Ram extruder

Granular polymer may also be extruded, albeit at very low rates (l-6in/min, 2.5-16 cm/min), by means of both screw and ram extruders. In both machines the extruder serves to feed cold powder into a long, heated sintering die whose overall length is about 90 times its internal diameter. The polymer, preferably a presintered grade of 600 pim particle size, is compacted, sintered and partially cooled before leaving the die. Since compacting is still taking place as the polymer enters the sintering zone it is possible to obtain extrudates reasonable free from voids, a factor which is reflected in their high tensile strength and elongation.  [c.370]

In a typical process a preform billet is produced by compacting a mixture of 83 parts PTFE dispersion polymer and 17 parts of petroleum ether (100-120°C fraction). This is then extmded using a vertical ram extruder. The extrudate is subsequently heated in an oven at about 105°C to remove the lubricant, this being followed by sintering at about 380°C. By this process it is possible to produce thin-walled tube with excellent flexing fatigue resistance and to coat wire with very thin coatings or polymer.  [c.371]

The Melt Flow Rate Test is a method used to characterise polymer melts. It is, in effect, a single point ram extruder test using standard testing conditions (BS  [c.373]

Shear Stress, Ram Extruder  [c.487]

Now the cone and plate gives true shear rate whereas the ram extruder uses apparent shear rate. The Non-Newtonian correction factor is  [c.487]

Therefore the true shear rate on the cone and plate is equivalent to a shear rate of 0.69(1.18) = 0.817 on the ram extruder  [c.487]

However, it is not always possible to run a pilot-plant test in order to determine the depth of cut. A well-accepted alternative approach makes use of the more sophisticated test leaf illustrated in Fig. 18-97. This test leaf is designed so that the cake and precoat are extruded axially out the open end of the leaf. The top of the retaining wall on this end of the leaf is a machined surface which serves as a support for a  [c.1698]

An alternative approach to size enlargement is by compression agglomeration, where the mixture of particulate matter is fed to a compression device which promotes agglomeration due to pressure. Either continuous sheets oi sohd material are produced or some solid form such as a briquette or tablet. Heat or cooling may be apphed, and reaction may be induced as for example with sintering. Carrier fluids may be present, either added or induced by melting, in which case the product is wet extruded. Continuous compaction processes include roll presses, briquetting machines, and extrusion, whereas batch-like processes include tableting. Some processes operate in a semicontinuous fashion, such as ram extrusion.  [c.1875]

Figure 8.1. (a) Extrusion—material is pumped, in the above ease with a screw pump, through a die to give a product of constant cross-section, (b) Injection moulding—material is pumped by a screw pump to the front end of the injection cylinder with the screw moving to the rear in order to provide space for the material the screw then moves forward as a ram injecting molten material into a relatively cool mould into which the material sets, (c) Extmsion blow moulding—the extruder tube is inflated in the mould while still above softening point, (d) Calendering—softened material is flattened out into sheet between rolls  [c.160]

It is also possible to extrude alcohol-containing celluloid compositions through either ram or screw extruders under carefully controlled conditions. The process is now believed to be universally obsolete.  [c.619]

In the intermittent processes, single or multiple parisons are extruded using a reciprocating screw or ram accumulator. In the former system the screw moves forward to extrude the parisons and then screws back to prepare the charge of molten plastic for the next shot. In the other system the screw extruder supplies a constant output to an accumulator. A ram then pushes melt from the accumulator to produce a parison as required.  [c.269]

There are two types of cold feed extruders, the standard screw design type (Fig. 15) and one with a screw feed using a ram action to feed the extruder. In both  [c.456]

There are two types of cold feed extruders, the standard screw design type (Fig. 15) and one with a screw feed using a ram action to feed the extruder. In both  [c.457]

There are two types of hot feed extruders, one similar to the screw type cold feed extruder, except that the strip feeding the extruder is taken directly off the two-roll mill. The mill is used to further blend and heat the compound. It is then taken off the mill in strip form and fed directly into the extruder. The second type of hot feed extruder is based on the action of a ram being used to feed the compound into the extruder die (Fig. 16). The compound is placed on a two-roll mill to further blend and heat rubber. It is then taken off the mill in pig form to fill the extruder chamber.  [c.458]

Basic types of extruders include axial end plate, radial screen, rotary cyhnder or gear, and ram or piston. For a review, see Newton [Powder Technology Pharmaceutical Processes, Chuha et al. (eds.), Elsevier, 391 (1994).]  [c.1902]

Cost versus t (Figure 31.13) to optimize t and hence, the cost of the conductor and the enclosure. For this /, the diameter may be modified to arrive at a more economical design. A higher / will mean a lower diameter and vice versa, and may be modified to satisfy the conductor s current-carrying and the enclosure s heat-dissipating requirements. Since the size of a hollow conductor, for large to very large current ratings, is not standardized the cylindrical diameter (d) and the wall thickness (/) can be varied, depending upon the rating, the extruded sections available and the cooling system adopted by the manufacturer. The exact d and t is then established by trial, and optimized as noted above. Figures 31.12 and 31.13 suggest that for a more economical design, the thickness must be less than the depth of penetration (5p). In enclosures a more economical design is achieved by keeping t in the vicinity of 50-60% of 5p. This may mean some field in the space, but its severity is already mitigated by arresting most of it by the enclosure. Leading manufacturers have established their own data and programmed them on computers for routine reference and designing a bus system. These data are then checked for their accuracy by conducting heat run tests on sample lengths (Section 32.3.4). After a few initial designs it is possible to optimize and predefine the vital parameters for a particular rating.  [c.944]

Most mass processes used today are a variation of that developed by Wolff in Germany before Word War II. In this process the styrene is prepolymerised by heating (without initiators) in a prepolymerisation kettle at 80°C for two days until a 33-35% conversion to polymer is reached (see Figure 16.6). The monomer-polymer mixture is then run into a tower about 25 ft high. The tower is fitted with heating and cooling jackets and internally with a number of heating and cooling coils. The top of the tower is maintained at a temperature of about 100°C, the centre at about 150°C and the bottom of the tower at about 180°C. The high bottom temperature not only ensures a higher conversion but boils off the residual styrene from the polymer. The base of the tower forms the hopper of an extruder from which the melt emerges as filaments which are cooled, disintegrated and packed.  [c.430]

From the third reactor the polymer is then run into a devolatilising ( stripping ) vessel in the form of thin strands. At a temperature of 225°C the solvent, residual monomer and some very low molecular weight polymers are removed, condensed and recycled. The polymer is then fed to extruder units, extruded as filaments, granulated, lubricated and stored to await dispatch.  [c.431]

A 60% aqueous solution of the salt is then run into a stainless steel autoclave together with a trace of acetic acid to limit the molecular weight (9000-15000). The vessel is sealed and purged with oxygen-free nitrogen and the temperature raised to about 220°C. A pressure of 2501bf/in (1.7 MPa) is developed. After 1-2 hours the temperature is raised to 270-280°C and steam bled off to maintain the pressure at 250 Ibf/in (1.7 MPa). The pressure is then reduced to atmospheric for one hour, after which the polymer is extruded by oxygen-free nitrogen on to a water-cooled casting wheel, to form a ribbon which is subsequently disintegrated. Nylon 610 is prepared from the appropriate salt (melting point 170°C) by a similar technique. Nylon 612 uses decane-1, 10-dicarboxylic acid. Azelaic acid is used for nylon 69. Nylon 46, introduced in the late 1970s as Stanyl by DSM, is prepared by reacting 1,4-diaminobutane with adipic acid.  [c.486]

USATHAMA) completed a trial burn of explosive, contaminated soil in a rotary kiln (Noland, 1984). Soil contaminated from red and pink water lagoons was successfully burned. A transportable rotary kiln yrstem was set up. The technology by Therm-All, Inc., had been used in industry for destruction of solid wastes. The normal screw feed system was not used, due to fear of a soil explosion during the extruded plug feed process. Therefore, the soil was placed in combustible buckets and individually fed by a ram into the incinerator. The feed rate was 300 to 400 Ib/hr and the operational temperature was 1200° to 1600°F in the kiln and 1600° to 2000°F in the secondary chamber.  [c.163]

See pages that mention the term Ram extruder : [c.369]    [c.371]    [c.252]    [c.278]    [c.467]   
Plastics engineering Изд.3 (2002) -- [ c.371 ]