The Melting Process

As discussed in Chapter 5, the solids-conveying rate for a specific screw is directly proportional to screw speed. That is, if the screw speed is increased by a factor of two the solids-conveying rate will nearly double. The melting flux of the screw as measured in kg/(h-m2) at the barrel wall, however, will not increase at the same rate. Typically, the melting flux will increase by 40% for a doubling of the screw speed [1]. In order to complete the melting process, additional area at the 

The melting process is the primary mode for mixing in single-screw machines. This concept can be observed from Maddock solidification experiments. Melting as a method for mixing is presented in Section 8.4. 

This chapter describes the processes that occur in the transition section or melting section of the screw. First, the historical melting process as initially outlined by 

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Properties of sodium sulfate help speed up the melting process in glassmaking. Its use reduces the tendency for alkaline gas bubbles to form in the glass and provides a less expensive form of Na20 than soda ash (6). Sodium sulfate improves the working properties of high siUca glasses. 

Pecrystallisation of a copolymer having 15 wt % VC has been found to be nucleated by material that survives the melting process plus new nuclei (74). The maximum crystallisation rate occurred at 373 K the maximum nucleation rate at 283 K. Attempts to melt all the polymer led to degradation that interfered with recrystallisation. 

Graphite electrodes are consumed in the melting process. For iron and steel production, the average consumption is ca 2—5 kg/1, depending on the... 

The melt processing of plasticised PVC normally involves the following stages ... 

These materials were first introduced by Du Pont in 1956 and are now known as Teflon FEP resins. (FEP = fluorinated ethylene-propylene.) Subsequently other commercial grades have become available (Neoflon by Daikin Kogyo and Teflex by Niitechim, USSR). These copolymers may be regarded as the first commercial attempt to provide a material with the general properties of PTFE and the melt processability of the more conventional thermoplastics. 

The review of Duvall and Graham [77D01], the paper of Brown and Shaner [84B02], and the book of Young [91Y02] provide thermodynamic descriptions of the melt process. 

The type of manufacturing process, reaction conditions, and catalyst are the controlling factors for the molecular structure of the polymers [4-8]. The molecular features govern the melt processability and microstructure of the solids. The formation of the microstructure is also affected by the melt-processing conditions set for shaping the polymeric resin [9]. The ultimate properties are, thus, directly related to the microstructural features of the polymeric solid. 

The melting process of potassium fluorotantalate, K2TaF7, was investigated by IR emission spectroscopy using thick layers of the melt [356]. It should be mentioned that in some cases, if the temperature of the sample is high enough, the above method enables to obtain spectra of the material in solid state as well. 

The advantage of using for the melt processing powder or pellets in the P form, rather than in other forms of s-PS, has been also shown [122], In this case, in fact, the crystalline form of the manufacts depends only on the cooling rate, being independent of the melting conditions [9]. 

Polyvinylidene fluoride (Kynar) (PVDF) is probably the most widely used fluorinated polymer for chemical applications. It can be melt-processed using virtually all the melt-processible procedures. PVDF components such as pipe fittings, tubing, sheet, shapes, and... 

Although U-series disequilibria have been observed in MORB for over 20 years, consensus about how the disequilibria are generated by the melting process does not yet... 

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