Aging Resistance Research Articles

Fabrication of Polycaprolactone-Based Polyurethanes with Enhanced Thermal Stability.

The benefit of being acquainted with thermal properties, especially the thermal stability of polyurethanes (PU), and simplified methods for their improvement is manifold. Considering this, the effect of embedding different amounts of unmodified and surface-modified TiO2 nanoparticles (NPs) within PU, based on polycaprolactone (PCL) and Boltorn® aliphatic hyperbranched polyester, on PU properties was investigated. Results obtained via scanning electron microscopy, swelling measurements, mechanical tests and thermogravimetric analysis revealed that TiO2 NPs can be primarily applied to improve the thermal performance of PU. Through surface modification of TiO2 NPs with an amphiphilic gallic acid ester containing a C12 long alkyl chain (lauryl gallate), the impact on thermal stability of PU was greater due to the better dispersion of modified TiO2 NPs in the PU matrix compared to the unmodified ones. Also, the distinct shape of DTG peaks of the composite prepared using modified TiO2 NPs indicates that applied nano-filler is mostly embedded in soft segments of PU, leading to the delay in thermal degradation of PCL, simultaneously improving the overall thermal stability of PU. In order to further explore the thermal degradation process of the prepared composites and prove the dominant role of incorporated TiO2 NPs in the course of thermal stability of PU, various iso-conversional model-free methods were applied. The evaluated apparent activation energy of the thermal degradation reaction at different conversions clearly confirmed the positive impact of TiO2 NPs on the thermal stability and aging resistance of PU.

The association of regional cerebral blood flow and glucose metabolism in normative ageing and insulin resistance

Rising rates of insulin resistance and an ageing population are set to exact an increasing toll on individuals and society. Here we examine the contribution of age and insulin resistance to the association of cerebral blood flow and glucose metabolism; both critical process in the supply of energy for the brain. Thirty-four younger (20–42 years) and 41 older (66–86 years) healthy adults underwent a simultaneous resting state MR/PET scan, including arterial spin labelling. Rates of cerebral blood flow and glucose metabolism were derived using a functional atlas of 100 brain regions. Older adults had lower cerebral blood flow than younger adults in 95 regions, reducing to 36 regions after controlling for cortical atrophy and blood pressure. Lower cerebral blood flow was also associated with worse working memory and slower reaction time in tasks requiring cognitive flexibility and response inhibition. Younger and older insulin sensitive adults showed small, negative correlations between relatively high rates of regional cerebral blood flow and glucose metabolism. This pattern was inverted in insulin resistant older adults, who showed hypoperfusion and hypometabolism across the cortex, and a positive correlation. In insulin resistant younger adults, the association showed inversion to positive correlations, although not to the extent seen in older adults. Our findings suggest that the normal course of ageing and insulin resistance alter the rates of and associations between cerebral blood flow and glucose metabolism. They underscore the criticality of insulin sensitivity to brain health across the adult lifespan.

Molecular dynamics study of cross‐linking degrees effect on the aging resistance of epoxy asphalt: Insights from oxygen diffusion

AbstractTo interpret the diffusion behavior of oxygen in epoxy asphalt with different cross‐linking degrees, epoxy asphalt‐oxygen diffusion layer models were constructed. The effect of temperature on oxygen diffusion and the number of oxygen molecules penetrating the epoxy asphalt was quantitatively analyzed. Fick's second law was used to determine the oxygen diffusion coefficient. The Mean square displacement (MSD) was extracted to analyze the effect of cross‐linking degree on the molecular motion of the base asphalt. The results show that as the cross‐linking degree increases, the number of oxygen in the epoxy asphalt decreases, accompanied by a reduction in the oxygen diffusion coefficient. Temperature significantly affects the rate of oxygen diffusion, with higher temperatures leading to greater diffusion depths over the same simulation time. The oxygen diffusion coefficient of epoxy asphalt ranges from 4.60 × 10−11 to 2.20 × 10−10 m2/s at temperatures of 298–373 K. The epoxy system markedly restricts the movement of base asphalt molecules, with saturate being most affected by cross‐linking degree and asphaltene the least. A high cross‐linking network impedes the asphalt‐oxygen contact oxidation, enhancing epoxy asphalt's anti‐aging capacity. These findings provide support for optimizing epoxy asphalt formulations and guiding the development of anti‐oxidant epoxy asphalt.

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.

Effects of polypropylene compositions and processing conditions on its aging resistance under tropical environments

This study investigates the weathering resistance of three polypropylene grades (impact-resistant, recycled and UV-stabilized) processed by Fused Filament Fabrication (FFF), injection and thermo-compression. Samples undergo accelerated aging, simulating conditions equivalent to six months in tropical environments with high hydrothermal and UV exposures. They are characterized by chemical, thermal, rheological, mechanical and microstructural analyses. 3D-printed impact-resistant and UV-stabilized PP resist to the considered aging conditions, attributed to the presence of stabilizers. On the contrary, the properties of recycled PP deteriorate over time due to low stabilizer concentration and the presence of impurities post-recycling. Samples processed by thermo-compression and injection display lower aging resistance compared to their 3D-printed counterparts, due to degradation and alteration in the crystalline structure induced by the processing method, like the ‘skin effect’ observed in injection. These findings highlight the importance of re-stabilization during recycling and the potential of 3D-printing for enhancing the aging resistance of polypropylene.

Enhancement of bitumen aging resistance by nanomicron porous eggshell loaded with waste engine oil prepared under mechanical force

Volatilization of lightweight components during long-term service is one of the main causes of bitumen aging. In this study, porous eggshell powder (EP) loaded with waste engine oil (LEPWEO) was prepared by the oil milling process, which released lightweight components during bitumen aging to improve bitumen aging resistance. The results showed that the pore volume of the EP was increased by 135.7 % after oil milling and waste engine oil (WEO) loaded in the pore was 16.41 wt%. Nano-pores and micron-pores were observed by transmission electron microscopy (TEM) and scanning electron microscope (SEM) tests, which were attributed to the crushing and compressive effects of mechanical force. Compared to unmodified bitumen, LEPWEO effectively retarded the aging of bitumen. And its carbonyl group, sulfoxide group, and microhardness change rates after long-term aging were reduced by 53.2 %, 90.0 % and 65.9 %, respectively. Moreover, LEPWEO had superior dispersibility and compatibility with bitumen. The contact angle of EP with bitumen was reduced from 30.4° to 12.7° after oil mill modification, which contributed to the uniform release of lightweight components. In this work, a porous biomass material with a lightweight composition is prepared by the oil milling process, which proposes a foundation for the application of retarded bitumen aging.

Laboratory performance and field demonstration of asphalt overlay with recycled rubber and tire fabric fiber

The escalating number of vehicles has precipitated a surge in tire production, resulting in an increased accumulation of waste materials such as ground tire rubber (GTR) and tire fabric fibers. Integrating recycled materials into asphalt pavement stands as a viable solution to mitigate the issue of waste accumulation. The objective of this study was to assess the durability and aging resistance of hot mix asphalt (HMA) enhanced with GTR and tire fabric fibers, in contrast to traditional HMA. A high-quality pavement incorporating GTR, and tire fibers was constructed in Michigan. Findings indicated that the inclusion of tire fabric fibers markedly bolstered the rutting and cracking resistance of HMA. Viscoelastic testing further confirmed the superior rutting and cracking resistance of the asphalts modified with GTR alone and in combination with tire fibers, relative to conventional asphalt. Additionally, field evaluations of noise levels showed a 2–3 dB decrease in noise with GTR-modified asphalt pavements, and after two years in service, the overlays modified with GTR and fibers exhibited no cracking. Ultimately, asphalt pavements modified with both rubber and tire fibers demonstrated enhanced performance over traditional pavements, offering a quieter and more durable roadway solution.

Polyaniline/hollow glass beads/carbon fiber powder composite film for multifunctional military tarpaulins

In this paper, a composite film with a thickness of 0.25 mm was prepared, which has the functions of infrared stealth, ultraviolet protection, sound absorption, and thermal insulation. Firstly, polyaniline was synthesized through chemical oxidative polymerization using aniline as a monomer, acetic acid as a dopant, and ammonium persulfate as an oxidant. Then, the synthesized polyaniline (PANI), hollow glass beads (HGB), and carbon fiber powder (CFP) were sequentially added to waterborne polyurethane, and a film coating machine was used to prepare a multifunctional composite film of PANI/HGB/CFP. Finally, the composite film's infrared properties, ultraviolet protection properties, sound absorption properties, thermal constants, resistance to water penetration properties, bending properties, tensile properties, chemical corrosion resistance, and aging resistance were tested. The results show that the prepared PANI/HGB/CFP composite film has an infrared emissivity of 0.668 and an ultraviolet protection factor (UPF) of 1072, indicating that it can block more than 99 % of ultraviolet rays. Additionally, it has an acoustic absorption coefficient of 0.386. At the same time, the thermal conductivity is 0.04629 W/mK, making it a highly efficient material for heat preservation and thermal insulation. The prepared PANI/HGB/CFP composite film is expected to be a new multifunctional military tarpaulin.

Synergy of devulcanized rubber and rock asphalt for asphalt modification

Rock asphalt (RA) has gradually been recognized as a green and efficient asphalt modifier. However, the weakness of low-temperature performance and fatigue resistance for RA modified asphalt limited its application and popularization in asphalt pavement. To overcome the above shortcomings, this study aimed to synergistically apply devulcanized rubber powder (DRP) with American rock asphalt (ARA) for asphalt modification. Multiple experiments such as dynamic shear rheology (DSR) and bending beam rheology (BBR) were conducted to evaluate the rheological properties and road performance of composite modified asphalt (CMA). Cigar tube test (CTT) was applied to assess storage stability of CMA. In addition, Fourier transform infrared spectrometer (FTIR) and microscopic test (MT) were used to investigate the modification mechanisms. The results showed that CMA modified by DRP and ARA exhibited comparable storage stability, low-temperature performance and rutting resistance as SBS modified asphalt. ARA tended to cause aging problems of asphalt, but the addition of DRP effectively improved the aging resistance performance of modified binder blends, especially long-term aging resistance. The mixing of DRP, ARA and base asphalt is a physical process without chemical reactions. Even though the ash in ARA slightly lowered its storage stability, it significantly improved dispersion and homogenous interface of DRP in asphalt.

Enhancing alkali resistance of recycled GFRP fibers and mechanical performances of cement mortars with microbial induced carbonate precipitation

Applying the recycled glass fiber reinforced plastic (rGFRP) fiber to reinforce cement-based materials is a promising way to reuse this massively waste material. However, rGFRP fiber is prone to be corroded in the alkali environment of cement. To solve this problem, the rGFRP fiber was treated with microbial induced CaCO3 precipitation (MICP) technique. The effects of MICP treatment on the rGFRP fiber and the reinforced mortar were investigated. It was revealed that the alkali resistance of the rGFRP fiber was significantly modified by CaCO3 deposition, which was increased with the concentration of mineralizing solution and treating time. The tensile strength and aging resistance of the rGFRP fiber reinforced mortar were all improved by MICP treatment, since fiber-cement friction, fiber-cement compatibility, microstructural compactness and cement hydration degree were enhanced by the properly precipitated CaCO3 crystals on fiber surface. However, excessive MICP treating process was detrimental for effective CaCO3 precipitation. The rGFRP fiber treated in the mineralizing solution of 1.0 mol/L for 3 times with 24 h/time (1−24−3) had the most promising modification effect on the rGFRP fiber and the reinforced mortar in this study. The 1–24–3 rGFRP fiber had similar alkali resistance to the alkali resistance glass fiber, which increased the tensile strength of mortar by 34.1 % and improved the bending strength of mortar by 10.8 % after accelerated aging. The MICP technique was used on modifying rGFRP fiber and the reinforced mortar for the first time, which would benefit the durability of rGFRP fiber and its wider application in cement-based materials, while the long-term performance of rGFRP fiber reinforced mortar should be studied in the future.

Effect of Salt Solution Environment on the Aging of Styrene-Butadiene-Styrene (SBS)-Modified Asphalt.

The aim of this paper is to investigate the aging mechanism of asphalt in the sea salt erosion environment from a rheological point of view. In order to simulate the real pavement aging process in the sea salt erosion environment, base asphalt and Styrene-Butadiene-Styrene (SBS)-modified asphalt were selected for salt environment aging tests. The asphalt samples were aged via a thin film oven test (TFOT) and a pressure aging vessel (PAV) test. Then, thermo-oxidizing conditions were created after the samples were immersed in salt solution, mixed with four different concentrations of sodium chloride (NaCl) and sodium sulphate (Na2SO4), to investigate the aging state of asphalt. Temperature scan (TS), frequency scan (FS), and multiple stress creep and recovery (MSCR) tests performed using a Dynamic Shear Rheometer (DSR) were used to investigate the effects on the rheological properties of aged asphalt in a salt environment. The results showed that both base asphalt and SBS-modified asphalt were aged to different degrees under mixed salt solutions. The two asphalt samples aged in a salt environment showed increased hardness. SBS-modified asphalt exhibited higher aging resistance compared with base asphalt in the sea salt environment. However, due to the degradation of the SBS modifier and the aging of base asphalt, the properties of the SBS-modified asphalt showed more obvious complexity with changes in salt solution concentrations.

Design of degradable hybrid dual-crosslinked polymer for high-efficiency profile control in high temperature reservoirs

Profile control and water plugging are key technologies to enhance oil and gas recovery. Traditional plugging materials, due to short gelation time, low mechanical strength, and difficulty in balancing plugging and protection, thus limiting application in high temperature reservoirs. Herein, a degradable hybrid dual-crosslinked polymer was prepared by employing a copolymerization - dual-grafting and physical adsorption design strategy. The dual-crosslinked process and reaction mechanism were analyzed using infrared spectroscopy and differential scanning calorimetry. The mechanical properties, water dilution resistance, aging stability and degradability of the dual cross-linked composite were also investigated. The solvation forces enable silica particles to exhibit excellent suspension stability in a PEG solvent. The temperature ranges from normal atmospheric temperature (20 °C) to reservoir temperature (140 °C), with the apparent viscosity falling within the range of 10–1200 mPa·s, meeting the requirements for mixing and injection. The combination of free radical copolymerization and click reaction is utilized to control the gelation time (2–10 h) in high temperature environment (140 °C), which is favorable for regulating the action position of the plugging agent in the reservoir. The cured material exhibits excellent mechanical strength owing to the presence of dual-crosslinking and inorganic hybridization, with a compressive strength of 0.221 MPa and a peak strain of 55.3 %. Furthermore, this composite material undergoes hydrolysis through an addition-elimination reaction, transitioning from a solid to a liquid state within 24 h, thereby aiding in the restoration of productivity in the temporarily shielded target layer. Compared to traditional materials, this dual-crosslinked composite system have the advantages of controllable gelation time, high mechanical strength, aging resistance, and degradability, making it suitable for profile control in high temperature reservoirs (140 ℃, 21.81×104 mg/L).

Evaluating Effectiveness of Multi-Component Waste Plastic Bags on Bitumen Properties: Physical, Rheological, and Aging.

This study examines the applicability of an unknown composition waste plastic bag sample as bitumen modifier. The waste components were initially characterized to identify the type of plastics and the level of impurity. Asphalt binder performance was examined for rutting, thermal, and age resistance. The results revealed that the waste plastic bags, predominantly consisted of Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE) and contained 6.1% impurities. The binder tests indicated that the waste plastic bags enhanced the rutting resistance of bitumen by one grade, with its modification more similar to LLDPE, rather than LDPE. The thermal degradation and aging properties of the modified binders demonstrated that the bitumen modified by the waste plastic bags exhibited slightly lower resistance to temperature and aging compared to virgin LDPE and LLDPE. This was attributed to the impurities contained in the waste plastic. In conclusion, the analyzed waste plastic bags proved to be suitable for use in binder modification, presenting a viable alternative to virgin LLDPE.

Synthesis and characterization of polyurethane-based self-luminous pavement coatings: a performance evaluation study

Improving the nighttime vision of drivers is essential, given the growing advancements in urban transportation. In this study, polyurethane-based self-luminous pavement coatings (PSCs) were prepared by doping luminous powders (LPs) into the polyurethane materials. The superior optical properties and chemical stabilities of these coatings were ensured by synthesizing the polyurethane-based material. Then, the PSCs were evaluated for their comprehensive performances, such as luminescence, aging resistance, and abrasion resistance, using various characterization methods, including fluorescence spectral analysis, Fourier-transform infrared spectroscopy, fluorescence microscopy, and mechanical property testing. The results show that the 50-mesh LP has the optimal overall performance, with an initial luminescence that exceeds those of the 100 and 400 meshes. The initial brightness of the PSC is mainly influenced by the LP and increases with dosage. The lattice structure and luminescent properties of the luminescent material did not change after coating preparation. The peak excitation wavelength of 420 nm implies that the coating has the best excitation effect under UV light. The primer-marking coating effectively improves the abrasion resistance of the PSC, and the mass loss of the PSC with a coating thickness of 0.4 kg/m2 is 52.9% of that without the primer-marking coating, with the optimal coating thickness being 0.6 kg/m2. This research provides an innovative solution to improve nighttime roadway lighting, which provides useful support for the sustainable development of urban transportation infrastructures and construction of intelligent transportation systems.

Preparation and properties of unsaturated zinc carboxylate/EPDM composites

ABSTRACT The unsaturated zinc carboxylate/Ethylene-Propylene-Diene Monomer (EPDM) composites were prepared by mechanical blending. The effects of hydroxy (2-methylprop-2-enoato-O)zinc (ZMMA) and zinc dimethacrylate (ZDMA) on the hydrophobicity, mechanical properties, ageing resistance, and electrical properties of the composites were studied. The results show that the mechanical properties, crosslinking rate, crosslinking density, and oil resistance of the composite are significantly improved with the increase of ZMMA and ZDMA content. The crosslinking density of EPDM filled with 15 phr of ZDMA composite material is 3.22 × 10−3 mol/cm3, compared with the samples without ZDMA filling, the improvement was 175.2%, and the tensile strength reaches 16.9 MPa, which increases by 33.6%. The addition of a small amount of unsaturated carboxylate has a positive effect on the electrical properties of EPDM matrix composites. The volume resistivity of the EPDM filled with 5 phr of ZDMA is 16.2 × 1013 Ω·m, an increase of 36.1%.

Durable and robust broadband radiative cooling coatings for multi-temperature scenarios

Passive daytime radiative cooling presents a promising avenue for revolutionizing cooling solutions by reflecting sunlight and radiative heat to outer space without consuming energy. Previous studies often focus on a single temperature scenario, neglecting the complexity of real-world applications in which the target object may have heat sources. Here, we have successfully prepared a Cooling Paint for Multi-Temperature Scenarios (CPMTS) by incorporating nanometer boron nitride into the photocured monomer Tricyclodecane Dimethanol Diacrylate (DCPDA). CPMTS exhibits excellent broadband thermal emittance (∼0.955), reflectance (∼0.778, from 300 nm to 2.5 μm), and thermal conductivity (∼0.51 W m−1 K−1). Notably, it achieves a maximum cooling of 20.1 °C and 8.8 °C under ∼790 W m−2 and ∼507 W m−2 of solar irradiation in the absence and presence of a 1 W heat source continuously heating, respectively. Continuous and significant radiative cooling performance has been observed on cloudy days or at night. CPMTS shows excellent radiative cooling performance in practical application scenarios. Excellent ageing resistance, adhesion, stability, and color matching ability make CPMTS expected large-scale application through spray or brush. This research provides a potential solution for cooling in real-world diverse temperature scenarios. The obtained radiative cooling coatings demonstrate scalability and durability in practical applications.

Use of expanded perlite as green filler for the preparation of EPDM‐perlite rubber composites with improved thermal stability and insulation properties

AbstractThe present study investigated the use of expanded perlite (e‐perlite) as a sustainable and cost‐effective filler for EPDM (ethylene propylene diene monomer) rubber composites. Various amounts of e‐perlite were incorporated into EPDM to assess its impact on the composite properties, such as curing characteristics, physical and mechanical properties, crosslink density, thermal conductivity, thermal stability, surface roughness, and contact angle. The composite with 15 phr of e‐perlite exhibited approximately 20% higher crosslink density and a 12% increase in hardness, while slight decreases were observed in elongation at break and tensile strength. The FE‐SEM (field emission‐scanning electron microscopy), atomic force microscopy, and contact angle analysis have been performed to investigate the surface morphology and the hydrophobicity. The thermal properties of the composites were assessed through thermogravimetric analysis, thermal aging tests, and thermal conductivity measurements. The results showed that e‐perlite significantly improved the aging resistance and the thermal stability. The composites with 15 phr e‐perlite exhibited a 21% reduction in thermal conductivity and enhanced thermal isolation properties compared to the EPDM composite without e‐perlite. This work demonstrated the potential utilization of e‐perlite in EPDM as a green sustainable filler to enhance the thermal insulation and the stability properties of the composites, which may have practical applications in automotive, aerospace, construction, and electronic industries.Highlights E‐perlite enhances the thermal insulation property of EPDM rubber composites. Higher e‐perlite content increases composite hardness and crosslink density. The thermal conductivity of EPDM is reduced by increasing e‐perlite content. EPDM/e‐perlite exhibits improved thermal stability and aging resistance. Potential uses in automotive, aerospace, construction, and defense industries.

Preparation of Al-doped mesoporous silica spheres (Al-MSSs) for the improvement of mechanical properties and aging resistance of dental resin composites

ObjectiveThe purpose of this study was to synthesize Al-doped mesoporous silica spheres (Al-MSSs) and evaluate the effect of them as functional fillers on the mechanical properties and aging resistance of dental resin composites. MethodsAl-MSSs were prepared by a two-step method. The effect of Al-MSSs on the performance of the composites was evaluated using neat resin matrix, commercial composites 3M Z350XT and samples containing mesoporous silica spheres (MSSs) and nonporous silica spheres (NSSs) as control. The neat resin matrix consisted of resin monomer (Bisphenol A glycerolate dimethacrylate/triethylene glycol dimethacrylate, 49.5/49.5, wt%) and photoinitiator (camphor quinone/Ethyl-4-dimethylaminobenzoate, 0.2/0.8, wt%). The mechanical properties (flexural strength, flexural modulus, compressive strength and microhardness) of them were evaluated by a universal testing machine and microhardness tester. The mechanical stabilities of the prepared composites in wet environment were evaluated by immersing them in deionized water at 37 °C. In addition, we evaluated the effect of Al-MSSs on other properties of the dental resin composites such as polymerization shrinkage, degree of conversion, curing depth, contact angle, water sorption and solubility according to ISO 4049: 2019. ResultsThe synthesized Al-MSSs possessed good dispersibility with an average particle size of about 505 ± 16 nm. The mechanical properties of resin composites gradually increased with the increase of the loading amounts of inorganic fillers. The reinforcing effect of Al-MSSs was similar to that of MSSs and better than that of the NSSs groups at the same filler loading. After aging in deionized water at 37 °C for 30 days, the mechanical properties of all resin composites decreased. However, the decrease percentage of the composites filled with Al-MSSs was significantly lower than the other groups, indicating that the stability of the dental composites in wet environments was significantly improved by the Al-MSSs fillers. Furthermore, Al-MSSs had no obvious influence on the biocompatibility and other properties of dental resins. SignificanceThe prepared Al-MSSs could effectively improve the mechanical properties and aging resistance without sacrificing other physic-chemical properties of dental resin composites.

Effects of Aging on Rheological Properties and Microstructural Evolution of SBS Modified Asphalt and Crumb Rubber Modified Asphalt Binders

Focusing on the comparison of aging resistance between styrene-butadiene-styrene (SBS) modified asphalt (SBSMA) and crumb rubber modified asphalt binders (CRMA), the influences of aging on rheological properties and microstructural characteristics of different modified asphalts were investigated in this work. Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests were carried out, and the variations in rheological properties for different modified asphalts after the rotating thin film oven test (RTFOT) were analyzed with the rutting factor aging index (RAI) and creep rate aging index (CAI). By using Fluorescence microscopy (FM) and Fourier transform infrared (FTIR) spectroscopy, the evolutions of microstructure and chemical composition for two modified asphalts were analyzed with carbonyl index growth rate (CIR) and sulfoxide index growth rate (SIR). Then, The relationships between CIR/SIR and RAI/CAI were established to show the correlation between the deterioration of macroscopic performance and the evolution of micro-structure. The results indicated that the aging degree of asphalt increases with elevated temperatures, leading to decreasing low-temperature performance while improving high-temperature performance. Nevertheless, SBSMA exhibited strong sensitivity to aging temperature. Under thermo-oxidative aging, the RAI and CAI of SBSMA were lower than those of CRMA, whereas the regularities of CIR and SIR were opposite, indicating that CRMA was superior to SBSMA in terms of anti-aging properties due to the rupture of the cross-linked network structure of SBSMA. However, CRMA experienced aging accompanied by full swelling, and thus, relatively minor performance declined. The CIR and SIR exhibited a better correlation with the RAI and CAI, illustrating that both CIR and SIR could characterize the aging degree of modified asphalts well.

Association of Vitamin D with Perfluorinated Alkyl Acids in Women with and without Non-Obese Polycystic Ovary Syndrome.

Perfluorinated alkyl acids (PFAAs) are persistent organic pollutants affected by BMI and ethnicity, with contradictory reports of association with vitamin D deficiency. Twenty-nine Caucasian women with non-obese polycystic ovary syndrome (PCOS) and age- and BMI-matched Caucasian control women (n = 30) were recruited. Paired serum samples were analyzed for PFAAs (n = 13) using high-performance liquid chromatography-tandem mass spectrometry. Tandem mass spectrometry determined levels of 25(OH)D3 and the active 1,25(OH)2D3. Women with and without PCOS did not differ in age, weight, insulin resistance, or systemic inflammation (C-reactive protein did not differ), but the free androgen index was increased. Four PFAAs were detected in all serum samples: perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorohexane sulfonic acid (PFHxS). Serum PFOS was higher in PCOS versus controls (geometric mean [GM] 3.9 vs. 3.1 ng/mL, p < 0.05). Linear regression modeling showed that elevated PFHxS had higher odds of a lower 25(OH)D3 (OR: 2.919, 95% CI 0.82-5.75, p = 0.04). Vitamin D did not differ between cohorts and did not correlate with any PFAAs, either alone or when the groups were combined. When vitamin D was stratified into sufficiency (>20 ng/mL) and deficiency (<20 ng/mL), no correlation with any PFAAs was seen. While the analyses and findings here are exploratory in light of relatively small recruitment numbers, when age, BMI, and insulin resistance are accounted for, the PFAAs do not appear to be related to 25(OH)D3 or the active 1,25(OH)2D3 in this Caucasian population, nor do they appear to be associated with vitamin D deficiency, suggesting that future studies must account for these factors in the analysis.