Thermal Oxidative Aging Research Articles

Hollow N doped carbon/SiCN hierarchical structures for thermostable electromagnetic absorptions

Electromagnetic absorption materials present widespread application prospects. The thermal oxidative aging issues for electromagnetic absorption materials have received little attention. In this paper, N-doped carbon tubes, and the SiCN ceramics are combined to realize thermostable electromagnetic absorptions. The hierarchical structures show significantly enhanced broadband electromagnetic absorption with an optimal RL of -53.61 dB at 14 GHz under a thickness of 2 mm. The effective electromagnetic absorption bandwidth reaches 5.53 GHz, and the coverage range is 11.88–17.41 GHz. More importantly, after 1 h calcination at 300 °C, the optimum RL of NCT/SiCN-1 h is still -45.67 dB under the thickness of 2.5 mm. The effective electromagnetic absorption bandwidth increases to 5.95 GHz, and the coverage range is 10.69–16.64 GHz. Our work proves the possibility for improving the thermostable electromagnetic absorptions of carbon materials, and provides referencing ways for the design of thermostable electromagnetic absorption materials.

Investigation on the Performances of Esterified Waste Cooking Oil Rejuvenator and Recycled Asphalt.

Waste cooking oil (WCO) recycled asphalt is facing issues regarding insufficient thermal oxidation stability and aging resistance. In this research, glycerol esterification was adopted to pretreat WCO, and the consequences of this treatment on the aging resistance and thermal stability of WCO were analyzed. The impacts of varying levels of esterification of WCO on the high-temperature, low-temperature performances, fatigue properties, and aging resistance of recycled asphalt were investigated. Furthermore, the mechanisms of regeneration and the anti-aging of deeply esterified WCO recycled asphalt were revealed by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) tests. The results indicated that variations in the physical properties of WCO during the aging process were reduced, and its aging resistance was improved following glycerol esterification therapy. The initial thermal decomposition temperature was increased by approximately 115 °C, which resulted in the enhancement of thermal stability significantly. Recycled asphalt obtained from deeply esterified WCO exhibited superior high-temperature, low-temperature performances, and fatigue properties. Moreover, the thermal oxidation stability and aging resistance of recycled asphalt with deep-esterified WCO could be promoted by reducing the oxidation and volatilization of light components during the aging process, with the complex modulus ageing resistance index decreasing by 13.27% and the phase angle ageing resistance index increasing by 14.71%.

Prediction of the residual lifetime of bitumen coatings on urban gas pipelines from the change in their mechanical characteristics during thermal-oxidative aging

Residual life of bitumen insulation is an important parameter of urban gas pipelines. Its fast and reliable estimation is necessary for timely health monitoring and coating restoration. In this study, we propose to define lifespan of bitumen insulation in situ from the mechanical characteristics measured during its thermal-oxidative aging. For evaluation of elastic and viscous properties, micro-impact dynamic indentation was applied. We determined the values of activation energy under thermal destruction and the dependence of transient electrical resistance on the critical values of coating's mechanical properties. Obtained experimental data foster real-time estimation of service time of insulation without coating removal.

Development of sustainable Lignin-Based coatings for layered double Hydroxides: Enhancing synergistic Anti-Aging properties in bitumen

Layered Double Hydroxides (LDHs) have poor dispersibility in bitumen and limited effectiveness in enhancing its thermal oxidative aging resistance. To address these issues, this study aims to purify lignin to improve its radical scavenging efficiency and use the purified lignin to coat LDHs (Φ@LDHs), thereby increasing their lipophilicity and radical scavenging efficiency for use in bitumen. sodium lignosulfonate (SL) was fractionated into five parts using a stepwise water/ethanol fractionation method, and these fractions were then applied to coat the LDHs to produce Φ@LDHs. The morphology, antioxidant activity, and chemical structure of Φ@LDHs were analyzed. Subsequently, the effect of Φ@LDHs on the aging properties of bitumen was evaluated. The test results indicated that SL and its fractions effectively coated the surfaces of LDHs, thereby enhancing their interlayer spacing and hydrophobicity. Among all fractions, lower molecular weight fractions, F4 and F5, retained most of the phenolic hydroxyl groups in SL, demonstrating significant antioxidant activities. The incorporation of F4@LDHs and F5@LDHs effectively mitigated changes in rheological properties of bitumen and oxidation product formation during thermal oxidation and UV aging, with F5@LDHs showing the best performance. Furthermore, a synergistic anti-aging mechanism was elucidated for the F4@LDHs and F5@LDHs composites. The purified F4 and F5 fractions not only improved the compatibility of LDHs with bitumen but also delayed the oxidative reactions initiated by free radicals to achieve a synergistic anti-aging effect.

Experimental and Statistical Modeling the Influence of Temperature Regimes of Asphalt Concrete Mix Production and Volumes of Supplied Protective Gases on the Process of Thermal Oxidative Aging

Experimental and Statistical Modeling the Influence of Temperature Regimes of Asphalt Concrete Mix Production and Volumes of Supplied Protective Gases on the Process of Thermal Oxidative Aging

Highly enhanced toughness and thermal oxygen aging resistance of PA 6 via novel designed macromolecular antioxidants

Polyamide 6 (PA6) is widely utilized, yet it confronts challenges such as susceptibility to thermal oxidative aging and high sensitivity to notch impact during usage. In addressing these issues, two novel toughening macromolecular antioxidants, 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid 2-acrylamidoethyl ester styrene copolymer (PAS) and 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid 2-acrylamidoethyl-N-phenylmaleimide copolymer (PAN), were synthesized via free radical copolymerization. Upon incorporation into PA6, their effects on PA6 performance were investigated. Relative to pure PA6, PA6/PAN and PA6/PAS exhibited significant improvements in fracture elongation, with increases of 136.91 % and 313.83 % respectively, along with notch impact strength enhancements of 18.55 % and 24.89 % respectively. This enhancement can be attributed to PAN and PAS reducing the hydrogen bond density between PA6 molecular chains. Subsequent long-term accelerated thermal aging tests conducted at 150 °C, as well as performance testing of samples before and after aging, revealed that the aging of PA6/PAN and PA6/PAS could be delayed by 4–12 days. The exceptional anti-thermal oxidative aging ability and toughening effect of these two macromolecular antioxidants in PA6 showcase promising prospects for its expanded applications.

The Influence of Oil and Thermal Aging on the Sealing Characteristics of NBR Seals.

Nitrile Butadiene Rubber (NBR) is widely used as a sealing material due to its excellent mechanical properties and good oil resistance. However, when using NBR material, the seal structure is unable to avoid the negative effects of rubber aging. Hence, the influence of oil and thermal aging on the characteristics of NBR seals was studied by coupling the mechanical behavioral changes with the tribological behavioral changes of NBR in oil and the thermal environment. For this paper, aging testing and compression testing of NBR were carried out. Additionally, friction testing between friction pairs under different aging times was carried out. The surface morphology of the NBR working surface under different aging conditions was also observed. Finally, coefficients of different test conditions were introduced into the finite element model of NBR seals. It can be seen from the results that the elastic modulus increased with the increase in aging time in the thermal oxidative aging testing. The elastic modulus after 7 days of thermal oxidative aging increased by 135.45% compared to the unaged case, and the elastic modulus after 7 days of oil aging increased by 15.03% compared to the unaged case. The compression set rate of NBR increased significantly with the increase in aging time and temperature. The coefficient of friction (COF) between friction pairs increased first and then decreased with the increase in aging time. The maximum contact pressure decreased by 2.43% between the shaft and sealing ring and decreased by 4.01% between the O-ring and groove. The proportion of the effective sealing area decreased by 3.05% between the shaft and sealing ring and decreased by 6.11% between the O-ring and groove. Furthermore, the sealing characteristics between the O-ring and groove were better than those between the shaft and sealing ring.

Characterization of temperature regulating, high-temperature rheological and anti-aging properties of asphalt mastic modified with SSPCMs

The objective of this study is to explore the potential of utilizing self-developed SSPCMs as additives for heat storage temperature regulation in asphalt mastic modification. To achieve this aim, a variety of asphalt mastics with different F-A volume ratios and SSPCM contents were formulated, and their high-temperature rheological properties, modification mechanisms, thermoregulation capabilities, and aging resistance performances were analyzed. The results of temperature regulation test indicated that the maximum cooling amplitude of asphalt mastic could reach 11.3°C, showing a great promising application for cooling asphalt pavements. Additionally, the incorporation of SSPCMs generally resulted in positive impacts on both the high-temperature rheological properties and temperature sensitivity of the asphalt mastics. Moreover, the aging indices GAI, ICO and ISO of the modified asphalt mastic with 30 % SSPCMs decreased by 5.6 %, 18.3 % and 8.7 %, respectively, compared with control asphalt mastic, implying that the incorporation of SSPCMs can retard the aging process of asphalt and enhance the thermal oxidative aging resistance of the asphalt mastics. In summary, the current study demonstrates the feasibility, improved performance, and effective thermoregulation properties of SSPCMs in asphalt mastics.

Investigation on rheological properties and aging mechanism of asphalt under multiple environmental conditions

Under climatic conditions such as high temperature plus ultraviolet radiation and water, the mechanical properties of asphalt pavement will be significantly attenuated. Present research mainly focused on thermal oxidation and ultraviolet radiation aging, and there were many controversies about the effect of water on the aging performance of asphalt. In addition, the relationship between the aging behavior of asphalt under complex environments and the standard PAV test needs to be further clarified. This research comprehensively evaluated the rheological properties, microscopy, and functional group of matrix asphalt, SBS, and high viscosity modified asphalt under different climatic conditions. Compared with thermal oxidation aging, daily exposure to UV radiation can increase the aging degree of matrix and modified asphalt by about 5 % and 1.5 %, respectively. Compared with thermal oxidation aging, the presence of water and the coupling effect of UV and water can reduce the aging degree of asphalt by 3.5 % and 2.6 %, respectively. After 5 days of thermal oxidation and UV coupling, the aging degree was close to or even greater than that of the PAV experiment. Asphalt aging caused an upward shift in the complex modulus master curve, and a downward shift in the phase angle master curve of matrix asphalt and high viscosity modified asphalt. Due to the synergistic effects of hardening and polymer degradation, the phase angle master curve of SBS modified asphalt showed an upward trend in the low frequency range. Under the influence of climatic conditions, the polymer of asphalt would degrade, the particle size of the polymer phase decreased, and the brightness of fluorescent image became darker. The rich polymer phase structure of high viscosity modified asphalt enabled it to maintain excellent mechanical properties even after long-term aging.

Effect of Phosphate-Bridged Monomer on Thermal Oxidative Behavior of Phthalonitrile Thermosets.

Phthalonitrile thermosets are known for their excellent mechanical, physico-chemical, and fire-retardant properties, making them attractive for aerospace and mechanical engineering applications. When producing and applying phthalonitrile-based structural parts, it is essential to consider aspects such as processability and the long-term stability of the material's properties at high temperatures. In our previous studies, we demonstrated that resins containing phosphate-bridged bisphthalonitrile monomers are easily processable due to their low melting temperature and wide processing window. In this study, we investigated the impact of bis(3-(3,4-dicyanophenoxy)phenyl)phenyl phosphate (PPhPN) monomer content on physico-chemical and mechanical properties, thermal stability, and thermal oxidative stability. This research highlights the importance of conducting long-term thermal oxidative aging studies in addition to thermogravimetric analysis to properly assess the stability of thermosets. The findings indicate that adding less than 15% of PPhPN results in the formation of a crystalline phase, which impairs the resin's processability. Conversely, a high PPhPN content reduces the material's thermal oxidative stability. Therefore, based on mechanical and physico-chemical tests after thermal oxidative aging, it can be concluded that a 10-15% concentration of the phosphate-containing monomer enables easy processability of the phthalonitrile resin and provides excellent long-term thermal oxidative stability at temperatures up to 300 °C, while maintaining a flexural strength exceeding 120 MPa and an elasticity modulus of 4.3 GPa.

Gaussian process regression driven rapid life-cycle based seismic fragility and risk assessment of laminated rubber bearings supported highway bridges subjected to multiple uncertainty sources

Structural attributes, corrosion of steel rebars in reinforced concrete (RC) columns, thermal oxidative aging of inherent rubber in laminated rubber bearings (LRBs), replacement of LRBs, and the time-dependent seismic hazard level at the bridge site are well recognized as the main factors that affect the accurate assessment of the seismic performance of RC bridges implemented with LRBs. However, the probabilistic seismic demand model (PSDM) and probabilistic structural capacity model (PSCM) of deteriorated bridge components may not exhibit homoscedastic log-linearity. And the expansion of seismic fragility surfaces and seismic risk curves in the temporal dimension requires a considerable computational cost on the nonlinear analysis, which regretfully has not been well addressed in current studies. To fill in this gap, this study proposes a life-cycle based seismic fragility and risk assessment framework for LRBs supported RC bridges considering deterioration mechanisms of bridge components during their life cycles demonstrated by a three-span LRBs supported highway bridge considering multiple uncertainties such as the replacement interval for LRBs. In this framework, Gaussian process regression (GPR) is employed to effectively construct the PSDM and PSCM of deteriorated bridge components, and then the time-dependent seismic fragility surfaces of bridge components and bridge system are established. Life-cycle based seismic risk analysis is conducted to quantify the coupled time-dependent effects of deterioration and site seismic hazard on a newly built bridge during its design service life and a deteriorated bridge within its remaining service life, respectively. Results indicate that GPR can successfully capture the nonlinearity and heteroscedasticity characteristics of PSDM and PSCM, leading to a significant reduced number of nonlinear analysis cases to generate the time-dependent seismic fragility surfaces and seismic risk curves. Consequently, the proposed framework using GPR can significantly improve the accuracy and efficiency of life-cycle based seismic performance assessment when uncertainties of structural attributes, deterioration progress and seismic hazard are taken into consideration.

Natural Rubber/Styrene-Butadiene Rubber Blend Composites Potentially Applied in Damping Bearings.

Natural rubber (NR) composites have been widely applied in damping products to reduce harmful vibrations, while rubber with only a single composition barely meets performance requirements. In this study, rubber blend composites including various ratios of NR and styrene butadiene rubber (SBR) were prepared via the conventional mechanical blending method. The effects of the rubber components on the compression set, compression fatigue temperature rising and the thermal oxidative aging properties of the NR/SBR blend composites were investigated. Meanwhile, the dynamic mechanical thermal analyzer and rubber processing analyzer were used to characterize the dynamic viscoelasticity of the NR/SBR blend composites. It was shown that, with the increase in the SBR ratio, the vulcanization rate of the composites increased significantly, while the compression fatigue temperature rising of the composites decreased gradually from 47 °C (0% SBR ratio) to 31 °C (50% SBR ratio). The compression set of the composites remained at ~33% when the SBR ratio was no more than 20%, and increased gradually when the SBR ratio was more than 20%.

The Impacts of Red Mud on Road Performance and Aging Resistance of Asphalt Mixture

Abstract Red mud as an asphalt modifier has been investigated in some studies, but few studies are further concerned about the effect of red mud on performance of asphalt mixture. In this study, the impact of red mud on road performance and aging endurance of asphalt mixtures was evaluated. Primarily, the optimal asphalt content was determined based on mechanical strength and volumetric properties. Then, the performance evaluations, including Marshall stability, low-temperature splitting, freeze-thaw splitting, indirect tensile fatigue, and thermal-oxidative aging, were executed. The outcomes demonstrate that in comparison with the base asphalt mixture, red mud asphalt mixture exhibits worse high-temperature stability and moisture resistance, and superior temperature shrinkage cracking resistance and fatigue performance. After the surface of red mud has been modified, the adhesion between asphalt mastics and aggregate is strengthened, and the distribution of red mud in asphalt mixture becomes more uniform, which intensifies the rigidity and road performance (except for low-temperature cracking resistance) of asphalt mixture. Furthermore, since red mud absorbs a portion of asphalt content, it can hinder the physical hardening and oxidation rate of asphalt mixture. The anti-aging ability of asphalt mixture is further reinforced by the incorporation of organic red mud.

Critical role of vacancy defects in graphene nanosheets for enhancing asphalt binder

Clarifying the interaction between the intrinsic structure of graphene and asphalt binder is critical to achieve the practical application of graphene modified asphalt. Herein, the thermal-mechanical properties and thermal-oxidative aging resistance of asphalts modified by two types of exfoliated graphene (EG) with less vacancy and vacancy-defected graphene (VDG) were investigated via multi-scale methods, aiming at elucidating the role of vacancy defects in graphene. Rheological measurements demonstrate that VDG have stronger capability of improving the deformation resistance and aging resistance of asphalt than EG. Atomic force microscopy analysis further verifies that VDG has a strong interaction with the non-polar components of asphalt, forming dense micellar structures. In addition, molecular dynamics simulations evidence that the vacancy defects in graphene can form the electrostatic adsorption between asphalt hydrocarbon molecules (light components), increasing the concentration and densification of asphaltenes, promoting the transformation of asphalt from sol structure to gel structure, thereby significantly improving the thermal-mechanical and anti-aging properties of asphalt binder. And the interaction is also verified by infrared spectral analysis and gaussian calculation through peak displacement. The discovery of the effect of vacancy defects in graphene for reinforced asphalt deepens the understanding for developing high performance graphene modified asphalts.

The evolution of structure and properties in high-tenacity poly(ethylene terephthalate) industrial fibers during thermal-oxidative aging process

The changes in performance of the high-tenacity poly(ethylene terephthalate) (HT PET) industrial fibers during the thermal-oxidative aging process have been investigated over a broad temperature range from 120 °C to 200 °C. Additionally, the mechanism of the thermal-oxidative aging process has been studied by utilizing structural information obtained from the fibers at varying length scales. It was observed that a significant increase in breakage elongation when the fibers were subjected to temperatures above 160 °C for more than 8 h during the aging process. Macro defects induced by thermal-oxidative aging began to appear after 96 h of exposure at temperatures exceeding 160 °C. Microscopically, the crystal structure of fibers remained stable and did not show significant changes unless the aging temperature exceeds 160 °C. When subjected to lower thermal aging temperatures or shorter aging times, the molecular chains in the amorphous region relax and become disoriented. This leads to a significant decrease in amorphous orientation, lamellar long period, and an increase in elongation at break. As the temperature and aging duration time continue to increase, thermo-degradation and recrystallization become more prominent. Consequently, the overall macromolecular orientation initially decreases due to degradation but later increases due to the formation of crystalline structures within the fibers. These findings indicate that molecular degradation in ester group is the primary factor contributing to the breakage elongation changes, while the formation of newly crystalline structures within the fibers contributes to the prevention of breakage strength to some extent.

RETRACTED: Screening of hindered phenol antioxidants by quantum chemical method for improving the aging properties of polyurethane railpad in railway

Polyurethane material has excellent performance and is widely used as railpad in railway, but it is prone to aging and fatigue during long-term service, resulting in a decrease in its performance. In order to improve the aging and fatigue resistance of polyurethane railpad, as well as the efficiency of screening antioxidant, this paper first used quantum chemical method to calculate three types of grafted hindered phenolic antioxidants. Then, polyurethane elastomer railpads with grafted preferred hindered phenolic antioxidants were prepared, and thermal oxidative aging experiments and thermo-oxygen-fatigue coupling aging experiments were conducted. The research results indicate that 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid molecules have better antioxidant properties. When the degradation rate is less than 20%, the activation energy of polyurethane railpads with grafted hindered phenolic antioxidants is about 20% higher than that of ungrafted materials. After 200 days of thermal oxidative aging, polyurethane railpads with grafted hindered phenolic antioxidants maintain high tensile strength and elongation at break, while maintaining stable static stiffness. Their carbonyl index and loss tangent increase only by 10% and 14.8%, respectively, while unmodified samples increase by 29.4% and 26.4%. Scanning electron microscopy also shows a significant reduction in surface cracks on polyurethane railpads grafted with hindered phenolic antioxidants.

Cost-effective enhancement of high viscosity modified bitumen anti-aging properties using organic layered double hydroxide/fume silica nanoparticles composite nanomaterials

High-viscosity modified bitumen (HVMB) is prone to thermal-oxidative and photooxidative aging, resulting in pavement diseases. The use of conventional Nano-modifiers to enhance the aging resistance of bitumen is often hindered by high costs, limiting their adoption in widespread applications. This study aims to evaluate the impact of a cost-effective Multi-Dimensional Nano-Composite (MDNC) modifier on the durability of HVMB, which includes organically modified Layered Double Hydroxides (OLDHs) and Fumed Silica Nanoparticles (FSNPs). Additionally, Zero-Dimensional Nanomaterials (ZDNs) such as FSNPs, Nano-SiO2, or Nano-TiO2, in combination with various MDNC modifiers consisting of OLDHs and ZDNs, were also utilized as comparative anti-aging modifiers for HVMB binders. FTIR, XRD, and contact angle tests indicate that LDHs modified with KH560 (OLDHs) exhibit improved hydrophobicity and increased interlayer distance. The temperature sweep test of the unaged binders and the FESEM test of the Nano-modifier indicate that the branched network structure of the FSNPs significantly enhances the high-temperature elasticity of the HVMB binders. Rheological test results have shown that both ZDNs and MDNC modifiers can delay the changes in rheological parameters after aging. Combining FTIR and SARA (Saturates, Aromatics, Resins, Asphaltenes) results, it was found that the combination of OLDHs/FSNPs synergistically inhibited the increase in the content of heavy components in bitumen during thermal oxygen and ultraviolet aging. The enhancement of the HVMB's thermal oxidation aging resistance by OLDHs/FSNPs composite modifiers is primarily due to the multidimensional structure of the composite nanomaterial, which effectively prevents the penetration of oxygen molecules. Meanwhile, the improvement in resistance to ultraviolet aging is mainly due to the absorption and scattering characteristics of FSNPs. Therefore, OLDHs/FSNPs are demonstrated to be a cost-effective multidimensional nano-modifier.

Potential of industrial symbiosis of petroleum residues and recycled polyethylene

In this work, a comparative study of the properties of polyethylene composites filled with the residue of solvent deasphalting of tar and asphaltenes isolated from it was carried out. Scanning electron microscopy analysis found that the compatibility of petroleum residue with the matrix was better than for asphaltenes. The observed effect was related to the present of petroleum resins, which have less polarity and long alkyl substituents that can improve molecular distribution asphaltenes in the nonpolar environment of polyethylene. Fourier transform infrared, thermo-gravimetric analysis, differential scanning calorimetry, and electron paramagnetic resonance methods have shown that asphaltenes play a key role in the thermal stabilization of composites. It is assumed that the radical traps in asphaltenes are free stable radicals, particles with unpaired electrons strongly delocalized on the π-system of polyaromatic molecules. Their antiradical action was associated to interactions with radicals formed during the thermal and thermo-oxidative decomposition of polyethylene result in the recombination and inhibition of further free-radical destruction. An analysis of the properties showed that the addition of a petroleum residue to the polyethylene makes it possible to maintain good mechanical properties after thermal-oxidative aging of composites. Thus, such asphaltene concentrates can be recommended as promising fillers for polyolefins in the polymer industry.

Exploring the structure, characteristics, and thermal degradation of composites comprising thermoplastic polyolefin and graphene oxide under high-temperature dynamic shear conditions

Dynamic high-temperature shear aging tests were conducted on thermoplastic polyolefin (TPO)/graphene oxide (GO) composite materials using a Hakke torque rheometer. The study employed ATR-FTIR, DSC, SEM, oxygen performance testing, and TGA to analyze the structure, properties, thermal degradation behavior, kinetics, and mechanisms of TPO/GO composites. The results demonstrated that the high-temperature dynamic shear thermal oxidative aging of TPO/GO composite materials establishes a dual protective mechanism, incorporating physical (intercalation oxygen resistance) and chemical (inorganic oxygen resistance) effects. This can be attributed to the polar surface and honeycomb structure of GO, as well as the shear-induced more uniform physical distribution of GO within TPO. Consequently, TPO/GO composite materials exhibit significantly enhanced resistance to dynamic shear thermal oxidative aging compared to TPO alone.

Improving Thermal-oxidative Aging Resistance of Styrene-butadiene Rubber by Antioxidant Loaded Silica Aerogel

Improving Thermal-oxidative Aging Resistance of Styrene-butadiene Rubber by Antioxidant Loaded Silica Aerogel