Man-made materials

The discovery and development of polypropylene, the one genuinely new large tonnage thermoplastics material developed since World War II, forms part of what is arguably the most important episode in the history of polymer science. For many years it had been recognised that natural polymers were far more regular in their structure than synthetic polymers. Whilst there had been some improvement in controlling molecular architecture, the man-made materials, relative to the natural materials, were structurally crude. 

Most polymers used in oil field operations and resource recovery are synthetic. The man-made materials in common use are polyO-amidoethylene) ( = polyacrylamide ), poly( 1-amidoethylene-r-( sodium 1-carboxylatoethylene ) ( = partially hydrolyzed polyacrylamide ), poly(l-amidoethylene-r-( sodium 1-(2-methylprop-1N-yl-1-sulfonate)amidoethylene) (AMPS-acrylamide copolymer), and xanthan gum. Xanthan gum is a synthetic because no one finds a pool or river contaminated with Xanthomonas compestris that experiences the right sequence of solute to naturally produce the exocellular gum polymer. A fermenter is a man made object, a tree is not. 

The high specific surface area supports (10 to 100 m2/g or more) are natural or man-made materials that normally are handled as fine powders. When processed into the finished catalyst pellet, these materials often give rise to pore size distributions of the macro-micro type mentioned previously. The micropores exist within the powder itself, and the macropores are created between the fine particles when they... 

Tiller, W. A. 1964. Dendrites. Understanding of this familiar phenomenon has led to the development of useful man-made materials. Science. 146 871-879. 

Continuing with the mini-theme of computational materials chemistry is Chapter 3 by Professor Thomas M. Truskett and coworkers. As in the previous chapters, the authors quickly frame the problem in terms of mapping atomic (chemical) to macroscopic (physical) properties. The authors then focus our attention on condensed media phenomena, specifically those in glasses and liquids. In this chapter, three properties receive attention—structural order, free volume, and entropy. Order, whether it is in a man-made material or found in nature, may be considered by many as something that is easy to spot, but difficult to quantify yet quantifying order is indeed what Professor Truskett and his coauthors describe. Different types of order are presented, as are various metrics used for their quantification, all the while maintaining theoretical rigor but not at the expense of readability. The authors follow this section of their... 

Esqjosure to natural toxins prdaably enables insects to adapt more readily to man-made materials such as insecticides (2) ... 

Insects have developed resistance to cyanide, chlorinated hydrocarbons, organophosfiiates, carbamates, synthetic pyrethroids, and other insecticides ( ). This is not surprising vrtien considering the same complex of detoxifying enzymes, mainly r resented by hydrolytic, conjugative, and oxidative enzymes 9) is capable of detoxifying natural toxins as well as man-made materials. This ability is due to apprcpriate enzymes and/or isozymes that results in broad-substrate capabilities. For insects that feed on a wide variety of hosts (polyphagy), the spectrum of toxins that can be dealt with is truly remarkable. 

The release of man-made materials into the environment can have numerous harmful effects, as well as beneficial ones, but the cautious and conservative approach is to assume that any change in the environment could be potentially harmful unless proven otherwise. Actually, there is no way to prove that all the changes from the introduction of a product can be investigated within a given time period and are beneficial or neutral so, in effect, a strict application of this principle would mean a total ban on all product innovations and many existing products. 

During the last two decades, chemists have become increasingly focused on how molecules interact, i.e. on supramolecular chemistry. Dynamic intermolecular processes provide opportunities for incorporation of control, adaptation and function in man-made materials, as observed in living systems. In biology, these processes are tightly controlled by the catalytic action of enzymes. In this chapter, we focus on enzymatically controlled supramolecular polymerisation, whereby self-recognising molecular building blocks assemble to form extended onedimensional (ID) structures, or supramolecular polymers, with unique adaptive features. 

While natural and man-made materials can share the same physical and optical properties, there are still considerably differences, the main one being rarity. A natural gem takes considerable time to form and is usually millions of years old. Plus, many feel they have aesthetic quaUties not found in mass-produced materials. While natural and man-made materials appear nearly identical, their values vary considerably. For this reason it is important to be able to distinguish between the two. 

Man-made materials which can, to different degrees, self assemble, self diagnose, self repair, and recognize and discriminate physical and/or chemical stimuli, and, at the extreme, which have the capability of learning and self replicating The term is often considered to be synonymous with intelligent materials . 

Man-made materials having superior mechanical, thermal, electrical, optical, and other desirable properties. 

In testing the abrasiveness of floor finish of man-made materials, special variations of Shore s scleroscope are commonest. For ceramic and rock floor tiles, the commonest testers are Bohme s disc and the Teledyne Abra-der. For sewage and chemical stoneware, the standards now in force recommend abrasiveness tests with the use of a sandblasting jet blower. For technical reasons, a more precise Mackensen blower method for stoneware testing has been in use in Poland for several years. From the experience gained over years, a standard recommending Mackensen s method has been laid down for stoneware abrasiveness tests. Research results proved the usefulness of this method also for other ceramic materials. 

Of all the man-made materials, the synthetic materials are perhaps used most. What are synthetic materials ... 

Some of the man-made materials and chemicals used in our daily life are... 

Photooxidation Diffusion Chemical changes due to photochemical reactions Introduction of contaminants from man-made materials, such as solvents from polyvinyl chloride (PVC) materials and PVC cement, plasticizers, and phthalates from polyethylene and polypropylene materials Protection from exposure to light, use of amber glass bottles Use of inert materials (PTFE, fiberglass-reinforced epoxy materials) steam-cleaning of groundwater well components prior to installation... 

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