Onset Decomposition Temperature Research Articles

Regulation of ester contents enabled tunable thermal and mechanical properties of poly(ester amide)

AbstractPoly(ε‐caprolactone‐co‐ε‐caprolactam) was synthesized through ring‐opening copolymerization of ε‐caprolactone (CLO) and ε‐caprolactam catalyzed by ethylmagnesium bromide (EtMgBr) or sodium ε‐caprolactam. Varied ester contents were achieved from 0 to 100 mol%. EtMgBr enabled the copolymerization with high yield of over 95%. Thermal properties vary with different ester contents. With increasing CLO content, the onset decomposition temperature (273.36 to 240.97 °C) and glass transition temperature (52.1 to −56.3 °C) gradually decreased. The results of melting behavior of resultant poly(ester amide)s through differential scanning calorimetry and theoretical calculation indicated a eutectic temperature of 46.6 °C. The mechanical properties of obtained copolymers were systematically investigated. The enhancement of CLO incorporation led to a decrease in tensile strength (70.99 to 9.88 MPa) and Young's modulus (690.03 to 19.18 MPa). Copolymer with CLO incorporation of 70 mol% exhibited a eutectic temperature of 46.6 °C, and enabled a high elongation at break (658%) and enhanced impact strength (138.5 kJ m−2). © 2023 Society of Chemical Industry.

Highly stable hybrid porous polymers containing polyhedral oligomeric silsesquioxane (POSS)/Dibenzo[g,p]chrysene and Dibenzo[b,d]thiophene units for efficient Rhodamine B dye removal

In this study, we employed the Heck reaction method to synthesize three types of hybrid porous organic/inorganic polymers (HPPs) incorporating octavinylsilsesquioxane (OVS) units. Specifically, we synthesized OVS-TBN-DBTH, OVS-TBN-THS, and OVS-TBN-THSO2 HPPs by reacting OVS with different brominated organic compounds, namely, 2,7,10,15-tetrabromodibenzo[g,p]chrysene (TBN-Br4)/2,8-dibromodibenzo[b,d]thiophene (DBTH-Br2), TBN-Br4/2,3,7,8-tetrabromothianthrene (THS-Br4), and TBN-Br4/2,3,7,8-tetrabromothianthrene-5,5,10,10-tetraoxide (THSO2-Br4). Based on thermal analysis (TGA), the onset decomposition temperatures (Td10) for these HPPs were as follows: OVS-TBN-DBTH at 575 °C, OVS-TBN-THS at 313 °C, and OVS-TBN-THSO2 at 490 °C. Additionally, these HPPs exhibited high char yields, with values of 83, 53, and 67 wt% for OVS-TBN-DBTH, OVS-TBN-THS, and OVS-TBN-THSO2 HPPs, respectively. Furthermore, when analyzed using nitrogen adsorption–desorption measurements, both OVS-TBN-DBTH and OVS-TBN-THSO2 HPPs demonstrated impressive specific surface areas (SBET) of up to 380 m2/g. In addition, the OVS-TBN-DBTH and OVS-TBN-THSO2 HPPs provide an adsorption capacity of 70.62 and 77.1 mg g−1 (qmax from Langmuir isothermal Mode) toward RhB dyestuff at room temperature. In this adsorption system, after calculation, the OVS-TBN-THS HPP could be inferred that the adsorption is a pseudo-first order adsorption model. The OVS-TBN-THS HPP and OVS-TBN-THSO2 HPP in the pseudo-secondary order model have a better representation of the adsorption system for rhodamine B. This study introduces an innovative method for developing HPPs as adsorbents for water treatment and purification.

The impact of oxygen-clustering on the transformation of electrochemically-derived graphite oxide framework

Oxygen-clustering in graphene oxide is the activated process of diffusion of oxygen functionalities: hydroxyls and epoxides, to form clusters and to trigger sp2 percolation, a key element for electrical conductivity. Impact of oxygen-clustering is thoroughly analyzed in electrochemically-derived graphite oxide (EGO), amine-functionalized frameworks (EGOF), and their pyrolyzed forms. Amine pillars within EGOF were suspected to amplify oxygen-clustering in EGOF as onset temperature of thermal decomposition was smaller in EGOF than in EGO. Thermochemical analysis proves that pillars within EGOF significantly augment oxygen-clustering aiding the reduction mechanism as inferred by the activation energy of thermal decomposition. Defective oxygen-clustering mechanism is evidenced using multiple techniques, including XRD, and is harnessed to enhance nitrogen doping. The pyrolytic morphological transformation from lamellae of EGOF into ravioli is revealed through SEM. A labyrinthic network of array prismatic dislocations provides stability to pyrolyzed EGOF ravioli whilst confining long chains of electron delocalization (localized π-orbitals), as unprecedently confirmed by HR-TEM/EELS and conductive AFM (C-AFM). Oxygen-clustering not only improves nitrogen doping in ravioli, but also improves density of array prismatic dislocations, which ultimately boosts Faradaic redox activity as observed in cyclic voltammetry (CV). Results show that Faradaic response originating from redox-active nitrogen groups predominantly relies on abundance of extended localized π-orbitals, which are geometrically and chemically confined within ravioli array prismatic dislocations. Our first-of-a-kind HR-TEM/EELS, C-AFM, and CV comparative and correlative analysis of pyrolyzed forms of EGO, EGOF, and their oxygen-clustered derivatives, confirms emergent role of confined electron delocalizations in amplifying Faradaic redox activity.

Microstructure and hydrogen storage properties of Mg1.8Y0.2Ni1−yCoy (y = 0, 0.05, 0.1, 0.15, 0.2) alloys

The Mg1.8Y0.2Ni1−yCoy (y = 0, 0.05, 0.1, 0.15, 0.2) hydrogen storage alloys were prepared following the principles of metallurgy, the phase composition and microstructure of the alloys were studied using XRD and SEM/EDS techniques, and the hydrogen absorption and desorption properties of the alloys were studied using PCT and DSC techniques. The results showed that the addition of Co did not affect the phase composition of Mg1.8Y0.2Ni1−yCoy alloys in the as-cast state and after hydrogen absorption. The Co addition could help refine the microstructure of the alloys to a certain extent. The de-/hydrogenation kinetics of Mg1.8Y0.2Ni1−yCoy (y = 0, 0.1, and 0.2) alloys were improved by adding Co, and the best results were obtained at y = 0.1. The onset decomposition temperature of Mg1.8Y0.2Ni1−yCoy (y = 0, 0.1, and 0.2) alloys were recorded to be 180 °C, 156 °C, and 210 °C, respectively, which were significantly lower than that of Mg2Ni (253 °C). The results revealed that the addition Co could improve the thermodynamic performance of the dehydrogenation process.

Exploring the High‐Temperature Window of Operation for Organic Photovoltaics: A Combined Experimental and Simulations Study

AbstractThe global climate change negatively affects the photovoltaic performance of traditional solar cell technologies. This article investigates the potential of organic photovoltaics (OPV) for high‐temperature environments, ranging from urban hot summers (30—40 °C) and desert regions (65 °C) up to (aero) space conditions (130 °C), the thermal window in which OPV can operate. The approach is based on a combination of experiments and simulations up to 180 °C, moving significantly beyond the conventional temperature ranges reported in the literature. New 2H‐benzo[d][1,2,3]triazole‐5,6‐dicarboxylic imide‐based copolymers with decomposition onset temperatures above 340 °C are used for this study, in combination with non‐fullerene acceptors. Contrary to their inorganic counterparts, OPV devices show a positive temperature coefficient up to ≈90 °C. At temperatures of 150 °C, they are still operational, retaining their room temperature efficiency. Complementary simulations are performed using an in‐house developed software package that numerically solves the drift‐diffusion equations to understand the general trends in the obtained current–voltage characteristics and the materials’ intrinsic behavior as a function of temperature. The presented methodology of combined high‐temperature experiments and simulations can be further applied to investigate the thermal window of operation for other OPV material systems, opening novel high‐temperature application routes.

Fabrication of Energetic Metal-Organic Frameworks: Potassium 5-Carboxylato-3,4-Dinitropyrazole and Potassium 5-(Hydrazinecarbonyl)-3,4-Dinitropyrazole.

Energetic materials have been widely applied in civil and military fields, whose thermostability is a key indicator to evaluate their safety levels under severe conditions. Herein, two novel energetic metal-organic frameworks (EMOFs), namely, 4 and 6, were experimentally obtained and comprehensively characterized. The two EMOFs both possess unique three-dimensional (3D) coordination structures. With a high crystal density of 2.184 g·cm-3, EMOF 4 exhibits outstandingly superior thermostability (onset: 290 °C; peak: 303 °C), while EMOF 6 features onset and peak decomposition temperatures of 220 and 230 °C. The calculated energetic parameters of 4 and 6 are as follows: detonation velocity: 8731 m·s-1 and 8294 m·s-1; detonation pressure: 26.5 and 26.4 GPa. Compared to EMOF 6, EMOF 4 features high energy, excellent thermostability, and low mechanical sensitivities, which should be partly attributed to more plentiful coordination interactions. More coordination bonds are conducive to strengthening the EMOF framework, which needs much more energy to collapse, thereby maintaining higher thermal stability. The above favorable characteristics not only indicate EMOF 4 has a promising future in applications as a thermostable explosive but also provide an effective and feasible strategy for developing novel heat-resistant energetic materials via reinforced frame structures of EMOFs.

Effects of Overload on Thermal Decomposition Kinetics of Cross-Linked Polyethylene Copper Wires.

During an overload fault in an energized wire, the hot metal core modifies the structure of the insulation material. Therefore, understanding the thermal decomposition kinetics of the insulation materials of the overloaded wire is essential for fire prevention and control. This study investigates the thermal decomposition process of new and overloaded cross-linked polyethylene (XLPE) copper wires using thermogravimetry-Fourier-transform infrared spectroscopy and cone calorimetry. The thermal decomposition onset temperature and activation energy of the overloaded XLPE insulation materials were reduced by approximately 15 K and 20 kJ mol-1, respectively, and its reaction mechanism function changed from D-ZLT3 to A2 (0 < α < 0.5). The FTIR shows that the major spectral components produced during the pyrolysis of the XLPE insulation material are C-H stretching, H2O, CO2, C-H scissor vibrations, and C=O and C=C stretching. Additionally, the four functional groups in the PE chains produced the spectral components in the following decreasing order of wavenumber: C-H stretching > CO2 > C-H scissor vibration > C=O and C=C stretching.

Fire-Resistant Bio-based Polyurethane Foams Designed with Two By-Products Derived from Sugarcane Fermentation Process

There is a growing interest in replacing conventional fossil-based polymers and composites with waste-based materials and fillers for environmental sustainability. This study designed water-blown polyurethane rigid foams using two by-products from the Amyris fermentation process of producing β-farnesene. The distillation residue (FDR) served as the main polyol component in the foam’s formulation (PF), supplemented with 4.5% sugarcane bagasse ash (SCBA) as a fire-retardant filler (PFA). The study assessed the impact on foam properties. Based on the analysis of all compiled data (foam structure, mechanical, and thermal properties), it can be inferred that ash particles acted as nucleating points in the reaction media, leading to a reduction in foam density (from 134 to 105 kg/m3), cell size (from 496 to 480 nm), and thermal conductivity. The absence of chemical interaction between the ash filler and the polyurethane matrix indicates that the ash acts as a filler with a plasticizing effect, enhancing the polymer chain mobility. As a result, the glass transition temperature of the foam decreases (from 74 to 71.8 ºC), and the decomposition onset temperature is delayed. Although, the incorporation of 4.5% SCBA (grain size below 250 μm) was ineffective in the increment of the compressive strength, that small amount was enough to increase the foam’s specific strength from 1009 to 1149 m2/s2 suggesting that other factors (e.g. polyol feedstock, grain size, ash packing, etc.) are yet to be accounted. The flammability test results indicate that sugarcane bagasse ash improved the foam performance, reducing burning time from 251 to 90 s, time of extinguishment from 255 to 116 s, and burning length from 132 to 56.7 mm, meeting the fire protection standard UL 94, class HB. Despite the need for further improvement and detailed flammability evaluation, the results support the notion that polyurethane foams from renewable waste by-products offer a sustainable alternative to both edible and fossil-based sources. Additionally, sugarcane bagasse ash can be a suitable silica source for reinforcing composites with reduced flammability, potentially replacing harmful halogenated chemicals used for the same purpose.Graphical

Heat-Treated Aramid Pulp/Silica Aerogel Composites with Improved Thermal Stability and Thermal Insulation.

In this work, we prepared heat-treated aramid pulp/silica aerogel composites (AP/aerogels) and investigated in detail the feasibility of improving thermal stability and thermal insulation via tailored heat treatment. The microstructure and FTIR spectra reveal that AP/aerogels are formed by a physical combination of the silica aerogel matrix and aramid pulps. When the heat treatment temperature increases, the density slightly decreases and then increases to the maximum due to the significant volume shrinkage. The pyrolysis of aramid pulp and the collapse of silica skeletons occur during heat treatment; nevertheless, the typical structures of AP/aerogels do not change significantly. It is also found that both the hydrophobicity and the thermal insulation decrease with the increasing heat treatment temperature. We note that when the heat treatment is at 600 °C, the AP/aerogel still maintains a low density of 0.19 g/cm3 and a contact angle of 138.5°. The thermal conductivity is as low as 26.11 mW/m/K, measured using the transient hot wire method. Furthermore, the heat-treated AP/aerogels can avoid heat shock and possible thermal hazards during practical thermal insulation applications. The onset temperatures of the thermal decomposition of AP/aerogels increase from 298.8 °C for an untreated one to 414.7 °C for one treated at 600 °C, indicating that the thermal stability of AP/aerogels is improved significantly. This work provides a practical engineering approach to expand the thermal insulation applications of silica aerogel composites.

Hydrogen storage properties and reaction mechanism of the Mg-Li-Na-Al ternary hydride system

This research uses the ball milling technique to study the preparation of the MgH2-LiAlH4-NaAlH4 with a molar ratio of 4:1:1 ternary-hydride system. The hydrogen storage behavior and reaction mechanisms have been carefully explored. The result demonstrates a reduction in the onset decomposition temperature of the 4MgH2-LiAlH4-NaAlH4 ternary composite compared to the as-milled MgH2, LiAlH4, and NaAlH4 components. Four substantial dehydrogenation processes, corresponding to the decomposition of LiAlH4, NaAlH4, and MgH2 were detected in a system with a total hydrogen capacity of 8.4 wt%. The onset decomposition temperature of LiAlH4 in this system is around 110 °C, while NaAlH4-relevant decomposition began releasing hydrogen at 153 °C, approximately 52 °C lower than the as-milled NaAlH4. Meanwhile, the destabilized system modifies the reaction route of MgH2, where MgH2-relevant decomposition begins around 270 °C, 82 °C lower than the as-milled MgH2. The apparent activation energy, Ea, for the decomposition of MgH2 in the composite was lowered to 124 kJ/mol based on the Kissinger analysis. It is believed that the enhancement of the dehydrogenation properties was attributed to the formation of intermediate compounds, including Li-Mg, Mg-Al and Li-Al alloys, upon dehydrogenation, which improved the thermodynamics properties by altering the de/rehydrogenation pathway.

Effect of durian peel fiber on thermal, mechanical, and biodegradation characteristics of thermoplastic cassava starch composites

This study is focused on developing and enhancing the properties of durian peel fiber (DPF) reinforced thermoplastic cassava starch (TPCS) composites. The proposed DPF was extracted from agro-waste and incorporated into TPCS with various contents of DPF (10, 20, 30, 40, and 50 wt%) via compression molding. The mechanical and thermal characteristics of the fabricated composites were studied. The thermal properties of the biocomposite were improved with the addition of DPF, as evidenced by an increase in the material's thermal stability and indicated by a higher onset decomposition temperature. The integration of DPF into TPCS improved the biodegradation rate process of the composites. Besides, the results indicated that incorporating DPF in TPCS composites enhanced tensile and flexural properties, with a 40 wt% DPF content exhibited the highest modulus and strength. The tensile and flexural strengths of TPCS/DPF composites were raised significantly from 2.96 to 21.89 MPa and 2.5 to 35.0 MPa, respectively, compared to the control TPCS sample, as DPF increased from 0 to 40 wt%. This finding was consistent with Fourier-Transform Infrared (FT-IR) spectroscopy and scanning electron micrograph (SEM), which showed good interaction between DPF and TPCS matrix. The analysis revealed that DPF at a 40 wt% ratio was the best composition compared to the other ratio. Finally, based on improved results, DPF was identified as a potential resource of green reinforcement for the biodegradable TPCS matrix.

Introducing a new approach for designing advanced epoxy film adhesives with high mechanical, adhesion, and thermal properties by adding hybrid additives for structural bonding

BackgroundEpoxy-based adhesives are widely used in different industries in various forms. Among them, epoxy film adhesives are particularly applicable in constructing honeycomb structures in aerospace systems. However, these adhesives suffer from brittleness, low flexibility, and thermal stability. In the current paper, the effect of pure and functionalized SiO2 and ZrO2 nanoparticles (NPs), the addition of a block copolymer (butyl acrylate-block-styrene), and Novolac resin on the mechanical, thermal, and adhesive properties of the epoxy film adhesive were thoroughly studied. MethodsThe mechanical properties, thermal stability, and surface morphology of the epoxy adhesive samples were evaluated using tensile, thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FE-SEM) images, respectively. More importantly, the Lap shear and Peel tests were utilized to investigate the adhesive properties. Significant findingsPure and functionalized NPs were added to the prepared epoxy adhesive samples. Intriguingly, compared to the non-functionalized NPs, by only adding 1 phr of each functionalized NPs to the formulation, the tensile modulus, tensile strength, and toughness increased to 66 %, 197 %, and 553 %, respectively. More importantly, the single lab shear and T-peel strength were increased as high as 121 % and 101 %, respectively, indicating a synergistic effect. After optimizing the parameters effective on the properties, FE-SEM images of the fractured surface of optimized samples were used to study the possible fracture mechanisms, including crack deflection, crack pinning, nanoparticle debonding, and shear band formation. Also, this synergistic effect was observed in the thermal stability where the only addition of 1 phr of functionalized NPs increased the decomposition onset temperature up to 40 ℃ higher than the neat one. This simple and applicable method can pave the way for using functionalized NPs in modifying epoxy adhesives.

Novel Macromolecular and Biobased Flame Retardants Based on Cellulose Esters and Phosphorylated Sugar Alcohols.

The increasing demand to provide sustainably produced plastic materials requires, a.o., the development of biobased flame retardants (FRs) for applications where flame retardancy is essential. To meet those challenging new sustainability requirements, a set of novel phosphorus-containing cellulose esters were synthesized by an efficient two-step procedure. In the first step, cellulose was treated with acrylic anhydride to synthesize acrylate-functionalized cellulose esters-more specifically, cellulose acrylate butyrate (CeAcBu) and propionate (CeAcPr). Subsequently, phosphorylated anhydro erythritol (PAHE), synthesized from the sugar alcohol erythritol, was added to the acrylate-functionalized cellulose esters via Phospha-Michael addition. For comparison a cellulose ester based on 6H-Dibenzo[c,e][1,2]oxaphosphorin-6-on (DOPO) was prepared analogously. The acrylate-functionalized cellulose esters and novel FRs were characterized by NMR spectroscopy. TGA investigations of PAHE-functionalized CeAcBu revealed an onset temperature of decomposition (2% mass loss) of approx. 290 °C. The novel PAHE-based FR was incorporated into a polypropylene-polyethylene copolymer (PP-co-PE) together with poly-tert-butylphenol disulfide (PBDS) (8 wt.%/2 wt.%) as a synergist. The PP-PE samples achieved V2 classification in the UL 94 V test. In addition, specimens of a rapeseed oil-based polyamide containing PAHE-functionalized CeAcBu at 20 wt.% loading yielded a V2 rating with short burning times.

Thermal and thermomechanical properties of boron nitride-filled acrylonitrile butadiene styrene (ABS) composites

The present study aims at investigating the effect of hexagonal boron nitride (hBN) nanoplatelets on the properties of acrylonitrile butadiene styrene (ABS) polymer. Composites containing 0-30 vol% hBN were prepared through batchwise melt compounding, which was followed by compression molding. Subsequently, the thermal and thermomechanical properties of the fabricated samples were investigated. The dynamic mechanical analysis (DMA) revealed that the storage modulus of the samples was markedly improved in the entire examined temperature range, while the glass transition temperature also gradually increased as a function of hBN content. According to the thermogravimetric analysis (TGA), the incorporated boron nitride particles enhanced the thermal stability of ABS composites, exhibiting a notably higher decomposition onset temperature. Additionally, the thermal conductivity of the ABS/hBN composites significantly increased by 570% when the hBN content was 30 vol%.

A Novel UV Barrier Poly(lactic acid)/Poly(butylene succinate) Composite Biodegradable Film Enhanced by Cellulose Extracted from Coconut Shell.

Cellulose was extracted from coconut shell powder (CSP) as a renewable biomass resource and utilized as a reinforcing material in poly(lactic acid)/poly(butylene succinate) (PLA/PBS) solvent casting films. The extraction process involved delignification and mercerization of CSP. Microscopic investigation of the extracted microfibers demonstrated a reduction in diameter and a rougher surface characteristic compared to the raw CSP. The cellulose prepared in this study exhibited improved thermal stability and higher crystallinity (54.3%) compared to CSP. The morphology of the cycrofractured surface, thermal analysis, mechanical property, and UV transmittance of films were measured and compared. Agglomeration of 3 wt.% of cellulose was observed in PLA/PBS films. The presence of cellulose higher than 1 wt.% in the PLA/PBS decreased the onset decomposition temperature and maximum decomposition temperature of films. However, the films loading 3 wt.% of cellulose had a higher char formation (5.47%) compared to neat PLA/PBS films. The presence of cellulose promoted the formation of non-uniform crystals, while cellulose had a slightly negative impact on crystallinity due to the disruption of polymer chains at lower cellulose content (0.3, 0.5 wt.%). The mechanical strength of PLA/PBS films decreased as the cellulose content increased. Moreover, PLA/PBS film with 3 wt.% of cellulose appeared to show a 3% and 7.5% decrease in transmittance in UVC (275 nm) and UVA (335 nm) regions compared to neat PLA/PBS films while maintaining a certain transparency.

Effect of the Filler Modification on the Thermal and Mechanical Properties of Composite Polypropylene/Wollastonite Drawn Fibers.

Polypropylene (PP) is one of the most commercially used thermoplastics, while a significant amount of PP is used in the form of fibers. In this study, the effects of modification of the filler on the thermal and mechanical properties of composite polypropylene/wollastonite drawn fibers were investigated. In this direction, the surface modification of wollastonite with various organic acids, such as myristic, maleic, malonic glutaric, pimelic, and suberic acid, and the use of two solvents were studied. The surface-modified wollastonite particles were used to produce composite polypropylene drawn fibers. The modification efficiency was found to be slightly better when a non-polar solvent (carbon tetrachloride) was used instead of a polar one (ethanol). FTIR experiments showed that myristic, maleic, malonic, and pimelic acid can strongly interact with wollastonite's surface. However, the mechanical strength of the composite fibers was not increased compared to that of the neat PP fibers, suggesting inadequate interactions between PP and wollastonite particles. Furthermore, it was observed that the drawing process increased around 10% the crystallinity of all samples. Wollastonite modified with malonic acid acted as a nucleating agent for β-crystals. The onset decomposition temperature increased by 5-10 °C for all samples containing 2% wollastonite, either modified or not. The suggested modifications of wollastonite might be more suitable for less hydrophobic polymers.

Enhanced interfacial interaction, mechanical properties and thermal stability of basalt fiber/epoxy composites with multi-scale reinforcements

ABSTRACT In this work, epoxy (EP) resin composites with multi-scale reinforcements were prepared by hand lay-up and hot-pressing. The epoxy was reinforced with basalt fibers (BF) modified with a silane coupling agent (KH560). Carboxylated multi-walled carbon nanotubes (CNTs) were also grafted onto the surface of the modified BF using an impregnation method to achieve BF/CNTs multi-scale reinforcement. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) showed that KH560 was successfully grafted onto the BF surface. Scanning electron microscopy (SEM), indicated a better resin adhesion on the BF and thus a stronger interfacial interaction in the BF/CNTs-reinforced composite. It was observed that the mass fraction of KH560 was a significant parameter in achieving desirable CNT immobilization and mechanical properties of the composites. At an optimal mass fraction of KH560 (5%), the tensile, flexural, and interlaminar shear strength (ILSS) of the modified composite (BF-5%KH560-CNT/EP) increased by 12.5%, 20.9%, and 25.5% respectively compared with the BF-washed/EP composite due to more efficient load transfer. In addition, compared with BF-washed/EP, the decomposition onset temperature of BF-5%KH560-CNT/EP increased from 387°C to 396°C, the maximum decomposition rate temperature increased from 400°C to 408°C, and the residual weight increased by 5.8%.

Thermal Properties of Acetylated Betung Bamboo (Dendrocalamus asper) Pulp – Polypropylene Biocomposites

Thermal properties are important factors to determine the proper manufacturing, processing, and storing of biocomposites. Therefore, the thermal properties of the biocomposite made from acetylated betung bamboo pulp and polypropylene (PP) were investigated. The biocomposite was manufactured by hot pressing at 180 oC for 2 minutes and the fiber contents of the acetylated bamboo pulp used were 10 and 20% according to PP weight. The influence of acetylation and fiber content of bamboo pulp on the thermal properties of the biocomposite were investigated by using differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA). The results showed that acetylated bamboo pulp-PP biocomposite’s were higher than its pure and untreated biocomposites. The rate of crystallization growth of the acetylated bamboo pulp-PP biocomposites was faster up to 4.5 fold than pure PP composite. In addition, its acetylated bamboo pulp-PP had higher onset and maximum decomposition temperature than its untreated fiber-PP biocomposites but lower than PP. According to the results, the best thermal properties of biocomposite were obtained by acetylation of bamboo pulp with 10% fiber content.

Recycled polystyrene/polyvinylpyrrolidone/reduced graphene oxide nanocomposites for optoelectronic devices

Polymer nanocomposites based on recycled polystyrene (PS) and polyvinylpyrrolidone (PVP) with various reduced graphene oxide (rGO) loadings were prepared through a facile casting technique for enhancing the electrical conductivity of the insulator waste polystyrene to be applicable in electronic devices. The prepared nanocomposites were investigated by different techniques. FTIR analysis shows a reduction and shift of the main vibrational peaks of the blend, which confirms the introduction of (rGO) to the polymeric matrix, while XRD diffractograms provide complementary evidence for the transformation of graphene oxide into (rGO). The SEM image of the fractured edge of the sample points to a homogenous distribution of the PVP inside the major phase of the PS matrix. Moreover, the TEM image shows graphene oxide nanoparticles appearing in the form of dark lamellar structures with some light dots on a gray background, representing the polymeric domain. Besides, the TGA shows the existence of (rGO) led to some shifts in the PS and PVP onset decomposition temperatures when compared to the reference blend sample. Besides, the conductivity and dielectric properties of the prepared nanocomposites were characterized over a wide frequency range. Introducing (rGO) considerably enhanced their dielectric constant and ionic conductivity. The conductivity of these nanocomposites ranged from 10−11 to 10−6 S/m. The dielectric constant and dielectric loss of these composites were tested through frequencies, 0.1 Hz - 1 MHz, at 30 °C. The obtained values of the dielectric constant, loss tangent, and DC conductivity (σdc) suggested that the prepared nanocomposites could be used in various technological sectors such as energy storage, electronics, anti-static, and electro-static dissipation applications.

Thermal Transport and Physical Characteristics of Silver-Reinforced Biodegradable Nanolubricant

In this investigation, the thermal transport behavior of biodegradable lubricant reinforced with silver nanostructures (AgNs) at various filler fractions of 0.01, 0.05, 0.10, and 0.20 weight percent was evaluated over a temperature scan analysis, ranging from room temperature up to 60 °C. The experimental results revealed significant gradual enhancements in thermal conductivity as AgNs concentration and evaluating temperatures were increased. These improvements showed the important role of nanostructures’ interaction within the biodegradable lubricant. The thermal conductivity performance improved for nanolubricants ranging from 6.5% at 30 °C and 0.20 wt.% AgNs content up to a maximum 32.2%, which was obtained at 60 °C with 0.20 wt.% AgNs concentration. On the other hand, the thermal stability of reinforced lubricants was assessed through thermogravimetric kinetics analyses. The predictive curves resulting from the analyses indicated that there is an enhancement in both the onset temperature for decomposition and the percentage conversion under isothermal conditions for lubricants reinforced with AgNs. Specifically, the results show that the required temperature to achieve a 5% conversion is 100 °C higher than that calculated for bare lubricant. Moreover, the predictive analyses indicate that there is a delay in the decomposition time at isothermal conditions.