Polymers issues

General Polymers issues a monthly newsletter, Cyclelhne Tips, which contains technical tips on processing, tool design, etc. The current and past issues of CycleTime Tips may be accessed from the General Polymers webpage (http //www.ashchem.com/ home/index.asp nav id=4 sub nav=4)... 

Audebert, R, S. Sadki, F. Moinmandre, and G. Clavier. 2004. First example of an electroactive polymer issued from an oligothiophene substituted tetrazine. Electrochem Commun 6 144—147. 

The first experiments in this field, on racemic a-olefins, appeared in 1955 when crystalline isotactic polymers issued from racemic 4-methyl-1-hexene were described by Natta etal [161a]. Several racemic a-olefins 3-methyl-l-pentene (a), 4-methyl-1-hexene (b), 5-methyl-1-heptene (c), and 3,7-dimethyl-l-octene (d) were polymerized by a catalytic... 

Melt blowing is used commercially as a one-step process for converting polymer resin directly into a nonwoven mat of superfine fibers. In the melt blowing process, high velocity hot air streams impact upon a stream of molten polymer as the polymer issues from a fine capillary. The result of this impact is that the polymer is rapidly (in about 50 ps) attenuated into fiber as fine as 1 pm in diameter. 

Small molecules can penetrate and penneate tlirough polymers. Because of this property, polymers have found widespread use in separation teclmology, protection coating, and controlled delivery [53]. The key issue in these applications is the selective penneability of the polymer, which is detennined by the diffusivity and the solubility of a given set of low-molecular-weight compounds. The diffusion of a small penetrant occurs as a series of jumps... 

The April 1988 issue of the Journal of Chemical Education contains a number of articles on polymers including a historical review enti tied Polymers Are Everywhere (pp 327-334) and a glossary of terms (pp 314-319)... 

We conclude this chapter and wrap up the last three chapters with a few remarks about the application of the ideas contained herein to polymer technology. Chapters 2-4 have been concerned with various aspects of the mechanical states of polymers. The opinion was expressed in Chap. 1 that if polymers did not possess the mechanical properties they have, this whole class of compounds might be relegated to the category of laboratory curiosities. On the basis of any number of criteria-the number of scientists employed, the number of industries involved, the number of publications released, the number of patents issued—polymer science proves to be very viable indeed. 

Furfural is a resin former under the influence of strong acid. It will self-resinify as well as form copolymer resins with furfuryl alcohol, phenoHc compounds, or convertible resins of these. Conditions of polymerization, whether aqueous or anhydrous, inert or oxygen atmosphere, all affect the composition of the polymer. Numerous patents have issued relating to polymerization and to appHcations. Although the resins exhibit a degree of britdeness, they have many outstanding properties a number of appHcations are discussed under "Uses."... 

The first criterion was associated with improved secondary and tertiary petroleum recovery processes. This is the justification for the patent appHcations issued to the Dow (50) and Exxon (51) corporations. The additional costs of production and the increased adsorption of such modified water-soluble polymers are detrimental to the commercial appHcation of such polymers and even the academic studies in this area have decreased in recent years. 

Rayon is unique among the mass produced man-made fibers because it is the only one to use a natural polymer (cellulose) directly. Polyesters, nylons, polyolefins, and acryflcs all come indirectly from vegetation they come from the polymerization of monomers obtained from reserves of fossil fuels, which in turn were formed by the incomplete biodegradation of vegetation that grew millions of years ago. The extraction of these nonrenewable reserves and the resulting return to the atmosphere of the carbon dioxide from which they were made is one of the most important environmental issues of current times. CeUulosic fibers therefore have much to recommend them provided that the processes used to make them have minimal environmental impact. 

Until 1990 the EPA maintained a Hst of chemicals suitable for potable water treatment ia the United States. Siace then the entire question of certification and standards has been turned over to a group of organi2ations headed by the National Sanitation Eoundation, which has issued voluntary standards. As of January 1992, standards had been issued for most of the principal inorganic products, but only for two polymers, poly(DADMAC) and Epi-DMA (epichl orohydrin dimethyl amine) polymers (78). Certifications for commercial products meeting specified standards are issued by the National Sanitation Eoundation, Underwriter Laboratories, and Risk Eocus/Versar (79). 

In the area of municipal and iadustrial wastewater treatment, the principal environmental issue is the toxicity of residual flocculating agents ia the effluent. Laboratory studies have shown that cationic polymers are toxic to fish because of the iateraction of these polymers with giU. membranes. Nonionic and anionic polymers show no toxicity (82,83). Other studies have shown that ia natural systems the suspended inorganic matter and humic substances substantially reduce the toxicity of added cationic polymer, and the polymers have been used successfully ia fish hatcheries (84—86). Based on these results, the EPA has added a protocol for testing these polymers for toxicity toward fish ia the presence of humic acids (87). The addition of anionic polymers to effluent streams containing cationic polymers to reduce their toxicity has been mentioned ia the patent Hterature (83). 

Cables are available in a variety of constmctions and materials, in order to meet the requirements of industry specifications and the physical environment. For indoor usage, such as for Local Area Networks (LAN), the codes require that the cables should pass very strict fire and smoke release specifications. In these cases, highly dame retardant and low smoke materials are used, based on halogenated polymers such as duorinated ethylene—propylene polymers (like PTFE or FEP) or poly(vinyl chloride) (PVC). Eor outdoor usage, where fire retardancy is not an issue, polyethylene can be used at a lower cost. 

A Macromolecular Division of lUPAC was created in 1967, and it created a permanent Commission on Macromolecular Nomenclature, parallel to the other nomenclature commissions. The Commission over the years has issued recommendations on basic definitions, stereochemical definitions and notations, stmcture-based nomenclature for regular single-strand organic polymers and regular single-strand and quasisingle-strand inorganic and coordination polymers, source-based nomenclature for copolymers, and abbreviations for polymers. AH of these are coUected in a compendium referred to as the lUPAC Purple Book (99). 

Recommendations on additional aspects of macromolecular nomenclature such as that of regular double-strand (ladder and spiro) and irregular single-strand organic polymers continue to be pubHshed in I ure and Applied Chemistty (100,101). Recommendations on naming nonlinear polymers and polymer assembHes (networks, blends, complexes, etc) are expected to be issued in the near future. 

By 1980, research and development shifted from relatively inexpensive surfactants such as petroleum sulfonates to more cosdy but more effective surfactants tailored to reservoir and cmde oil properties. Critical surfactant issues are performance in saline injection waters, adsorption on reservoir rock, partitioning into reservoir cmde oil, chemical stabiUty in the reservoir, interactions with the mobiUty control polymer, and production problems caused by resultant emulsions. Reservoir heterogeneity can also greatly reduce process effectiveness. The decline in oil prices in the early 1980s halted much of the work because of the relatively high cost of micellar processes. 

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