Aging degradation

Brittleness with age. Degradative oxidation can be produced, even after vulcanization, due to oxygen and ozone attack to the carbon-carbon double bonds. Adequate antioxidants must be added if ageing is a key factor in performance. 

This report provides an aging assessment of electric motors and was conducted under the auspices of the USNRC NPAR. Pertinent failure-related information was derived from LERs, IPRDS, NPRDS, and NPE including failure modes, mechanisms, and causes for motor problems. In addition, motor design and materials of construction were reviewed to identify age-sensitive components. The study included consideration of the seismic susceptibility of age-degraded motor components to externally-induced vibrational effects. 

As discussed earlier under Section 2.3, Carbonyl index, in one relatively recent comparison of the photo-oxidative and thermal (oven-aged) degradation behaviour of different polyethylenes, additive free grades of a metallocene (mPE), an HDPE and a linear low-density PE (LLDPE) were analysed by a combination of mid-IR spectroscopy, TGA and CL [13]. The mid-IR... 

With continuous ageing, degradation of the cross-links occurs resulting in loss of flexural strength in the cured polyester. Use of proper antioxidants improves the resistance to heat deterioration. 

The weave of the cloth is seen to be a 3-to-l herringbone twill (7) [supposedly typical of near-Eastern cloths of antiquity (23)]. The fibrils on the surface show mechanical wear indicative of many flexions and aging degradation. 

Surface or bulk chemical reactions, including erosion and degradation are important aspects of polymeric systems. These processes can be desired, as is the case for surface modification reactions to increase, e.g., biocompatibility or drug delivery applications, while other processes are unwanted, such as ageing, degradation in harsh environments, or erosion. AFM approaches offer a unique possibility to study these processes in many cases under realistic conditions and thereby help identify the underlying mechanisms. 

In practice, it is very important to obtain a high primary hydroxyl content with minimum EO quantity. A high EO content leads to turbid polyether polyols because longer poly[EO] chains are insoluble in liquid polypropylene oxide. The flexible PU foams made with highly ethoxylated polyols have poor humidity/ageing/degradation characteristics and a lower compression strength. 

As a general rule, castor oil and its derivatives confer on the resulting PU hydrophobicity and water repellency. These polyols have an excellent compatibility with the pentanes that are used as blowing agents and the resulting PU foams have excellent resistance to humid ageing degradation. 

Performance, Degradation aging see Durability, Degradation aging. Degradability, etc. 

The remaining cell wall polymers are recombined through these cross-linking reactions thus some of the strength properties that were lost to aging degradation are restored. 

Residual amounts of some of these problematical substances remain in the product (low molecular components) and permeate to the outside during the utilization phase. Other processes (aging, degradation) continue throughout the hfecycle of the product beginning with new status. The aging rate, for example hydrolysis, depends on enviromnental conditions such as temperature, pressure, mediums, and time. 

Porter, M. L. and B. A. Barnes (1998). Accelerated aging degradation of glass fiber composites. Second International Conference on Composites in Infrastructure, University of Arizona, Tucson, AZ,pp. 446 59. 

Chemical resistance. Resists usual agents of age degradation (e.g., moisture, oxidation, rot, mildew, and many organic chemicals). 

Age. Has age degraded the motor skills, reflexes, memory, sense, or other capabilities to the point that job tasks can no longer be performed... 

DSC Monitors the difference In temperature between a sample and a reference material as a function of time and temperature In a specified atmosphere. Quantitatively measures heat absorbed or released by a material undergoing a physical or chemical change Glass transition, melt and phase change temperatures, heats of reaction, heat capacity, crystallinity, aging, degradation, and thermal history. 

Albertsson A-C et al. (1995) Degradation product pattern and morphology changes as means to differentiate abiotically and biotically aged degradable polyethylene. Polymer. 36(16) 3075-3083. 

Components and systems susceptible to ageing degradation should be so located as to facilitate free access for surveillance and testing. 

The intrinsic viscosity usually is the characteristic value that is used to specify the storage stability and the quality of a product (see Chap. 4). Based on the storage stability a change of the intrinsic viscosity [q] in dependence of the time gives information on the stability (aging, degradation). Based on a constant product quality (for example different batches), the intrinsic viscosity has to stay the same. 

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