Gutta percha


To provide a good price / performance ratio.  [c.535]

Apart from the technical data, the customer expects good price/performance-ratio.  [c.856]

All the double bonds in rubber have the Z (or cis) con figuration A different polymer of isoprene called gutta-percha has shorter polymer chains and E (or trans) double bonds Gutta percha is a tough horn like substance once used as a material for golf ball covers  [c.408]

Gutta percha is a natural polymer of isoprene (3-methyl-l,3-butadiene) in which the configuration around each double bond is trans. It is hard and horny and has the following formula  [c.1062]

Gutta percha (hard rubber) 1.2-1.95 (65-95) 3-8 4000-10,000 104  [c.1067]

Figure 1.3 shows several repeat units of cis-l,4-polyisoprene and trans-1,4-polyisoprene. Natural rubber is the cis isomer of 1,4-polyisoprene, and gutta-percha is the trans isomer.  [c.28]

Although the conditions of the polymerization reaction may be chosen to optimize the formation of one specific isomer, it is typical in these systems to have at least some contribution of all possible isomers in the polymeric product, except in the case of polymers of biological origin, like natural rubber and gutta-percha.  [c.29]

Gas—Tungsten Arc Welding. The GTAW process, often called the tungsten—inert gas or TIG process, is shown in Figure lb. Here the electrode is nonconsumable and shielding is provided by the flow of inert gas through the welding-torch nozzle. Argon and helium are commonly used, as well as argon—helium mixtures traces of hydrogen are sometimes present. The arc may be used alone to fuse base metal together or, as shown in Figure lb, separately added filler rod can be fed into the weld pool.  [c.342]

Plasma Arc Welding. In the transferred-arc mode of the PAW process, shown in Figure Ic, the arc is between a nonconsumable electrode and the base metal, in a manner similar to the GTAW process. The unique feature is the flow of inert gas around the electrode and through a restricted orifice, which constricts the arc to form a plasma jet. A second, outer stream of shielding gas protects the molten metal from atmospheric contamination. In the nontransferred arc mode of the PAW process, the arc is between the electrode and the constricting orifice. This mode is used for plasma spraying and for heating nonmetals.  [c.342]

Selective catalytic abatement uses a catalyst and ammonia fuel to selectively reduce nitrogen oxides in preference to combustion with the much higher levels of oxygen in the tail gas. This method can operate over a wide range of pressures but requires temperatures to be 210—410°C. Eor effective abatement, a slight excess of ammonia is used, leaving 5—20 ppmv in the treated tail gas. Higher concentrations of ammonia present a potential safety hazard that has to be avoided by the use of good process controls. Ammonia at low temperatures can form ammonium nitrate and nitrite, which might accumulate in downstream equipment and pose an explosion hazard upon being heated. Base metal oxides (titanium and vanadium) are commonly used as the catalysts, although platinum, palladium, or zeoHtes may also be used. The catalysts are usually shaped as honeycombs or flat parallel plates. The treated tail gases are also reheated for improved expander energy recovery.  [c.43]

Bakelite, bleached 20-60 0.22 Gutta percha 20 1.983 zontal axis 0-100 0.0832  [c.174]

UF Membranes Design of UF membranes prizes high retention, hydrolytic stabihty, and good process flux. Since fouling is the principal impediment to flux, and membranes which are hydrophilic gener ly foul less rapidly, there is competition between the truly stable hydrophobic membranes and the less-fouhng-prone hydrophilic ones.  [c.2038]

Another way to study corrosion in pipe lines is to install in the line short sections of pipe of the materials to be tested. These test sections should be insulated from each other and from the rest of the piping system by means of nonmetalhc couphngs. It is also good prac-tice to provide insulating gaskets between the ends of the pipe specimens where they meet inside the couplings. Such joints may be sealed with various types of dope or cement. It is desirable in such cases to paint the outside of the specimens so as to confine corrosion to the inner surface.  [c.2438]

When a candidate toller is not currently regulated by a governmental process safety requirement and the proposed toll project will not trigger regulation, evidence of other good process safety practices should be still be sought and evaluated. Tollers should consider the benefits to their business that come from using recognized tools available through implementing a process safety system as defined by these regulations, or similar systems as defined by CMA s Responsible Care Codes or CCPS publications. These include key elements such as  [c.31]

Any resemblance to the first package cost and any later spare costs, unfortunately, is a coincidence. It is suggested, if funds permit, that at least the first spares be purchased with the compressor because they can be expected to come at a good price.  [c.456]

By 1900 the only plastics materials available were shellac, gutta percha, ebonite and celluloid (and the bitumens and amber if they are considered as plastics). Early experiments leading to other materials had, however, been carried out. The  [c.4]

The advent of war brought plastics more into demand, largely as substitutes for materials, such as natural rubber and gutta percha, which were in short supply. In the United States the crash programme leading to the large-scale production of synthetic rubbers resulted in extensive research into the chemistry underlying the formation of polymers. A great deal of experience was also obtained on the large-scale production of such materials.  [c.7]

Related to stereoregularity is the possibility of cis, trans isomerism. The molecule of natural rubber is a c/s-1,4-polyisoprene whilst that of gutta percha is the trans isomer.  [c.69]

These different forms Figure 4.7) take up different crystalline structures and consequently the bulk properties of the polymer differ. At room temperature gutta percha is a stiff leathery material.  [c.69]

Non-elastomeric chemical derivatives of natural rubber are discussed in Chapter 30 in which chemically related naturally occurring materials such as gutta percha and balata are briefly considered.  [c.289]

Gutta Percha and Related Materials 865  [c.865]

GUTTA PERCHA AND RELATED MATERIALS  [c.865]

Chemical nature Isolation of casein from milk Production of casein plastics Properties of casein Applications Miscellaneous Protein Plastics Derivatives of Natural Rubber Gutta Percha and Related Materials Shellac  [c.926]

GUTTA-PERCHA SOLUTION 1205 900-32-2  [c.224]

If good process flow diagrams or process and instrumentation diagrams exist they will identify the plant sections.  [c.124]

For example, hazards assessments programs might be an early priority. Although a good Process Hazards Assessment program may exist within PSM, there may not be programs of comparable quality in occupational safety (job safety analysis) or environmental management. Developing an integrated program will provide early benefit to the occupational safety and environmental management. Using the existing PSM program as a basis will likely ensure success, yet there will be enough challenge from integrating other ESH needs for hazards assessment to be a credible test of integration.  [c.95]

Condensation of isoprene (2-methyl-1,3-butadiene) either leads to a polymer in which all double bonds are trans ( natural rubber ) or in which they are cis (gutta-percha).  [c.250]

Fig. 1. (a) The shielded-metal arc-weldiag (SMAW) process, (b) The gas—tungsten arc-welding (GTAW) process, (c) The plasma arc-welding (PAW) process, (d) The gas—metal arc-welding (GMAW) process, (e) The flux-cored arc-welding (FCAW) process, (f) The submerged arc-welding (SAW)  [c.342]

Natural mbber (Hevea) is 100% i7j -l,4-polyisoprene, whereas another natural product, gutta-percha, a plastic, consists of the trans-1,4 isomer. Up until the mid-1900s, all attempts to polymerize isoprene led to polymers of mixed-chain stmcture.  [c.469]

In atactic polyisoprene, R and S configurations occur at random. The different modes of enchainment of isoprene (1,2-, 3,4-, cis-1 4- and trans-1 4-) and the different stereochemical configurations that are possible result ia eight possible stereoregular polyisoprenes. The best known polyisoprenes of high stereoregularity are i7j -l,4-polyisoprene and /n j -l,4-polyisoprene. Natural mbber (Hevea, Guayule, tree mbber) and synthetic i7j -l,4-polyisoprene (Natsyn), currendy produced ia the United States by The Goodyear Tire Rubber Co., are examples of i7j -l,4-polyisoprene. Natural balata and gutta-percha and synthetic /n j -l,4-polyisoprene, currendy produced by the Kuraray Co., Ltd. of Japan, are examples of /n j -l,4-polyisoprene. A  [c.3]

In 1955, /n j -l,4-polyisoprene having a stmcture identical to that of natural gutta-percha was prepared using a triethylalurninum-a-titariium trichloride catalyst (39). Since then, vanadium catalysts, especially vanadium trichloride, with tri alkyl aluminums have been found to be the most active and stereospecific, and give the highest yields of /n j -l,4-polyisoprene (17). Polymerization of isoprene in heptane using triaLkylalurninium—vanadium trichloride catalyst yielded very high /n j -l,4-polyisoprene (40), and a triethylalurninum—vanadium trichloride catalyst gave about 97% /ram-1,4 microstmcture (nmr analysis) (41). Modification of the triaLkylalurninum—vanadium trichloride catalyst with ethers, such as diisopropyl ether, increased the polymer yield (42). Increased polymer yields have also been obtained with vanadium trichloride deposited on inert supports, eg, kaolin (43).  [c.4]

Whether the assets of a company are financed largely by stockholders equity (also called net woitn), or largely by debt, or by some combination of the two depends on a number of factors. If sales do not fluctuate, a company is in a good position to pay the fixed interest charges on debt. This is also the case if the revenue from sales is steadily increasing. In this case, any new common stock issued by the company is likely to command a good price, and it also increases the attractiveness of equity financing.  [c.841]

Current policy in API is to avoid commercial language in the API standard. API standards do not include a guarantee and warranty section. In the revisions, as they occur, other paragraphs deemed commercial are disallowed. This puts the burden of guarantee and warranty verbage on the user. A practical solution, if the user is not familiar with industry practices, is to solicit from the vendor a proposed guarantee that should be a zero tolerance on head and capacity. This would only be good prac-  [c.454]

The introduction to western civilisation of another natural resin from the east took place in the middle of the 17th century. To John Tradescant (1608-1662), the English traveller and gardener, is given the credit of introducing gutta percha. The material became of substantial importance as a cable insulation material and for general moulding purposes during the 19th eentury and it is only since 1940 that this material has been replaced by synthetic materials in undersea cable insulation.  [c.2]

J. Pharm. Soc. Japan, 1927, No. 549, 124. (17) Goto, Proc. Imp. Acad. Tokyo, 1920, 2, 414 see also Goto and Takubo, Bull. Chem. Soc. Japan, 1931, 6, 126. (18) Goto, ibid., 1929, 4, 129. (19) Goto and Nakamura, ibid., 1929, 4, 196. (20) Goto and  [c.274]

In the case of process safety, however, the situation is much less clear cut. The introduction of computer control increasingly changes the role of the worker to that of a problem solver and decision maker in the event of abnormalities and emergencies. In this role, it is not sufficient that the worker is trained and conditioned to avoid predictable accident inducing behaviors. It is also essential that he or she can respond flexibly to a wide range of situations that cannot necessarily be predicted in advance. This flexibility can only be achieved if the worker receives extensive support from the designers of the system in terms of good process information presentation, high-quality procedures, and comprehensive training.  [c.49]

All the double bonds in rubber have the Z (or cis) configuration. A different polymer of isoprene, called gutta-percha, has shorter polymer chains and E (or trans) double bonds. Gutta-percha is a tough, hornlike substance once used as a material for golf ball covers.  [c.408]


See pages that mention the term Gutta percha : [c.1005]    [c.1062]    [c.1070]    [c.62]    [c.467]    [c.524]    [c.40]    [c.390]    [c.2]    [c.313]    [c.424]   
Plastics materials (1999) -- [ c.2 , c.4 , c.7 , c.70 ]