Accelerated Aging Procedures Research Articles

Development of an accelerated ageing protocol for the study of phytocannabinoid stability in Cannabis sativa L.

Cannabis sativa L. is a plant belonging to the Cannabaceae family known primarily for its recreational use due to the psychoactive properties of Δ9-tetrahydrocannabinol (THC). Despite this, several compounds belonging to the category of phytocannabinoids have shown in recent years a number of potentially promising therapeutic effects that have increased the interest in the pharmaceutical field towards this plant. However, the content of these compounds is very variable and influenced by different factors, such as growing conditions and time of the year. An indication of the status and age of Cannabis samples is provided by the content of CBN, a minor phytocannabinoid and degradation product of other phytocannabinoids, including THC. In this research work an innovative, solid state analytical approach has been developed to observe and evaluate the variations in the content of two phytocannabinoids (CBN and CBD) in Cannabis-derived products over time. In order to simulate the ageing of the Cannabis samples, an artificially accelerated ageing procedure has been developed and optimised by using high temperatures. The analyses were carried out using an innovative ATR-FTIR method for solid state analysis, enabling direct analysis of a solid sample without any pretreatment phase. This study has allowed the development of an innovative analytical approach for the evaluation of the age and state of conservation of Cannabis samples and may be a useful tool both in the industrial, pharmaceutical and forensic fields.

Study of liquid photopolymer 3D printing resins exposed to accelerated aging for cultural heritage purposes

PurposeThis paper aims to study the suitability of a selection of 3D printing liquid photopolymer resins for their application in the cultural heritage context.Design/methodology/approachThe main concerns regarding the conservation and restoration of cultural assets are the chemical composition and long-term behavior of the new materials that will be in contact with the original object. Because of this, four different LED curing resins were exposed to an accelerated aging procedure and tested to identify the materials which demonstrated a better result. Some specific properties of the material (color, glossiness, pH and volatile organic compound emissions) were measured before and after the exposure.FindingsSome of the properties measured reported good results demonstrating a decent stability against the selected aging conditions. The main changes were produced in the colorimetric aspect, probably indicating other chemical reactions in the material. Likewise, a case study could be also executed to demonstrate the usefulness of these materials in the cultural field.Research limitations/implicationsIt is necessary to study in more detail the long-lasting behavior of the materials employed with these technologies. Further analysis should be carried out highlighting the chemical composition and degradation process of the materials proposed.Originality/valueThis paper contributes to the introduction of curing 3D printing resins in the restoration methodologies of cultural assets. For this, the study of a selection of properties represents the first stage to suggest or reject their use.

Accelerated aging procedure of epoxy structural adhesive for marine offshore applications

Knowledge of the long-term performance of adhesive connections is undoubtedly of paramount importance to enable their deployment in civil, mechanical, and other engineering applications. Over time, adverse environmental conditions can strongly influence the performance of adhesive joints leading to a progressive deterioration of their initial mechanical properties. The use of adhesive connections for secondary structures in offshore applications is a technology that allows for the rapid creation of structural members that, however, cannot ignore the influence of hydrothermal effects on mechanical performance due to environmental conditions. In this context, the investigation of the hygrothermal durability of adhesive connections was undertaken through an extensive experimental programme. More specifically, 130 cylindrical steel joints bonded with a commercially epoxy resin for structural applications were tested in Mode I using an Arcan-modified device. Prior to test, the specimens were placed in climatic ovens capable of combining the effects of temperature and humidity for approximately 320 days. In addition, the glass transition temperature, Tg, was assessed by employing the differential scanning calorimeter (DSC) technique to correctly define the experimental ageing conditions. The experimental results show how ageing conditions influence the mechanical properties of the epoxy resin investigated. Finally, some predictive formulations are proposed to calculate the loss of strength of adhesive joints over time.

On the Occurrence of Filiform Corrosion on Organic-Coated Carbon Steel Exposed to Cyclic Aging Test

Filiform corrosion (FFC) is one of the possible failure mechanisms of organic-coated steel. Beyond cathodic delamination, FFC causes paint detachment and the dramatic loss of the protective properties given by the applied paint. As both failure mechanisms occur during in-field exposure (depending on the environment), when assessing the performance of the protective paint by lab scale tests, we must be aware of the failure mechanism we induce with different accelerated aging cabinets. In this study, we investigate the effect of the prohesion test on the initiation and propagation of FFC. We highlight the concurrent development of FFC and cathodic blistering, which includes the change between the cathodic and anodic delamination front, during an accelerated aging procedure that cycles between saturated humidity and dry stages. The role of the presence of aggressive contaminants (Cl− and ) is discussed. According to our findings, cyclic aging tests seem to better stick to the failure mechanism occurring during in-field exposure, particularly due to the wet/dry cycles.

Development of Isotopic Reference Materials for <sup>13</sup>C-Urea Breath Tests

Over 30 standards and certified measurement techniques are currently used in Russia to determine carbon, oxygen, and hydrogen isotope ratios. The techniques implemented in these documents are based on foreign reference materials (RMs). Similar domestically-produced RMs are not available, which makes the use of these techniques limited in the near future. This study aims to develop a certified RM (CRM) for the isotopic composition of carbon dioxide for 13C-urea breath tests. The following objectives were formulated: to develop a technique for obtaining RMs; to manufacture an RM pilot batch; to carry out type approval tests. The RM was manufactured by gravimetric mixing of carbon dioxide of two different isotopic composition from different sources with synthetic air. The mixing ratio was calculated using a specially developed technique. The RM stability was tested by an accelerated aging procedure. Following type approval tests, the developed CRM was included in the Federal Information Fund for Ensuring the Uniformity of Measurements under the registration number GSO 11999–2022. The practical significance of the obtained results is related to the possibility of using the developed CRM for improving the accuracy and validity of 13C-urea breath tests. Compared to the analogs, the developed CRM demonstrates a higher chemical purity.

Use of Dregs as a Replacement for Hydrated Lime in Cement Coating Mortar

The pulp and paper industry generates a significant volume of solid waste during its operations. In order to mitigate the environmental impact caused by this industry, one of its residues was applied in eco-friendly composites. Therefore, this research aims to use green liquor dregs as a partial replacement for lime in coating mortars. Hydrated lime was replaced by dregs in percentages of 10%, 15%, 20%, and 30%, and the manufactured mortar specimens were tested in terms of their flowability, air content, and specific gravity in the fresh state. In the hardened state, physical and chemical characterization was carried out to determine the influence of the introduction of the dregs on the properties of the different types of mortar. Mechanical testing of the mortar specimens’ compressive, flexural, and adhesive strengths was carried out, and scanning electron microscopy was performed to evaluate the microstructural features of the cement composites. In general, the types of mortar with dregs showed a high degree of similarity to conventional mortar in all studied aspects, including the 30% replacement group. The obtained SEM images indicated that the presence of dregs in the mortar did not change the formational mechanism of C-S-H crystals, maintaining the mechanical properties of the material even after the accelerated aging procedure was performed, reaching similar levels of flexural, compressive, and tensile bond strengths when compared to the neat mortar. Furthermore, tensile bond levels reached approximately 0.9 MPa for all the studied types of mortar, allowing the material to be used in external applications.

Accelerated Aging Procedure and Online Method for Stator Insulation Monitoring of Induction Motors

Online methods for stator insulation monitoring have been investigated with increasing interest in the last 15 years. These methods rely on the high-frequency behavior of the electric machine. In converter-fed machines, the high-frequency behavior is visible through the current ringings occurring during the switching commutations of the power electronics. As the lifetime of electric machines can last several decades, a faster way to evaluate insulation monitoring methods is through accelerated aging tests. This work aims to perform an accelerated aging procedure on an induction motor to test an online insulation monitoring method. The motor has a randomly-wound stator winding and it is aged by means of thermal cycles without the need for an oven. A custom converter is employed during the accelerated aging procedure to apply the thermal cycles and to record the current ringings. The proposed insulation monitoring method is based on a metric that quantifies the current ringing variations in a simple manner, following the quasi-linear variation of the parasitic capacitances during the motor aging.

Impact of Laboratory Long-Term Aging Procedures on Intermediate-Temperature Behavior of Asphalt Binders in Asphalt Fine Aggregate Matrix Mixtures

The durability of asphalt mixtures and flexible pavements are closely related to the properties of the asphalt fine aggregate matrix (FAM) with aging. However, there are still no uniform aging procedures specified for laboratory-prepared FAM. In this study, the intermediate-temperature behavior of FAM under various accelerated aging procedures was investigated at the binder scale to reveal the influence of the FAM aging. Three different long-term aging procedures were considered, including loose mixes aging (95°C and 135°C) and pressure aging vessel (PAV) protocols. Frequency sweep test and linear amplitude sweep (LAS) test were carried out on binders extracted from aged FAMs. Rheological tests were also performed on corresponding binders with standard PAV procedure to show the impact of FAM during the aging process. Moreover, an aging kinetics model was put forward to qualify the linear rheological property evolutions for fast and constant aging reaction stages under various aging conditions. The results show that 135°C loose FAM mixes aging significantly reduces the fatigue performance of styrene-butadiene-styrene (SBS) modified binder, and employing 95°C loose mixes aging and PAV aging procedures can avoid this adverse effect. Moreover, to match the aging degree of asphalt and FAM, an aging duration more than 40 h is recommended.

Colorimetric evaluation of 3D printing polymers exposed to accelerated aging for Cultural Heritage applications

Abstract3D printing has become a widespread technology that allows the creation of physical objects from different materials. The conservation and restoration of Cultural Heritage field has recently introduced this technology as a complement to its traditional methods. However, the main concern in the application of 3D printing in this context is the long‐term behavior of the materials used. The key objective of this research was the identification of the suitability of 3D printing filaments for conservation purposes. The methodology followed in this study consisted of a selection of 13 3D printing filaments for Fused Deposition Modeling (FDM) technologies, which were tested and exposed to an accelerated aging procedure. In order to classify and recommend the materials that present better results, the properties of color, the glossiness, the pH and the Volatile Organic Compounds emission were investigated. This paper collects the results of the analyses carried out, focusing discussion on the colorimetric behavior. The results demonstrate the usefulness of some of the materials studied, highlighting the performance of EP as one of the most stable and reliable materials while Flex is one of the most changeable ones in the Cultural Heritage context. Even though this research provides an overview of the aging of the materials studied, further analyses should be performed to understand the chemical composition and its behavior when exposed to a long‐lasting aging process.

Advanced UV-fluorescence image analysis for early detection of PV-power degradation

Reliability and durability of photovoltaic modules are a key factor for the development of emerging PV markets worldwide. Reliability is directly dependent on the chemical and physical stability of the polymeric encapsulation materials. One method capable of detecting ageing effects of the polymeric encapsulant directly on-site is UltraViolet Fluorescence (UVF) imaging. This work deals with advanced imaging analysis of UVF images and the subsequent correlation to electrical parameters of PV modules, which were exposed to climate-specific, long-term, accelerated aging procedures. For establishing a correlation, a so called UVF area ratio was established, resulting from the typical fluorescence patterns of the encapsulant material, which arise due to stress impact (e.g., water vapor ingress, elevated temperature, irradiation) and aging/degradation processes. Results of the data analysis show a clear correlation of the UVF area ratios and the electrical parameters with increasing aging time. In particular, the relationship between power and series resistance could be confirmed by extensive long-term test series with different climate-specific aging processes. Assuming the same type of polymeric encapsulation and backsheet and a comparable climate, determining the UVF area ratio can be used to estimate the service life and electrical power dissipation of each module installed in a PV array.

In vitro evaluation of the color stability and surface roughness of a new composite flow.

The aim of this study was to evaluate the color stability and the surface roughness of a bulk-fill composite flow (SDR® Plus) by comparison to an ORMOCER-based composite (Ceram.x® Universal SphereTEC™) in order to confirm the validity of using SDR® Plus in the anterior region and to allow the prediction of its long-term results. 35 composite specimens of the same shade (A2), thickness (2mm) and shape of both types of composite were prepared. The specimens were cured and polished according to the manufacturer's instructions. The initial shade of the specimens was measured using a calibrated EasyShade spectrophotometer. The initial surface roughness of the specimens was measured by AFM. Afterwards, the specimens were subjected to an accelerated aging procedure through thermo-cycling, a coffee stain challenge and brushing to simulate two years in the oral environment. The shade and surface roughness of the specimens were measured again after the accelerated aging procedure. The mean ΔE was significantly larger than 3.368 in Ceram.x® group (-p-value<0.001) and SDR® Plus group (-p-value<0.001). The mean surface roughness has significantly increased for both groups after aging with no significant difference between the two groups. It however remained clinically acceptable. SDR® Plus and Ceram.x® showed similar surface roughness when subjected to the same testing conditions. Concerning the color stability, both composites displayed noticeable discoloration, with higher ΔE values registered for Ceram.x®. Key words:Composite resins, spectrophotometry, atomic force microscopy, dental material, resin-based material.

Evaluating the color stability of two esthetic ceramic materials after different surface treatments and accelerated aging procedures

Aim: Observing and evaluating the long/short-term discoloration tendency of the esthetic prosthetic materials of lithium disilicate-based glass-ceramics (IPS e.max CAD LT) and leucite-based feldspathic glass-ceramics (VITA Mark II) materials, which are esthetically very close to each other at first glance.&#x0D; Methodology: 80 samples of A2 colored lithium disilicate and feldspathic blocks samples were overglazed and polished separately to evaluate the surface treatment procedures according to CIELAB color coordinates. For accelerated aging purposes, half of the examples were treated to red wine, and the other half were treated to coffee. Color changes were calculated using the ΔE formula. The results were put into record as ΔE-1, ΔE-2, and ΔE-3. Records of the results were evaluated using IBM SPSS Statistics Standard Concurrent User V 25 statistics package program. Data distribution regarding numerical variety and changes were evaluated using the Shapiro Wilk normality test and Q-Q graphics. &#x0D; Results: The data was evaluated using O'Brien clinical color tolerance scales. None of the samples has shown a perfect (ΔE=0-0.5) color match after 4 weeks of accelerated aging. Every group has shown results of significant statistical changes at various rates and percentages and divided into 4 subgroups as excellent, good, clinically acceptable and incompatible categories.&#x0D; Conclusion: Since aging procedures affect ceramic systems' ΔE values in a variety of ways, the aging protocol utilizing in vitro aging techniques for color changing should be evaluated alongside ceramic type and surface finishing procedures.

Durability of a Soya‐Derived Flexible PU Foam for Mattresses: Effects of Different Artificial Aging

AbstractThe aim of this work is to investigate the durability on long timescales of an innovative sustainable soy‐derived PU flexible foam used for mattresses fabrication. The foam samples have been submitted to two different accelerated aging procedures, by exposure in an environmental chamber at controlled temperature, humidity, and UV radiation, and by performing cyclic fatigue loadings in a mattress aging station. The effects of the changes on structural properties and foam comfort levels (i.e., hysteresis loss, surface firmness, and resistance to bottoming out) have been evaluated after both artificial weathering experiments. The results show that the different weathering factors reduce the foam comfort factors in static conditions, causing a progressive softening of the aged samples accompanied by a decrease of their ability to distribute body weight. Oxidation phenomena due to UV weathering mainly affects the chemical structure of the polyurethane foam, giving a yellowing of the material, whereas the fatigue cycles determine a partial disruption of the cellular structure, with the formation of very large pores.

Influence of Accelerated Aging on the Wear Behavior of Cross-Linked Polyethylene Liners-A Hip Simulator Study.

Sequential cross-linked and annealed ultra-high-molecular-weight polyethylene (SX-PE) is known as a low-wear articulating partner, especially for total hip endoprostheses. Aging of polymeric materials, irrespective of if induced by shelf or in vivo life, can degrade their tribological and mechanical properties. However, changes in wear behavior of aged SX-PE liners have not been not quantified so far. An accelerated aging procedure, to simulate shelf and in vivo aging, was performed on thin SX-PE liners after five million load cycles using a simulator (“worn-aged”) as well as on new SX-PE liners (“new-aged”). A subsequent hip simulator test was performed with both thin SX-PE liner sets in combination with large-diameter ceramic femoral head, representing a combination known as advantageous for treatment after revision because of dislocation. Oxidation indices were measured on the liners after each step of the procedure. SX-PE liners after accelerated aging show bedding-in phases during simulator test, which was a characteristic only known from clinical investigations. Hence, the wear rates of the “new-aged” ((1.71 ± 0.49) mg/million cycles) and of the “worn-aged” ((9.32 ± 0.09) mg/million cycles) SX-PE were increased in the first period compared to new unaged SX-PE liners. Subsequently, the wear rates decreased for “new-aged” and “worn-aged” inserts to (0.44 ± 0.48) mg/million cycles and (2.72 ± 0.05) mg/million cycles, respectively. In conclusion, the results show promising effects of accelerated aging on SX-PE liners in simulator testing and for potential long-term use in clinical applications.

Corrosion monitoring by open circuit potential in steel reinforcements embedded in cementitious composites with industrial wastes

Corrosion is one of the main issues affecting service life of reinforced concrete structures. The Open Circuit Potential (OCP) technique is a non-destructive method used to survey and monitor this problem. This test can also be used in laboratory environment and provide valuable information supporting the selection process of supplementary materials for durable concretes. Although this qualitative technique is commonly used, there is still a lack of consensus on the suitability of specific procedures for experimental analysis, such as type of reference electrode and influence of accelerated aging procedures (adoption of wetting/drying cycles and level of immersion of specimens). Therefore, the present study aims to evaluate the method for prediction of early steel corrosion activity in the accelerated OCP tests. The paper is focused on testing eco-efficient cementitious composites containing industrial wastes, such as sugarcane bagasse ash sand (SBAS) and water treatment plant sludge (WTPS), in replacement of natural sand. The results showed that an adoption of combined wetting/drying cycles, together with a partial (rather than total) immersion of specimens in NaCl solution, leads to earlier appearance of corrosion. This allows to shorten the period of testing by almost 10 weeks. It is due to higher access to oxygen and higher concentration of free chlorides from the saline solution accumulated in a porous system. The type of reference electrode is of lesser importance. Moreover, incorporation of 30% SBAS and 3% WTPS results in higher protection for steel corrosion, confirming wide applicability of the OCP technique to any cementitious matrices with or without industrial wastes.

New Insights into the Origin of Volatile Sulfur Compounds during Wine Fermentation and Their Evolution during Aging

Volatile sulfur compounds (VSCs) are associated with unpleasant reductive aromas and are responsible for an important reduction in wine quality, causing major economic losses. Understanding the origin of these compounds in wine remains a challenge, as their formation and further evolution during winemaking can involve both chemical and biological reactions. Comparing the VSCs profile (i) of fermenting synthetic grape juices supplemented with a selected VSC (eight compounds tested) and incubated in presence or absence of yeast, and (ii) during storage of wines under an accelerated aging procedure, allowed us to elucidate the chemical and metabolic connections between VSCs during fermentation and aging. Yeast metabolism, through the Ehrlich pathway and acetylation reactions, makes an important contribution to the formation of compounds such as methionol, 3-methylthiopropionate, 3-methylthiopropylacetate, 3-mercaptopropanol, 2-mercaptoethanol and thioesters. By contrast, chemical reactions are responsible for interconversions between thiols and disulfides, the formation of thiols from thioesters or, more surprisingly, the formation of ethylthiopropanol from methionol during fermentation. During aging, variations in heavy VSC concentrations, such as an increase in 3-methylthiopropylacetate and a decrease in ethyl-3-methylthiopropionate formation, were evidenced. Overall, this study highlights that it is essential to consider both yeast metabolism and the high chemical reactivity of VSCs to understand their formation and evolution during winemaking.

Desert label development for improved reliability and durability of photovoltaic modules in harsh desert conditions

We present strong arguments and experimental findings for the definition of a photovoltaic module accelerated ageing procedure for high irradiance and desert conditions to create a Desert Label for the particular Atacama Desert climatic conditions. A special focus on high ultraviolet solar radiation dosage in combination with either damp heat, salt mist or aggressive thermal cycling are presented. Indoor experimental results, strengthened by outdoor monitoring of sister mini-modules at the Atacama Desert, allowed selecting the appropriate ageing tests while exploring the reliability and durability of a wide range of module configurations, including various typical encapsulants, high efficiency cell technologies and module designs, for industrial applications.

Can Accelerated Aging Procedures Predict the Long Term Behavior of Polymers Exposed to Different Environments?

During their useful life, polymers are subject to degradation processes due to exposure to specific environmental conditions over long times. These processes generally lead to changes, almost always irreversible, of properties and performances of polymers, changes which would be useful to be able to predict in advance. To meet this need, numerous investigations have been focused on the possibility to predict the long-term performance of polymers, if exposed to specific environments, by the so called “accelerated aging” tests. In such procedures, the long-term behavior of polymeric materials is typically predicted by subjecting them to cycles of radiations, temperatures, vapor condensation, and other external agents, at levels well above those found in true conditions in order to accelerate the degradation of polymers: this can produce effects that substantially deviate from those observable under natural exposure. Even following the standard codes, different environmental parameters are often used in the diverse studies, making it difficult to compare different investigations. The correlation of results from accelerated procedures with data collected after natural exposure is still a debated matter. Furthermore, since the environmental conditions are a function of the season and the geographical position, and are also characteristic of the type of exposure area, the environmental parameters to be used in accelerated aging tests should also consider these variables. These and other issues concerning accelerated aging tests applied to polymers are analyzed in the present work. However, bearing in mind the limitations of these practices, they can find useful applications for rating the durability of polymeric materials.

Physical and chemical mechanisms involved in adhesion of orthodontic bonding composites: in vitro evaluations

BackgroundBond strength of orthodontic composite is strongly influenced by molecular and structural mechanisms. Aim of this in vitro study was to compare bond strength of light-cure orthodontic composites by measuring debonding forces and evaluating locations of bond failure. Investigations on chemical compositions clarified adhesive behaviors and abilities, exploring effects of ageing processes in this junction materials.MethodsTwelve enamel discs, from human premolars, were randomly coupled to one orthodontic adhesive system (Transbond XT™ 3 M UNITEK, USA, Light-Cure Orthodontic Paste, LEONE, Italy and Bisco Ortho Bracket Paste LC, BISCO, Illinois) and underwent to Shear Bond Strength test. Metallic brackets were bonded to twenty-seven human premolar, with one of the adhesive systems, to quantify, at FE-SEM magnifications, after debonding, the residual material on enamel and bracket base surfaces. Raman Spectroscopy analysis was performed on eight discs of each composites to investigate on chemical compositions, before and after accelerated aging procedures in human saliva and sugary drink.ResultsOrthodontic adhesive systems showed similar strength of adhesion to enamel. The breakage of adhesive-adherent bond occurs in TXT at enamel-adhesive interface while in Bisco and Leone at adhesive-bracket interface. Accelerated in vitro aging demonstrated good physical–chemical stability for all composites, Bisco only, was weakly contaminated with respect to the other materials.ConclusionA similar, clinically adequate and acceptable bond strength to enamel for debonding maneuvers was recorded in all orthodontic adhesive systems under examination. No significant chemical alterations are recorded, even in highly critical situations, not altering the initial mechanical properties of materials.

Effects of hygrothermal, UV and SO2 accelerated ageing on the durability of ETICS in urban environments

External Thermal Insulation Composite Systems (ETICS) have been extensively used for either new constructions or building facades retrofitting in the last decades. These systems can provide improved thermal performance to the building envelope. However, their long-term durability remains a pervasive concern, with some systems presenting relevant anomalies after few years from their application. The durability assessment of ETICS is defined by the EAD 040083-00-0404 guideline, which stated an accelerated ageing procedure based on the hygrothermal and freeze-thaw behaviour. Nevertheless, further important environmental urban conditions, such as UV radiation and atmospheric pollutants, as well as bio-susceptibility, are not envisaged in the guideline. This paper presents the results of an experimental campaign with the aim of evaluating the durability of the rendering system of several commercially available ETICS exposed to an innovative accelerated ageing procedure, which consists of hygrothermal cycles, UV radiation and air pollutants (SO2) exposure. Physical and chemical-morphological tests were carried out prior and after each ageing cycle in order to evaluate the durability of ETICS. Biological susceptibility to moulds was also assessed. The experimental results showed that both surface hardness and surface gloss decreased after the combined effect of the hygrothermal, UV, and SO2 ageing cycles, whereas an increase of surface roughness was observed. Substantial colour change for all systems after the ageing procedure was observed, confirming aesthetic alteration. Traces of biological growth were detected on the systems after ageing and the contact angle decreased after the hygrothermal cycles, indicating a lower surface hydrophobicity of the systems.