Plastification

In most of these routes, premixing is carried out in a trough mixer at room temperature to give a damp powdery mass or mush . This may then be fluxed on a two-roll mill, in an internal mixer, or in a continuous compounder such as the Werner and Pfleiderer Plastificator. For many operations the compounded mass... 

An amino-formaldehyde resin or acetone-formaldehyde resin has the capability to harden in alkaline media, in contact with a cement solution with a pH of 11 to 12. The presence of sintered CaO provides the required conditions for hardening of the methylol groups of the formaldehyde resin with Ca + ions and a further simultaneous reaction of the methylol groups that formed hydrate compounds, resulting in an improved dispersion and plastification of the solution. 

Influence of Plastification of Polymer on the Molecular Mobility and Rate Constant of Bimolecular Reaction [7,14,15,21]... 

FIGURE 19.2 The correlation of rate constants of various free radical reactions with molecular mobility of nitroxyl radical in the polymer matrix of different polymers with addition of plastificator I in IPP, II in preliminary oxidized IPP, III in PE, and IV in PS. Line 1 for the reaction of 2,6-bis(l,l-dimethy-lethyl)phenoxyl radical with hydroperoxide groups at T — 295 K line 2 for the reaction of 2,2,6, 6-tetramethyl-4-bcnzoyloxypiperidinc-/V-oxyl with 1-naphthol at T = 333 K line 3 for the reaction of 2,2,6,6-tetramethyl-4-benzoyloxypiperidine-iV-oxyl with 2,6-bis(l,l-dimethylethyl)phenol at T = 333 K line 4 for the same reaction at 7 — 303 K line 5 for the same reaction at T = 313 K and line 6 for the same reaction at T — 323 K [18]. 

GriinschloB, E., A New Style Single Screw Extruder with Improved Plastification and Output Power, 7/it. Polym. Process., 17, 291 (2002)... 

Figure 1.4-10. Stresses in an autofrettaged thick-walled cylinder (plastification 50% through the wall)...

It should be understood that the positive effects of autofrettage are always based on two different sources compressive residual stresses, which permit a larger amplitude of the operational stress and, depending on the material, the improved local strength of the material owing to strain-hardening by local plastification. 

On an industrial scale, the most commonly used pastes are those based on polyvinyl chloride (PVC), the plastificators being the mentioned organic liquids. Pigments, fire-retardants, antistatic agents, as well as other ingredients usually added to PVC may also be introduced. 

Shtarkman BP (1975) Plastification of polyvinyl chloride. Khimiya, Moscow, p 245... 

The hydrolytic stability of crosslinked nadimides has been investigated. It was concluded that moisture absorption is responsible for a reversible plastification effect. However after long-term cycling, the Tg decrease becomes non-reversible due to a chemical degradation [107]. 

Just 20 years later, in the 1960s, the wording was as follows Vorrichtung zum Kneten, Plastifizieren und Extrudieren von Polymeren (Apparatus for kneading, plastification and extrusion of polymers). 

Each processing step is linked to the next. Therefore the different steps cannot be considered independently from each other. For example, coloring processes already take place in the plastification zone, the incorporation of fibers added to the melt takes place not only in the designated dispersing zone but also in the discharge zone and in partially filled screw channels. 

Pressure/RtHng degree proflto Temperature profile Residence time distribution Dlspersion/mixing quality Plastification characteristics Intake characteristics Degassing efficiency... 

When conveying solids with a low bulk density, high fill rates in the intake zone can cause fluidization, if the air that is drawn in cannot escape from the extruder. This can be avoided by a partially filled downstream plastification zone (e. g., with conveying kneading blocks) and a vent opening installed downstream of the plastification zone. 

Varying the barrel temperature in the plastification zone makes hardly any difference to the melting process. 

Along with the actual melting, part of the key tasks of dispersion and homogenization also takes place in the plastification zone. 

Depending on the subsequent process steps, achieving 100% melting at the end of the plastification zone may not be mandatory. Solid particles still present after the plastification zone can be melted in subsequent zones, e. g., in the dispersion or discharge zones. Figure 4.6 illustrates a typical melting profile along a plastification zone. 

Figure 4.6 Melting profile along a plastification zone [10]...

Up to 80 % of the overall mechanical energy input in the twin screw extruder takes place in the plastification zone. Unfortunately, currently only rudimentary modeling capacities for the melting process are available. 

Figure 4.9 Energy input as a function of throughput for polyamide melting with kneading block and MPE plastification zones [13]...

The energy input via the screw elements and kneading discs results in splaying forces, particularly in the plastification zone, which can cause wear to the cylinders (see Fig. 4.10). This can be reduced by an appropriate design of the plastification zone and by heating the cylinder wall, which results in the formation of a melt film [8]. 

In the split feed process, the additives are fed into the polymer melt via a side feeder downstream of the plastification zone. Here, gravimetric feeding is always used (see Fig. 4.32). 

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