Thermo-oxidative Stability Research Articles

Taking advantage of the functional synergism between carbon nanotubes and graphene nanoplatelets to obtain polypropylene-based nanocomposites with enhanced oxidative resistance

Carbon Nanotubes (CNT) and Graphene Nanoplatelets (GNP) were incorporated in Polypropylene (PP) as single filler (CNT = 1, 2 and 4 %wt. and GNP = 2, 4, and 6 %wt.) and in hybrid form (CNT:GNP weight ratio 2:2, 2:4 and 4:2) using a prototype miniature Twin Screw Extruder (TSE) coupled with a double slit rheological die, in order to assess in-line the extent of nanofiller dispersion and to deliver PP-based nanocomposites with enhanced thermo-oxidative stability. The morphological, electrical and mechanical properties, as well as the resistance to thermal and photo degradation of the composites containing single nanofillers (PP/CNT and PP/GNP) were compared with those of hybrid PP based nanocomposites (PP/CNT:GNP). The results highlight that the presence of the two carbonaceous nanofillers exerts a positive synergic effect on the nanocomposite properties. Moreover, the radical scavenging role of the carbonaceous nanofillers was investigated under thermo-mechanical, thermo- and photo degradation conditions, the results confirming that aspect ratio, loading and dispersion level of the filler play a determinant role in the nanocomposite durability.

Development of organically modified montmorillonite/polypropylene composite powders for selective laser sintering

Organically modified montmorillonite/polypropylene (OMMT/PP) composite powders for selective laser sintering (SLS) were developed using four powder preparation methods including melt extrusion combined with cryogenic grinding, thermally induced phase separation (TIPS), surface coating, and mechanical mixing. Evaluations were conducted on the shape and size, powder-bed surface roughness, and thermal behavior of the developed composite powders as well as the mechanical properties of their injection-moulded tensile specimens. Melt extrusion proved to be the most favorable as the powders exhibited the highest thermo-oxidative stability (Td,max = 378 °C) and enhanced mechanical strength and ductility. TIPS could produce powders with reduced crystallization temperatures and increased melt enthalpies that were beneficial for SLS, and with powder morphology ideal for SLS without post-processing. It was found that at low loadings, nanofillers with sheet-like structures such as OMMT could limit the increase in crystallization temperatures of the composite powder, thus ensuring their wide sintering windows for SLS.

Meteoritic Nanodiamonds: Alternative Composition of Xenon Components

For the first time, abundances of the main xenon components (Xe-P3, Xe-P3(fr), Xe-P6 and Xe-pr instead Xe-HL) in the nanodiamonds of Orgueil (CI), Tieschitz (H3.6) and Indarch (EH3-4) meteorites have been calculated. The Xe-pr component is the excess fraction of xenon isotopes in the Xe-HL component relative to Xe-P3 (fr) and mainly consists of the 124, 126, 134, 136Хе isotopes formed in p- and r-processes of nucleosynthesis in a type II supernova explosion. Analysis of the data has shown the following. (1) The main nanodiamond component of Xe is Xe-P3 (fr), and its maximum during pyrolysis, like Xe-pr and Xe-P6, is high-temperature (>1000°C), irrespectively of the petrological type of meteorites. (2) The relative abundance of the Xe-pr component in the nanodiamonds of Indarch meteorite, which is most enriched in anomalous xenon components, is about 15% of the total xenon abundance in the diamond of this meteorite, which is significantly lower than the abundance of the Xe-HL component – about 87%. (3) The xenon components are contained in the individual populations of the diamond grains with different thermo-oxidative stability. The data we obtained and in (Huss, Lewis, 1994b) on the abundances and the yield kinetics of xenon components in meteoritic nanodiamonds, based on the Xe-pr and Xe-HL isotope compositions, respectively, most likely show their limiting values. Тhe real properties of xenon components are assumed to be similar to those obtained when using Xe-pr component for calculations, taking into account the data on the carbon isotope composition in the nanodiamond grains of the Allende meteorite (Lewis et al., 2019).

Inorganic Fibers for Composite Materials with Ceramic Matrix (Review)

Forms of inorganic fibers as reinforcing fillers for various types of composite materials are examined. Methods for the production of the fibers and their effect on the physicomechanical characteristics, phase composition, and the thermooxidative stability of the fibers are described. The prospects for the use of the fibers as reinforcing fillers for the composites are demonstrated. The work was realized within the scope of comprehensive scientific project 13.1 “Binders for polymeric and composite materials for constructional and specialized purposes.” (“Strategic directions in the development of materials and their processing technologies for the period up to 2030”) [1].

Degradation of beeswax by NOx pollution and UV light studied by DSC and FTIR measurements

This work is focused on the study of the effect of polluted atmosphere NOx and UV light irradiation on the thermooxidative stability of beeswax. Differential scanning calorimetry (DSC) and infrared spectroscopy (FTIR) were chosen to study the influence of ageing conditions. Thermooxidative stability of material was estimated by non-isothermal DSC measurements and changes in the chemical structure were investigated by FTIR analysis. It was found that both UV exposure and presence of NOx negatively impact beeswax stability. The kinetic analysis of DSC data revealed significant reduction in the length of oxidation induction periods. After five days’ storage in NOx-polluted air (2000 ppm, v/v) the predicted lifetime of beeswax at 23 °C was shortened by more than 60 %. Similar deteriorative effect on stability was observed after 50 h of continuous UV light exposure (4.5 mW/cm2). These results are consistent with that obtained from FTIR analysis where extinction of ester groups accompanied by increase in free fatty acids content was observed.

Classification of motor oils by parameters of thermo-oxidative stability

The results of research of thermal-oxidative stability of motor oils of different underlying fundamentals. Proposed indicators for classification of engine oils, including a potential resource, the temperature of the beginning of the transformation process and the critical temperature. Based on the studies, it is shown that the application of the proposed method for the classification of motor oils allows you to get additional information about their quality, including indicators such as: potential resource, the temperature at which transformations in oil begin and the critical working temperature.

Thermal-oxidative stability control of motor oils by thermal energy with cyclic temperature change

The results of the study of the thermo-oxidative stability of Castrol Magnatec R 10W-40 SL/CF partially synthetic engine oil with cyclic test temperature changes from 150 to 180 °C and from 180 to 150 °C taking into account the thermal energy absorbed by the products of oxidation and evaporation are presented. The graphical dependences of the decimal logarithm of the thermal energy absorbed by thermostatic products on the decimal logarithm of the test time are obtained, which are described by linear equations in the cycles of increasing and lowering the test temperature, which made it possible to determine the effect of time on the indicators of thermo-oxidative stability.

Metal-containing nanocomposites based on isotactic polypropylene

The effect of additives of metal-containing nanofillers, including zinc oxide nanoparticles, on the properties of nanocomposites based upon isotactic polypropylene (PP), using X-ray phase analysis (XPA) and thermogravitometric (TGA) analysis was studied.The improvement of the strength and rheological indexes, as well as the thermooxidative stability of the nanocomposites obtained was revealed.

Thermal and Thermo-Oxidation Stability of Plasticized Fiber-Filled Composite Materials Based on Polyphenylene Sulfone

The effect of plasticization on the thermal properties of carbon- and glass-filled composites based on polyphenylene sulfone was studied with the methods of thermogravimetric analysis and gas chromatography. A relationship is established between the composition of composites and the nature of fiber fillers, as well as the effect of the composition on the thermal and thermo-oxidative properties of materials.

Effect of Graphene Oxide Modified with Organic Amine on the Aging Resistance, Rolling Loss and Wet-skid Resistance of Solution Polymerized Styrene-Butadiene Rubber.

Graphene oxide (GO) was modified by p-phenylenediamine (PPD), aiming at improving the wet-skid resistance and reduce the rolling loss of solution polymerized styrene-butadiene rubber (SSBR). PPD with amino groups enabled GO to obtain anti-aging function. The structure of modified GO (PPD-GO) was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy. Mechanical tests showed that the mechanical properties of SSBR before and after aging were improved by adding PPD-GO. The results of thermogravimetric-differential scanning calorimeter synchronization analysis (TGA-DSC) indicated that SSBR/PPD-GO obtained good thermo-oxidative stability. The dynamic mechanical analysis (DMA) of SSBR composites showed that the mechanical loss factor (tanδ) peak moved to high temperature with the content of PPD-GO. The tanδ values of SSBR composites showed that it had a good effect on improving the wet-skid resistance and reducing the rolling loss of SSBR by adjusting the content of PPD-GO. In particular, with the addition of 4 phr GO, SSBR was effectively improved in mechanical properties, aging resistance, wet-skid resistance and low rolling loss.

Thermooxidative stability of hot melt adhesives based on metallocene polyolefins grafted with polar acrylic acid moieties

The present paper describes the thermal oxidation of a mixture applied as hot melt adhesive and particularly of its essential polymeric component ethylene-propylene copolymer Licocene 2602 either virgin or grafted by acrylic acid. Chemiluminescence in oxygen under both nonisothermal and isothermal conditions was used as the tool for evaluation of oxidation stability of samples. The effect of various concentrations of stabiliser Naugard XL1 acting as a metal deactivator and phenolic antioxidant was also determined and the antioxidant selected was found to be an efficient thermooxidative stabiliser. The results appear to be of importance for practical multiple application of hot melt adhesives to be used for binding books.

Effect of additives on the thermal and thermo-oxidative stability of poly(ethylene furanoate) biobased polyester

Polyesters based on 2,5-furan dicarboxylic acid are a new class of biobased polymers with properties superior of those of their fossil-based homologues. However, similarly to poly(ethylene terephthalate) (PET), poly(ethylene 2,5-furan dicarboxylate) (PEF) degrades during its thermal processing and as a result its molecular weight drops, and discoloration occurs. This is mainly attributed to thermal and thermo-oxidative degradation reactions. The addition of several types of thermal stabilizers during the synthesis or the processing of thermoplastic polyesters is a common practice. In this work, a commercial phenolic antioxidant (Irganox 1098), and two phosphorus-containing thermal stabilizers (phosphoric acid and triphenyl phosphate) were added in PEF polyester during synthesis with the use of antimony acetate catalyst. The effect of these additives on the molecular weight, thermal properties, thermal, thermo-oxidative stability and physical aging of PEF was evaluated. It was found that all additives slightly improved the thermal stability of PEF, with phosphoric acid and mainly triphenyl phosphate being the most efficient ones.

Thermal stability and flame retardance of EVA containing DNA-modified clays

In this paper, two natural clays (namely, Sodium Cloisite and Sepiolite) were modified with low MW DNA from herring sperm and compounded in EVA copolymer (19 % of vinyl acetate) at 10 wt.% loading, using an internal mixer. The effect of the presence of the biomacromolecule-modified fillers on the thermal properties and on the flame retardance of the resulting composites was thoroughly investigated. In particular, thermogravimetric analyses showed that the presence of the DNA-modified filler enhanced the thermal and thermo-oxidative stability of the polymer matrix. Despite a very limited effect on flammability, cone calorimetry tests revealed that the DNA-modified nanofillers were able to significantly decrease the heat release rate, the peak of heat release rate, the total smoke production, and the specific extinction area. Finally, the presence of the modified nanofillers was responsible for the increase of stiffness, as well as for a certain decrease of ductility of the polymer matrix, as assessed by tensile tests.

Flame-retardant and water-repellent coating on cotton fabric by titania–boron sol–gel method

This work aims to prepare a series of sols based on Titanium (IV) butoxide (TBT) and using boric acid as a functional additive. The sols were applied onto the cotton fabric by the pad-pry-cure process. The as-obtained cotton fabrics were characterized using Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analysis in order to determine their chemical composition and their surface morphology, respectively. The results indicate the formation of TiO2–boron-based coating over the surface of coated cotton fabric. X-ray diffraction (XRD) patterns showed that the coating did not affect the crystallographic structure of the cellulosic fabric. The functional properties of the treated samples were measured from thermo-oxidative stability and burning behavior performance, drop absorption and water uptake measurements. The results showed that the coated cotton fabrics by the sol–gel approach through the application of TiO2–boron-based coating with 2.5 molar ratio of boric acid possessed high thermal stability and flame retardancy. Most importantly, a total burning time of 2 s and a residue of more than 90% were obtained after 10 s of flame application, indicating that the functionalized cotton fabric self-extinguished the fire rapidly. The water-repellent properties were also enhanced and the obtained results mentioned that the drop time and the water uptake were improved compared with untreated cotton fabric. The effect of the application of TiO2–boron-based coatings on the mechanical properties of cotton samples, as well as their washing fastness were studied.

Time-Resolved Quantification of Phenolic Antioxidants and Oxidation Products in a Model Fuel by GC-EI-MS/MS

Phenol-type components, such as butylated hydroxytoluene (BHT), are used as antioxidants (AOs) to enhance the thermo-oxidative stability of kerosene-type Jet A-1 fuel. Although the antioxidative effect of BHT is well known and often published, there is far less information about the degradation products of BHT in fuels and their impact on stability toward oxidation. In order to monitor a time-resolved depletion of BHT in model kerosene, an artificial alteration method adapted for regular sampling was applied. Subsequently, the molecular structure of degradation products of BHT was identified by gas chromatography with electron impact ionization mass spectrometry (GC-EI-MS). For the quantification of the residual BHT as well as the two representatives of degradation products, namely, 3,5-di-tert-butyl-4-hydroxybenzaldehyde (HBA) and 2,6-di-tert-butyl-p-benzoquinone (BQ), an analytical technique comprising a GC-EI triple quadrupole mass spectrometer run in the MS/MS mode was developed. The limit of detection (LOD) and the limit of quantification (LOQ) for BHT, BQ, and HBA were determined below 1 ppb. The formation of BQ and HBA was observed shortly after the nascent degradation of BHT, while an increase of oxidation products derived from the fuel ascended remarkably after a full depletion of both the initial AO BHT and the monitored oxidation products BQ and HBA. As the evolution of BQ and HBA followed a characteristic trend, these compounds can be used as markers to reliably predict the residual time until a total consumption or a predefined threshold of BHT is reached. This way, the quality management of in-service or stored kerosene-type fuels is enhanced.

Preparation and Characterization of Alumina HDPE Composites.

In this study, effects of two different types of porous alumina nanoparticles have been incorporated into high-density polyethylene (HDPE) to study their impact on the properties of the HDPE composite. The dispersion of fillers in the HDPE matrix was evaluated by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) integrated with Fourier transform infrared spectroscopy (FTIR) were applied to investigate the calorimetric behavior and thermal stability and to analyze the polymer decomposition, respectively. The dielectric properties were determined by a broadband dielectric spectroscopy. The effect of filler loading on the tensile properties and melt flow index was also examined. A homogenous distribution of the fillers was observed at low loading of alumina particles (below 5 wt. %). However, agglomerates of sub-micro size were formed extensively on samples with high loading of fillers (above 7 wt. %). A significant improvement of the thermo-oxidation stability of the composite was observed. The permittivity values of the prepared composites also increased with the addition of the fillers. The incorporation of fillers also increased the electrical conductivity values of the prepared composites at high frequencies.

Thermo-oxidative stability and flammability properties of bamboo/kenaf/nanoclay/epoxy hybrid nanocomposites.

In this study, three types of nanoclay [halloysite nanotube (HNT), montmorillonite (MMT) and organically modified MMT (OMMT)] were incorporated into bamboo/kenaf (B/K) reinforced epoxy hybrid composites to compare their thermo-oxidative (TOD) stability and flammability properties. B/K (50 : 50) hybrid nanocomposites were fabricated by adding 1% loading (by weight) nanoclay through a hand lay-up technique. Wide angle X-ray scattering (WAXS) and field emission scanning electron microscopy (FESEM) were used to study the morphology of the nanoclay–epoxy mixture. The TOD stability of the hybrid nanocomposites was studied with a thermogravimetry analyzer (TGA) under oxygen atmosphere. The flammability properties were evaluated using the Underwriters Laboratories 94 horizontal burning test (UL-94HB), limiting oxygen index (LOI), cone calorimetry and smoke density test. The morphological study reveals that MMT/epoxy and HNT/epoxy are highly agglomerated while OMMT/epoxy reveals a more uniform distribution morphology. The obtained results reveal that B/K/HNT shows better TOD stability below 300 °C, but B/K/MMT and B/K/OMMT show high residue content and decomposition temperatures above 300 °C. The flame retardancy of the hybrid nanocomposites improved with the loading of all types of nanoclay, but B/K/OMMT shows higher flame retardancy than B/K/MMT and B/K/HNT hybrid nanocomposites. Hybrid nanocomposites show improvement in flame properties in terms of peak heat release rate (pHRR), total heat release, fire growth rate index (FIGRA) and maximum average rate of heat emission (MARHE) and smoke growth rate index (SMOGRA) indicators. The findings from this work can be utilized to prepare high-performance fire retardant natural fiber reinforced epoxy hybrid composites for automotive and construction applications to save human lives.

Sol–gel synthesis of large-sized polycrystalline stannous oxide and its oxidation behavior

The large-sized polycrystalline stannous oxide (SnO) synthesized by a sol–gel method was found to have attractive crystal structural properties and thermo-oxidative stability.

Использование деструктата макулатурного картона для повышения адгезионной прочности и термоокислительной стабильности резин на основе каучука скмс-30 аркм-15

Использование деструктата макулатурного картона для повышения адгезионной прочности и термоокислительной стабильности резин на основе каучука скмс-30 аркм-15

Свойства композитов на основе изотактического полипропилена и полиэтилена высокого давления с медьсодержащими нанонаполнителями

The effect of additives of nanofillers (NF) containing nanoparticles (NP) of copper oxide, stabilized by a polymer matrix of maleized polyethylene (MPE), obtained by the mechanochemical method, on the properties of composites based on isotactic polypropylene (PP) and high-pressure polyethylene (PE) was studied by X-ray phase (XRD) and thermogravimetric (TGA) analyzes. The enhancement of strength, deformation, and rheological parameters, as well as the thermo-oxidative stability of the obtained nanocomposites was revealed, which, apparently, is due to the synergistic effect of the interaction of copper-containing nanoparticles with anhydride groups of MPE. It is shown that nanocomposites based on PP/PE/NF can be processed both by pressing and injection molding and extrusion, which expands the scope of its application.