Polymer life-time prediction: The role of temperature in UV accelerated ageing of polypropylene and its copolymers

2014 ◽  
Vol 36 ◽  
pp. 82-87 ◽  
Author(s):  
Jiří Tocháček ◽  
Zlata Vrátníčková
Keyword(s):  
Life Time ◽  
Accelerated Ageing ◽  
Time Prediction

scholarly journals LIFE-TIME PREDICTION FOR POLYMER MATERIALS

2021 ◽  
Vol 59 (5) ◽  
Author(s):  
Chinh Thuy Nguyen ◽  
Hoang Thai
Keyword(s):  
Thermal Degradation ◽  
Fatigue Testing ◽  
Life Time ◽  
Working Life ◽  
Accelerated Testing ◽  
Polymer Materials ◽  
Accelerated Ageing ◽  
Time Prediction ◽  
Structure Morphology ◽  
Safe Working

Polymer testing including natural, accelerated testing or creep and fatigue testing, etc. is very important to evaluate the changes in properties, structure, morphology and durability of polymer materials. This is also the basis for experts to predict life-time or service working life or safe working life of polymer materials. This review presents an overview of the life-time prediction for polymer materials owing to natural tests or accelerated ageing tests and the methods for extrapolation of data from induced thermal degradation.  

Zeit und gutes Leben

2020 ◽  
Vol 74 (4) ◽  
pp. 493-513
Author(s):  
Holmer Steinfath
Keyword(s):  
Internal Structure ◽  
Good Life ◽  
External Factor ◽  
Life Time ◽  
The Good Life ◽  
Adequate Understanding ◽  
Gutes Leben

Time is a neglected subject in recent, especially analytically minded reflections on the good life. The article highlights the fundamental role of time and temporality for an adequate understanding of the good life. Time functions both as an external factor with which we have to reckon in our practical deliberations and as an internal structure of living our lives. It is argued that striving for a good life also means striving for being in harmony with the time of one's life. The exploration of this idea allows to link analytical with phenomenological approaches to time and good life.

scholarly journals Intracellular pH modulates the availability of vascular L-type Ca2+ channels.

1994 ◽  
Vol 103 (4) ◽  
pp. 647-663 ◽  
Author(s):  
U Klöckner ◽  
G Isenberg
Keyword(s):  
Intracellular Ph ◽  
Single Channel ◽  
Surface Membrane ◽  
Life Time ◽  
Bicarbonate Buffer ◽  
State Changes ◽  
Channel Currents ◽  
Inside Out ◽  
Ca2 Channels

L-type Ca2+ channel currents were recorded from myocytes isolated from bovine pial and porcine coronary arteries to study the influence of changes in intracellular pH (pHi). Whole cell ICa fell when pHi was made more acidic by substituting HEPES/NaOH with CO2/bicarbonate buffer (pHo 7.4, 36 degrees C), and increased when pHi was made more alkaline by addition of 20 mM NH4Cl. Peak ICa was less pHi sensitive than late ICa (170 ms after depolarization to 0 mV). pHi-effects on single Ca2+ channel currents were studied with 110 mM BaCl2 as the charge carrier (22 degrees C, pHo 7.4). In cell-attached patches pHi was changed by extracellular NH4Cl or through the opened cell. In inside-out patches pHi was controlled through the bath. Independent of the method used the following results were obtained: (a) Single channel conductance (24 pS) and life time of the open state were not influenced by pHi (between pHi 6 and 8.4). (b) Alkaline pHi increased and acidic pHi reduced the channel availability (frequency of nonblank sweeps). (c) Alkaline pHi increased and acidic pHi reduced the frequency of late channel re-openings. The effects are discussed in terms of a deprotonation (protonation) of cytosolic binding sites that favor (prevent) the shift of the channels from a sleepy to an available state. Changes of bath pHo mimicked the pHi effects within 20 s, suggesting that protons can rapidly permeate through the surface membrane of vascular smooth muscle cells. The role of pHi in Ca2+ homeostases and vasotonus is discussed.

Lifetime Distribution Estimation of Boot Seals in Automotive Applications by Bayesian Method

2006 ◽  
Vol 129 (3) ◽  
pp. 275-282 ◽  
Author(s):  
Fabrice Guerin ◽  
Ridha Hambli
Keyword(s):  
Finite Element ◽  
Bayesian Method ◽  
Life Time ◽  
Automotive Applications ◽  
Fatigue Lifetime ◽  
Time Prediction ◽  
Steering Mechanism ◽  
Market Requirements ◽  
Distribution Parameters ◽  
Lifetime Testing

The constantly increasing market requirements of high quality vehicles ask for the automotive manufacturers to perform lifetime testing to verify the reliability levels of new products. A common problem is that only a small number of examples of a component of system can be tested. In the automotive applications, mechanical components subjected to cyclic loading have to be designed against fatigue. Boot seals are used to protect velocity joint and steering mechanisms in automobiles. These flexible components must accommodate the motions associated with angulation of the steering mechanism. Some regions of the boot seal are always in contact with an internal metal shaft, while other areas come into contact with the metal shaft during angulation. In addition, the boot seal may also come into contact with itself, both internally and externally. The contacting regions affect the performance and longevity of the boot seal. In this paper, the Bayesian estimation of lognormal distribution parameters (usually used to define the fatigue lifetime of rubber components) is studied to improve the accuracy of estimation in incorporating the available knowledge on the product. In particular, the finite element results and expert belief are considered as prior knowledge. For life time prediction by finite element method, a model based on Brown–Miller law was developed for the boot seal rubber-like material.

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