Dynel fibers


We have already diseussed this important teehnology in Chapter 5, but a review may be helpful in plaeing its importanee to sludge proeessing into perspeetive. The vacuum filter for dewatering sludge is a drum over which is laid the filtering medium eonsisting of a eloth of cotton, wool, nylon, dynel, fiber glass or plastie, or a stainless steel mesh, or a double layer of stainless steel coil springs. The drum with horizontal axis is set in a tank with about one quarter of the drum submerged in conditioned sludge. Valves and piping are so arranged that, as a portion of the  [c.520]

Another preparative method for the enone 554 is the reaction of the enol acetate 553 with allyl methyl carbonate using a bimetallic catalyst of Pd and Tin methoxide[354,358]. The enone formation is competitive with the allylation reaction (see Section 2.4.1). MeCN as a solvent and a low Pd to ligand ratio favor enone formation. Two regioisomeric steroidal dienones, 558 and 559, are prepared regioselectively from the respective dienol acetates 556 and 557 formed from the steroidal a, /3-unsaturated ketone 555. Enone formation from both silyl enol ethers and enol acetates proceeds via 7r-allylpalladium enolates as common intermediates.  [c.364]

Aqueous media, such as emulsion, suspension, and dispersion polymerization, are by far the most widely used in the acryUc fiber industry. Water acts as a convenient heat-transfer and cooling medium and the polymer is easily recovered by filtration or centrifugation. Fiber producers that use aqueous solutions of thiocyanate or zinc chloride as the solvent for the polymer have an additional benefit. In such cases the reaction medium can be converted directiy to dope to save the costs of polymer recovery. Aqueous emulsions are less common. This type of process is used primarily for modacryUc compositions, such as Dynel. Even in such processes the emulsifier is used at very low levels, giving a polymerization medium with characteristics of both a suspension and a tme emulsion.  [c.279]

An example of a commercial semibatch polymerization process is the early Union Carbide process for Dynel, one of the first flame-retardant modacryhc fibers (23,24). Dynel, a staple fiber that was wet spun from acetone, was introduced in 1951. The polymer is made up of 40% acrylonitrile and 60% vinyl chloride. The reactivity ratios for this monomer pair are 3.7 and 0.074 for acrylonitrile and vinyl chloride in solution at 60°C. Thus acrylonitrile is much more reactive than vinyl chloride in this copolymerization. In addition, vinyl chloride is a strong chain-transfer agent. To make the Dynel composition of 60% vinyl chloride, the monomer composition must be maintained at 82% vinyl chloride. Since acrylonitrile is consumed much more rapidly than vinyl chloride, if no control is exercised over the monomer composition, the acrylonitrile content of the monomer decreases to approximately 1% after only 25% conversion. The low acrylonitrile content of the monomer required for this process introduces yet another problem. That is, with an acrylonitrile weight fraction of only 0.18 in the unreacted monomer mixture, the low concentration of acrylonitrile becomes a rate-limiting reaction step. Therefore, the overall rate of chain growth is low and under normal conditions, with chain transfer and radical recombination, the molecular weight of the polymer is very low.  [c.279]

Cloths from synthetic fibers are superior to many of the natural cloths thus far considered. They do not swell as do natural fibers, are inert in many acid, alkaline and solvent solutions and are resistant to various fungus and bacterial growths (the degree depending on the particular fiber and use). Several synthetic fibers resist relatively high temperatures, and have a smooth surface for easy cleaning and good solids discharge. Some of the most widely used synthetic filter media are nylon, Saran, Dacron, Dynel, Vinyon, Orion, and Acrilan. Table 2 compares the physical properties of several synthetic fiber filter media. Tightly woven, monofilament (single-strand) yarns consist of small-diameter filaments. They tend to lose their tensile strength, because their small diameters reduce their permeability thus multifilament yarns are normally used. Monofilament yarns in loose weaves provide high flowrates, good solids discharge, easy washing and high resistance to blinding, but the turbidity of the filtrate is high and recirculation is usually necessary, initially at least.  [c.129]

Indicate, if known, preferred bag material that will withstand environment, e.g., fibers of glass, polyester, Teflon , Nomex , polypropylene, polyethylene, cotton, wool, nylon, Orion , Dacron , and Dynel . The type of weave of fiber should be recommended by the manufacturer. The fabrics may be felted or woven [47,48] in weaves of plain, satin, or twill, and should be resistant to any corrosive material in the solid particles or the gas stream.  [c.273]

Acrylic fibers are a major synthetic fiber class developed about the same time as polyesters. Modacrylic fibers are copolymers containing between 35-85% acrylonitrile. Acrylic fibers contain at least 85% acrylonitrile. Orion is an acrylic fiber developed by DuPont in 1949 Dynel is a modacrylic fiber developed by Union Carbide in 1951.  [c.368]

Dynel, a modacrylic fiber, is produced by copolymerizing vinyl chloride with acrylonitrile. Solution spinning is also used where the polymer is dissolved in a solvent such as acetone. After the solvent is evaporated, the fibers are washed and subjected to stretching, which extends the fiber 4-10 times of the original length.  [c.369]

Acrylic fiber breaking strength ranges between 22,000 and 39,000 psi and they have a water absorption of approximately 5%. Dynel, due to the presence of chlorine, is less flammable than many other synthetic fibers.  [c.369]

Flame-Resistant Fibers. Acryhcs have reasonably good flame resistance compared to cotton and regenerated ceUulosic fibers. In addition, acryhcs tend to chat when burning rather than forming melts as do polyesters and nylons. Additional flame resistance is requited for certain end uses, such as children s sleepwear, blankets, carpets, outdoor awnings, and drapery fabrics. This can be achieved by copolymetizing acrylonitrile with halogen-containing monomers such as vinyl chloride, vinyl bromide, and vinyUdene chloride. ModacryUcs ate used where a high resistance to burning is requited. In such fibers the level of halogen-containing monomers may be over 50%, as in Dynel, one of the earliest modacryhcs. This fiber, no longer produced, was 50/60 acrylonitrile—vinyl chloride copolymer. Tennessee Eastman s Vetel, an acrylonitrile—vinyUdene chloride copolymer, has also been discontinued.  [c.284]

In spite of its graduate status, the new department did offer some undergraduate courses, initially for students in other departments. One of the members of faculty was Jack Frankel, who was a disciple of Daniel Rosenthal at the University of California, Los Angeles... who had developed such a course there . Frankel worked out some of the implications of this precursor by developing a broadly based undergraduate lecture course at Northwestern and, on the basis of this, writing a book entitled Principles of the Properties of Materials (Frankel 1957). Fine remarks that this course and Jack s thinking were key elements in developing materials science at Northwestern . Various other departments accepted this as a service course. According to the minutes of a faculty meeting in May 1956, it was resolved to publish in the next University Bulletin a paragraph which included the statement A student who has satisfactorily completed a programme of study which includes most of these (undergraduate) courses will be adequately prepared for professional work or graduate study in metallurgy and materials seienee . So, from 1957, undergraduates could undertake a broad study of materials in a course provided by what was still a metallurgy department. In February of 1958, a memorandum was submitted to the responsible academic dean, with the title The Importanee of Materials Science and Engineering. One sentence in this document, which was received with favour by the dean, reads Traditionally the field of material science (even at this early stage, the final s in the adjective, materials , was toggled on and off) has developed along somewhat separate channels - solid state physics, metallurgy, polymer chemistry, inorganic chemistry, mineralogy, glass and ceramic technology. Advance in materials science and technology is hampered by this artificial division of the whole science into separate parts. The document went on to emphasise the advantages of bringing together a group of specialists in the various types of materials and allowing and encouraging their cooperation and free interchange of ideas . Clearly this proposal was approved at a high level, for at a meeting a few months later, in December 1958, the metallurgy faculty meeting resolved, nemine contradicente, to change the name of the Graduate Department of Metallurgy to Graduate Department of Materials Science, and in January 1959 the university trustees approved this change.  [c.4]


See pages that mention the term Dynel fibers : [c.274]    [c.1471]    [c.360]   
Chemistry of Petrochemical Processes (2000) -- [ c.369 ]