Aging Resistance Research Articles

Morphology Control of Electrospun Brominated Butyl Rubber Microfibrous Membrane.

Brominated butyl rubber (BIIR) is a derivative of butyl rubber, with the advantage of high physical strength, good vibration damping performance, low permeability, aging resistance, weather resistance, etc. However, it is hard to avoid BIIR fiber sticking together due to serious swelling or merging, resulting in few studies on BIIR electrospinning. In this work, brominated butyl rubber membrane (mat) with BIIR microfiber has been prepared by electrospinning. The spinnability of elastomer BIIR has been explored. The factors influencing the morphology of BIIR microfiber membranes have been studied, including solvent, electrospinning parameters, concentration, and the rheological property of electrospinning solution. The optimal parameters for electrospinning BIIR have been obtained. A BIIR membrane with the ideal microfiber morphology has been obtained, which can be peeled from aluminum foil on a collector easily without being broken. Anti-bacterial property, the electrical conductivity of these membranes, and the mechanical properties of these samples were studied. The optimized BIIR electrospinning solution is Bingham fluid. The results of these experiments show that a BIIR membrane can be used in the field of medical prevention, wearable electronics, electronic skin, and in other fields that require antibacterial functional polymer materials.

Molecular design and properties of a P‐N synergistic flame retardant epoxy resin curing agent

AbstractThe utilization of epoxy resin (EP) is widespread across various industries. Nevertheless, its combustibility restricts its broader utilization. Additive flame retardants have proven effective in enhancing EP flame retardancy in recent decades. However, poor weather and aging resistance have always been the defects of added flame retardants. A reactive flame retardant (VPD) was synthesized from 3, 5‐diamino‐1, 2, 4‐triazole and phenylphosphonic dichloride, and was used to prepare VPD/EP flame retardant epoxy thermosets. The mechanical properties of the VPD/EP flame retardant epoxy thermosets are lower than those of pure epoxy, because the distance between molecules of VPD is increased compared with that of DDM, the cross‐linking density of the polymer after curing is decreased, and the intermolecular force is reduced. The VPD/EP flame retardant epoxy thermosets have a 40% reduction in total heat release compared to pure EP, an increase in limiting oxygen index value from 24.7% (pure EP) to 29.4%, and a V‐1 rating in UL‐94 testing. The obtained EP has not only good flame retardancy but also better weather resistance and aging resistance than additive flame retardants.Highlights An intrinsic flame‐retardant P and N coacting EP was designed and synthesized. The intrinsic flame‐retardant EP has excellent weather and aging resistance. The presence of the P, the residual char generated by combustion is denser.

Bismaleimide resin co‐modified by allyl ether of resveratrol and allyl ether of eugenol‐grafted polysiloxane with enhanced toughness, heat resistance, and flame retardancy

AbstractModifying bismaleimide (BMI) resin to improve its toughness and flame retardancy without sacrificing the glass transition temperature (Tg) and thermal decomposition stability is still a challenge. In this study, we employed the allyl ether of resveratrol (AER) and eugenol allyl ether grafted polysiloxane (PMES‐Allyl) to co‐modify BMI resin. For the BMI/AER/PMES‐Allyl (BAPA) resin, the content of PMES‐Allyl was 15 wt%, and the molar ratio of maleimide and allyl groups was controlled as 1:0.8. Compared to commercial 2,2′‐diallyl bisphenol A modified BMI (BD) resin, the BAPA resin exhibited superior thermal properties after curing, due to the role of AER in improving the crosslinking density and chain rigidity of the network. The cured BAPA resin had a Tg more than 380°C, and its initial thermal decomposition temperature (Td5%) and char yield (Y800°C) reached 424.8°C and 46.4%, respectively. Meanwhile, PMES‐Allyl as a rubber phase could effectively improve the toughness of the cured resin. The impact strength of the cured BAPA resin was 15.2 kJ/m2. Moreover, the two modifiers both helped to improve the flame retardancy of the material. Compared with the cured BD resin, the cured BAPA resin showed a decrease of peak heat release rate (PHRR), total heat release (THR), and maximum average rate of heat emission (MARHE) by 25.5%, 35.5%, and 31.5%, respectively. Its total smoke production (TSP) was only 35.6% of that of the cured BD resin. In addition, the cured BAPA resin also displayed a lowered water absorption and improved thermal aging resistance. Therefore, it is suggested to be a promising and high‐performance thermosetting resin for cutting‐edge applications.

Novel two-step strategy for the construction of weathering-resistant hydrophobic wood to extend its service life

As a renewable biomaterial resource, the applicability of natural wood is limited by its poor weathering resistance. A properly designed multifunctional coating can enhance the weathering resistance of wood while maintaining its natural aesthetic texture. In this study, polydimethylsiloxane (PDMS), SiO2, and TiO2 were impregnated into a wood sample to fabricate coatings with UV-shielding, transparent, and hydrophobic properties. The water contact angle of the wood in three directions was investigated under different environmental conditions. Results suggested that the PDMS/SiO2/TiO2-wood (PSTW) exhibited excellent hydrophobicity under harsh environmental conditions, which includes sandpaper abrasion, ultrasonic treatment, corrosive solvent immersion, freeze–thaw cycles, and UV aging. Moreover, PSTW demonstrated outstanding repellency to the most common liquids (such as milk, juice, and tea) in daily life. The fabricated hydrophobic coatings improved the mechanical stability, anti-icing, chemical stability, antifouling, self-cleaning, and UV aging resistance of the wood. The proposed method is an effective strategy to enhance the utilization of wood in outdoor environments and extend its service life.

Multi-scale evaluation of sodium dodecyl sulfate intercalated LDHs on the ageing resistance of SBS modified bitumen

Sodium dodecyl sulfate (SDS) intercalated layered double hydroxides (LDHs) were prepared to enhance the ageing resistance of SBS modified bitumen (SMB). X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that SDS has been intercalated into the interlayers of LDHs. Compared to LDHs, the interaction between SDS intercalated LDHs (OLDHs) and SMB was obviously stronger, and OLDHs exhibited better dispersity and stability in SMB. After ageing, the viscoelastic properties of SMB were deteriorated. LDHs and OLDHs could obviously alleviate the deterioration of ageing on the properties of SMB, which could improve the ageing resistance of SMB, especially OLDHs. Additionally, the enhancement mechanisms of OLDHs and LDHs for the ageing resistance of SMB at the microscopic scale were investigated by molecular dynamics. The incorporation of LDHs could obstruct the invasion of oxygen into the interior of SMB and inhibit the diffusion rate of oxygen in SMB, which reduced the oxidation reaction probability of SMB during ageing, and eventually achieved the improvement on ageing resistance of SMB. The effectiveness of LDHs was further improved after SDS intercalated modification, that was, SDS intercalated modification was beneficial to enhance the ageing resistance of LDHs for SMB.

Aging and Fracture Resistance of Implant-Supported Molar Crowns with a CAD/CAM Resin Composite Veneer Structure.

Chipping of implant-supported molar crowns (iSCs) is a frequently reported complication. This study aimed to investigate the in-vitro aging and fracture resistance of iSCs with a CAD/CAM resin composite veneer structure fabricated with the Rapid Layer Technology (RLT) approach. Eight iSCs per group were fabricated by using two different CAD/CAM resin composites (Shofu Block HC: SH; Grandio blocs: GB) for veneer structures, and zirconia (ZrO2), polyetheretherketone (PEEK), and cobalt-chromium (CoCr; control) as framework materials. The surfaces to be bonded were sandblasted, cleaned in an ultrasonic bath, and a coupling agent was applied. A self-adhesive resin luting composite was used to adhesively lute the veneer structures to the frameworks. The crowns were semi-permanently cemented to the abutments. After storage in deionized water, iSCs were loaded in a chewing simulator (TCML, 10,000 thermal cycles 5 °C to 55 °C for 20 s, 1.2 million, loading force 50 N). Four ZrO2 and one CoCr crown did not survive the TCML. The fracture force was determined after 24 h storage in deionized water and yielded values of ≥974 N. Lowest fracture forces were yielded in the PEEK-SH group in comparison to CoCr or ZrO2 groups (p ≤ 0.031). For identical framework materials, no significant influence of the veneering material was observed. All PEEK-GB frameworks fractured, and chipping occurred for ZrO2-SH and all CoCr frameworks. PEEK-SH and ZrO2-GB presented both chipping and framework fractures. Within the limitations of this in-vitro study, the RLT with a CAD/CAM resin composite veneer structure might be a promising approach to veneer iSCs. Yet, the choice of the CAD/CAM resin composite and of the framework material determine the fracture resistance.

Research on the Preparation Process of SBS-Modified Asphalt Using Early Shearing Instead of High-Speed Shearing of Modifier

To investigate the effect of pre-shredding as a replacement for high-speed shearing in the preparation process of SBS-modified asphalt, the particle size and mixing time of pre-shredded SBS modifier were studied. Laser confocal microscopy was used to observe the morphological changes and dispersion state of the SBS modifier during the mixing process, and process parameters were determined through rheological performance tests. FTIR tests were conducted on the original asphalt and PAV-aged modified asphalt to assess the impact of the pre-shredding process on the chemical composition and aging resistance of the modified asphalt. The specific conclusions were as follows. During the preparation process of the SBS modifier using low-speed mixing, the morphological changes of the SBS modifier can be summarized as follows: It cycles through edge networking, mesh fiberization, and filamentous granulation, and eventually presents a granular atomization form after multiple cycles. It is recommended that the mixing time be maintained between 30 and 60 min, which results in the microstructure of the modified asphalt consisting of filamentous and point-like combinations. This asphalt exhibited excellent performance in high-temperature rut resistance, fatigue resistance, and low-temperature crack resistance. When the mixing time was too long, the SBS modifier formed small granules in an atomized state, which weakened the strength of the mesh structure and led to a decrease in overall performance. It is recommended that the SBS be shredded into particles sized between 18 and 30 mesh or 30 and 100 mesh. SBS-modified asphalt with SBS particles sized between 18 and 30 mesh exhibited greater hardness in the mesh structure, resulting in better high-temperature rut resistance. SBS-modified asphalt with SBS particles sized between 30 and 100 mesh had better extensibility in the mesh structure, leading to superior performance in medium-temperature fatigue resistance and low-temperature crack resistance. Compared to the conventional process, the pre-shredding process for preparing SBS-modified asphalt improved aging resistance by 10% to 13%. Additionally, SBS-modified asphalt prepared using the pre-shredding process saved 1 to 3 h of processing time compared to the traditional preparation method, reducing energy consumption. Furthermore, the asphalt produced through the new process exhibited better performance, reducing road wear and saving maintenance costs.

Luminescent properties of Eu (III) complexes with carboxylate ligands and their light conversion films

This study reports the synthesis and characterization of four europium (III) complexes with different carboxylate ligands, namely 2-pyridine-acrylic acid (H2-PA), 2-pyridine-carboxylic acid (HPic), benzoic acid (HBen), and cinnamic acid (HCin), as well as a binuclear europium-lanthanum complex with HCin as the only ligand. The obtained complexes and the light conversion films prepared from them were extensively characterized by various techniques, including elemental analysis, infrared spectroscopy (IR), X-ray single crystal diffraction, thermogravimetric analysis (TGA), and fluorescence spectroscopy. Efforts were made to systemically investigate the structural, coordination, photophysical, and thermal properties of the luminescent materials, and elucidate the correlations between the ligand triplet energy levels and the luminescent properties of the complexes. The results reveal that the introduction of LaIII cannot only enhance the luminescent intensity of the light conversion agent and corresponding film, but also have obvious effect on enhancing the ultraviolet aging resistance of the light conversion film. Moreover, the proper doping concentration (0.5%) of the EuIII complex La-Eu-Cin in film may better balance the properties and cost.

Enhancing the Mechanical Properties and Aging Resistance of 3D-Printed Polyurethane through Polydopamine and Graphene Coating.

Three-dimensional (3D) printing is a versatile manufacturing method widely used in various industries due to its design flexibility, rapid production, and mechanical strength. Polyurethane (PU) is a biopolymer frequently employed in 3D printing applications, but its susceptibility to UV degradation limits its durability. To address this issue, various additives, including graphene, have been explored to enhance PU properties. Graphene, a two-dimensional carbon material, possesses remarkable mechanical and electrical properties, but challenges arise in its dispersion within the polymer matrix. Surface modification techniques, like polydopamine (PDA) coating, have been introduced to improve graphene's compatibility with polymers. This study presents a method of 3D printing PU scaffolds coated with PDA and graphene for enhanced UV stability. The scaffolds were characterized through X-ray diffraction, Fourier-transform infrared spectroscopy, mechanical testing, scanning electron microscopy, and UV durability tests. Results showed successful PDA coating, graphene deposition, and improved mechanical properties. The PDA-graphene-modified scaffolds exhibited greater UV resistance over time, attributed to synergistic effects between PDA and graphene. These findings highlight the potential of combining PDA and graphene to enhance the stability and mechanical performance of 3D-printed PU scaffolds.

Water-based kaolin/polyacrylate cooling paint for exterior walls

Passive daytime radiative cooling (PDRC) coatings for building exteriors are important for building energy efficiency. The development of inexpensive and environmentally friendly radiative cooling (RC) coatings with high adhesion, waterproofing and UV-ageing resistance for building facades remains a highly challenging task. In this work, kaolin/polyacrylate (K/P) paints with excellent overall performance were prepared by spraying method using green waterborne acrylate as binder, cheap and easily available K as filler, and polymethylhydrosiloxane (PMHS) as hydrophobic modifier. The K/P coating has excellent optical properties with a solar reflectivity (SR) of 86.6% and an infrared thermal emissivity (ITE) of 96.8%. RC temperatures of 13.2 °C (under shielded condition) and 3.1 °C (under open condition) were achieved under direct outdoor daylight with an average irradiance of 778 W/m2. In addition, building energy simulations show that the K/P coating improves heating energy consumption while reducing building cooling energy consumption. However, for most cities in China, the energy savings of the K/P coating on annual building energy consumption is still as high as 6.6%. In particular, the K/P paint used as an exterior wall coating has high adhesion, excellent water resistance, and strong UV ageing resistance, and its optical properties (solar reflectance and infrared thermal emittance) remain unchanged after 10 accelerated ageing cycles. Therefore, the K/P coatings have excellent comprehensive performance and have a wide range of application prospects in the field of green and energy-saving buildings.

Performance of Oil-Absorbing organogel Polystyrene-Stearyl methacrylate as a fume suppressant of asphalt binder

Hazardous fumes can be generated during the high-temperature construction of asphalt pavement. Various fume suppressants have been developed, but many may compromise the performance of asphalt binder, which shortens the service life of asphalt pavement. This study aims to investigate the performance of a novel fume suppressant, namely oil-absorbing organogel polystyrene-stearyl methacrylate (P(S-SMA)), which can reduce the construction fumes of asphalt binder while maintaining good rheological performance. The results of the Fourier Transform Infrared Spectroscopy (FT-IR), Fluorescence Microscopy (FM) and asphalt fume mass tests showed that adding P(S-SMA) can improve the aging resistance of asphalt binder and reduce the particles (≥1 μm) and volatile organic compounds (VOCs) released up to 19.6 % and 30.4 % within 1 h, respectively. The rheological test results indicated that P(S-SMA) could effectively improve the viscoelastic properties, high-temperature performance and fatigue resistance of asphalt binder due to the combination of “supporting” and “hardening” effects after adding P(S-SMA). With 5% P(S-SMA) added, elastic and viscosity properties were increased by 90.6 % and 25.3 % and fatigue life was increased by 38.9 % and 26.4 % at the strain levels of 2.5% and 5%, respectively. This study proved the feasibility of using P(S-SMA) as a novel performance-enhancing fume suppressant of asphalt binder.

Achieving superior anti-corrosion properties of vinyl ester resin coatings via compositing with 3-methacryloxy propyl trimethoxysilane functionalized MXene nanosheets

Exposure of steel to harsh marine environment can cause serious corrosion, which significantly affects its durability. In this study, a novel two-dimensional MXene nanosheets were functionalized with 3-methacryloxy propyl trimethoxysilane (γ-MPS@MXene) followed by introducing into the vinyl ester resin (VER) through solution blending method to enhance the anti-corrosion properties of the coatings. The effects of γ-MPS@MXene incorporation on the mechanical properties, thermal stability, dynamic thermo-mechanical properties, UV aging resistance, anti-corrosion properties of the VER nanocomposites were systematically investigated. The optimum tensile strength, elastic modulus, hardness, thermal stability and UV aging resistance of γ-MPS@MXene VER nanocomposites can be achieved when composited with 0.08 wt% γ-MPS@MXene. The electrochemical impedance spectroscopy(EIS) results demonstrate the introduction of γ-MPS@MXene nanosheets into the VER enhanced the anti-corrosion properties of the composites coating remarkablely and the anti-corrosion mechanism was also revealed. The favourable interfacial interaction between γ-MPS@MXene and VER matrix through covalent cross-linking diminished interfacial defects of the composite coating and was also beneficial to enhancement of the compatibility, the well-dispersed γ-MPS@MXene in VER created a “labyrinth effect”, which prolonged the diffusion path of corrosive medium to the carbon steel substrate. This research provides a promising strategy for the fabrication of heavy anti-corrosion nanocomposite resin coatings, which can realize long-term corrosion protection of metal substrates.

Preparation of polyethylene glycol/polyacrylamide interpenetrating network hydrogel for simultaneously enhancing the fire protection and aging resistance of fireproof glass

AbstractTo enhance the flame retardancy and aging resistance of grouting fireproof glass, different molecular weights of polyethylene glycol (PEG) were mixed with acrylamide (AM) to construct interpenetrating network hydrogels, then the obtained hydrogels were mixed with flame retardants to prepare a series of transparent flame‐retarded hydrogels applied in the fireproof glass. The effects of PAM/PEG hydrogel with varying PEG molecular weight on the optical transparency, heat insulation and aging resistance of fireproof glass were investigated. Optical transparency analysis shows that the light transmittance of grouting fireproof glass decreases with the increase of PEG molecular weight in the PAM/PEG interpenetrating network. Fire tests show that PAM/PEG hydrogel significantly enhances the heat insulation and aging resistance of the grouting fireproof glass compared to the single PAM network hydrogel. The flame‐retarded and anti‐aging effects of PAM/PEG hydrogel in the fireproof glass varies with the PEG molecular weight, and the order is PAM/PEG2000 > PAM/PEG1500 > PAM/PEG1000 > PAM/PEG800. Accelerated aging test shows that PAM/PEG interpenetrating network hydrogel is less affected by aging conditions and exerts durable heat insulation and transmittance. Especially, the backside temperature of 3600 s and transmittance of PAM/PEG2000 system after 264 h aging test only changed 38.3°C and 1.3%, respectively, compared to the unaged PAM/PEG2000 system.

Independent of technology and generating curiosity – paper as an age-resistant data store medium

Abstract. Humankind is known to be curious and inquisitive. Even if the code were lost, future individuals would be eager to find out what kind of message a printed paper offers. This was already the case when hieroglyphs were deciphered. Printed paper does not need additional equipment to be recognized as a data carrier. Therefore, paper as an analogue data store medium provides an interesting redundancy to deliver important information to future generations. The presentation deals with topics of age resistance of paper and inks as well as recommendations of how to empower printed or written paper to be a long-term data store. Different ageing conditions, different inks, different printing processes, and different fibre sources reveal the opportunities and threats. Data obtained during a 2-year-long project together with BASE (Bundesamt für die Sicherheit der nuklearen Entsorgung – Federal Authority for the Safety of Nuclear Waste Management) on the long-term stability of paper (Langzeitbeständigkeit von Papier – Labest Papier) emphasize the feasibility (Arbeitsstandberichte AP1–AP3 (literature, typical damage, recommendations), unpublished data). The ageing mechanisms of paper are known, as are countermeasures. This leads to standards and recommendations for the use of paper for documents. ISO 9706 (1994) is the main proponent of the direction that longevity can be ensured solely via the composition of the paper and the initial situation at the beginning of ageing. DIN 6738 (2007), on the other hand, takes as its basis the approach of assessing the physical ageing of the paper based on artificial ageing and the strength losses observed in the process. Other standards vary the approaches somewhat or mix them in part, for which the lecture presents a comparison table. The usability of a document depends on two essential factors. Firstly, the residual strength after an ageing process must be high enough for the document to be usable. Secondly, the information written on it must still be legible or at least recognizable (ISO 11798, 2023). However, although certain fibre resources that are recommended by different standards dealing with the long-term storage of documents as well as some fibre sources are denied, we must consider that all fibre sources undergo an ageing process. Different combinations of fibre and ink will lead to different results after natural or artificial ageing. This does not necessarily mean that only the best combination is able to fulfil the requirements related to transport information to an address in the far future. Albeit less strong or with higher optical changes, even by current standards, a rejected fibre source may nevertheless be able to keep the printed information over a long period of time. Paper has been a proven reliable information carrier for approx. 1000 years as the oldest known paper document archived in Palermo is from 1109 CE. It is reasonable to expect a reliability for many more years because the “Ebers” papyrus (worldwide longest, complete, and best-preserved papyrus scroll) stored at the University of Leipzig is already 3500 years old. Compared to modern information storage media such as digital media or microfilm, paper also has the advantage of a long migration time and that no reading or decoding device is necessary. Taking this into account, paper documents are predestined to play a major role in record, knowledge, and memory (RK&M) strategies, as described by Pescatore and Palm (2023). Finally, it remains to say that there can never be an intactness in the sense of being completely untouched. Paper, however, is a material consisting of natural polymers that prove their longevity in the world's oldest tree, a 9500-year-old spruce in Sweden.

Effect of uniaxial stretching on gas separation performance of polyimide membranes

Fine-tuning of the physical stacking structure for microporous polyimide (PI) membranes via the stretching processing is a practical way of achieving advanced membrane materials with improved aging resistance as well as high gas separation performance. Here, a fluorinated polyimide 6FDA:BPDA-TFDB(1:1:2) is used as a prototype and a series of stretched membranes X%-PI are fabricated by uniaxially stretching the membrane to different elongation ratio and then annealing. Based on birefringence and wide-angle X-ray diffraction measurements, it's found that regular orientation of polymer chains along the stretching direction and fine-tuning of d-spaces from interchain packing and π-π stacking happen during the uniaxial stretching process. As such, compared to pristine PI membrane, the stretched membranes show better mechanical and thermal stability, especially for the one with higher stretching ratio. In addition, owing to the increased packing density of polymer chains, the highly stretched membrane of 40%-PI shows significantly improved gas perm-selectivity by 32.8%, 24.3%, and 12.6% for He/CH4, H2/CH4, and CO2/CH4 gas pairs, respectively, in comparison to pristine membrane. Furthermore, 40%-PI exhibits much higher gas permeability retention rate than that of other membranes after three months' aging. We expect that this work can offer polymer materials processing guidance for the preparation of high-performance gas separation membrane in future.

A coupled analysis on human thermal comfort and the indoor non-uniform thermal environment through human exergy and CFD model

The importance of human thermal comfort evaluation lies of the development of healthy buildings as well as low-carbon buildings. In recent years, the applications of the second law of thermodynamics to thermal comfort offered a new perspective and this study, for the first time, an integrated human exergy model and the indoor CFD model for a coupled analysis is put forward, which supplements a critical link between human and building environment. In this paper, a predefined office model is investigated to improve the efficiency and thermal comfort of occupants. Based on the human exergy model, the parameters of metabolism, respiration, evaporation, convection, radiation, skin, and core heat storage terms are optimized. Additionally, the effects of gender, age, and clothing thermal resistance on the exergy model values are also separately explored. Finally, the optimized human exergy model is combined with computational fluid dynamics (CFD) to calculate, under different air supply conditions, the distribution of exergy consumption values in the predefined room model. The results show that the factors of gender, age, and thermal resistance of clothing have some influences on human exergy consumption, while the above factors do not have a significant enough influence on the model in the thermal comfort interval. Moreover, the combination of the human exergy model and CFD can offer some suitable air supply conditions for the development of indoor thermal comfort and work efficiency. This study presented a new tool that bridges human thermal sensation and indoor thermal environment.

Sustainable Utilization of Recycled Waste in High-Viscosity Asphalt Binders: Case for Improvement in Aging Resistance

Sustainable Utilization of Recycled Waste in High-Viscosity Asphalt Binders: Case for Improvement in Aging Resistance

Aging Resistance of Bitumen Modifiers: A Comprehensive Review

Abstract The deterioration of physical and mechanical properties of bituminous materials that are attributable to the aging of bitumen is one of the major causes of reduction in service life of flexible pavements. Thermal-oxidation and photo-oxidation aging are the two major types of aging of bitumen. Heat and oxygen cause thermal-oxidative aging, whereas ultraviolet irradiation and oxygen causes ultraviolet photo-oxidative aging of bitumen. Aging of binder leads to significant changes in the chemical composition of bitumen resulting in reduction of cracking resistance of bituminous mixes because of hardening of bitumen. So, it is quintessential to reduce the rate of hardening of bitumen induced by aging for prevention of premature failure of flexible pavements. The type of bitumen used for production of bituminous mixes have a significant effect on aging resistance of bitumen. The bitumen can be modified by using different types of modifiers such as antioxidants, bio-oils, nanomaterials, polymers, rubber, and ultraviolet absorbers. In addition to this, the modifiers such as fillers, warm mix additives, and rejuvenators also affect the aging resistance of bitumen. However, the effectiveness of these modifiers in preventing the hardening of bitumen because of aging varies with type of aging. The modifiers that exhibit improvement in thermal-oxidative aging resistance of bitumen are found to be less effective in improvement in photo-oxidative aging resistance and vice-versa. So, it is imperative to understand the effectiveness of different types of bitumen modifiers for the prevention of thermal-oxidative and photo-oxidative aging of bitumen. This review documents the resistance of different types of modifiers to thermal-oxidative and photo-oxidative aging. Finally, the scope for future work based on the critical gaps identified from existing works is also provided to assist further research.

Study on UV aging characteristics of low-grade asphalt in the desert climate

The Taklamakan Desert in China’s Xinjiang region faces severe heat conditions that cause rutting in asphalt pavements. In order to combat this issue, local construction management has been advocating for the utilization of low-grade asphalt with penetration levels between 20 and 50, to enhance the pavement’s resistance to rutting. However, there is limited research on the durability of low-grade asphalt under intense UV irradiation in the region. To this end, a multiscale investigation was conducted, examining three different types of asphalt (30#, 50#, and 70#), under various conditions such as virgin, UV aging, and Pressure Aging Vessel aging. Analytical techniques such as Atomic Force Microscope, Gel Permeation Chromatography, Fourier Transform Infrared Spectroscopy, Dynamic Shear Rheology, and Bending Beam Rheometer were employed. The results revealed that the surface roughness of the three types of asphalt increased by 15.50% (30#), 5.99% (50#), and 2.70% (70#) after UV aging, compared to the virgin samples. Furthermore, the adhesion properties of lower-grade asphalt were less affected by UV aging. Weight-average molecular weight of the three types of asphalt increased significantly after UV aging, with a 26.96% increase in 30#, 51.92% increase in 50#, and 43.76% increase in 70# compared to the samples prior to UV aging. The 30# asphalt with higher large molecule content exhibited slower UV aging. The 30# asphalt also exhibited the smallest increase of C=O and S=O after UV aging among the three types of asphalt. The study also found that UV aging had a lesser effect on the high- and low-temperature performance of asphalt, compared to PAV aging. Overall, the effects of UV irradiation on various properties of 30# asphalt were less pronounced than those of 50# and 70# asphalt. These findings offer valuable insights into aging resistance in the Taklamakan Desert, benefiting road contractors and the academic community.

Study on preparation process and seawater corrosion resisting properties of chopped CF/PEEK composites

CF/PEEK composite material is widely used in marine engineering construction due to its characteristics of lightweight, high strength, corrosion resistance, and aging resistance, and it will inevitably produce side materials and wastes in the forming process. Therefore, the research on CF/PEEK recycling is of great significance. Due to the characteristics of PEEK’s high melting point and high viscosity of the solution, it is difficult to recycle and reuse such materials. In this paper, a certain amount of PEEK resin powder is added to improve the hot pressing technology of the chopped prepreg. Through a simulated seawater corrosion experiment, the influence of simulated seawater corrosion on the microstructure and mechanical properties of the composite materials is studied. Combined with the principal component analysis method, the corrosion resistance of the chopped CF /PEEK composite was evaluated comprehensively, which provided a reference for the recycling of thermoplastic prepreg and thermoplastic composite products. The results show that the surface quality and mechanical properties of the composites with resin powder are obviously improved. The resin matrix on the surface of the sample was subjected to salt corrosion by chloride ions in a simulated seawater solution to form local corrosion, resulting in pores, cracks, and other defects. The longer the corrosion time of simulated seawater is, the more serious the surface damage of the composite material is, and the more obviously the mechanical property declines. Principal component analysis showed that the resin content had little effect on the seawater corrosion resistance of chopped CF/PEEK composite.