Effect of the Environment on the Characteristics of a Polymer

The polycarbonate (PC) is a highly valued polymeric material for its various characteristics and low cost. Its transparency and impact resistance justify its use in a severe radiation and temperature environment. The aim of this article is to subject this material to aging under ultraviolet (UV) radiation with a wavelength of 253 nm and a temperature of 80°C for various times. The physicochemical and mechanical characterizations of the virgin and aged material have allowed the revelation of the aging effects on the properties. The Fourier Transform Infrared Spectroscopy (FTIR) technique highlight breaks in chemical bonds in the molecular chains of the PC subjected to the combined effects of UV and heat. X-ray analysis have showed a reduction in crystallites and a tendency towards an amorphous state at short times, but the degree of crystallinity increases again at long exposure times of the material. As a result, the microhardness of the aged material is strongly affected on the exposed surface with less effect depending on the depth.

Properties of Polyethylene Terephthalate (PET) after Thermo-Oxidative Aging

The influence of the thermo-oxidative aging semi-crystalline polyethylene terephthalate process on the thermal and mechanical properties was analysed in the article. For this purpose, PET was aged at 140 °C for 21, 35 and 56 days. The research showed that as a result of aging, the amount of the crystalline phase increases by about 8%, which translates into the properties of the aged material. The glass transition and melt temperature of lamellar crystals formed during first and second crystallisation increase with aging. The mechanical properties of the material were analysed in the temperature range of 25 to 75 °C. The tests were showing an increase in Young’s modulus and a decrease in elongation at the break as a result of aging. This phenomenon was particularly visible during tests at 75 °C and during the morphological observation of the fracture surface, where the fracture character of the material changes from ductile to brittle. In the case of the material aged for the longest time, the temperature has a negligible influence on the elongation at break.

Mechanical, thermal and physico-chemical behavior of virgin and hydrothermally aged polymeric pipes

In this paper, an experimental study was conducted to characterize industrial PVC pipes and to investigate the effect of hydrothermal aging on their physico-chemical, thermal, and mechanical behavior. Three temperature (25°C, 60°C and 90°C) and full immersion in distilled water were retained as accelerated hydrothermal conditions. Kinetic of water absorption was examined and Fickian behavior was observed. The aging temperature was found to influence the water uptake behavior of PVC samples. Thermogravimetric analysis (TGA) has proved that the pipe material is not pure, while it consists of PVC reinforced with calcium carbonate (CaCO3). After exposure to accelerated aging, TGA and FTIR analysis exhibit preliminary signs of degradation of PVC samples under the retained conditions. Changes affecting the shape and the color of aged samples were examined. Mechanical properties have been characterized, after immersion of 30 days, with an improvement of strength and stiffness of the aged samples, in particular at elevated aging temperature. However, the aging response is accompanied by a loss of ductility for the aged material. These results, even for brief exposure, could help to understand the behavior of PVC composite pipes under hydrothermal conditions.

Guiding principles for creating new high strength-high conductivity copper alloys

Solid solution strengthened alloys such as brass and bronze have been widely used as contact materials for energisation in a range of devices due to the fact that they are relatively low cost. In more recent times precipitation strengthened alloys such as copper-beryllium, copper-titanium and copper-nickel-silicon are used due to their excellent strength and conductivity. Yet, little headway has been made in the development of precipitation hardening copper alloys due to the difficulty associated with departing from existing alloy designs and structure control methods. One team of researchers is exploring the use of over-aged material instead of the conventional peak-aged material. This is because previous studies have suggested that wires of this type may have improved strength and conductivity. But there remain many unknowns. Associate Professor Satoshi Semboshi is a researcher based at the Institute for Materials Research, Tohoku University, Japan, who is seeking to shed light on these unknowns.

Lifting Agent Granuloma

Objectives Histologic findings after endoscopic resection using submucosal lifting agents Eleview and ORISE gel are described. Methods Four cases were identified based on the histologic presence of ORISE gel. Cases were selected to illustrate the histologic appearance of the lifting agent immediately after injection (day 0) and after an interval of approximately 2 months. Results Immediately after injection, the gel had an appearance similar to acellular mucin on H&E stain and showed mucicarmine positivity but was negative for periodic acid-Schiff stain and Alcian blue. At 2 months, the appearance changed drastically and was characterized by a hard, homogenous eosinophilic quality and elicited a robust foreign body-type giant cell reaction; we have proposed the name lifting agent granuloma for this histologic appearance. The aged material may be mistaken for amyloid or a pulse (legume) granuloma; however, the material was negative on Congo red stain and had a different clinical history and distribution in the tissue from those of a pulse granuloma. Conclusions It is important to take note of the histologic appearance of these new submucosal lifting agents over a varying time interval, as outlined here, so that they are readily recognized and not mistaken for other entities.

Stereological Evaluation of Precipitates within Ferrite Grains in Heat-Treated 1.25Cr0.5Mo Steel Previously Exposed to Service

The objective of this work was to study the effect of the heat treatment and further operation aging on the stereological parameters (size, quantity and volume fraction) of precipitates within ferrite grains of a creep-resistant 1.25Cr0.5Mo steel after long-term operation. The heat treatment was similar to the treatment that is carried out in industrial steam pipelines after welding (post weld heat treatment - PWHT) during installation and/or repairing. The operation aging corresponds to a subsequent long in-service operation after repairing. To determine the stereological parameters, SEM digital images were taken from samples of this material after conditions of in-service-aged (after long-term operation), in-service-aged and heat-treated (simulating repairing) and in-service-aged, heat-treated and in-laboratory aged (simulating subsequent long-term operation after repairing). The results indicate that the changes in the stereological parameters of the precipitates within ferrite grains after PWHT is associated with the coarsening process of the within-ferrite-grain precipitates as well as stabilizing the microstructure, since the material aging after PWHT of an in-serviced aged material would not change the stereological parameters.

The impact of technological methods of heat treatment of membranes on the properties of the aneroid sensors

The study of the effect of hardering temperature on the properties of beryllium bronze in subsequent aging were made. It is shown that the elastic properties of the aged material, with the hardening is carried out from 750 °C, significantly lower than hardering from 760 °C. With the increase of quenching temperature, this difference decreases after quenching from temperatures 770–800 °С with the level of hardening of the alloy during subsequent aging is practically the same. Comparative studies of the structure and properties of elements heat – treated under different conditions (furnaces with controlled air atmosphere, vacuum containers, molten salts). It is established that the main reason for the shrinkage value is the difference in their structural state caused by the unequal heating time of the material to the aging temperature.

Retrofitting of Imperfect Halved Dovetail Carpentry Joints for Increased Seismic Resistance

This paper presents possibilities for anti-seismic improvement of traditional timber carpentry joints. It is known that the structural response of historical roof frameworks is highly dependent on the behavior of their joints, particularly, their capacity for rotation and energy dissipation. Any strengthening, or retrofitting, approach must take into account conservation requirements, usually expressed as conditions involving minimal intervention. Several retrofitting methods were tested on replicas of historical halved joints within various national and international research projects. The joints were produced with traditional hand tools, and made using aged material taken from a demolished building. The paper presents two approaches, each utilizing different retrofitting technologies that avoid completely dismantling the joint and consequently conserve frame integrity. The energy dissipation capacity is increased by inserting mild steel nails around a wooden pin, and connecting the two parts of the halved joint. In the second case, two thin plates made of a material with a high friction coefficient are inserted into the joint and fastened to the wooden elements. This is done by removing the wooden connecting pin and slightly opening a slot for the plates between the halved parts. In addition, the paper presents an application for disc brake plates, as well as thin plates made of oak.

Synthesis of Zeolite from Water Treatment Sludge and its Application to the Removal of Brilliant Green

In this work, water treatment sludge from the water treatment plant was used to synthesize zeolite material. In the synthesis, the washed sludge was mixed with sodium hydroxide and then heated at 600ºC for 6 h. After agitation, the aged material was heated in a water bath at 80ºC for different period of aging times. Based on XRD and SEM analyses, Faujasite zeolite was obtained. Then, the feasibility of employing the obtained zeolite as adsorbent for Brilliant Green (BG) removal was investigated. The effect of adsorbent dosage and contact time were examined. Adsorption kinetics and isotherm were also evaluated. The results showed that the obtained zeolite has potential for applying as low-cost adsorbent for the removal of BG from wastewater with higher than 97% adsorption efficiency.

Toughening Behavior in Alloy 617 with Long Term Ageing

The influence of ageing at temperature 700°C for up to 20 000 hours on the deformation, damage and fracture behavior of Alloy 617 has been investigated by two toughness tests. Dense nano γ` phase and carbides are the main precipitates. However, the long-term aged material still shows high toughness. The mechanism has been studied using electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI). The results show that dense nano/micro-twins have been formed in the adjacent of the fracture front during the impact toughness or CTOD testing. Increase of ageing time reduces the number of nano/micro-twins, but they can be observed in all aged materials in spite of different strain rates. This indicates that besides dislocation slip, twinning is another deformation mechanism in long term aged material during the toughness tests. Formation of nano/micro-twins may be one of contributions to high toughness in the aged material, which is termed as twin induced toughening.