Accelerated Aging Temperature Research Articles

Effect of Accelerated Aging Temperature under Artificial Seawater on the Properties of Carbon Fiber/Epoxy Composites and the Erosion Mechanism

Effect of Accelerated Aging Temperature under Artificial Seawater on the Properties of Carbon Fiber/Epoxy Composites and the Erosion Mechanism

Uniaxial Compression Behavior of Short Square and Circular RC Piles Constructed with GFRP Bars and Spirals Preconditioned in Simulated Marine Environments

The current experimental investigation assessed the durability of reinforced concrete (RC) piles with glass fiber-reinforced polymer (GFRP) bars and spirals exposed to simulated marine environments. A total of 18 specimens—9 square (300 mm in cross section) and 9 circular (304 mm in diameter)—and short RC piles were prepared and tested under uniaxial compression. For each pile geometry, three specimens were reinforced with pristine GFRP bars as reference piles. The other six piles were reinforced with GFRP bars that had been exposed to marine environments at subtropical regions (22°C) or accelerated aging temperature (60°C) for 12 months, three specimens for each environment. Mechanical property and microstructural analysis tests were carried out to characterize the conditioned/aged GFRP bars. The GFRP-RC piles conditioned at 60°C exhibited similar behavior to their reference counterparts. The current environmental reduction factors for GFRP reinforcing bars stipulated in design codes and guidelines are conservative. A more accurate design equation to calculate the axial capacity of piles should consider the contribution of longitudinal GFRP bars even when exposed to marine environments.

Effective Stabilization of Viral Vectors in Liquid Using an Algorithm-Based Development Approach

Background In recent years approvals of both CAR-T cell therapies and promising clinical data of gene therapy trials such as in hemophilia or sickle cell disease, prove that significant progress of gene and cell therapy in the field of hematological malignancies as well as rare hematologic genetic disorders has been made. Replication-deficient recombinant viral vectors such as adenovirus serotype 5 (Ad5), adeno-associated virus (AAV) and members of the poxvirus family represent a rapidly growing field of vaccine development and gene therapy. Viral vectors are known as complex supra-molecular ensembles of macromolecules produced by living organisms (nucleic acids, proteins, polysaccharides and in the case of lipid enveloped viruses of phospholipids) which are prone to a variety of complex chemical and physical degradation pathways, in particular due to stress induced by manufacturing, storage and distribution; hence representing a significant hurdle for the development and administration of stable vector-based pharmaceuticals such as vaccines or gene therapeutics. AIM To effectively develop stabilizing formulations for replication-deficient recombinant viral vectors, we applied a database and algorithm-based development strategy including Design of Experiment (DoE). Methods As a representative example of viral vectors we used Ad5. DoE was applied to select the most effectively stabilizing formulations. Ad5 was stored at 37 °C and 25 °C as accelerated aging temperature to identify the most effective stabilizing excipients and combinations thereof. Based on these results, the best selected formulations were further iteratively optimized and used for real-time storage at 5 °C in both liquid and lyophilized formulation. Infectivity was measured by titration assay and immunostaining of the Ad5 specific Hexon protein in HEK293 cell culture. ResultS By analysis of the infectious virus titers and mathematical combination of these results with the DoE matrix, the linear influence of each amino acid used in the DoE matrix was determined. The accelerated aging conditions were shown to be predictive for real-time aging. Several of the excipients indicated a neutral influence, whereby a well-balanced combination of the components was important regarding concentration and stabilizing interactions. The predictive power of this approach was confirmed by by long-term storage of two iteratively improved formulations tailored for Ad5. Conclusion The highly efficient pre-selection strategy of effectively stabilizing excipients by an algorithm-based development approach and an accelerated aging model enables the generation of best-in-class stable liquid formulations for viral vectors in short development time. Stable titres in liquid formulations can avoid lyophilization, loss of infectivity via freeze/thaw procedures or high overage and thus significantly reduce manufacturing costs. This approach is transferred to AAV and could have beneficial impact when applied early in downstream processing. A transfer to the frequently applied gene therapy vector system AAV is currently being implemented and an update will be presented at the conference. Disclosures No relevant conflicts of interest to declare.

PF448 EFFECTIVE STABILIZATION OF VIRAL VECTORS IN LIQUID USING AN ALGORITHM‐BASED DEVELOPMENT APPROACH

Background:With both the approvals of CD19 CAR‐T cell therapies and promising clinical data of gene therapy trials such as in hemophilia or sickle cell disease, recent years have seen significant progress of gene and cell therapy in the field of hematological malignancies as well as rare hematologic genetic disorders. Hence, replication‐deficient recombinant viral vectors such as adenovirus serotype 5, adeno‐associated virus and members of the poxvirus family represent a rapidly growing field of vaccine development and gene therapy.Viral vectors are known as complex supra‐molecular ensembles of macromolecules produced by living organisms (nucleic acids, proteins, polysaccharides and in the case of lipid enveloped viruses of phospholipids) which are prone to a variety of complex chemical and physical degradation pathways, in particular due to stress induced by manufacturing, storage and distribution. This represents a significant hurdle for the development of stable vector‐based pharmaceuticals such as vaccines or gene therapeuticsAims:Here, we studied whether LEUKOCAREs formulation platform may also efficiently protect viral vectors in thermal stress experiments. As a representative example of viral vectors we used adenovirus serotype 5 (Ad5).Methods:In an algorithm‐based development approach, we used Design of Experiment (DoE) to select the most effectively stabilizing formulations for Ad5. We stored Ad5 at 37 °C and 25 °C as accelerated aging temperature to identify the most effective stabilizing excipients after short term storage as well as at 5 °C for real time storage. Based on these results, the best selected formulations were further iteratively optimized and used in long term storage at 5 °C.Results:By analysis of the infectious virus titers and mathematical combination of these results with the DoE matrix, the linear influence of each amino acid used in the DoE matrix was determined. The accelerated aging conditions were shown to be predictive for real‐time aging. Several of the excipients indicated a neutral influence, whereby we observed the importance of a well‐balanced combination of the components with each other regarding concentration and stabilizing interactions. The predictive potential of this approach was confirmed by two iteratively composed formulations tailored for Ad5 during long‐term storage.Summary/Conclusion:The pre‐selection strategy of effectively stabilizing excipients by means of an algorithm‐based development approach and the applied accelerated aging model is highly efficient and enables the generation of best‐in‐class stability formulations for Ad5 viruses and viral vectors in liquid. Moreover, this approach could have beneficial impact when applied early in downstream processing, which could enable significant reduction of viral vectors manufacturing costs for gene therapy.

Determination of essential parameters influencing service life time of polyurethane insulation in district heating pipes

Pre-insulated district heating pipes (DHP) have been in use during the last forty years. Many improvements and development have been done in the system. However, life-time prediction is still an uncertain issue. This paper is a part of a bigger project with the objective to determine mechanisms related to the deterioration of the mechanical and insulation properties of pre-insulated heating pipes as a result of ageing. The focus in this project is on degradation mechanisms of the PUR material at high temperatures. In this paper some results of the two types of exposure are presented. The first type comprises a condition where the new pipes are subjected to accelerated ageing at three different temperatures. The second type comprises condition, when the PUR material itself is aged in different atmospheres in order to identify different degradation mechanisms. The chosen ageing temperatures in the first condition were 130°C, (close to the supply temperature), 150°C and 170°C, (accelerated ageing temperature in EN 253 [1]). Changes in thermal insulation and the adhesion force between the PUR and the steel pipe were evaluated using the transient plane source (TPS) technique and the SP plug method respectively. The results of ageing show that the degradation of PUR is a multi-stage process composed of a rapid change in properties followed by a plateau phase which changes later to a gradual deterioration of the properties. The results of the PUR material exposure at 150°C in air and in nitrogen showed significant differences in the degradation characteristics between the two environments as were revealed by DSC and FTIR methods.

The establishment of reliability model for LED lamps**Project supported by the National High Technology Research and Development Program of China (Nos. 2015AA03A101, 2013AA03A116), the Cuican Project of Chinese Academy of Sciences (No. KZCC-EW-102), and the Jilin Province Science and Technology Development Plan Item (No. 20130206018GX).

In order to verify which of the distributions and established methods of reliability model are more suitable for the analysis of the accelerated aging of LED lamp, three established methods (approximate method, analytical method and two-stage method) of reliability model are used to analyze the experimental data under the condition of the Weibull distribution and Lognormal distribution, in this paper. Ten LED lamps are selected for the accelerated aging experiment and the luminous fluxes are measured at an accelerated aging temperature. AIC information criterion is adopted in the evaluation of the models. The results show that the accuracies of the analytical method and the two-stage method are higher than that of the approximation method, with the widths of confidence intervals of unknown parameters of the reliability model being the smallest for the two-stage method. In a comparison between the two types of distributions, the accuracies are nearly identical.

Method for lifetime estimation of power transformer mineral oil

Large amounts of mineral oil are used in electrical equipments as insulation and cooling medium. To avoid damages and cut-off of power electricity supply it is necessary to evaluate the mineral oil condition. Lifetime estimation of mineral oil which is based on accelerated thermal ageing at three temperatures (according to IEC 60216-1/2001) requires a long experimental time. This standardized method permits the lifetime calculation using a model based on the equation lnD(T)=a+bT, where a is the intercept and the slope of the plot lnτx versus 1/T, b is a material constant, T is the accelerated ageing temperature and τx is the time to reach the acceptable limit value of a chosen degradation parameter. In the present paper, mineral oil lifetime at 80°C (D1=1.53×105 h) has been obtained on the basis of accelerated ageing tests at three different temperatures (115°C, 135°C and 155°C) and choosing the oil electrical resistivity (ρ) as degradation parameter. The activation energy of the ageing process determined in these conditions was 101.8kJ/mol.To reduce the test duration, this paper proposes a simpler method based on a single ageing test at a higher temperature and the activation energy of the oxidation reaction being determined from non-isothermal Differential Scanning Calorimetry (DSC) measurements. According to the proposed method, the plot ρ versus τ (ageing time) was drawn only for the accelerated ageing temperature T=155°C and the lifetime value (τx) for this temperature was experimentally obtained. In this case, the activation energy value Ea corresponding to oxidation reaction was determined (Ea=102.4kJ/mol). Based on both Ea and the τx at 155°C, the lifetime at 80°C (D2=1.86×105 h) was determined and compared with D1. The differences between D1 and D2 values are acceptable and the proposed method is effective in terms of costs and experimental time (the experimental time is reduced by a factor of 12–14) as compared to the present standardized method.

Oxidative stability of virgin olive oil enriched with carnosic acid

Abstract The aim of this study was to evaluate the effect of the addition of carnosic acid on the oxidative stability of virgin olive oil. Two different amounts of carnosic acid (0.01 and 0.1 g/100 g oil) and two different temperatures (accelerated aging temperature, 60 °C; deep frying temperature, 180 °C) were considered. The influence of carnosic acid and heating time on the stability of the oils was studied by experimental design. The results obtained at 60 °C showed a dose dependent inhibition in the formation of primary and secondary oxidation products and a dose dependent enhancement of radical scavenging activity, which was only less significantly influenced by heating time. On the contrary, at 180 °C no protective effect against lipid oxidation was observed and the radical scavenging activity was practically zeroed by heating, probably as a consequence of a fast decomposition of carnosic acid.

Predicting the lifetime of fluorosilicone o-rings

Long-term (up to 1000 days) accelerated oven-aging studies on a commercial fluorosilicone o-ring seal are used to predict the sealing lifetime at room temperature (23 °C). The study follows force decay (relaxation) on squeezed o-ring material using isothermal compression stress relaxation (CSR) techniques. The relaxation is normally a complex mix of reversible physical effects and non-reversible chemical effects but we utilize an over-strain approach to quickly achieve physical equilibrium. This allows us to concentrate the measurements on the chemical relaxation effects of primary interest to lifetime assessment. The long-term studies allow us to access a fairly broad temperature range (80–138 °C) which results in improved modeling of the temperature dependence of the accelerated data. Non-Arrhenius behavior is observed with evidence of a significant lowering of the activation energy at the lowest accelerated aging temperature (80 °C). This observation is consistent with numerous recent accelerated aging studies that probed temperature ranges large enough to observe similar non-Arrhenius behavior. The extrapolated predictions imply that significant loss of sealing force requires on the order of 50–100 years at 23 °C. Field aging results out to ∼25 years at 23 °C are shown to be in reasonable accord with the significant change in Arrhenius slope observed from the accelerated aging study.

Accelerated aging and thermal-mechanical fatigue modelling of Cu-plated through holes with partial solder filling

The reliability of connector-to-board solder joints was investigated by accelerated aging experiments and finite element analysis (FEA), with a strain-based criterion for fatigue failure of Cu vias. The accelerated aging temperature cycle was ?55?C to +125?C. The pin/through hole solder joints were examined by metallography after test intervals up to 1000 thermal cycles. Partial solder filling of the joints was observed and attributed to Au contamination of the solder and thin solder gaps between the connector pins and Cu-plated vias. All fatigue cracks observed in the vias after thermal cycling were associated with partial solder filling of the joints. The effects of partial solder fill on failure location were confirmed by FEA and acceptable agreement was found between the predicted cycles to failure and the experimentally observed onset of via cracking. The model and experimental results were used to predict component lifetimes for milder thermal-cycle conditions typically found in service.

Time–temperature superposition method for predicting the permanence of paper by extrapolating accelerated ageing data to ambient conditions

In this paper we present a time-temperature superposition method for predicting the permanence of paper by extrapolating accelerated paper ageing data to ambient conditions. The presented method includes a test for the presence of shift factors to superpose all of the raw accelerated ageing data over the temperature range studied to obtain a master curve, a numerical fit of the master curve for producing a master equation representing the kinetics of paper degradation, a critical examination of applying Arrhenius equation for explaining the relationship between the empirically determined shift factors and the accelerated ageing temperature, and a verification of the Arrhenius activation energy extrapolation assumption. Unlike the usual approach that extrapolates the Arrhenius relationship between lifetime and temperature, without corroborating evidence, to ambient temperatures, we test the Arrhenius activation energy extrapolation assumption by determining the influence of acidity on cellulose hydrolysis reactions, and have found that detection and identification of the acid-sensitive linkages in cellulose substances is an ultra-sensitive and reliable method to measure degradation of cellulose and paper in what is normally the extrapolation region (ambient temperatures). Taking the examples of natural ageing data in literature from 18 bleached kraft dry-lap pulps for 22 years under ambient conditions and three handsheet samples for 22 years under controlled conditions, comparison of the predictions with natural ageing results has been addressed.

Lifetime predictions of EPR materials using the Wear-out approach

The Wear-out approach for lifetime prediction, based on cumulative damage concepts, is applied to several ethylene propylene rubber (EPR) cable insulation materials. EPR materials typically follow “induction-time” behavior in which their material properties change very slowly until just before failure, precluding the use of such time-dependent properties to predict failure. In the Wear-out approach, a material that has been aged at its ambient aging temperature T a or at a low accelerated aging temperature is subsequently aged at a higher “Wear-out” temperature T w in order to cause the material to reach its “failure” condition. In the simplest case, which involves the same chemical processes underlying degradation at T a and T w, a linear relationship is predicted between the time spent at T a and the time required at T w to complete the degradation. Data consistent with this expectation are presented for one of the EPR insulation materials. When the degradation chemistry at the two temperatures is different, a linear relationship between the time spent at T a and the time required at T w to complete the degradation is not generally expected. Even so, the Wear-out results for a second EPR material, which has evidence of changing chemistry, are reasonably linear and therefore useful from a predictive point-of-view. The Wear-out approach can therefore be used to transform non-predictive time-dependent material property results into predictive lifetime estimates. As a final example, the Wear-out approach is applied to an EPR insulation that had been aged in a nuclear power plant environment (∼51 °C) for times up to 23 years to show its likely viability for the hundreds of years predicted at this aging temperature from accelerated aging tests on EPR insulation materials.

402 AZ91 マグネシウム合金の摩擦・摩耗特性に及ぼす人工時効温度の影響

402 AZ91 マグネシウム合金の摩擦・摩耗特性に及ぼす人工時効温度の影響

Paper Conservation Using Aqueous Solutions of Calcium Hydroxide/Methyl Cellulose 2. The influence of accelerated ageing temperature on properties of treated paper

Sur la base des resultats obtenus par le vieillissement accelere de papiers fabriques a partir de cellulose de bois tendre blanchie et de chiffons, l'energie d'activation apparente de la degradation de la cellulose a ete estimee a 103-106 kl/mol. Les temperatures de vieillissement de 40° et 60°C ne semblent pas appropriees pour etudier la degradation de la cellulose dans les echantillons traites a l'hydroxyde de calcium Ca(OH)2 ou Ca(OH)2 + solutions de conservation de MC parce que dans ces conditions aucun changement du degre de polymerisation ne peut etre observe. Les resultats obtenus ont demontre qu'une reduction de la resistance des feuilles de papier traitees par ces solutions au cours du vieillissement accelere etait causee par la degradation de la cellulose de methyle. L'augmentation de la reserve alcaline obtenue par le traitement fournit au papier une meilleure protection contre la degradation hydrolytique de la cellulose. Le renforcement de la resistance du papier de pâte de sulphite de bois tendre blanchi, traite a 40° et 60°C, est le resultat d'une formation de corne qui est due plutot a la formation de ponts d'hydrogene qu'a un reseau de liaisons covalentes.

Study of stability of high‐temperature polyimides using TG/MS technique

AbstractThe oxidative stability of the carbon fiber‐reinforced composite of polyimide was examined, in real time, using the evolved gas analysis techniques. Off‐gas degradation products suggested the onset temperature for chain scissions to be fairly low at about 190–220°C. Based on the off‐gas products present and the trend of their release, the composite degradation mechanism appeared to be similar between 190 and 371°C, thereby marking 371°C to be the highest accelerated aging temperature for its long‐term lifetime prediction. Beyond 371°C, different degradation mechanisms would apply. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1219–1227, 2002