Extruding processes

A major difference between extrusion and IM is that the extruder processes plastics at a lower pressure and operates continuously. Its pressure usually ranges from 1.4 to 10.4 MPa (200 to 1,500 psi) and could go to 34.5 or 69 MPa (5,000 or possibly 10,000 psi). In IM, pressures go from 14 to 210 MPa (2,000 to 30,000 psi). However, the most important difference is that the IM melt is not continuous it experiences repeatable abrupt changes when the melt is forced into a mold cavity. With these significant differences, it is actually easier to theorize about the extrusion melt behavior as many more controls are required in IM. 

Table 9.4 Baseline Extruder Process Conditions and Performance for the Profile Line...

Figure 12.5 An extrusion process with a downstream gear pump with the screw operating in inlet pressure control and followed by the screw in manual operation (constant screw speed). The large level of variation in the motor current during constant screw speed control suggests that the extruder process is unstable, and the control algorithm is not the root cause for the variation in the motor current...

Figure 15.5 In-line NIR predicted levels of component 3 (circles) and laboratory analysis for component 3 in pellets taken from the extruder process (triangles). Reprinted with permission from McPeters et al. (1992). "...

Fielden KE, Newton JM, Rowe RC. The influence of lactose particle size on spheronization of extrudate processed by a ram extruder. Int J Pharm 1992 81 205-224. 

Kohler et al. (4) extruder processed polyphenylenesulfide containing the bisazo-methine of 4-nitrobenzaldehyde and bis-(4-aminophenyl)methane with 40 wt% glass fibers and the product used molding compositions. 

Mustakas et al. (46) evaluated the effects of extruder-processing on nutritional quality, flavor, and stability of the product in an attempt to describe extruder conditions which would be acceptable in all three respects. Urease activity was used as an estimation of trypsin inhibitor activity thus the area between the two urease curves in Figure 2 indicates processing conditions which strike a balance between too much and too little heat treatment, showing optimal nutritional quality. Using the flavor and peroxide value isograms, processing conditions may be chosen such that acceptable flavor and stability may also be achieved. 

The high rate of polymerization which is especially enormous at temperatures above the melting point of the polymer where the polymer is formed within a few seconds, can be exploited in a continuous polymerization extruding process which make unnecessary to produce the polymer as an intermediate (99). 

Films for lithium-ion batteries are manufactured in a similar process to that described above. However, no fillers are used in this process and the requirement for an even higher oil content complicates the process, because the oil must be added in stages in several mixing zones. A longer extruder processing section and a larger number of metering pumps are also required. 

Blow Molding Blow molding is an extruding process that is used to manufacture hollow products. 

Postforming identifies plastic sheet, rods, tubes, and other profile shapes that are formed into different shapes (coils, corrugated tubings, tubular nets, etc. Its major use is inline with an extruder processing... 

For the depolymerization of PMMA, molten metal bath, dry distillation, extruder processes and fiuidized-bed processes are used [19], The depolymerization reactor of a molten metal bath consists essentially of a gas- or oil-heated metal bath. The metals used are those which have a low melting point such as tin and lead. The PMMA regrind is fed from the storage silos onto the stirred metal bath. Bath temperature and a residence time of some minutes are important for good yield and quality of the MMA. 

Reactive Compatibilization has been discussed in earlier reviews [Brown and Orlando, 1988 Tzoganakis, 1989 Brown, 1992 Liu and Baker, 1992a]. As practiced commercially. Reactive Compatibilization is a continuous extruder process with material residence time usually 1 -5 min. Such a process permits large scale preparation of a polymer blend as needed ( Just-In-Time inventory control). 

FFSFs and grits are the least refined soy protein ingredients. Three types of FFSFs are produced (i) enzyme-active, (ii) toasted, and (iii) extruder-processed. Re-fatted flours are sometimes referred to as fully-fatted or full-fat, but they are described in this chapter in the section on defatted SF because the original fat is removed and replaced with refined, bleached, and deodorized (RED) oil. 

Extruder-processed FFSFs were used to prepare high-protein content foods and beverage bases for worldwide child and infant feeding programs (Mustakas et al., 1971). Studies also show that lipids are quite stable in full-fat flours cooked to 30 NSI, but antioxidants are required to ensure stability in FFSFs processed to <20 NSI (Howard et al., 1980). 

Mustakas, G.C. J.W. Albrecht G.N. Bookwalter J.E. McGhee W.F. Kwoiek E.L. Griffin, Jr. Extruder —processing to improve nutritional quality flavor, and keeping quality of full-fat soy flour. J. PoodTechnol. 1970,24, 1290-1301. 

Concrete is a cheap fire and corrosion resistant material. However, active species, especially easily soluble ions such as cesium, can be leached from it by water. Addition of plastic binders to the concrete in order to improve its properties have been suggested. In the continuous bitumen extruder process for semi-liquid wastes all water is directly eliminated, considerably reducing the waste volume. The bitumen mixture is placed in steel drums of standard size (150-2001). When additional shielding is desired, the filled drums are placed into disposable or reusable sleeves of concrete, iron, or lead. Such a sleeve of 12 cm lead weighs 7 t, and reduces the surface dose rate by a factor of —10. A typical unshielded bitum i drum may have a surface dose rate of 1 Sv h necessitating remote handling. 

Finally, shear viscosity is strongly affected by the clay in the blends, especially at high PEN contents. A lubricating effect rather than a filler effect reveals the possibility that the clay is not well dispersed in the polymer blend, and migration of particles in the flow to the wall region can explain the observed reduction in shear viscosity. When MMT clay is mixed with crystallizable polymers such as polyesters, some processing problems arise because the crystallization process is modifled by nucleation effects induced by the nanoparticles. Moreover, these particles also influence the kinetics of transesteriflcation between PET and PEN, besides other factors such as the reaction time and extruder processing temperature. In Reference 72, a quaternary alkyl ammonium compound (Cl8) and MAH were used to modify the surface properties of the clay... 

Although other processes are described, thermosetting coating powders are produced exclusively by the extruder process. This method is employed because it is the cheapest and the most widely applicable and flexible it allows large plants to be supplied with material of consistent quality. Production with extruders includes the following steps ... 

---