaluate the performance of CNF in the presence of amorphous hemicellulose as a reinforcement material in a polypropylene (PP) nanocomposite. Two types of CNF were prepared: SHS-CNF, which contained about 11% hemicellulose, and KOH-CNF, with complete hemicellulose removal. Mechanical properties of the PP/SHS-CNF and PP/KOH-CNF showed an almost similar increment in tensile strength (31% and 32%) and flexural strength (28% and 29%) when 3 wt.% of CNF was incorporated in PP, indicating that hemicellulose in SHS-CNF did not affect the mechanical properties of the PP nanocomposite. The crystallinity of both PP/SHS-CNF and PP/KOH-CNF nanocomposites showed an almost similar value at 55–56%. A slight decrement in thermal stability was seen, whereby the decomposition temperature at 10% weight loss (Td10%) of PP/SHS-CNF was 6 °C lower at 381 °C compared to 387 °C for PP/KOH-CNF, which can be explained by the degradation of thermally unstable hemicellulose. The results from this study showed that the presence of some portion of hemicellulose in CNF did not affect the CNF properties, suggesting that complete hemicellulose removal may not be necessary for the preparation of CNF to be used as a reinforcement material in nanocomposites. This will lead to less harsh pretreatment for CNF preparation and, hence, a more sustainable nanocomposite can be produced.

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

AbstractThe article reports recent advances in reference to the existing literature and presents a knowledge gap and potential solution ideas for polylactide (PLA) nanocomposites as sustainable materials. Various types of nanoparticles have been used for the development of PLA nanocomposites; however, this work focuses on PLA nanocomposites of nanoclay, nanocelluloses, carbon nanotube, and graphene. By providing a wholistic overview of the fundamental knowledge pertaining to PLA, and covering all critical aspects related to processing, characterization, and applications of PLA nanocomposites, this review provides a direction for future developments in the field of PLA nanocomposites suitable for various advanced applications, which is still scarce in the literature, including review articles. Moreover, the effects of dispersion/distribution of various types of nanoparticles on the degradation characteristics and special properties, such as cytocompatibility, electrical conductivity, and antimicrobial properties, of PLA nanocomposites are critically reviewed with regard to the nature of nanoparticles used for nanocomposite formation. In summary, this review provides new insight into the design and formulation of advanced PLA nanocomposites for a wide range of applications as sustainable materials.

Recycled polypropylene matrix nanocomposites reinforced with silane functionalized geopolymer concrete waste

The objective of this work is the processing of recycled polypropylene (rPP) matrix and geopolymer concrete waste (GCW) to develop novel sustainable nanocomposites for engineering applications. Specimens of these nanocomposites were produced from GCW added in proportions of 20, 40 and 50wt% to rPP. The pulverized waste, with nanometric particles, was used as neat, GCW, or as surface functionalized with vinyl trimethoxy silane (GCW/VTS). Separately, both GCW and GCW/VTS were mixed with rPP by means of extrusion reactive extrusion and injection processing before final molding of specimens. The composition microstructure, thermal stability and tensile properties of the specimens were studied by wide angle X-ray diffraction, thermogravimetry, differential scanning calorimetry, water absorption, tensile tests, and field emission gun scanning electron microscopy with energy dispersive spectroscopy. The main findings were an increased thermal stability and enhanced elastic modulus with incorporation of both GCW and GCW/VTS. A high degree of interaction between GCW filler and rPP matrix, including the first time observed mechanism of PP nanofilaments adhesion, is responsible for a negligible water absorption. A decrease in the crystallinity suggests an interference of GCW in the rPP arrangement of macromolecular chains.

A sustainable nanocomposite for removal of heavy metals from water based on crosslinked sodium alginate with iron oxide waste material from steel industry

Abstract Industrial activities with zero waste have been recently targeted for the sake of cleaner environment. Therefore, industrial wastes are recycled and reused in self-manufacturing processes or employed in other industrial sectors and applications. In this work, steel industrial waste material such as iron oxide fine powder was utilized to remove some heavy metal such as lead, cadmium and copper from water. Iron oxide waste was grinded to produce iron oxide waste nanoparticles (IOWNPs) and was crosslinked to alginate as a biodegradable polymer to produce IOWNPs-Alg nanocomposite. The nanocomposite structure was validated using FTIR, SEM, TEM, TGA and XRD. The equilibrium sorption was obtained after 30 min with maximum capacities for lead, copper and cadmium; 564 mg g−1, 158 mg g-1 and 102.2 mg g−1, respectively. Adsorption behaviors were investigated using five isotherm models. The pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham`s kinetic models were used for kinetic behavior evaluations. The adsorption kinetic study referred to satisfactory adsorption of cadmium via pseudo-first order, while pseudo-second order was the best model to describe adsorption of copper and lead ions onto IOWNPs-Alg nanocomposite. The adsorption behaviors of evaluated heavy metal ions were found to obey Freundlich isotherm model and confirm surface heterogeneity and exponential distribution of active sites. The assembled IOWNPs-Alg nanocomposite was further confirmed as an effective nanosorbent for removal of lead, cadmium and copper from wastewater samples.

PVC/rice straw/SDBS-modified graphene oxide sustainable Nanocomposites: Melt mixing process and electrical insulation characteristics

The incorporation of nanomaterials in the mixing process of polymers can effectively improve the melt mixing rheology of composites. This fact can be employed to control the morphology of sustainable composites comprised of incompatible ingredients such as natural fibers and polymers. The conventional solution to the incompatibility of natural-fiber fillers and polymers is to surface modify the natural filler. In this work, the role of graphene oxide and surface-modified graphene oxide nanosheets on the mixing rheology of a PVC/rice straw system are studied and impacts these nanosheets have on the viscosity of this sustainable system are used to reduce the morphological imperfections. The introduction of either graphene oxide or sodium dodecylbenzenesulfonate (SDBS)-modified graphene oxide nanosheets increased the melt mixing viscosity of PVC/rice straw compounds. Such a change in the melt mixing rheology of compounds resulted in an improvement in the morphological and structural characteristics. When only 1 phr SDBS-modified graphene oxide nanosheets were introduced in a PVC system filled with 15 phr rice straw fibers, more than 23 and 41% enhancement in the tensile ultimate strength of the system is achieved, compared to the neat PVC and the PVC/15 phr rice straw composite, respectively. Moreover, dynamic-mechanical results confirm that the incorporation of 1 phr SDBS-modified graphene oxide nanosheets resulted in more than 7% reduction in the damping peak intensity of the system, suggesting the formation of interactions between system ingredients. The electrical conductivity of the fabricated sustainable PVC/rice straw/SDBS-modified graphene oxide nanocomposite is in the range of 10−9–10−5 S/m, suggesting it can be a good candidate for insulating applications.

Sustainable Nanocomposites for Water Treatment

Nanocomposites are now commonly employed to augment the standard polymeric membrane materials that are used in water treatment processes. In recent years, nanocomposite membranes have greatly attracted the attention of scientists for water treatment applications such as wastewater treatment, water purification, removal of microorganisms, chemical compounds, heavy metals, etc. The incorporation of different nanofillers, such as carbon nanotubes, metal nanocomposites, metal oxide nanocomposites, and some other novel nano-scale materials into polymeric membranes have provided great advances, e.g., enhancing on hydrophilicity, suppressing the accumulation of pollutants and foulants, enhancing rejection efficiencies and improving mechanical properties and thermal stabilities. The use of membrane-based technologies has been applied for water treatment applications; however, the limitations of conventional polymeric membranes have led to the addition of inorganic fillers to enhance their performance. Thereby, the aim of this review is to provide up-to-date information related to those novel nanocomposite membranes and their contribution for water treatment application.

Enhanced Mechanical and Barrier Performance of Poly (Lactic Acid) Based Nanocomposites Using Surface Acetylated Starch Nanocrystals

Poly (lactic) acid (PLA) based nanocomposites reinforced with starch nanocrystals (SNC) extracted from high amylopectin waxy maize starch and acetylated starch nanocrystals (Ac-SNC), were prepared and their influence on the overall properties of PLA nanocomposites were studied. The two nanofillers (SNC and Ac-SNC) were incorporated in PLA at two different loadings (1 and 3 wt%) by solvent casting and evaporation technique. Surface acetylation of SNC was confirmed by Fourier Transform infra-red spectroscopy and nuclear magnetic resonance spectroscopy and the crystalline structure by X-ray diffraction. This paper reports the influence of incorporating unacetylated and surface acetylated starch nanocrystals on morphological, barrier, mechanical, and rheological properties of PLA based nanocomposites. While both nanofillers improved the properties of PLA, the PLA-Ac-SNC had superior properties to that of PLA-SNC nanocomposites, due to better filler dispersion and interaction with the polymer matrix. These sustainable nanocomposites with improved properties will expand the application of these bio-sourced starch nanocrystals.

Hyperbranched polyurethane/reduced carbon dot-zinc oxide nanocomposite-mediated solar-assisted photocatalytic degradation of organic contaminant: An approach towards environmental remediation

Photocatalysis has carved out a niche in the recent times, as an environmentally benign, renewable and innovative technology for degradation of common organic pollutants in nature. The present work focuses on the development of a sustainable hyperbranched polyurethane (HPU) nanocomposite with reduced carbon dot-zinc oxide nanohybrid (RCD-ZnO) as a prospective solar energy-assisted heterogeneous photocatalyst for degradation of anionic surfactant contaminants. RCD-ZnO nanohybrid was synthesized by a simple and eco-friendly protocol by employing Colocasia esculenta leaf extract as bio-reductant, and fabricated with a starch-based HPU by an in situ polymerization process. Structural characterizations were performed by FT-IR, UV–Visible, EDX, TEM, TGA and DSC techniques. Optical studies revealed optical band gap of RCD-ZnO (2.12 eV) was reduced considerably in comparison to bare RCD (3.18 eV) and ZnO (3.3 eV). The RCD-ZnO nanohybrid-reinforced HPU nanocomposite displayed significant enhancement in mechanical properties like strength (1.9 folds), elongation (1.39 folds), scratch hardness (1.53 folds), toughness (3.54 folds) over pristine HPU as well as improved thermal stability (25 °C enhancement). Furthermore, the RCD-ZnO nanohybrid-reinforced HPU nanocomposite demonstrated high efficiency as a heterogeneous recyclable photocatalyst for degradation of aqueous surfactant contaminants, dodecylbenzenesulfonate (96.7% in 110 min) and commercial detergent (94.8% in 150 min) upon exposure to sunlight, following the pseudo-first order kinetics model. Thus, the current work holds good potential for the development of such high performance sustainable nanocomposite as an efficient solar energy-assisted heterogeneous recyclable photocatalyst for large scale applications.

Self-organization of sepiolite fibbers in a biobased thermoset

A self-organization of sepiolite fibbers have been found during the synthesis of sustainable nanocomposites. These auto-structured networks are synthesized starting with an epoxidized linseed oil (ELO), a bio-based hardener of dicarboxylic class and sepiolite fibbers. For the first time, the auto-organization of sepiolite fibbers into empty or solid spheres insight a bio-based thermoset matrix have been highlighted and synthesized. The influence of the thermoset formulation and the sepiolite concentration on self-organization are emphasized. The thermomechanical properties of nanocomposites have been investigated highlighting an increasing of elastic modulus from 30 to 40% in the vitreous states and from 25 to 45% in the rubbery state. This peculiar organization and behaviour of sepiolite, similar to that of surfactants, is of great interest as fundamental, applicative and industrial level.

Thermal Properties of Multilayer Nanocomposites Based on Halloysite Nanotubes and Biopolymers

This paper reports a novel procedure to fabricate multilayer composite biofilms based on halloysite nanotubes (HNTs) and sustainable polymers. Among the biopolymers, the non-ionic (hydroxypropyl cellulose) and cationic (chitosan) molecules were selected. The nanocomposites were prepared by the sequential casting of ethanol solutions of hydroxypropyl cellulose and aqueous dispersions of chitosan/HNTs. The composition of the bio-nanocomposites was systematically changed in order to investigate the effect of the hydroxypropyl cellulose/HNTs ratio on the thermal properties of the films, which were investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). DSC studies were conducted in the static air (oxidative atmosphere), while TG measurements were carried out under nitrogen flow (inert atmosphere). The analysis of DSC data provided the enthalpy and the temperature for the oxidative degradation of the bio-nanocomposites. These results were helpful to estimate the efficacy of the well-compacted middle layer of HNTs as a flame retardant. TG experiments were performed at a variable heating rate and the collected data were analyzed by the Friedman’s method (non-isothermal thermogravimetric approach) with the aim of studying the kinetics of the hydroxypropyl cellulose degradation in the multilayer nanocomposites. This work represents an advanced contribution for designing novel sustainable nanocomposites with excellent thermal behavior as a consequence of their peculiar multilayer structure.

Sustainable nanocomposites of epoxy and silica xerogel synthesized from corn stalk ash: Enhanced thermal and acoustic insulation performance

Abstract The synthesis of silica xerogel from corn stalk ash in ambient pressure drying was carried out by sol-gel method. With the usage of silica xerogel (0.5, 1.0 and 1.5 wt%) in epoxy resin (ER), silica xerogel/epoxy nanocomposites were successfully prepared. The uniform dispersion of silica xerogel in neat ER was observed except nanocomposite including 1.5 wt% silica xerogel. The low density nanocomposites showed high thermal stability and low thermal conductivity. The char residue at 600 °C and thermal conductivity of nanocomposite including 1.5 wt% silica xerogel were specified as 20.30% and 0.220 W/mK, respectively. The acoustic velocity of the nanocomposites was decreased with increasing amount of silica xerogel. The water sorption of the nanocomposites was slightly higher than neat ER. The water contact angle of the nanocomposites were between 75° and 70°. The study provided a new thermal and acoustic insulation material instead of expensive and health risk traditional materials.

Preparation of sustainable nanocomposite as new adsorbent for dyes removal

Sustainable nanocomposite from chitosan, silk fibroin and hydroxyapatite was investigated as adsorbent for organic dyes removal from waste water. Chitosan/silk fibroin bioactive blend initiated successfully the mineralization of hydroxyapatite rod-like crystals with ~40 nm diameter. The formed nanocomposite was applied for methylene blue (MB) removal from waste water. The adsorption kinetics were fitted with Pseudo-second order kinetic model. Adsorption results well fitted to the Langmuir model and showed maximum adsorption capacity 476 mg/g. The current nanocomposite is sustainable and efficient adsorbent for organic dyes removal from waste water.

3-Aminopropyl-triethoxysilane-functionalized rice husk and rice husk ash reinforced polyamide 6/graphene oxide sustainable nanocomposites

Rice husk and rice husk ash are two well-known sustainable materials for wastewater purification applications. In this work, functionalized-rice husk and -rice husk ash reinforced polyamide 6/graphene oxide nanocomposites are fabricated using the solution casting method. 3-Aminopropyl-triethoxysilane is used as the functionalizing agent for the surface modification of rice husk and rice husk ash particles. Siloxane bonding between silanol groups of the functionalizing agent and silica containing particles can result in the introduction of amino groups on the surface of particles, which can react with either terminal carboxyl groups or amide groups of the polyamide 6. Functionalized-rice husk ash, which contains a large amount of nano silica, forms distributed nano-sized aggregates in the structure of the polyamide 6. Moreover, the simultaneous presence of graphene oxide and rice husk ash, as an organic/inorganic nano-system, in the matrix structure results in a clear enhancement in the structural and mechanical characteristics of final nanocomposites. This is the result of possible strong interactions between the polymeric matrix and the organic/inorganic nano-system. The influences of the organic/inorganic nano-system on the melting process, morphology and dynamic-mechanical properties of reinforced nanocomposites are investigated in details. Moreover, the impacts of the organic/inorganic nano-system loading on the thermal stability of fabricated nanocomposites are studied. Considering results presented here and the well-known adsorbent characteristics of rice husk ash nanoparticles, the functionalized-rice husk ash/graphene oxide/polyamide 6 sustainable nanocomposite is a perfect candidate for fabricating nanofibers, which are applicable in wastewater purification applications.

A study on the thermodynamic changes in the mixture of polypropylene (PP) with varying contents of technological and post-user recyclates for sustainable nanocomposites

The use of recycled materials can address some of the issues associated with the cost and environmental implications of non-renewable materials. So the prime aim of this work was to determine the thermodynamic changes in the polypropylene (PP) mixtures depending on the percentage amount of different origin recyclates for sustainable nanocomposites. In this study, different polypropylene mixtures with the addition of PP recyclates from a selective waste collection system and in-plant recycling system have been subjected to detailed analysis. It was obvious that recyclates from technological waste were of higher quality than post-user recyclates obtained from a selective waste collection system. The influence of the source of the recyclates on the different properties of the processed materials has been studied in detail. The content of the repeatedly processed material in the technological recyclates was found to explain the unexpected influence of the recyclates content on the properties of the final product. A mathematical model was also formulated to calculate the content of the material with certain amount of recirculations in the in-plant recycling system since no analyses concerning the content of the repeatedly processed material in the technological recyclates added to the original material were found in the literature.

Graphene oxide as a compatibilizer for polyvinyl chloride/rice straw composites

Abstract In this study, polyvinyl chloride (PVC)/rice straw (RS)/graphene oxide (GO) sustainable nanocomposite was prepared using the direct compounding method. Structural, morphological and mechanical properties of fabricated sustainable nanocomposites were compared with unfilled and RS-filled PVC compounds. Mechanical characteristics of PVC decreased with loading RS fibers. The main reason for the mechanical failure of PVC/RS composite is the incompatibility between PVC and RS fibers. GO nanosheets are used here to improve the compatibility between RS fibers and PVC macromolecules. Compared to the neat PVC, maximum strength of the RS/GO-loaded PVC composite increased up to 31%, with incorporating only 1 wt% of GO nanosheets. This enhancement in the mechanical characteristics of PVC/RS/GO nanocomposite can only be due to the role of GO nanosheets as a compatibilizer, as 1 wt% GO loading can only increase the mechanical strength of PVC compounds up to 9%. Fourier transform infrared spectroscopy results are used here to study the nature of these behaviors. It is suggested that the non-covalent and physical interactions between cellulose/hemicellulose portions of RS fibers and GO functional groups result in the enhancement of mechanical characteristics. Consequently, GO can be considered as a new compatibilizer for fabricating high performance PVC-based sustainable nanocomposites.

Engineering flame retardant biodegradable polymer nanocomposites and their application in 3D printing

Flame retardant, environmentally sustainable nanocomposites were made by melt blending poly (lactic acid) (PLA) with melamine polyphosphate (MPP) and Cloisite 30B (C-30B). The composition of the nanocomposite was highly specific and guided by interfacial energy minimization principals which balanced enthalpic and mechanical contributions. In this critical range, even small changes in the filler concentration can have a large impact on the performance of the material. We showed that while addition of 17% MPP can increase the flame resistance of PLA, (achieving a UL-94 V2 rating) the mechanical properties were significantly degraded. Addition of only 1% C-30B reversed these effects and yielded a nanocomposite with enhanced mechanical properties and passing the UL-94 V0 flame test. This compound was able to be extruded and fed into a Makerbot Replicator 2X Fused Deposition Modeling (FDM) 3D printer, where the printed samples were indistinguishable mechanically from their molded counterparts and also achieved the UL-94 V0 rating. The enhanced performance occurred only within a very narrow composition window. Cone calorimetry revealed that while a significant decrease in the heat release rate, accompanied by the formation of an intumescent char, was achieved by the addition of 1% C-30B to the MPP/PLA blend, a very poor char, corresponding the increase in the heat release rate, was obtained with addition of 2% C-30B. These results were explained in view of the altered phase morphology observed in Transmission Electron Microscopy (TEM).

A renewable resource based carbon dot decorated hydroxyapatite nanohybrid and its fabrication with waterborne hyperbranched polyurethane for bone tissue engineering

Carbon dot decorated hydroxyapatite/water borne hyperbranched polyurethane nanocomposite.

Physicochemical and micromechanical investigation of a nanocopper impregnated fibre reinforced nanocomposite

This paper outlines the synthesis of a novel sustainable nanocomposite and the investigation of its physicochemical and mechanical properties using micromechanical models.