Sabatier Paul


A phenomenon that may develop, especially at small sliding speeds, is known as stick-slip friction in which the slider moves in jumps that may be of quite high frequency. This effect is partly a consequence of having some play and lack of rigidity in the mechanism holding the slider. Once momentary sticking occurs, the slider is pushed back against the elastic restoring force of the holding mechanism as a result of the continued motion of the latter. When the restoring force exceeds that corresponding to Us, the slider moves forward rapidly, overshoots if there is sufficient play, and sticks again. The greater the difference between static and sliding frictional coefficients, the more prone is the system to stick-slip friction with lubricated surfaces, there may be a fairly well defined temperature above which the phenomenon is observed. Friction force microscopy on smooth graphite surfaces illustrates molecular stick-slip friction [11]. Slip occurs when the derivative of the periodic force equals the spring constant of the AFM. Stick-slip friction is encouraged if uk decreases with sliding speed (why ) and with increasing W [12]. A very common, classroom illustration of stick-slip friction is, incidentally, the squeaking of chalk on a chalkboard. An important and interesting feature of current models of earthquakes is stick-slip motion of the tectonic plates.  [c.436]

Many important adhesives are made from glassy or elastomeric polymers. There are familiar examples encountered in everyday life such as epoxy resins used to repair broken china and rubber cement and adhesive tape applied to paper. There are two primary mechanisms for polymer adhesion (for a good review, see Brown [98]). Elastomers are crosslinked polymers above their glass transition temperature. On fracture, these polymers dissipate energy through viscoelastic losses depending on the speed of crack propagation and the crosslink density [99]. A low crosslink density will produce a viscous material having insufficient elasticity to resist flow. Too much crosslinking will render the material too rigid for good adhesion. Thus an optimal crosslink density exists and is tailored to the end use such as removable adhesives in tape and note pads. Glassy polymers adhere by entanglements and specific interactions between chains. The final strength of a polymer-polymer interface depends on the rupture [100] or pull-out [101,102] of chains.  [c.455]

The design and control of molecular processes has of late become possible thanks to advances in laser technology, at first through the appearance of femtosecond laser pulses and of pump-probe techniques [179] and, more recently, through the realization of more advanced ideas, including feedback and automated control [180-183]. In a typical procedure, the pump pulse prepares a coherent superposition of energy eigenstates, and a second delayed pulse probes the time-dependent transition between an excited and a lower potential energy surface. When the desired outcome is a particular reaction product, this can be promoted by the control of the relative phases of two fast pulses emanating from the same coherent laser source. One of the earliest works to achieve this is [184]. A recent study focuses on several basic questions, for example, those regarding pulsed preparation of an excited state [92]. In between the two, numerous works have seen light in this fast expanding and technologically interesting field. The purpose of mentioning them here is to single out this field as an application of phases in atomic [25,95,96] and molecular [84-90] spectroscopies. In spite of the achievements in photochemistry, summarized, for example, in [185], one hardly expects phases to play a role in ordinary (i.e., not state-selective or photon-induced) chemical reactions. Still, interference (of the kind seen in double-slit experiments) has been observed between different pathways during the dissociation of water [186,187]. Moreover, several theoretical ideas have also been put forward to produce favored reaction products through the involvement of phase effects [188-194]. Calculations for the scattering cross-sections in the four-atom reaction OH -1- H2 H2O -f H showed a few percent change due to the effect of phase [195].  [c.107]

Energy minimisation and normal mode analysis have an important role to play in the study of the solid state. Algorithms similar to those discussed above are employed but an extra feature of such systems, at least when they form a perfect lattice, is that it is can be possible to exploit the space group symmetry of the lattice to speed up the calculations. It is also important to properly take the interactions with atoms in neighbouring cells into account.  [c.309]

Ensure that all the individual components in the assembly are adequately supported when in position the friction between contiguous ground-glass surfaces does not provide adequate support. Therefore always use clamps, the claws of which are lined with rubber or other soft material. When assembling apparatus, allow some play in the clamps until the individual parts are in position, and then secure the position of the assembly by gently increasing the pressure of the clamps.  [c.42]

Ensure that all the individual components in the assembly are adequately supported when in position the friction between contiguous ground-glass surfaces does not provide adequate support. Therefore always use clamps, the claws of which are lined with rubber or other soft material. When assembling apparatus, allow some play in the clamps until the individual parts are in position, and then secure the position of the assembly by gendy increasing the pressure of the clamps.  [c.42]

Polyurethanes. The hard portion of polyurethane consists of a chain extender and polyisocyanate. The soft component is composed of polyol segments.  [c.1024]

Polyesters. The hard portion consists of copolyester, and the soft portion is composed of polyol segments.  [c.1024]

Solidification begins as atoms of weld metal attach themselves to the soHd metal grains at the weld pool edge this initial growth is epitaxial, ie, the atomic orientation of the base-metal grains continues into the weld pool. Weld metal grain growth continues in the direction of the maximum temperature gradient, which is initially perpendicular to the edge of the weld pool and tends to remain so for fast welding speeds, but which turns toward the arc in a direction parallel to the weld axis for a slower welding speeds (Fig. 6). Cellular and cellular dendritic are the most common weld solidification modes the mode itself is affected by temperature gradient, speed of solidifica tion, and solute content of the weld metal.  [c.345]

Fig. 6. Weld pool shape and resultant weld—metal solidification direction, (a) Slow welding speed, (b) Rapid welding speed. Fig. 6. Weld pool shape and resultant weld—metal solidification direction, (a) Slow welding speed, (b) Rapid welding speed.
The routine compositional and functional testing done on the adhesives includes gas chromatographic testing for purity, potentiometric titrations for acid stabilizer concentrations, accelerated thermal stabiUty tests for shelf life, fixture time cure speed tests, and assorted ASTM tests for tensile shear strengths, peel and impact strengths, and hot strengths.  [c.178]

In several commercial scmbbers, the dirty gas jets direcdy into a pool of water where the momentum of the larger particles allows them to penetrate. Some of the water is thus atomized into a spray aiding coUision between water droplets and smaller particulate. In one such scmbber careful control of the water level is necessary for efficient particle collection (284). These scmbbers have been used to collect coarser dusts such as from metal grinding they have good efficiencies on particles down to 3—5 p.m. Dynamic collectors employ a motor-driven centrifugal device resembling a water-sprayed centrifugal fan to cause impingement of soHd particles in a wetted film. Tests indicate that 1-p.m particles can be collected with 50% efficiency in an ordinary water-sprayed centrifugal fan if the wheel tip speed exceeds 90 m/s.  [c.410]

Endless belt percolation extractors (Fig. 5) such as the uncompartmented de Smet belt extractor and the compartmented Lurgi frame belt extractor are similar in principle and closely resemble a belt filter, and are probably the simplest type of percolation extractor from a mechanical point of view. These are fitted with a slow-moving perforated belt. The belt is made from steel mesh cloths when the soHds are fine, or coarser screens when the soHds are larger, and is attached to chains which pass over sprockets at each end of the extractor. The soHd is fed from a hopper at one end of the extractor to the moving belt, and the bed height is controlled by an adjustable damper at the oudet of the feed hopper. The two side walls of the extractor provide support for the bed on the moving belt. Fresh solvent is fed by spraying it onto the bed close to the discharge end of the belt, but leaving sufficient distance for adequate drainage of the bed prior to discharge. MisceUa draining from the bed is collected in a pan below the belt and circulated back to be sprayed onto the bed at a point closer to the soHds-feed end of the belt this process is repeated to achieve extraction operating with a countercurrent flow. The top of the bed is scraped by a hinged rake which has two functions (/) it prevents a layer of fine soHds from accumulating at the top of the bed thereby reducing permeabihty, and (2) it form a soHds pile which helps to prevent intermingling of misceUa from different feed points at the surface of the bed. The belt is effectively washed twice once by fresh solvent just after the soHds discharge point, and then at the other end of the belt return by misceUa. The extraction time and percolation rate determine the belt speed and the amount of drainage area, and hence linear length of belt, requited. These parameters control the plant capacity as the bed height is fixed by the mechanical design of the extractor.  [c.92]

Beatings used on fans may be either sleeve or antifriction type and must be designed to withstand loads resulting from dead weight, unbalance, and rotor thmst and be able to operate at the iatended maximum speed without excessive heating (see Bearing materials). When natural convection from the beatings is iaadequate, some other cooling method must be provided. Lubricating oil may be circulated through an external cooler, or the pillow blocks may be cored with passages for forced circulation of air or water. Fans operated at high temperatures iacrease the beating cooling problem caused by heat conduction along the shaft. A small external fan wheel on the shaft, called a heat slinger, is frequently provided, or forced-circulation water cooling is used. In addition to the beatings of fans operating on hot, low density gas at high pressure rise, special attention is needed to ensure high rigidity of the wheel and shaft. Fan wheels should be balanced both statically and dynamically, eg, ia the field with chalk and weights (15). Elaborate electronic test instmments are also available. An unbalanced condition causes a vibrational displacement of the beatings which is frequently checked. Table 2 fists typical displacements of fans operating at various speeds and various degrees of unbalance.  [c.109]

Even when crimp is fiiUy developed it is easy to pull out (low energy) and difficult to translate into noticeably bulkier woven and knitted fabrics. It does however improve the absorbency and the cohesion of the staple (important in spun-yam and nonwoven making) and gives a subtiy different texture  [c.349]

From about 1815, fast vessels gave Salem, Massachusetts a virtual monopoly of the pepper trade with Sumatra. In the nineteenth and twentieth centuries, the spice trade began to play a secondary role ia economic and pohtical influence. The demand for spices ia the United States directed the shift of the occidental spice center to New York while the oriental center was at Siagapore.  [c.24]

Lemon and lime peel oils are the most valuable essential oils recovered from citms. They are widely used in the soft drink industry in lemon—lime flavored beverages, and lime oil is an ingredient in cola flavor as well (14) (see Carbonated beverages Oils, essential). Lemon oil is used extensively in household products for its pleasant clean aroma. The principal lime oil of commerce is collected from the Key, or Mexican, lime which is too small to be extracted in conventional juice extractors. The whole fmit is cmshed in a screw press and the oil is obtained by vacuum deoiling, ie, partial distillation. Because the acidic juice and peel oil are in contact prior to distillation for oil recovery, chemical changes to the lime oil occur which give the oil a strong aroma and flavor not normally present (13). This stronger flavored oil has become the accepted oil of commerce for most lime flavoring uses (see Flavors AND spices).  [c.572]

Formation of Airborne Emissions. Airborne emissions are formed from combustion of waste fuels as a function of certain physical and chemical reactions and mechanisms. In grate-fired systems, particulate emissions result from particles being swept through the furnace and boiler in the gaseous combustion products, and from incomplete oxidation of the soHd particles, with consequent char carryover. If pile burning is used, eg, the mass bum units employed for unprocessed MSW, typically only 20—25% of the unbumed soHds and inerts exit the combustion system as flyash. If spreader-stoker technologies are employed, between 75 and 90% of the unbumed soHds and inerts may exit the combustion system in the form of flyash.  [c.58]

When a smelting campaign is started, carbonaceous material, eg, coke or a conductive material, is placed on the hearth. The electrodes are lowered and arc on this material is at a low power input. The charge materials (ores, reductants, etc) are added slowly. As the material becomes molten and conductive, the power input and charging rate are correspondingly increased to the desked production rate when the furnace is filled with the charge materials. The electrodes continue to arc on the pool of molten metal on the furnace hearth, and the furnace exhibits electrical characteristics similar to open-arc steelmaking furnaces which have an attendant current voltage phase shift. Submerged describes the operation in that the electrode tip is surrounded by charge material in different stages of melting or reduction. In the submerged-arc case, the space immediately beneath the electrode is filled with ionized gases through which the arcs travel, which is typical of siUcon alloy production operations. These gases travel upward through the burden, preheating it, and bum at the top with open flames. Generally the gases are collected to separate toxic materials and/or to recover waste heat.  [c.123]

Grant, Balaram Gupta, Alice Ku, Gao Liang, Henry Lin, Christine Lui, Chuck McFarland, Ripu Malhotra, Y. K. Mo, Dick Porter, Surya Prakash (who later in Los Angeles became my close colleague and a wonderful friend, see Chapter 8), George Salem, Jacob Shen, John Staral, Jim Svoboda, Paul Szilagyi, and John Welch.  [c.91]

Somewhat unexpected results are obtained when the degree of cross-linking is increased by incorporating triols in the original polyester. In contrast to results with hydrocarbon rubbers the greater the degree of cross-linking the lower is the tensile strength and tear resistance but the higher the elasticity. This effect is believed to be due to the fact that in rubbers of the Vulkollan type much of the strength of the material is derived from secondary forces, hydrogen bonding in particular. Cross-linking not only interferes with the effectiveness of such secondary forces but it also restricts crystallisation. Corroborating evidence for this is that at elevated temperatures, where secondary forces are greatly reduced, the more highly cross-linked polymers are rather stronger. The fact that the chain consists of blocks of hard polyurethane segments separated by soft polyol segments is also a contributing factor.  [c.787]

Commercial colchicine usually consists of yellow flakes or powder, or crystals containing chloroform of crystallisation. It can be crystallised from water as a trihydrate, or from ethyl acetate (Clewer et al. ) forming soft, pale yellow needles, m.p. 155-7°, — 120-8° (CHClg) or  [c.650]

The potential advantages of LPG concern essentially the environmental aspects. LPG s are simple mixtures of 3- and 4-carbon-atom hydrocarbons with few contaminants (very low sulfur content). LPG s contain no noxious additives such as lead and their exhaust emissions have little or no toxicity because aromatics are absent. This type of fuel also benefits often enough from a lower taxation. In spite of that, the use of LPG motor fuel remains static in France, if not on a slightly downward trend. There are several reasons for this situation little interest from automobile manufacturers, reluctance on the part of automobile customers, competition in the refining industry for other uses of and fractions, (alkylation, etherification, direct addition into the gasoline pool). However, in 1993 this subject seems to have received more interest (Hublin et al., 1993).  [c.230]

The contribution that Hocking wished to make was to refine the sensor system and the instrumentation paekage so as to be able to incorporate the necessary functionality within a lightweight portable battery operated instrument. This implied a lower power level and very low-noise instrumentation. We aimed also for a low cost instrument able to operate for several hours from fully charged batteries and able to operate at a pull speed of 500mm/second.  [c.321]

Our target is to detect a 2.5mm diameter OD pit, 40% through a 3mm wall of a 25mm diameter tube at a pull speed of 500mm per second  [c.323]

The local dynamics of tire systems considered tluis far has been eitlier steady or oscillatory. However, we may consider reaction-diffusion media where tire local reaction rates give rise to chaotic temporal behaviour of tire sort discussed earlier. Diffusional coupling of such local chaotic elements can lead to new types of spatio-temporal periodic and chaotic states. It is possible to find phase-synchronized states in such systems where tire amplitude varies chaotically from site to site in tire medium whilst a suitably defined phase is synclironized tliroughout tire medium 51. Such phase synclironization may play a role in layered neural networks and perceptive processes in mammals. Somewhat suriDrisingly, even when tire local dynamics is chaotic, tire system may support spiral waves  [c.3067]

Neural networks can learn automatically from a data set of examples. In the case of NMR chemical shiffs, neural networks have been trained to predict the chemical shift of protons on submission of a chemical structure. Two main issues play decisive roles how a proton is represented, and which examples are in the data set.  [c.523]

Now remove the tube from the furnace and make a deep file-mark completely round the tube about 15 cm. from the bottom then wash the outside of the tube to remove any powdered glass from the file-mark, and also all traces of charred paper, etc. Then, whilst holding the tube securely in a vertical position, press the molten end of a fine glass rod on to the file-mark, when the tube should crack cleanly around the scratch finally pull the two portions of the tube away from one another, so that the two ends have no opportunity of grating against one another and so causing fine splinters of glass to fall into the tube. Then wipe the two cut ends of the tube carefully in an outwards direction to r nove any splinters which, in spite of these precautions, may have formed. (Cutting the tube in this way aboui 15 cm. from the bottom has the advantage that the silver halide is now readily accessible, but has the disadvantage that the tube is usually too short to be used s ain. It is not advisable, however, to use soft-glass tubing a second time, as it often devitrifies on further heating and in any case usually gives an unsatisfactory sealed tube. Hard-glass tubing can sometimes be used for several consecutive estimations, and if this is intended the tube should be cut across gg (Fig. 72) the silver halide is now, however, not so readily removed from the tube.) Now smear a trace of vaseline around the outside portion of the cut ends of the two portions of the tube (to prevent drops of the liquid from subsequently running down the outside of the tube). Pour some distilled water into the portion of the tube containing the silver halide, loosen the contents by stirring them gently with a rod, and then tip the contents carefully into a beaker. If any fragments of silver halide still adhere to the Carius tube, loosen them further by means of a glass rod the end of which is covered with a short length of rubber tubing, and then finally wash out the inside of the tube (whilst the latter is inclined downwards over the beaker) with a fine jet of water from a wash-bottle. Now remove the small tube from the beaker (preferably with a pair of forceps), again loosen any adhering particles of silver halide, and wash the tube thoroughly whilst it is held over the beaker. Similarly wash the longer portion of the Carius tube, which however should not contain any particles of silver halide. Then boil the liquid in the covered beaker until the silver halide has thoroughly coagulated, and formed a heavy amorphous  [c.421]

Place 84 g. of iron filings and 340 ml. of water in a 1 - 5 or 2-litre bolt-head flask equipped with a mechanical stirrer. Heat the mixture to boiling, stir mechanically, and add the sodium m-nitrobenzenesulphonate in small portions during 1 hour. After each addition the mixture foams extensively a wet cloth should be applied to the neck of the flask if the mixture tends to froth over the sides. Replace from time to time the water which has evaporated so that the volume is approximately constant. When all the sodium salt has been introduced, boU the mixture for 20 minutes. Place a small drop of the suspension upon filter paper and observe the colour of the spot it should be a pale brown but not deep brown or deep yellow. If it is not appreciably coloured, add anhydrous sodium carbonate cautiously, stirring the mixture, until red litmus paper is turned blue and a test drop upon filter paper is not blackened by sodium sulphide solution. Filter at the pump and wash well with hot water. Concentrate the filtrate to about 200 ml., acidify with concentrated hydrochloric acid to Congo red, and allow to cool. Filter off the metanilic acid and dry upon filter paper. A further small quantity may be obtained by concentrating the mother liquid. The yield is 55 g.  [c.589]

Surround the reducing solution in the 1-Utre beaker (which is equipped with a mechanical stirrer) with a bath of crushed ice so that the temperature of the solution is about 10°. Attach, by means of a short length of rubber pressure tubing, to the stem of a dropping funnel a glass tube which dips well below the surface of the solution and is bent upwards at the end and constricted so that the opening is about 2 mm. (this arrangement ensures that the diazonium solution reacts with the ammoniacal solution in the beaker and prevents the latter rising in the stem of the funnel). Place about 45 ml. of the cold diazonium solution in the funnel and add it at the rate of about 10 ml. per minute whilst the mixture is stirred. Add the remainder of the diazonium solution at the same rate continue the stirring for 5 minutes after the addition is complete. Heat the solution rapidly to boiling and carefully acidify with 125 ml. of concentrated hydrochloric acid the diphenic acid precipitates as pale brown crystals. Allow to stand overnight and filter with suction wash the crude diphenic acid with about 25 ml. of cold water. Suspend the crude acid in 100 ml. of water and add 20 g. of sofid sodium bicarbonate. Filter the resulting solution by gravity, and then boil with about 0 5 g. of decolourising carbon filter and acidify the filtrate while stiU hot with excess of dilute hydrochloric acid (1 1). Collect the precipitated diphenic acid on a Buchner funnel, wash it with 20 ml. of cold water, and dry at 100°, The yield of diphenic acid is 18 g. it melts at 227-228° and usually possesses a fight cream colour.  [c.617]

It is a soft beta emitter although no gamma rays are emitted. X-radiation can be generated when beta particles impinge on elements of a high atomic number, and great care must be taken in handling it. Promethium salts luminesce in the dark with a pale blue or greenish glow, due to their high radioactivity. Ion-exchange methods led to the preparation of about 10 g of premethium from atomic reactor fuel processing wastes in early 1963. Little is yet generally  [c.183]

Now remove the tube from the furnace and make a deep file-mark completely round the tube about 15 cm. from the bottom then wash the outside of the tube to remove any powdered glass from the file-mark, and also all traces of charred paper, etc. Then, whilst holding the tube securely in a vertical position, press the molten end of a fine glass rod on tc the file-mark, when the tube should crack cleanly around the scratch finally pull the two portions of the tube away from one another, so that the two ends have no opportunity of grating against one another and so causing fine splinters of glass to fall into the tube. Then wipe the two cut ends of the tube carefully in an outwards direction to remove any splinters which, in spite of these precautions, may have formed. (Cutting the tube in this way about 15 cm. from the bottom has the advantage that the silver halide is now readily accessible, but has the disadvantage that the tube is usually too short to be used a n. It is not advisable, however, to use soft-glass tubing a aecond time, as it often devitrifies on further heating and in any case usually gives an unsatisfactory sealed tube. Hard-glass tubing can sometimes be used for several consecutive estimations, and if this is intended the tube should be cut across gg (Fig. 72) the silver halide is now, however, not so readily removed from the tube.) Now smear a trace of vaseline around the outside portion of the cut ends of the two portions of the tube (to prevent drops of the liquid from subsequently miming down the outside of the tube). Pour some distilled water into the portion of the tube containing the silver halide, loosen the contents by stirring them gently with a rod, and then tip the contents carefully into a beaker. If any fragments of silver halide still adhere to the Carius tube, loosen them further by means of a glass rod the end of which is covered with a short length of rubber tubing, and then finally wash out the inside of the tube (whilst the latter is inclined downwards over the beaker) with a fine jet of water from a wash-bottle. Now remove the small tube from the beaker (preferably with a pair of forceps), again loosen any adhering particles of silver halide, and wash the tube thoroughly whilst it is held over the beaker. Similarly wash the longer portion of the Carius tube, which however should not contain any particles of silver halide. Then boil the liquid in the covered beaker until the silver halide has thoroughly coagulated, and formed a heavy amorphous  [c.421]

In a plasma, collisions between atoms, positive ions, and electrons thermolize their kinetic energies the distribution of kinetic energies corresponds to what would be present in a hot gas thermally heated to an equivalent temperature. Direct heating of a gas is not used to form the plasma. Instead, a high-frequency electromagnetic field is applied through the load coil. This rapidly oscillating electromagnetic field interacts inductively with the charged species electrons and ions try to follow the field and are speeded up, gaining kinetic energy. In the rapidly oscillating field, random collisions of electrons and ions with neutral species redistributes this extra kinetic energy, and the whole ensemble becomes hotter. If the rapidly oscillating electromagnetic field is maintained, the ions and electrons continue to follow a chaotic motion as they gain more speed and undergo more collisions, which continue to redistribute the kinetic energies. Eventually, the kinetic energies become so high that the plasma reaches temperatures of 8,000-10,000°C. At these high temperatures, the plasma behaves like a flame issuing from the ends of the concentric quartz tubes, hence the derivation of the name plasma torch. As in a normal flame, atoms and ions are excited electronically in the collision processes and emit light. In the plasma torches used for mass spectrometry, the argon that is used emits pale-blue-to-lilac light as excited atoms relax and as a proportion of the electrons and ions recombine.  [c.87]

It was stated above that the focus of all masses will occur at a single position, the collector slit (Figures 24.5 and 24.6). However, because the actual shape of the field within and around the pole tips of the magnet varies with changing field, especially at higher field strengths, the final focal point of the beam shifts as field strength changes. This focal point shift leads to a change of focus with mass and affects the ability of the instrument to resolve small mass differences. On early mass spectrometers, the problem could be corrected by physically adjusting the position of the magnet for any given mass. On modem instraments, an electric field called the Y-focus is used to compensate for these imperfections (Figures 24.5 and 24.6). The aim of this lens is to focus the ions at the same po.sition (the collector slit) throughout the mass range. Thus, using the electric and magnetic sectors with a Y-focus lens ensures all ions are brought to the same focus and allows small differences in mass to be detected the resolution of the instmment is enhanced.  [c.179]

W. T. Yama2aki and C. T. Greenwood, eds.. Soft Wheat Production, Milling Uses, American Association of Cereal Chemists, St. Paul, Minn., 1981.  [c.361]

U.S. Pats. 2,356,459 (Aug. 22,1944) and 2,361,036 (Oct. 24,1944), E. E. King, and U.S. Pat. 3,002,017 (Sept. 26,1961), N. Wearsch and A. J. De Paola (to B. E. Goodrich Co.).  [c.159]

A wide variety of adhesives based on the cyanoacryhc esters are now available worldwide. Product distinctions are based on ester type and specific performance attributable to that ester, formulation, viscosity, and cure speed. A number of special performance grades have appeared that maximize performance in specific areas, sometimes quite significantly. Adhesive grades are now available with improved thermal resistance improved peel strengths, impact resistance, and toughness and low odor, low blooming characteristics. New formulations contain cure additives that reduce the sensitivity of cure to acidic surfaces and low atmospheric humidity. More recentiy, surface primers have been introduced that have dramatically improved bond strengths to traditionally hard-to-bond surfaces such as polyolefins and other low energy polymers.  [c.178]

Eor sheet, streamlined coat-hanger type dies are preferred over the straight manifold type. Typically, three highly polished and temperature controlled roUs are used to provide a smooth sheet surface and control thickness (140). Special embossing roUs can be substituted as the middle roU to impart a pattern to the upper surface of the sheet. ABS and non-ABS films can be fed iato the polishing roUs to provide laminates for special appHcations, eg, for improved weatherabiHty, chemical resistance, or as decoration. Two mbber pull roUs, speed synchronzied with the polishing roUs, are located far enough downstream to allow sufficient cooling of the sheet finally, the sheet goes iato a shear for cuttiag iato lengths for shipping.  [c.206]

Viber Glass. There are two basic forms of fiber glass being manufactured continuous filaments (415 ]lni dia) and fibers (6—9 ]lni dia and 20—40 cm long) (85,93). Single filaments can be combined into a strand that is easily unwound from a spool. The product is twisted textile yam. Staple fibers that meet diameter and minimum length requirements are twisted together into a tow that can also be easily unwound from a spool. The end product is staple yam. Glass fibers that do not meet these requirements are not suited for textile applications, but may be used for thermal and sound insulation in the form of glass wool (85). Nearly all continuous filament yam is made from E-glass which is weU-suited for electrical insulation (see Insulation,electric), heat-resistant appHcations (see Insulation, thermal) (93), and plastic reinforcement and mats (see Laminated and reinforced plastics). Most staple fibers are spun from C-glass which is more resistant to chemical corrosion and is used for chemical filtration fabrics, etc. A low cost soda—lime glass, T-glass, is used when high durability is not required, eg, coarse fiber mats for air filters and thermal and acoustical insulation (see Insulation, acoustic). For weathering resistance, SF-glass is used in fine and ultrafine wool products such as very low density thermal and acoustic insulators, paper additives, and high efficiency all-glass filter papers. Formerly, molten glass was formed into marbles which were remelted in an electric furnace and formed into filaments. However, many manufacturers now use the direct-melt method, where the molten glass is formed direcdy into filaments. Continuous filament yam is drawn from the molten glass as it comes through small holes in a high temperature alloy bushing. The high speed winders, operating as fast as 3000 m /min, pull the streams into filaments. Staple fibers are formed by jets of air that pull the fibers from the furnace and deposit them on a revolving vacuum dmm.  [c.310]


See pages that mention the term Sabatier Paul : [c.234]    [c.1822]    [c.2456]    [c.28]    [c.39]    [c.70]    [c.39]    [c.270]    [c.46]    [c.530]    [c.24]    [c.59]   
Carey organic chemistry (0) -- [ c.231 , c.591 ]