Aging test methods

Artificial ageing test methods simulate the behaviour of the cured adhesive in the bonded joint under environmental influences. The exposures are for example heat, cold, moisture, chemicals or UV-radiation and their combinations. Each ageing test method defines the duration of exposure, exposure temperature, type and concentration of chemicals and joint design. 

Failure of rubber parts used in domestic water applications has been frequently reported, and complaints include swelling and cracking and are related to nitrile and ethylene-propylene copolymer-type compounds. An ageing test method is developed, and effects of the different chemicals used in the purification processes on nitrile and EPDM vulcanisates compared. Butyl, halobutyls, ethylene-propylene copolymers and nitrile vulcanisates are evaluated two failure mechanisms are proposed and investigated. 7 refs. 

Antioxidants have been shown to improve oxidative stabiHty substantially (36,37). The use of mbber-bound stabilizers to permit concentration of the additive in the mbber phase has been reported (38—40). The partitioning behavior of various conventional stabilizers between the mbber and thermoplastic phases in model ABS systems has been described and shown to correlate with solubiHty parameter values (41). Pigments can adversely affect oxidative stabiHty (32). Test methods for assessing thermal oxidative stabiHty include oxygen absorption (31,32,42), thermal analysis (43,44), oven aging (34,45,46), and chemiluminescence (47,48). 

Because of the simplicity of the first test method, most of the comparisons are made usiag this technique. The effects of the aging process are usually measured on tensile properties such as tensile strength, elongation, and stress (modulus) at 300% elongation (42). 

In an age of consumei activism and increasing international trade, test methods and procedures assume more and more importance. Generally accepted... 

Let us say the first three samples tested were collected by Lab 2 from their production facility. These samples were retained from actual production lots. An aliquot from each retained jar was removed and shipped to Lab 1 in appropriate sealed containers. METHOD B testing was started at both laboratories the day following receipt of the samples to rule out any possible aging effects. METHOD A testing was performed in Lab 1 on the following day, while the METHOD A testing in Lab 2 occurred a week later. 

For single reactions with uncomplicated kinetics and with availability of a truly representative sample, the DSC can be used with different scan speeds (temperature/time) to determine kinetic constants in the Arrhenius equation. This method, proposed by Ozawa [83] has been accepted by the ASTM Method E698. After determining kinetic constants by this method, it is desirable to check the constants by running an isothermal DSC aging test for a period of time followed by a DSC scan to see if the predicted fraction decomposition... 

The American standard ASTM D-2307 [12] provides a test method for measuring Relative thermal endurance properties of film insulated magnet wire . The ageing philosophy is similar to that required by IEC 60216 [9] and is based on the Arrhenius ageing model. Oven ageing is carried out at three specific temperatures. The samples are twisted wire... 

Parameters such as ageing. Influence of pigment concentration and Influence of coalescence of emulsion paints can also be studied using AC Impedance test methods. 

Renwick et al. (2000) have performed an analysis of the need for an additional UF for infants and children. They considered that the proposal to introduce an additional 10-fold factor when exposure of infants and children is anticipated implies either age-related differences between species or differences within humans, which exceed those present in adults. Alternatively, the extra factor could be related to deficiencies of current testing methods or concerns over irreversibility in developing organ systems. They concluded that the available data did not provide a scientific rationale for an extra factor due to inadequacy of inter- and intraspecies UFs. Justification for the factor therefore must relate to the adequacy and sensitivity of current methods or concern about irreversible effects in the developing organism. They also pointed out that when adequate reproduction, multigeneration, or developmental studies are conducted, there will be no need for an additional 10-fold factor. 

The NSR technology is regarded as the most reliable and attractive de-NOx method. However, catalyst degradation by SOx poisoning is a big problem. Sulfate was detected on the NSR catalyst after the aging test. S02 is oxidized and reacts with the NOx storage materials to form sulfates, which means the... 

Some of the conditions used in rubber test methods may need modifying for application to thermoplastic elastomers because of their intrinsic thermoplastic nature. If the temperatures generally used in ageing and compression set tests on thermosetting rubbers were applied to thermoplastic materials they could appear to perform extremely badly. Whether this was significant would depend on the service temperature. Data sheets need to be checked as those for thermoplastic elastomers may have used much lower temperatures that would be found for conventional rubbers, and it is only too easy to get a misleading impression of performance. 

Generally, vulcanised rubber is dimensionally very stable (unless it is strained), which probably explains the lack of standard test methods for this property. In this context, thermal expansion and swelling in liquids are properties considered in their own right and not normally thought of as being measures of dimensional stability. This is a different situation to that which exists with plastics where a number of dimensional stability tests are in existence. If a measure of dimensional change is required, the appropriate dimensions of a suitable sized test piece can be measured by any of the methods mentioned in this chapter before and after an ageing treatment. 

Stress relaxation measurements can also be used as a general guide to ageing, and it is particularly relaxation due to chemical effects which is then studied. Such measurements are normally made in tension and will be considered in Chapter 15 as an ageing test. Hence, in this section, only relaxation tests in compression will be discussed as this mode of deformation is the only one commonly used and standardised to directly estimate the relaxation of rubbers in service. For an application in tension, the methods described in Chapter 15 could, of course, be adapted. It must be appreciated that the methods in compression do not only measure relaxation due to physical effects, especially when elevated temperatures and liquid environments are used, so that the distinction is a little blurred. 

The actual exposure clearly requires a very specialised facility but the methods used to monitor changes are the same as for other ageing tests. For example, change in hardness and tensile properties would serve for general purpose evaluation and compression set and stress relaxation are relevant for seals. 

US Military Standard MIL-STD-286A(196l) (Propellants, Solid Sampling, Examination and Testing) Method 202.2.2(Detn of EtCentr in newly manufd proplnts) Method 217.2. l(Detn of available stabilizer in aged proplnts) 35)PATR 2700 Vol 1(1960), pp A516 Sc A674 36)US Joint Army-Navy Specification JAN-E-255 [Ethyl Centralite(Carbamite)] 37)J.Apatoff J.Cohen, "Determination of Admixture of Diphenylamine and Ethyl Centralite in Propellants ,Test Report T62-15-1, Frankford Arsenal, Philadelphia, Pa (1962)... 

Kohler et al. discussed the potential of the chemiluminescence technique as an industrial test method. Imaging chemiluminescence was used to assess antioxidant performance. An advantage over oven aging was found to be the possibility for evaluation of the oxidative stability of samples with unusual geometries, such as fibres and powder particles [136]. A correlation was also found between oven aging and chemiluminescence measurements on stabilised PP and it was shown that chemiluminescence measurements done at... 

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