Resistance to the environment

Air Products and Chemicals pioneered the use of these potassium carbonate promoted hydrotalcite-based materials (K-HTC) for sorption-enhanced reforming of methane [26]. Mixing the K-HTC with a SMR catalyst in a 2 1 ratio gave high (90+%) conversions of methane at temperatures as low as 400 °C. In the first instance Ni-based catalysts were used, but they were not resistant to the environ-... 

Aromatic polyketones are semicrystalline materials that contain both ketone groups generally flanked by aromatic units. Many also have within them ether moieties that allow for some flexibility and better processing. They have good thermal stabilities, as well as offering good mechanical properties, flame resistance, impact resistance, and resistance to the environment. 

Evolution must be genomic exclusively because there is no pathway, within the extent of our understanding of molecular biology, that could feed back into our genome to effect changes that would make us more resistant to natural phenomena. Our brain, which makes us more resistant to the environment, was developed by genes but not by environmental vacillations. 

The ability of a flexible vinyl film to withstand the rigors of environmental exposure has been the subject of many studies, both reported and unreported. The extreme complexity of a vinyl system stems not only from the number of individual components necessary from a processing and performance point of view, but it is factorially compounded by the number of choices between components and their relative resistance to the environment. In many cases, the ability to formulate is not totally compatible with the performance requirement, and a compromise must be struck that will provide the optimum conformity to the most critical specifications. The development of unique products or additives to existing commercial materials to broaden formulating latitude has been and is a major stimulus to the growth of the vinyl industry. 

Active-passive behavior is dependent on the material-corrodent combination and is a function of the anodic or cathodic polarization effects, which occur in that specific combination. In most situations where active-passive behavior occurs, there is a thin layer at the metal surface that is more resistant to the environment than the underlying metal. In stainless steels, this layer is composed of various chromium and/or nickel oxides, which exhibit substantially different electrochemical characteristics than the underlying alloy. If this resistant, or passive, layer is damaged while in an aggressive environment, active corrosion of the freshly exposed surface will occur. The damage to... 

In summary, acrylic industrial coatings have been employed for almost half a century in applications where durability and resistance to the environment are paramount. Over the years, numerous chemical technologies have been developed to achieve specific properties. Because of their versatility and their inherent resistance properties, acrylic polymers have played a central role in the development of coating technology. The growth of new technologies for low-emission coatings has Increased this role even more. 

Three principal criteria were initially employed to select materials for evaluation. The first consisted of expectations, based upon an extensive computerized literature survey and manufacturers recommendations, that the materials would offer superior resistance to the environment of the collector. The next factor, that the sealant should not exhibit an extremely high cost, eliminated the very expensive high temperature specialty compounds. Thirdly, certain materials were examined because of their current extensive use in solar collectors although we did not expect them to display high thermal stability or good endurance characteristics. 

Plastics and rubbers are used as insulating and separating materials between different metallic materials to prevent galvanic corrosion. For this application specific requirements must be fulfilled, such as the necessary mechanical strength and thickness they must be fireproof, and resistant to the environment (including heat-resistant to a specified extent). In addition the following are important ... 

P(9) The information supplied by resin suppliers should be used as an initial guide in selection. If the consequences of failure (as defined by the service application) are great, then test data should always be provided to verify resistance to the environment. 

Pigments must be somewhat resistant to the environment and must be compatible with the resin. For example, calcium carbonate, which is attacked by acid, should not be used in an acid environment. Water soluble salts are corrosion promoters, so special low salt containing pigments are used in primers for steel. 

To design around these problems it is necessary to do several things. First, the material selected for the part should be examined for chemical resistance to the environment and for adequate temperature resistance. Some of these data are available but, it should be pointed out that a combination of several environmental factors such as heat and... 

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