Volume synthetic polymers

Polyethylene is, by a wide margin, the largest volume synthetic polymer made by mankind. As of this writing, about 77 million metric tons are produced annually and the growth rate is expected to continue at about 5% per year into the foreseeable future. Within the three minutes or so it takes to read this preface, over 400 tons of polyethylene will have been manufactured. It is produced in various forms on 6 continents and its applications are ubiquitous in daily life, from the trash bag you placed on the curb this morning to Uncle Fred s artificial hip. 

Initially, all of the SBR polymer known as GR-S produced during World War II was by the batch process. Later, it was thought that a higher volume of polymer would be needed for the war effort. The answer was found in switching from batchwise to continuous production. This was demonstrated in 1944 at the Houston, Texas, synthetic mbber plant operated by The Goodyear Tire Rubber Company. One line, consisting of 12 reactors, was lined up in a continuous mode, producing GR-S that was mote consistent than the batch-produced polymer (25). In addition to increased productivity, improved operation of the recovery of monomers resulted because of increased (20%) reactor capacity as well as consistent operation instead of up and down, as by batchwise polymerisation. 

Styrene—butadiene elastomers, emulsion and solution types combined, are reported to be the largest-volume synthetic mbber, with 28.7% of the world consumption of all synthetic mbber in 1994 (38). This percentage has decreased steadily since 1973 when SBR s market share was 57% (39). The decline has been attributed to the switch to radial tires (longer milage) and the growth of other synthetic polymers, such as polyethylene, polypropylene, polyester, and polystyrene. Since 1985, production of SBR has been flat (Table 3). 

Poly(viayl alcohol) (PVA), a polyhydroxy polymer, is the largest-volume synthetic, water-soluble resin produced in the world. It is commercially manufactured by the hydrolysis of poly(vinyl acetate), because monomeric vinyl alcohol caimot be obtained in quantities and purity that makes polymerisation to poly(vinyl alcohol) feasible (1 3). 

In addition to polymer standards, a number of broad distribution, water-soluble polymers can be characterized on TSK-PW columns using universal calibration. These include both fully and partially hydrolyzed PVA, PAAM, PEE, and dextran. PVA, the world s largest-volume, synthetic, water-soluble polymer, was first successfully separated on TSK-PW columns by Hashimota et al. (10). In the 1980s, the use of low-angle, laser light-scattering detection... 

Polyethylene s simplicity of structure has made it one of the most thoroughly studied polymeric materials. With an estimated demand of close to 109 billion pounds in 2000 of the homopolymer and various copolymers of polyethylene,24 it is by far the world s highest volume synthetic macromolecule. Therefore, it is still pertinent to study its structure-property relationships, thermal behavior, morphology, and effects of adding branches and functional groups to the polymer backbone. 

Many synthetic water-soluble polymers are easily analyzed by GPC. These include polyacrylamide,130 sodium poly(styrenesulfonate),131 and poly (2-vinyl pyridine).132 An important issue in aqueous GPC of synthetic polymers is the effect of solvent conditions on hydrodynamic volume and therefore retention. Ion inclusion and ion exclusion effects may also be important. In one interesting case, samples of polyacrylamide in which the amide side chain was partially hydrolyzed to generate a random copolymer of acrylic acid and acrylamide exhibited pH-dependent GPC fractionation.130 At a pH so low that the side chain would be expected to be protonated, hydrolyzed samples eluted later than untreated samples, perhaps suggesting intramolecular hydrogen bonding. At neutral pH, the hydrolyzed samples eluted earlier than untreated samples, an effect that was ascribed to enlargement... 

Most of the plastics and synthetic polymers that are used worldwide are produced from petrochemicals. Replacing petroleum-based feedstocks with materials derived from renewable resources is an attractive prospect for manufacturers of polymers and plastics, since the production of such polymers does not depend on the limited supply of fossil fuels [16]. Furthermore, synthetic materials are very persistent in the environment long after their intended use, and as a result their total volume in landfills is giving rise to serious waste management problems. In 1992,20% of the volume and 8% of the weight of landfills in the US were plastic materials, while the annual disposal of plastics both in the US and EC has risen to over 10 million tons [17]. Because of the biodegradability of PHAs, they would be mostly composted and as such would be very valuable in reducing the amount of plastic waste. 

At the symposium on which this book is based, the various authors presented papers on the general topic of polymer adsorption and particle stabilization/destabilization. In this volume both aqueous and nonaqueous systems are included, comprising work on both natural and synthetic polymers. Together the chapters constitute a comprehensive update of research in progress on these topics and provide broad coverage of both experimental and theoretical aspects. 

Indeed these qualities have been developed since the mid-Century so that in a particular segment of the information industry such as telephones and communications, our volume of synthetic polymers used annually exceeds that of any other class of materials, although the actual tonnage of metallic and inorganic matter still leads. For the world of tomorrow, we find microelectronics, thin film circuitry and systems and, especially now photonics, with lasers and light guides, to be dominant components. All of these strongly use polymers, for their special physical-chemical as well as familiar mechanical and electro-optical qualities. 

Equation (88) is the expression used commonly for solutions of synthetic polymers, but, where the nature of adsorption and binding is of critical interest, alternative forms exist. These differ mainly in the modes of expressing concentration (e.g. activity, molality, molarity, mass/unit volume). Interrelations among the units and expressions have been presented very clearly by Timasheff and Townend15. ... 

Over the years, modeling of carbohydrates has emphasized intramolecular rather than intermolecular structures. The same holds true in the study of synthetic polymers and polypeptides. Only one such study for carbohydrates comes to mind (1) where the unit cell dimensions and symmetry were not used. Even there, a volume constraint was used, limiting the possible structures. When such constraints are used, one does not obtain an explanation for why the crystal structure is the stable form. 

Blending of the lowest price commodity polymers from synthetic and carbohydrate polymer families [e.g., poly(ethylene) and starch] would appear to follow these laws. Although each polymer class is produced in large volume (first law), the production rate for com starch/synthetic polymer blends is much lower than that for the synthetic polymer this slower extrusion rate directly affects the final cost. Ignoring this limitation, the film properties of the blend are significantly poorer than those of the synthetic polymer film. Both deficiencies are related to the poor thermoplastic properties of water-soluble polymers such as cora-starch. 

Stereoselective catalysis using biocatalysts (e.g. enzymes) and also of rationally designed small chiral molecules, deals essentially with the same principle the spatial and selective docking of guest molecules to a chiral host molecule to form complementary interactions to form reversible transient molecule associates (see the specific sections in this volume). The enantiomeric excess of a certain reaction and hence the result will be determined by the degree of chiral discrimination. Along the same theoretical lines the concepts of protein (enzyme, antibody, etc.) mimicks via imprinted" synthetic polymers should be mentioned and will be discussed further. 

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