Onset Degradation Temperature Research Articles

Influences of printing parameters on mechanical properties of recycled PET and PETG using fused granular fabrication technique

This research presents an investigation of the feasibility of recycled polyethylene terephthalate (rPET) and glycol-modified polyethylene terephthalate (rPETG) thermoplastics using the fused granular fabrication (FGF) 3D printing technique. It focuses on the effects of FGF printing parameters on the mechanical properties of rPET and rPETG printed parts using a Gigabot X 3D printer. The design of experiments (DOE) was first performed considering the main FGF 3D printing parameters such as layer thickness, infill density and number of contours. The experimental studies were then carried out to study the effects of printing parameters on the tensile properties based on the DOE. The effect of interlayer bonding of printed parts on the tensile properties was also evaluated using finite element-based multiscale modelling. Scanning electron microscopy (SEM) and Fourier transformation infrared (FTIR) spectroscopy were used to observe the fracture morphology and chemical structure of post-FGF printing products. The tensile test results indicate that the highest tensile strength of 26.4 MPa was obtained for rPET when using a 1.1-mm layer thickness, a 70% infill density, and 3 contours, whereas, for rPETG, the maximum tensile strength of 44.8 MPa was attained with a 1.2-mm layer thickness, a 100% infill density, and 2 contours. FTIR analysis confirms no significant changes of characteristic peaks for PET in the printed products, suggesting that rPET and rPETG are viable materials for FGF printing. Thermal stability studies also reveal that the glass transition temperature and onset degradation temperatures are not significantly affected by the printing parameters. The study demonstrates the potential of rPET and rPETG as sustainable alternatives to virgin materials and provides insights into the optimal processing conditions for achieving high-quality 3D printed parts via the FGF technique.

Biodegradable packing food films based on PBAT containing ZnO and MoO3

AbstractMolybdenum trioxide (MoO3) and zinc oxide (ZnO) were incorporated into the poly(butylene adipate‐co‐terephthalate) (PBAT) matrix using casting method to obtain packing films for food transportation with outstanding properties and no formation of microplastics. Consequently, these films were evaluated using Fourier transform infrared spectroscopy, time domain and carbon‐13 nuclear magnetic resonance, x‐ray diffraction, contact angle measurement, and thermogravimetric analysis. The light barrier properties of the films were analyzed using transmittance mode in UV–VIS–NIR regions and the contact angle of composite films exhibited greater hydrophilicity compared to the pure polymer films. Regardless of the concentration, the fillers did not significantly modify the degradation onset temperature and the temperature of maximum degradation rate. However, ZnO caused a new thermal degradation event (around 330°C) that was not observed in the other films, possibly due to the second crystallization process. Composite films filled with 0.3% ZnO, 0.3% and 0.5% MoO3 showed greater molecular homogeneity than the pure polymer matrix, with the PBAT/MoO3 films demonstrating even greater homogeneity than PBAT/ZnO films; this response presumably comes from the satisfactory intermolecular interaction or adequate dispersion and distribution of the particles. The addition of 0.5% MoO3 in the matrix influenced the PBAT film, resulting in amorphous materials with the highest molecular mobility and opacity. Besides, in view of antimicrobial tests, all nanocomposites showed potential bacteriostatic activity. So, it can be conveniently used for food transportation and may avoid microplastic formation, after been discarded.

Comparative Examination of Cellulose Nanosphere from Corn Husk and Rice Straw

Cellulose nanosphere (CNS) is a novel material isolated through delignification, bleaching, acid hydrolysis, dialysis, and sonication of cellulose fibers from agricultural wastes such as corn husk and rice straw. Comparative examination through multiple characterizations of CNS from these cellulose sources was conducted to investigate its potential applications. Corn husk cellulose nanospheres (CHCNS) and rice straw cellulose nanospheres (RSCNS) were characterized by its chemical characteristics, crystallinity, surface morphology and thermal stability. FTIR showed the same transmittance patterns for both CNS samples. The peaks for CHCNS and RSCNS in the NMR analysis were comparable, and the presence of toluene enabled the CNS dissolve better in DMSO-d6. Higher crystallinity index was calculated in CHCNS than in RSCNS according to XRD analysis. TEM analysis demonstrated that CHCNS has shorter diameter than RSCNS. Lower onset degradation temperature relative to their corresponding bleached cellulose fiber was determined through TG Analysis. Biomedical applications such as drug delivery, wound dressings and tissue engineering are the most suitable applications based on the profiles of both CNS samples.

Enhancing Mechanical and Thermal Properties of Epoxy Composites with Fish Scale‐Derived Collagen Reinforcement

Epoxy polymer composites reinforced with fish scale‐derived collagen (EFC) have garnered significant interest due to their potential for enhancing mechanical properties and environmental sustainability. In this study, we investigated the mechanical, thermal, and morphological characteristics of epoxy composites reinforced with varying concentrations of EFC (5%, 10%, 15%, 20%, and 25% wt). Tensile strength testing revealed an initial increase in Young’s modulus with 5% and 10% EFC concentrations, followed by a decrease at higher concentrations, attributed to agglomeration effects. Flexural strength (FS) exhibited a decreasing trend with increasing EFC content, while flexural modulus (FM) showed improvement up to 20% EFC loading. Scanning electron microscopy (SEM) analysis highlighted the distribution of collagen particles, with agglomeration observed at higher concentrations. Fourier‐transform infrared spectroscopy (FTIR) spectroscopy indicated alterations in hydrogen bonding with the addition of EFC. Thermal analysis revealed a reduction at onset degradation temperature with EFC incorporation, attributed to poor dispersion and agglomeration effects, alongside a slight enhancement in thermal stability at higher concentrations. The study supports the sustainable use of EFC as a filler, by offering a renewable and eco‐friendly alternative to reinforcing polymer composites.

Graphite reinforced polymers for sealing geothermal wells

The objective of this study is to develop high-temperature resistant polymers for sealing geothermal wells by reinforcing inexpensive rubber with surface-treated graphite particles. We respectively treated two types of graphite particles, small-size lamellar graphite (SFG15) and graphite nanoplatelets (GNP), with a mixture of sulfuric and nitric acids. Through surface treatment, carboxylic groups are shown to be formed on graphite surfaces, and their oxygen contents are considerable. Polymer nanocomposites were made by compounding treated graphite particles with ethylene propylene diene monomer (EPDM). Uniform dispersion of treated graphite within developed polymer nanocomposites was achieved. Direct heating of prepared EPDM nanocomposites shows that treated SFG15 and GNP both enhance the temperature resistance of EPDM by over 80 °C. Also, the addition of treated graphite to EPDM remarkably enhances its storage modulus. Among all additive types and concentrations, 3.0 wt% of treated SFG15 performs the best in enhancing the storage modulus (by up to 215.83%) and reducing tan δ, namely the loss factor. Adding treated graphite significantly enhances the specific heat capacity of EPDM and remarkably increases the heat energy required to melt it. The onset degradation temperature of EPDM-SFG15 nanocomposites is 30 °C higher than that of plain EPDM. With these enhanced thermal and mechanical properties, the prepared nanocomposites are a promising candidate for the constituent polymer of seals applicable in geothermal wells.

Improvement of the Ductility of Environmentally Friendly Poly(lactide) Composites with Posidonia oceanica Wastes Plasticized with an Ester of Cinnamic Acid.

New composite materials were developed with poly(lactide) (PLA) and Posidonia oceanica fibers through reactive extrusion in the presence of dicumyl peroxide (DCP) and subsequent injection molding. The effect of different amounts of methyl trans-cinnamate (MTC) on the mechanical, thermal, thermomechanical, and wettability properties was studied. The results showed that the presence of Posidonia oceanica fibers generated disruptions in the PLA matrix, causing a decrease in the tensile mechanical properties and causing an impact on the strength due to the stress concentration phenomenon. Reactive extrusion with DCP improved the PO/PLA interaction, diminishing the gap between the fibers and the surrounding matrix, as corroborated by field emission scanning electron microscopy (FESEM). It was observed that 20 phr (parts by weight of the MTC, per one hundred parts by weight of the PO/PLA composite) led to a noticeable plasticizing effect, significantly increasing the elongation at break from 7.1% of neat PLA to 31.1%, which means an improvement of 338%. A considerable decrease in the glass transition temperature, from 61.1 °C of neat PLA to 41.6 °C, was also observed. Thermogravimetric analysis (TGA) showed a loss of thermal stability of the plasticized composites, mainly due to the volatility of the cinnamate ester, leading to a decrease in the onset degradation temperature above 10 phr MTC.

Valorization of Agricultural Waste Lignocellulosic Fibers for Poly(3-Hydroxybutyrate-Co-Valerate)-Based Composites in Short Shelf-Life Applications.

Biocircularity could play a key role in the circular economy, particularly in applications where organic recycling (composting) has the potential to become a preferred waste management option, such as food packaging. The development of fully biobased and biodegradable composites could help reduce plastic waste and valorize agro-based residues. In this study, extruded films made of composites of polyhydroxybutyrate-co-valerate (PHBV) and lignocellulosic fibers, namely almond shell (AS) and Oryzite® (OR), a polymer hybrid composite precursor, have been investigated. Scanning electron microscopy (SEM) analysis revealed a weak fiber-matrix interfacial interaction, although OR composites present a better distribution of the fiber and a virtually lower presence of "pull-out". Thermogravimetric analysis showed that the presence of fibers reduced the onset and maximum degradation temperatures of PHBV, with a greater reduction observed with higher fiber content. The addition of fibers also affected the melting behavior and crystallinity of PHBV, particularly with OR addition, showing a decrease in crystallinity, melting, and crystallization temperatures as fiber content increased. The mechanical behavior of composites varied with fiber type and concentration. While the incorporation of AS results in a reduction in all mechanical parameters, the addition of OR leads to a slight improvement in elongation at break. The addition of fibers improved the thermoformability of PHBV. In the case of AS, the improvement in the processing window was achieved at lower fiber contents, while in the case of OR, the improvement was observed at a fiber content of 20%. Biodisintegration tests showed that the presence of fibers promoted the degradation of the composites, with higher fiber concentrations leading to faster degradation. Indeed, the time of complete biodisintegration was reduced by approximately 30% in the composites with 20% and 30% AS.

Investigation of Cinnamic Acid Derivatives as Alternative Plasticizers for Improved Ductility of Polyvinyl Chloride Films.

This study investigates the viability of cinnamic acid derivatives as alternative plasticizers for polyvinyl chloride (PVC) films by addressing concerns about conventional phthalate-based options that pose health and environmental risks. By theoretical modeling, this research evaluates the compatibility between various cinnamic acid-based plasticizers and the PVC matrix, which suggests their potential effectiveness. Additionally, the incorporation of these plasticizers notably enhances the tensile properties of PVC films, particularly in terms of ductility and elongation at break by surpassing the neat PVC. Moreover, cinnamic acid-based plasticizers induce a drop in the glass transition temperature and storage modulus by, thereby, enhancing flexibility and reducing brittleness in the material. Although a slight reduction in the onset degradation temperature is observed, it does not impede the industrial processing of PVC plastisols at temperatures up to 190 °C. Optically, plasticized films exhibit high transparency with minimal UV and visible light absorption, which renders them suitable for applications necessitating clarity. The water vapor transmission rate analysis indicates increased permeability, influenced by molecular volumes. Atomic force microscopy reveals a compacted, homogeneous surface structure in most plasticized films, which signifies improved film quality. Thus, utilizing cinnamic acid derivatives as PVC plasticizers offers substantial mechanical and structural benefits, while compatibility ensures effective integration by contributing to environmentally sustainable PVC formulations with enhanced performance.

Accelerated weathering of sustainable and micro-filler Basalt reinforced polymer biocomposites: Physical, mechanical, thermal, wettability, and water absorption studies

This study intends to evaluate and comprehend the accelerated weathering behavior of various thermoset and thermoplastic composites loaded with an eco-friendly basalt micro-filler. Basalt incorporation into various polymer matrices is, in fact, a very innovative idea that might present some very exciting, as yet unexplored, perspectives. The four kinds of thermoset polymers (synthetic epoxy, bio-epoxy, polyester, vinyl ester) were reinforced with constant basalt reinforcement (30 wt %) and fabricated via the casting process. Whereas the three kinds of thermoplastic (polylactic acid, polypropylene, high-density polyethylene) polymers were also loaded with a constant basalt ratio and manufactured through an internal mixing process followed by a compression molding technique. The fabricated samples were employed inside the xenon arc light accelerated weathering equipment under ultraviolet (UV) rays, temperature, and humid conditions for 555.55 h as per ASTM G155-13 cycle 1. There is a significant improvement in the density of polymer composites due to highly dense basalt particle incorporation and maximum void percentage was observed in thermosets due to casting defects than in the thermoplastic samples. After weathering, the tensile, flexural, and impact properties of composites were significantly reduced due to the thermo-oxidative reaction and degradation under UV and moisture exposure. As a result of UV-induced chain scission, small fractures may develop. These spaces provide the ideal environment for moisture to infiltrate into the primary composite structures, weakening the links between the reinforcement and matrix. Scanning electron microscopy was used to analyze the significant changes in the surface morphology of weathered and unweathered tensile fractured samples. The hardness was considerably improved due to the presence of highly stiffen and hard basalt particles. The idea that accelerated weathering destruction creates hydrophobic surface characteristics in most of the composites due to a variety of factors, like physical and chemical transformations, is supported by the increased contact angle value and a decrease in surface free energy, particularly the polar section. The thermogravimetric analysis revealed that there is not much significant impact of weathering on composites, however, variations were observed in the thermomechanical analysis due to compatibility issues. It is observed that the onset and endset degradation temperatures got decreased with the reinforcement of 30 wt% basalts after the internal mixing process. This could be brought on by the molecular weight decreasing while mixing. The behavior of polymer composites in water absorption study is found to be unique depending on their hydrophilicity and defects raised during the fabrication.

Development of PLA/Lignin Bio-Composites Compatibilized by Ethylene Glycol Diglycidyl Ether and Poly (ethylene glycol) Diglycidyl Ether.

Poly (lactic acid) (PLA) is a promising green substitute for conventional petroleum-based plastics in a variety of applications. However, the wide application of PLA is still limited by its disadvantages, such as slow crystallization rate, inadequate gas barrier, thermal degradation, etc. In this study, lignin (1, 3, 5 PHR) was incorporated into PLA to improve the thermal, mechanical, and barrier properties of PLA. Two low-viscosity epoxy resins, ethylene glycol diglycidyl ether (EGDE) and poly (ethylene glycol) diglycidyl ether (PEGDE), were used as compatibilizers to enhance the performance of the composites. The addition of lignin improved the onset degradation temperature of PLA by up to 15 °C, increased PLA crystallinity, improved PLA tensile strength by approximately 15%, and improved PLA oxygen barrier by up to 58.3%. The addition of EGDE and PEGDE both decreased the glass transition, crystallization, and melting temperatures of the PLA/lignin composites, suggesting their compatabilizing and plasticizing effects, which contributed to improved oxygen barrier properties of the PLA/lignin composites. The developed PLA/lignin composites with improved thermal, mechanical, and gas barrier properties can potentially be used for green packaging applications.

Thermal and structural properties of polyzwitterions: Effects of monomer chemistry and salt addition

Thermal and structural properties of polyzwitterions (PZI)s comprising the sulfobetaine moiety were studied as a function of LiCl addition and variations in monomer chemistry. The polyzwitterions chosen for this study are: poly(sulfobetaine methacrylate), PSBMA; poly(sulfobetaine acrylate), PSBA; and, poly(ethyl sulfobetaine methacrylate), PESBMA. When LiCl salt is added, the Li+and Cl− ions disrupt the dipole-dipole electrostatic interaction of the PZI side groups. Fourier transform infrared spectroscopy shows that the vibrational frequencies of the symmetric and asymmetric S=O bonds increase as LiCl content increases. Structural studies by wide angle X-ray scattering show that all the PZIs are amorphous, and the average interatomic spacing, d, increases in the order: dPSBA(= 0.456±0.006nm) < dPSBMA (= 0.474±0.015nm) < dPESBMA (= 0.493±0.011nm). Upon the addition of LiCl, d-spacing for a given PZI decreases as LiCl content increases. Thermogravimetry showed that PZIs had degradation onset temperatures Td ∼ 300°C. As LiCl content increases, the onset temperature of degradation decreases suggesting that the disruption of dipole-dipole crosslinks destabilizes the polymer. All the PZIs are hydrophilic and hygroscopic, and a drying procedure was developed so that well-defined glass-to-liquid transitions could be observed in the dry solid state. PZIs without LiCl have glass transition temperatures, Tg, increasing in the order: Tg,PSBA(= 200±1°C) < Tg,PESBMA (= 204±1°C) < Tg,PSBMA (= 237±1°C). As the LiCl content increases, Tg decreases, and the liquid state heat capacity increases, in all PZIs. The specific heat capacity increment at Tg was studied for PSBA as a function of LiCl content. In PSBA, the heat capacity increment reached a maximum for molar ZI:LiCl content at and above 1:1, and its value agreed well with predictions based on an empirical bead model of polymers. Thermal data on the dry state of PZI-LiCl complexes suggest an analogy between electrostatically crosslinked, fully amorphous PZIs and semicrystalline polymers. The dipolar crosslinks confine the molecular motion of PZIs just as crystal domains confine the molecular motion of the amorphous phase in semicrystalline polymers.

Effect of Mixing Technique on Physico-Chemical Characteristics of Blended Membranes for Gas Separation

Polymer blending has attracted considerable attention because of its ability to overcome the permeability–selectivity trade-off in gas separation applications. In this study, polysulfone (PSU)-modified cellulose acetate (CA) membranes were prepared using N-methyl-2-pyrrolidone (NMP) and tetrahydrofuran (THF) using a dry–wet phase inversion technique. The membranes were characterized using scanning electron microscopy (SEM) for morphological analysis, thermogravimetric analysis (TGA) for thermal stability, and Fourier transform infrared spectroscopy (FTIR) to identify the chemical changes on the surface of the membranes. Our analyses confirmed that the mixing method (the route chosen for preparing the casting solution for the blended membranes) significantly influences the morphological and thermal properties of the resultant membranes. The blended membranes exhibited a transition from a finger-like pore structure to a dense substructure in the presence of macrovoids. Similarly, thermal analysis confirmed the improved residual weight (up to 7%) and higher onset degradation temperature (up to 10 °C) of the synthesized membranes. Finally, spectral analysis confirmed that the blending of both polymers was physical only.

Polylactic acid/polycaprolactone/sawdust based biocomposites trays with enhanced compostability

The major drawback associated with petroleum-based polymer products is pollution, leading to environmental hazards. Biodegradable polymers and biocomposites have the potential to play a major role in replacing the conventional polymers in specific applications on a case to case basis. In the current study, sawdust reinforced polylactic acid/polycaprolactone (PLA/PCL) biocomposites were developed using the melt extrusion technique. Primary processed fine sawdust was reinforced with PLA/PCL blend in a mini twin screw extruder in different weight fractions (10 %, 20 %, 30 %, and 40 %). The developed biocomposites were subjected to tensile testing, which indicated that the increased weight percent of sawdust reduced the tensile strength. The materials were further characterized, using sophisticated analytical such as field emission scanning electron microscopy, differential scanning calorimetry and thermogravimetry analysis. The composite containing 30 % sawdust concentration presented the best results with tensile strength of 26.5 MPa, tensile strain of 4.4 % and onset degradation temperature of 320 °C. The same formulation was successfully scaled up to the pilot level of 5 kg batch. It was further subjected to secondary processing to produce market ready cutlery items. Biodegradability studies in simulated composting environments revealed that addition of sawdust drastically reduces the lag phase in degradation and total degradation may be obtained in approximately 90 days. Based on the investigation, there is optimism that the PLA/PCL composites, blended with sawdust may ensure commercial application of sustainable polymer blends at affordable prices.

Recyclability of poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBH) for food packaging applications

This study is the first to investigate the recyclability of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), a small chain length PHA, and evaluate the gas barrier properties of the recycled materials. A recycling simulation of PHBH was performed through five twin-screw extrusion cycles. Although the onset degradation temperature and the chemical structure of the processed PHBH remained stable, size exclusion chromatography and melt flow index revealed a drop of 24.3% in the molar mass of the recycled materials. However, the recycled samples showed higher impact strength and, therefore, are less brittle and more elastic. Gas barrier properties of PHBH were found to enhance after the first recycling step. A significant decrease in both permeability and diffusion coefficients was observed after the first extrusion cycle. At the same time, the calculated mean integral diffusion coefficient <D> as well as the plasticization factor (γCeq) demonstrate a weak water plasticization effect for recycled materials.

Influence of alkali treated cellulose nanoparticles filled starch-based bioplastic films and their effect on thermal and mechanical properties

In this study, structural, thermal, mechanical and water uptake properties on the influence of alkaline treated cellulose nanoparticles (CNPs) filled starch-based bioplastic film is examined. Starch-based bioplastic films filled with alkaline treated CNPs at various concentration (0 to 5 wt%) were prepared by solution casting method. Thermal properties of film series are examined by Differential Scanning Calorimetry (DSC) and Thermogravimetry analysis (TGA) method. Alkaline treated CNPs addition induces crystallization to the bioplastic film. Degradation onset temperature ( Don), 10% mass loss ( T10) and 50% mass loss ( T50) values show the positive effect of CNPs addition into the biopolymer matrix with improved thermal stability. Tensile result shows that about 2.5 times increased is observed in 2 wt% CNPs filled bioplastic films. Water uptake result shows that the alkaline treated CNPs starch-based bioplastic film limit the biopolymer dissolution time and extended the breaking down of the bioplastic film. Leading to about 2.5 times reduced equilibrium water mass uptake is observed in 3 wt% CNPs filled bioplastic film when compared with unfilled bioplastic film.

Developing Filament Extruder and Characterization of Recycled High-Density Polyethylene for 3D Printing Filament Material

With the rise of additive manufacturing, the demand for 3D printing feedstock has increased exponentially and its sustainability is critical in the future. Many scholars are now concerned about how 3D printing filaments should be reproduced from recycled plastic. This study aimed to develop a filament extruder machine and investigate the potential of using recycled high-density polyethylene (HDPE), one of the most commonly used and recyclable thermoplastic, for 3D printing filament material. Desktop sized filament extruder machine was built, and a smooth and round-shaped 1.75±0.01mm diameter recycled HDPE filament was produced. Its mechanical, thermal, chemical, and physical properties were characterized by conducting various tests and validation test was conducted by comparing its properties with its virgin counterpart. The ultimate tensile strength of the recycled HDPE filament was obtained 19.02±0.35MPa, which is comparable to the ultimate tensile strength of virgin HDPE, making it a viable 3D printing feedstock for rapid prototyping. According to Thermogravimetric analysis (TGA), the recycled HDPE filament offers significant thermal stability with an onset degradation temperature of 430℃ and a full degradation temperature of 520℃. Its Fourier Transform Infrared (FTIR) spectrum shows the same functional groups as virgin HDPE polymer. The recycled HDPE filament has also excellent water-rejecting capability. In general, the study revealed a promising result for the use of recycled HDPE plastic as a more sustainable and environmentally friendly source material for 3D printing filament. To increase the potential and market competitiveness of recycled filaments, further investigation is required to optimize the filament extrusion and 3D printing process parameters, improve the mechanical properties, and overall development methods for both the recycled HDPE filament and 3D printed products.

Thermal and tribo-mechanical properties of high-performance poly(etheretherketone)/reduced graphene oxide nanocomposite coatings prepared by electrophoretic deposition

The thermal stability and degradation, near-to-surface mechanical properties, and scratch resistance and damage mechanism of poly(etheretherketone) (PEEK)/reduced graphene oxide (RGO) nanocomposite coatings are analyzed and discussed in terms of their nanosheet content and microstructure. Although RGO modified the thermal stability and degradation of the polymeric matrix, for instance, by slightly reducing the onset degradation temperature, its addition was not a limiting factor in the PEEK processing. Respecting the microstructural features induced by the nanosheets, the nanocomposite coatings were found to exhibit (i) a partially exfoliated and large-scale co-continuous morphology related to RGO nanosheets whose basal planes were mainly aligned with the coating surface, (ii) a dendritic morphology of PEEK domains related to transcrystallinity, (iii) and irregular domains associated with the deposition of PEEK particles wrapped by the nanosheets. The changes provoked by RGO in the morphology and PEEK crystalline phase influenced the near-to-surface mechanical properties, scratch resistance, and scratch damage mechanism of the nanocomposite coatings. Within this context, the interlayer strength between the nanosheets in the large-scale co-continuous morphology and PEEK transcrystallinity had an important effect. Furthermore, the random-bumpy surface texture formed by the irregular PEEK domains together with the conformal cracking damage mechanism was decisive in the scratch response of the PEEK/RGO nanocomposite coatings. The comprehensive characterization carried out in this work concludes that PEEK/RGO electrophoretic coatings are suitable for a variety of applications requiring tribo-mechanical resistance.Graphical

Particle size impact on pyrolysis of multi-biomass: a solid-state reaction modeling study

ABSTRACT Pyrolysis has gained significant attention due to its generation of value-added products from waste feeds in an environmentally friendly manner. The primary purpose of this study is to understand the effect of different particle sizes of biomass wastes – date stones (DS), cow manure (CM), and spent coffee grounds (SCG) – to understand better and design a biomass pyrolysis system. Thermogravimetric analysis of four different sizes of DS, SCG, and CM (range 1 mm to 125 μm) and a mixed sample (for each feed) was conducted at a heating rate of 10K/min from room temperature to 1173.15 K at inert conditions and employed model-based Coats–Redfern equations to understand the kinetic and thermodynamic parameters of the pyrolysis process. All the particle sizes except 355–125 μm for DS and SCG have the best-fit reaction mechanism of Ginstling-Brounshtein (D4). Both activation energy and pre-exponential factor decreased from 18.78 to 5.57 kJ/mol and 1.16 E+10 to 1.48 E+08 with reducing particle sizes. The onset degradation temperature, activation energy, change in enthalpy, and entropy decrease with particle sizes. The product formation is favored for all feeds and particle sizes, as the difference between the enthalpy and activation energies (Ea) is below 10 kJ/mol. As a result of their substantially lower activation energies and better reaction thermodynamics, mixed and smaller particle-sized biomass are favored.

Contribution of the Surface Treatment of Nanofibrillated Cellulose on the Properties of Bio-Based Epoxy Nanocomposites Intended for Flexible Electronics.

The growing interest in materials derived from biomass has generated a multitude of solutions for the development of new sustainable materials with low environmental impact. We report here, for the first time, a strategy to obtain bio-based nanocomposites from epoxidized linseed oil (ELO), itaconic acid (IA), and surface-treated nanofibrillated cellulose (NC). The effect of nanofibrillated cellulose functionalized with silane (NC/S) and then grafted with methacrylic acid (NC/SM) on the properties of the resulted bio-based epoxy systems was thoroughly investigated. The differential scanning calorimetry (DSC) results showed that the addition of NCs did not influence the curing process and had a slight impact on the maximum peak temperature. Moreover, the NCs improved the onset degradation temperature of the epoxy-based nanocomposites by more than 30 °C, regardless of their treatment. The most important effect on the mechanical properties of bio-based epoxy nanocomposites, i.e., an increase in the storage modulus by more than 60% at room temperature was observed in the case of NC/SM addition. Therefore, NC's treatment with silane and methacrylic acid improved the epoxy-nanofiber interface and led to a very good dispersion of the NC/SM in the epoxy network, as observed by the SEM investigation. The dielectric results proved the suitability of the obtained bio-based epoxy/NCs materials as substitutes for petroleum-based thermosets in the fabrication of flexible electronic devices.

Self-Healing Poly(urea formaldehyde) Microcapsules: Synthesis and Characterization.

Smart coatings and smart polymers have been garnering great interest in recent times due to their novel characteristics, such as being self-restoring, self-cleaning, and self-healing. However, most self-healing materials have a low glass transition temperature (Tg) and are inadequate for the repair of advanced composites. Because of their low Tg, the conventional self-healing materials plasticize and weaken the composites. In this study, moderate to high temperature self-healing microcapsules, capable of healing and thus stopping crack propagation, are prepared. The microcapsules were prepared using a two-step process involving the synthesis of poly(urea formaldehyde) (PUF) prepolymer, followed by the encapsulation of hexamethylene diisocyanate (HDI) in an oil-in-water emulsion to form a crosslinked PUF shell. Diisocyanates are of particular interest as self-healing encapsulants because of their diversity of structure and fast rate of hydrolysis. Successful encapsulation was verified by Fourier transform infrared spectroscopy (FTIR) and optical microscopy. Thermogravimetric analysis (TGA) was used to characterize the thermal properties of microcapsules. The onset temperature for microcapsule degradation varied from 155 °C to 195 °C. Dynamic mechanical analysis (DMA) was used to determine the thermomechanical response of microcapsule/epoxy films. DMA showed that the glass transition temperature (Tg) of the epoxy/microcapsule composite was greater than the Tg for neat epoxy and varied between 34 and 65 °C. The TGA analysis of the epoxy/microcapsule composite shows that the thermal stability and char retention of the epoxy/microcapsule composite increased and the low temperature decomposition peak at 150 °C, associated with the microcapsule, disappeared after the DMA test, indicating the occurrence of a reaction between HDI and the epoxy to form a crosslinked polyurea network structure.