DuPont continued polymers

Up to this point, it was considered that universities were where discoveries were made and industry was where they were put to some practical use. This separation between basic and applied work was quite prominent at this juncture and continues in many areas even today in some fields of work though the difference has decreased. But in polymers, most of the basic research was done in industry, having as its inception the decision by DuPont to bridge this unnatural gap between fundamental knowledge and application. In truth, they can be considered as the two hands of an individual, and in order to do manual work both hands are important. 

Viton. A trademark of the E.I. duPont de Nemours Co for a series of fluorelastomers based on the co-polymer of vinylidine fluoride and hexafluoropropylene with a repeating structure of [-CF2-CH2-CF2-CF(CF3H white, transparent solid sp grav 1.72—1.86. Resistant to corrosive liqs and chemicals up to 600°F, and useful in continuous service at 400—500°F. The material is resistant to weather, ozone, flame, oils, fuels, lubricants and many solvents According to Refs 2 3, Viton-A is used in many expl formulations developed by the Lawrence Livermore Laboratory, such as LX-04, LX-07, LX-10-0, LX-10-1 and LX-11-0 (see Vol... 

Nylon. In 1939 the DuPont Company introduced the first truly synthetic textile fiber. Dr. Wallace Carothers invented nylon as a result of his basic research into polymer science. Chemically, nylon is a polyamide fiber. The two major types of nylon polymer are used in textiles type 6,6 which is made by using hexam-ethylene glycol and adipic acid, and type 6, which is made by polymerizing e-caprolactam. Nylon fibers are made by melt-spinning the molten polymer. The result is a continuous filament fiber of indeterminate length. It is spun in many deniers, with its diameter varying from 10 to 50 microns. The cross-section usually is round, trilobal, or square with hollow channels when used as carpet fiber. 

Another area is the production of chemical intermediates from renewable feedstocks. Cargill-Dow and Dupont are just two of the companies beginning to market biobased polymers and plastics to replace petroleum based polymers. Again, the fermentation fundamentals originally developed for food manufacturing continue to apply to a wide variety of products. 

Greater success was achieved by DuPont who copolymerized, the sodium salt of 5-sulfoisophthalic acid into PET to render the polymer dyeable with cationic (basic) dyes. Basic dyeable PET was successfully launched as Dacron 64 in the form of a low-pill staple product [64]. The presence of the sulfonate groups in the polymer chain also acts as an ionic dipolar cross-link and increases the melt viscosity of the polymer quite markedly. Thus, it is possible to melt-spin polymer with IV 0.56 under normal conditions, giving a low-pill fiber variant. The fiber also has a greater affinity for disperse dyes due to the disruption of the PET structure. Continuing this theme, there are deep dye variant PET fibers, often used in PET carpet yarns, which are copolymers of PET with chain-disrupting copolymer units like polyethylene adipate. They have less crystallinity and a lower Tg. therefore, they may be dyed at the boil without the use of pressure equipment or carrier at the cost of some loss of fiber physical properties. 

PTFE is called a homopolymer, a polymer made from a single monomer. Recently, many PTFE manufacturers have added minute amounts of other monomers to their PTFE polymerizations to produce alternate grades of PTFE designed for specific applications. Fluoropolymer manufacturers continue to call these grades modified homopolymer at below 1% by weight of comonomer. DuPont grades of this type are called Teflon NXT resins. Dyneon TFM modified PTFE incorporates less than 1% of a comonomer perfluoropropyl vinyl eflier (PPVE). Daikin s modified grade is Polyflon M-111. 

Xylitol is a specialty chemical with the effects of extreme cooling, caries prevention and safety for diabetes, which are beneficial for manufacturing foods and mouth-care products. As a platform chemical, it also can be converted to various compounds for polymer synthesis and directly polymerized for production of unsaturated polyester resin (Werpy and Petersen, 2004). Danisco (currently part of Dupont Co.) is the largest xylitol producer, and many companies in China and South America (Brazil) manufacture xylitol commercially. The global market of xylitol is estimated to be more than 125,000 tons per year, with 4.5-5.5/kg for bulk purchase and 20/kg in supermarket (da Silva and Chandel, 2012). Xylitol has a 12% share of the total polyols market with growth estimated to increase threefold (da Silva and Chandel, 2012). The xylitol market continues to increase worldwide due to an enhancement in health consciousness and chewing gum market, and new application development as a chemical feedstock. 

Perfluorosulfonic add (PFSA) membranes continue to be the industry standard for low-temperature PEMFCs due to their excellent proton conductivity, mechanical and chemical stability that is difficult to surpass. The Nafion membrane produced by DuPont has been the most studied (Mauritz and Moore, 2004 Grot, 2008). Nafion membranes are coded according to the polymer equivalent weight (EW) (first two digits), the membrane thickness (in mil, 1/1000 inch, corresponding to 25 pm) - third, or third and fourth digits) thus Nafion N117 is polymer EW 1100,7 mil thickness. In parallel with these developments, advances have been made on related perfluorinated ionomers that differ from the Nafion -type polymer... 

---