Solidification experiment

J. A. Warren, J. S. Langer. Prediction of dendritic spacings in a directional solidification experiment. Phys Rev E 47 2102, 1993. 

Figure 2. Photographs of cellular and dendritic structures in a thin-film solidification experiment of an organic alloy (succinonitrile-acetone) reported by Ref. 6.

Figure 4.1 Density of the solid bed from a Maddock solidification experiment running PVDC resin [2]. The extruder was 63.5 mm in diameter and had an L/D of 21...

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. 

Figure 6.2 Photograph of resin solidified in the transition section after a Maddock solidification experiment for an ABS resin. The pushing flight is on the left side of the photograph...

Maddock s and Street s famous solidification experiments revealed that melting in many situations takes place in a specific order. The experiments showed that after melting began, there was a continuous solid bed and a melt film over the inner barrel surface. Later the solid bed was completely surrounded by melt. Farther downstream, a melt pool developed between the pushing flight and the solid bed. The... 

The melting process for a resin is complex and depends on many parameters, including screw speed, screw geometry, barrel temperatures, and channel pressures. Moreover, the compression ratio and compression rate also affect the pressure in the channel. The melting flux is known to increase with increasing pressure in the channel [1,12]. A series of Maddock solidification experiments were performed at... 

The locally high pressure underneath the solid bed and the positive dP/dx in Film D causes some flow of resin from Film D to the melt pool. Thus, for a local Az increment for Film D, there is material entering the element from the melting process and from the drag motion of the screw core, and there is material leaving the increment from the motion of the screw core and from the flow of material into the melt pool due to a positive dP/dx. These complex flows are consistent with observations from Maddock solidification experiments. This flow is shown in detail for the Maddock experiment shown in Fig. 6.35. 

At the start of the melting process, the pressure in the channel is relatively low and the solid bed may not be fully compacted. In this case, molten resin from all films has the ability to flow into the voids between the individual pellets. This process is often referred to as melt infiltration. A photograph of a cross section of a Maddock solidification experiment at the start of the melting process is shown by Fig. 6.21. For this figure, the molten material prior to the solidification was black. Melt infiltration is shown by the black resin that has flowed from the films and in between the pellets. The flow of resin into the solid bed will likely cause the pressure in the films to decrease. 

Figure 6.21 Photograph of a cross section from a Maddock solidification experiment at the start of the melting process. The black material shows the melt films and the regions where the melt infiltrated the loosely packed solid bed...

Figure 6.37 Photograph of a segment from a Maddock solidification experiment for a PVDC resin extrusion. The dark band is resin degraded due to a long residence time at the location...

The extrudate samples and the solidification experiment clearly show the importance of the melting process on the mixing quality of the extruder discharge. The cases shown here are for color masterbatches in natural or white resins, but the concept applies to any solid mixture or blend added to the hopper of an extruder. Color masterbatches were used here because it is much easier to visualize than other compositional variations or thermal gradients. 

Figure 10.2 Photograph of a Maddock solidification experiment a) the screw is being pushed out of the barrel with the solidified resin, b) the screw with resin solidified in the channels, and c) a cross-sectional view parallel to the screw axis in the melting section...

Figure 10.23 Select barrel (Z2 and Z3) and screw temperatures as a function of cooling time during a Maddock solidification experiment...

Figure 14.10 Cross-sectional views for a Maddock solidification experiment for the ET screw at a letdown ratio of 220 1 white-pigmented ABS resin to a black color concentrate [29]. The A and B channels are labeled along with the axial positions in diameters. The views were for a screw speed of 66 rpm and a rate of 70 kg/h using a 63.5 mm diameter extruder...

A Maddock solidification experiment was performed using ABS resin at a screw speed of 60 rpm [30]. Like the solidification experiment for the ET screw of Section 14.2.2, the feedstock resin contained 2% Ti02 compounded into the pellets, and a black-colored masterbatch was added at a letdown ratio of about 220 1. The cross-sectional views of the resin solidified in the channels are shown by Eig. 14.15. The white pellets and unmixed resin are visible in the views as white regions. The regions that are well mixed are an evenly colored dark or black color. 

Figure 14.23 Photographs of cross-sectional views of resin removed from a Maddock solidification experiment for a Stratablend screw. The labels are the axial positions of the views in diameters...

The alloy solidification experiments that have been performed on Spacelab missions generally fall into four categories 1) interfacial stability 2) evolution... 

Vol2] Volkmann, T., Herlach, D.M., Nucleation and Phase Selection in Undercooled Fe-Cr-Ni Melts Part II. Containerless Solidification Experiments , Metall. Mater Trans. A, 28A(2), 461-469 (1997) (Experimental, Kinetics, 32)... 

Car] Unidirectional solidification experiments, DTA measurements, microscopic analysis 1120-1200°C / Fe rich alloys with 3.9-4.3 mass% C and mass% 0.21-2.27 Si... 

A solidification experiment has been performed using a 21 L/D, 63.5 mm diameter extruder with an ET screw [26]. Details of the channel dimensions were summarized previously [26], but changes in the channel geometries are obvious from the cross-sectional views shown by Figure 5.36. 

Fig. 23. Influence of temperature gradient (G) and growth rate (R) on growth morphology and stability of the planar Y123/Liquid interface in directional solidification experiments (Shiohara and Endo 1997). Note that only high G/R ratios (>3300Kh/cm ) permit the interface to be planar during solidification resulting in large...

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