Screw fusion

The success and breakthrough innovation of Kruder s wave screw was further enhanced by coupling the wave technology with an upstream barrier section and a material reorientation section. The reorientation section was positioned between the barrier section and the wave section. This spin-off technology was patented by Womer, Buck, and Hudak [36] In 2004. Other improvements were patented later [37, 38]. 

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The first wave-dispersion-type screw was developed and patented by Kruder in 1975 [18], and the device was trademarked as the Wave screw. Numerous other wave dispersion screws were developed later based on Kruder s design. The term wave dispersion screw refers to screws with metering sections that have two or more channels with a flight between them that is selectively undercut to allow the dispersion of solid polymer fragments and molten resin. Several commercially available screws utilize this type of technology and are discussed in this section. These screws include Double Wave screws, Energy Transfer screws. Variable Barrier Energy Transfer screws, DM2 screws, and Fusion screws. 

Figure 14.21 Schematic of a 114.3 mm diameter Fusion screw with a barrier melting section. The lead length of the screw was 131 mm for all sections of the screw except for the barrier melting section. The lead length in the barrier section was 159 mm. The undercut clearance on the barrier flight and the secondary flight in the Fusion sections was 1.3 and 2.5 mm, respectively...

In addition to the screws discussed above, there are other patented screws such as the Fusion Screw [29] which was designed for injection molding application but may be evaluated for compounding polymer blends. Figure 5.47 shows a schematic of the melting, homogenization, and chaotic mixing section of the Fusion screw. 

Figure 5.47 Schematic of the melting, homogenization, and chaotic mixing sections of the Fusion screw.

Figure 5 shows the barrel temperature uniformity varied with position and inspection of Figures 4 and 5 shows it was proportional to the power level and proximity to the material feed. Comparison of the two induction curves in Figure 5 (produced with general purpose and Fusion screws) confirms that melt-stream uniformity may be further optimized by screw design. 

Transition joints are used to join dissimilar metals where flanged, screwed, or threaded connections are not practical. They are used when fusion welding of two dissimilar metals forms interfaces that are deficient in mechanical strength and the ability to keep the system leak-tight. Transition joints consist of a bimetallic composite, a stainless steel, and a particular kind of aluminum bonded together by some proprietary process. Some of the types in use throughout the cryogenic industry are friction- or inertia-welded bond, roll-bonded joint, explosion-bonded joint, and braze-bonded joint. 

Figure 14.20 Schematic of a wave section of a Fusion high-performance screw (courtesy of Timothy W. Womer of Xaioy incorporated)...

From the curve estimate the glass transition temperature, Tg, the melting temperature, Tm, the crystallization temperature, Tc and the heat of fusion, A, for this specific PET sample during the temperature ramp-up. If the heat of fusion for a hypothetically 100% crystalline PET sample is 137 kJ/kg [64], what was the degree of crystallinity in the PET bottle screw-top ... 

In the M procedure, the sample is fused with sodium carbonate, the cooled fusion mixture dissolved in HCl, filtered, diluted to volume, and stored in plastic screw-cap bottle. Two procedures are reported by the H procedures. One uses a lithium metaborate fusion followed by HNO3 dissolution. No filtration is indicated (this procedure is used only when silicon is to be determined). In the other H procedure, the sample is treated with HF, evaporated completely, and the residue taken up with HCIO4. 

Screw feed produces frictional heating, which speeds fusion of pellets or powder into a fluid mass. When processors want to delay fusion, usually in processing rigid vinyl, lubricants that reduce friction between the resin and the steel screw and channel may be useful to reduce frictional heating and thus delay fusion. 

Perhaps the best results of stand alone posterior techniques are those reported by Harms [15]. His approach consists of posterior decompression, resection of the dome of the sacrum (shortening of the sacrum similar to that reported by Bradford), transpedicular instrumentation with tri-axial screws, first distraction, then posterior interbody fusion with insertion of metallic cages, then compression, reduction of the slippage, under direct visualization of the nerve roots. This technique provides stable reduction, posterolateral, and anterior fusion, with what is reported to be a lessened incidence of neurologic complications. 

A paper presented at the 1990 SPE ANTEC (5) discussed techniques for compounding highly filled polymers with corotating twin-screw extruders. The fusion time as measured in a torque rheometer of 40 wt% filled polypropylene with melt flow index (MFI) of 15 was 2.4 min for glass fibers, 8 min for mica, and 13.5 min for talc. For a 30 wt% loading of mica, fusion time was reduced to about 5 min. 

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