Polymeric seal degradation in nuclear power plants: Effect of gamma radiation on sealing properties

An effort has been made to bridge the gap between academic knowledge of polymeric seal degradation and industrial practices. A series of physical and mechanical properties that can be related to the sealing behaviour of three commercial samples of nitrile rubber have been studied for their degradation when exposed to gamma radiation. For all samples the glass transition temperature, Tg, and Retention Factor, RF, were found to increase with total dose whilst Percentage Change in Mass, ΔM%, was found to decrease. The ultimate uptake of carbon dioxide, CO2, did not appear to change with radiation dose but the kinetics of the absorption process were found to decrease, suggesting the formation of crosslinks. The crosslinks formed appear to be dependent on the original material composition and comparison against degradation of material properties supports the theory behind butadiene, BDN, content being linked to a propensity for crosslink clustering

Impact of Oxygen Transport Properties on Polypropylene Thermal Oxidation, Part 1: Effect of Oxygen Solubility

A general kinetic model is proposed to describe the polypropylene thermal oxidation of thin polypropylene films in a wide range of temperatures (from 60 to 200°C) and oxygen partial pressures (from 0.02 to 5 MPa) using a single set of parameters. This model was calibrated with several series of experimental data including analyses of primary (hydroperoxides) and secondary oxidation products (carbonyl species), and subsequent changes in macromolecular properties (average molecular masses). It predicts the experimental data previously published in the literature in terms of induction times and maximal oxidation rates. The variability of the oxygen solubility coefficient allows to explain the scattering of induction times and oxidation rates among the whole iPP family, but also the dependence of this latter quantity with oxygen partial pressure. This variability is presumably due to iPP polymorphism in the temperature range where oxygen permeability is commonly measured. It is concluded that the kinetic model can be used to study the direct effect of iPP morphology on its thermal oxidation kinetics (chemistry of oxidation)

Assessment of Interchangeability of Postal Services in Terms of Value Added

This paper is focused on the issues of interchangeability of postal services. It presents the main terms related to the issues, the relevant legislation on postal services and describes the different aspects of the assessment of postal services interchangeability. It focuses mainly on the assessment of interchangeability of postal services in terms of value added. The aim of the article is to apply the method of determining the added value in assessing the interchangeability of postal services. The paper refers to a particular application of the proposed procedure and quantitative output of interchangeability evaluation of the postal services

Simulation of a Queuing System of a Post Office in Anylogic Software

This paper displays the design and application of a model that simulates the queuing system of a fictional post office. Starting point for solving more complicated optimization tasks is to create a system model that consists of elements of reality and the relationships between these elements. The key part of the paper includes the model of a queuing system of a post office created in Anylogic simulation software. The model of the post office displays post office with 5 postal counters, a certain input flow and a certain service time with an exponential probability distribution. The model also includes statistics and cost calculation

Biowastes from wine as natural additive of polyolefins: Thermo- and photo-oxidation efficiency

International audienceBiowastes generated from agricultural industries constitute a new source for added value products that can be used in the polymer industry. Grape marc, a residue of the winery industry, is well‐known to be a rich source of polyphenols. The present work reports the use of polyphenol cocktail extracted from black Pinot grape marc as natural antioxidant in polyolefins. The purpose is to advance in the field of green stabilizer, by using an innovating approach based on the direct use of an efficient cocktail rather than a single original molecule to stabilize polymer. The antioxidant efficiency of polyphenol cocktail is measured against photo‐ and thermo‐oxidation conditions in the well‐known polypropylene polyolefin. Attention is paid to molecular structure evolution by rheology, and the efficiency to delay oxidation by‐product formation is monitored with infrared. The results confirm that cocktail approach is a promising route to develop green stabilizers