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Poly(lactic acid) (PLA) has been found to be important in various applications, such as in the medical, pharma-ceutical, and packaging industries. However, the long-term associated degradation process of PLA is a limiting factor for some applications. Therefore, in this research, the influence of corona and radio-frequency (RF) surface plasma treatment on the degradation of PLA in accelerated weathering tests was studied. The accelerated weathering test was applied using standard UV irradiation for up to 2000 h. The morphological/topographical, chemical, crystallization, mechanical, and thermal changes were analyzed after 500, 1000, and 2000 h of accelerated weathering time. The introduction of the polar functional groups caused by plasma treatment on the PLA surface improved its wettability, and therefore, hydrolytic degradation was promoted over the accelerated weathering time. It was revealed that the plasma treatment enhanced the hydrolytic and UV degradation of the PLA, as was confirmed by investigation of the physical, chemical, mechanical, and thermal properties. Moreover, the RF plasma was more pronounced than the corona plasma in the degradation of the PLA. Such an approach represents a pathway to promote and tailor PLA degradation. This publication was supported by the Qatar University Collaborative Grant No. QUCG-CAM 19/20-3 and QUCG-CAM-20/21-3. The findings achieved herein are solely the responsibility of the authors. The authors thank Prof. Sergei Naza-renko, University of Southern Mississippi, United States, and his group for their help in conducting the GPC analysis, with special thanks to Ms. Karina Reynolds for her efforts in running the samples. SEM analysis was accomplished in the Central Laboratories unit, Qatar University. Scopus

Museums and galleries house increasingly large collections of objects and contemporary art made of plastic materials, many of which undergo rapid material change. The main degradation processes of poly(vinyl chloride) (PVC) are elimination of HCl and plasticizer migration or leaching. This results in visible discolouration, stickiness and cracking. Degradation is known to be a multi-stage process that includes HCl elimination, formation of conjugated polyenes and cross-linking. Elimination of HCl begins due to structural irregularities (allylic and tertiary chlorides) and results in the formation of polyenes. When at least 7 conjugated double bonds are present, discolouration of PVC becomes visible. Non-invasive techniques, such as IR and Raman spectroscopy are used for polymer identification and plasticizer quantification. Plasticizer degradation and particularly the late stages of PVC degradation can be investigated using SEC, GC-MS, TGA and DSC. Studies in heritage collections have revealed that, apart from HCl, PVC objects emit 2-ethylhexanol and other volatile degradation products, however, there is currently no indication that HCl is emitted at usual indoor conditions. There seems to be a general lack of systematic research into PVC degradation at the conditions of storage and display, which could result in the development of dose-response functions and in the development of preventive conservation guidelines for the management of PVC collections.

[EN] Polycaprolactone/Graphene oxide (PCL/GO) composites are shown to be promising substrates for tissue engineering as their degradation behavior is a key aspect in this type of application. The present paper studies the effect of different GO contents (0.1, 0.2 and 0.5 wt%) of PCL/GO composites on accelerated hydrolytic degradation at pH 13 and pH 1. Degradation kinetics at pH 13 is strongly affected by GO content, and speed up at higher percentages. The composite with 0.5 wt% of GO was completely degraded in 72 hours, while degradation at pH 1 presents a different profile and seems to have an induction period that lasts more than 1500 hours. Morphological changes, molecular weight distribution, weight loss, degree of swelling and calorimetric properties were obtained as a function of degradation time. According to the results obtained, the addition of small percentages of GO significantly influences the degradation behavior of the composites acting as degradation modulators., Isabel Castilla-Cortazar and Alberto J. Campillo-Fernandez are grateful for the support of the Spanish Ministry of Science, Innovation and Universities, through RTI2018-095872-B-C22/ERDE Ana Vidaurre would like to express her gratitude for the support of the Spanish Ministry of Science and Education, through the MAT2016-76039-C4-1-R Project, and also the support from CIBER-BBN, an initiative funded by the Sixth National R&D&i Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CII3ER Actions financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.

This study presents a systematic evaluation of the physical, thermal and mechanical performance of medical-grade semi-crystalline PLLA undergoing thermally-accelerated degradation. Samples were immersed in phosphate-buffered saline solution at 50 °C for 112 days and mass loss, molecular weight, thermal properties, degree of crystallinity, FTIR and Raman spectra, tensile elastic modulus, yield stress and failure stress/strain were evaluated at consecutive time points. Samples showed a consistent reduction in molecular weight and melting temperature, a consistent increase in percent crystallinity and limited changes in glass transition temperature and mass loss. At day 49, a drastic reduction in tensile failure strain was observed, despite the fact that elastic modulus, yield and tensile strength of samples were maintained. Brittleness increase was followed by rapid increase in degradation rate. Beyond day 70, samples became too brittle to test indicating substantial deterioration of their load-bearing capacity. This study also presents a computational micromechanics framework that demonstrates that the elastic modulus of a semi-crystalline polymer undergoing degradation can be maintained, despite a reducing molecular weight through compensatory increases in percent crystallinity. This study presents novel insight into the relationship between physical properties and mechanical performance of medical-grade PLLA during degradation and could have important implications for design and development of bioresorbable stents for vascular applications.

The EPDM (ethylene-propylene-diene monomer) hybrids with improved thermal and radiation strengths containing 1 and 5 phr of polyhedral oligomeric silsesquioxane (vinyl-POSS, Ov-POSS) and/or 2 phr of microalgae (Chlorella vulgaris (CV) and Spirulinaplatensis (SP)) powders were investigated in respect to their thermal stability after γ-irradiation. The material durability under accelerated degradation was qualified by chemiluminescence and gelation, which prove the contribution of inorganic filler and microalgae extracts on the increase of hybrid thermal stability, as well as the interaction between added components (POSS and CV or SP). The activation energies and the durabilities under accelerated degradation were calculated, indicating their suitable usage as appropriate materials in various applications. The reported results indicate the improvement effect of both microalgal powders on the oxidation strength, but the contribution of Spirulinaplatensis grabs attention on its efficient effects upon the prevention of degradation under accelerated aging conditions. The thermal performances of the tested EPDM based hybrids are remarkably ameliorated, if the certain formulation includes Ov-POSS (5 phr) and Spirulinaplatensis (2 phr), certifying its suitability for the pertinent applications.

In order to provide a hygienic storage drinking water reservoirs have been coated with mineral mortar linings in all epochs of European history. However, modern cement-based materials often show in this special operational environment an inadequate durability. Even though drinking water is commonly not considered particularly harmful to cementitious systems, the chemical degradation of mortar linings in drinking water storage systems can occur very fast compared to other common deterioration reactions. This results in cost intensive repair measures and thus high life-cycle costs as well associated with an ecological burden. Furthermore, an insufficient understanding of degradation mechanisms and their underlying physical, chemical as well as biological processes currently impedes performance-oriented approaches to improve durability. In this regard a research project aims to unravel the potentially combined multiple deterioration mechanisms, integrating results of case studies and laboratory experiments. In this context a specific issue of this research activity is to evaluate the applicability of an accelerated degradation test that takes advantage of the impact of electrical fields on the stability of cement-based materials in permanent contact to aqueous environments. Laboratory experiments show, that such tests are suitable to compare the resilience against reactive transport processes of materials and to draw conclusions regarding their performance, illustrating material changes in terms of depth and time. Furthermore, the results indicate, that the transport properties of the rim zone of cement-based materials are regulating its sturdiness in aggressive aqueous environments. This approach appears therefore suitable for a performance assessment in material development and provides as well new impulses for quality control in practice paving the path for increased durability of materials applied in drinking water supply infrastructure.

This study evaluated the insulation resistance characteristics of TFR-8 (Tray Frame Retardant power cable for fire service) and VCTF (Light PVC Sheathed Circular Cord) cables under external flame, over-current, and accelerated degradation tests. In the accelerated degradation test of the cable, aging times of 10, 20, 30, and 40 years were tested according to a temperature derived using the Arrhenius equation. The insulation resistance of the TFR-8 cables was reduced from a maximum of 7.5 T ohm to 0.008 T ohm during the flame contact and recovered to its original state after cooling. However, dielectric breakdown occurred in the VCTF cable during flame contact and the cable did not return to its original state, even after cooling. In the forced convection oven test, the insulation resistance of the cable was reduced at 160 °C, whereas the insulation resistance of the cable was reduced at 125 °C in the over-current test. This result implied that the over-current had a greater impact than did heat applied externally on the degradation of the cable insulator. In the accelerated degradation tests from 10–30 years, the TFR-8 cable did not show any reduction in insulation resistance at room temperature. However, after an induced aging time of 40 years, the cable showed a rapid reduction in insulation resistance at room temperature.

Freshly assembled proton exchange fuel cells (PEMFC) require conditioning to reach maximum power density. This process may last up to tens of hours and adds to the cost of commercial fuel cell technology. We present an accelerated conditioning procedure involving starving the cathode of oxidant. In single cells, this procedure conditions a membrane electrode assembly (MEA) within 40 min, without compromising durability. The performance and durability of MEAs conditioned using this technique are compared with US Department of Energy (DOE) and European Union (EU) harmonized protocols, and to an amperometric conditioning protocol. The time to reach peak power density using cathode starvation conditioning is

Accelerated degradation test is a useful approach to predict the product lifetime at the normal use stress level, especially for highly reliable products. Two kinds of the lifetime prediction based on Gamma processes were studied. One was to predict the lifetime of the population from accelerated degradation data, and the other was to predict the lifetime of an individual by taking the accelerated degradation data as prior information. For an extensive application, the Gamma process with a time transformation and random effects was considered. A novel contribution is that a deducing method for determining the relationships between the shape and scale parameters of Gamma processes and accelerated stresses was presented. When predicting the lifetime of an individual, Bayesian inference methods were adopted to improve the prediction accuracy, in which the conjugate prior distribution and the non-conjugate prior distribution of random parameters were studied. The conjugate prior distribution only considers the random effect of the scale parameter while the non-conjugate prior distribution considers the random effects of both the scale and shape parameter. The application and usefulness of the proposed method was demonstrated by the accelerated degradation data of carbon-film resistors.

In this work, accelerated degradation charge‐discharge tests have been applied to compare the performance of a bench‐scale vanadium redox flow battery (VRFB), when charged under galvanostatic conditions and under the highly variable conditions of current produced by wind turbines. Wind speed patterns applied for the VRFB charge were obtained during 3 representative days in winter, in Ciudad Real (Spain). The accumulated and delivered charge capacities and the different efficiencies (coulombic, voltage, and energy) were analyzed during 3 charge and discharge cycles. The conversion of the different vanadium species during the charge‐discharge cycles indicated that the operation mode had a strong influence on the performance of the VRFB and helped to explain the charge profiles obtained. Although, similar efficiencies and charge/discharge capacities were found, the VRFB operated in wind‐charging mode performs slightly worse than the VFRB operated in galvanostatic mode. Increased crossover of vanadium species in the negative electrolyte compartment explains the differences found. Nevertheless, it can be concluded that this type of technology seems to be promising for the storage of electricity produced by wind turbines.

The modifications occurring to two well-established synthetic formulations (Mowilith DMC2®, Mowilith DM5®), upon accelerated degradation, were investigated. Degraded films of copolymers were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Differential Thermogravimetry (DTG), Atomic Force Microscopy (AFM) and colorimetry. The study highlighted the varied degradation of the two adhesives, which exhibit yellowing, alteration of their thermal and spectroscopic features and changes in their surface morphology and viscoelasticity. The main degradation route is characterized by the loss of acetyl groups, resulting in conjugated double bonds, as suggested by colorimetry and confirmed by FTIR. The loss of volatile organic acids represents a conservation issue when these adhesives are used for the lining of canvas paintings, since acidity promotes the hydrolysis of canvas cellulose. Rearrangement of the adhesives' molecular structure, and a competition between depolymerization and cross-linking were suggested by AFM and thermal analyses (changes in molecular weight are known to affect the solubility of copolymers and the possibility of their removal from works of art). The representativeness of the accelerated degradation protocol was positively assessed through comparison with naturally degraded adhesives.

Colour photographs are very vulnerable to the environmental conditions they are stored in. Although ideal conditions of storage have been identified, these conditions are often not appropriate in archival collections. Therefore, it is essential to understand how these environmental conditions affect degradation in order to optimise material lifetime. Such information is typically obtained using accelerated degradation experiments following ‘one-factor-at-a-time’ methodologies. However, when planned using ‘Design-of-Experiment’ principles, such experiments provide more information with fewer experimental runs, while information is provided not only on factor effects but also on interactions between factors. This study employed a central composite experimental design plan to develop a dose–response function relating the rate of degradation of dyes in colour photographs to temperature (T), relative humidity (RH) and acetic acid concentrations (c(AA)), which had been identified as the environmental parameters of greatest concern for colour photographs in archival collections: ln ( Δ E R G B t ) = 32 + 0.0002 ( c ( AA ) ) + 0.01 ( RH ) − 11 ( 1000 T ) . This function now allows managers to appraise various options of environmental management within their collections.

Chromogenic colour prints are known to be sensitive to storage environments. However, limited research is available on the effect of atmospheric pollutants on these materials, especially pollutants generated indoors. The stability of photographic dyes is of particular interest and the rate of their change can be best described using the standard RGB colour model. Therefore, the colourimetric method was compared to dye extraction and liquid chromatographic analysis to justify its use as a rapid, non-destructive method for quantitative assessment of the rate of change in dye content of colour photographs during degradation. The effects of typical indoor (acetic acid, formaldehyde) and outdoor (nitrogen dioxide) generated pollutants on chromogenic colour prints were then investigated at 80 °C, 60% RH. It was identified that acetic acid leads to the most pronounced changes in photographic dye concentrations, which is significant considering that acetic acid is often the most prominent pollutant in archival environments. On the other hand, formaldehyde exhibited a slight protective effect in comparison to the blank experiment.

There is currently wide interest in room temperature storage of dehydrated DNA. However, there is insufficient knowledge about its chemical and structural stability. Here, we show that solid-state DNA degradation is greatly affected by atmospheric water and oxygen at room temperature. In these conditions DNA can even be lost by aggregation. These are major concerns since laboratory plastic ware is not airtight. Chain-breaking rates measured between 70 degrees C and 140 degrees C seemed to follow Arrhenius' law. Extrapolation to 25 degrees C gave a degradation rate of about 1-40 cuts/10(5) nucleotides/century. However, these figures are to be taken as very tentative since they depend on the validity of the extrapolation and the positive or negative effect of contaminants, buffers or additives. Regarding the secondary structure, denaturation experiments showed that DNA secondary structure could be preserved or fully restored upon rehydration, except possibly for small fragments. Indeed, below about 500 bp, DNA fragments underwent a very slow evolution (almost suppressed in the presence of trehalose) which could end in an irreversible denaturation. Thus, this work validates using room temperature for storage of DNA if completely protected from water and oxygen.

Automotive is one of the major manufacturing industries in Australia that requires extensive reliability test for the components used in vehicles. To achieve a shorter time-to-market and a highly reliable product while reducing the amount of physical prototyping, there is a growing need for better understanding on the effect that the design parameters have on the degradation of the product. This paper presents comprehensive descriptions of applying Artificial Neural Network (ANN) to capture the relationships between design and degradation. Consequently, two models of different practical significance are created as the result of the work. The vision of the models is to be used by the testers and designers as a guideline in design evaluation, so that time-consuming and expensive iterations of the product developmental cycle can be reduced substantially. The degradation of the folding force of a mechanical system is used to illustrate our approach.