Liquid injection casting

Figure 5.34 Example of a more accurate mixing of components for liquid injection casting via a moving wedge technique...

Foamed casting is a simple non-mechanical version of pouring (Chapter 11), reaction injection molding (RIM) (Chapter 12) or liquid injection molding (LIM) (Chapter 16). Liquid components of the plastic with... 

Different casting processes are used. They tend to overlap and could be identified by other processing methods. An example is liquid injection molding that can be identified as injection molding (Chapter 4) or reaction injection molding (Chapter 12). Many decades ago the reaction injection molding process was initially called liquid injection molding. 

Figure 11.1 Example of a liquid injection molding casting process...

Thermoplastio (Cont d) Barrier film reaine Casting resins Liquid injection moldng... 

Thermoplastic (Cont d) Barrier Eilm Resins Casting Resins Liquid Injection Molding... 

Straight steel pipes up to 600 mm in diameter and six or more metres in length are usually lined by centrifugal casting. In this technique, the prepared preheated pipe is fitted with end caps and placed into the heated casting oven. Freshly mixed liquid polyurethane is then injected into the pipe which is then spun round its longitudinal axis until the polyurethane has cured to form a solid lining. 

Urethanes are processed as rubber-like elastomers, cast systems, or thermoplastic elastomers. The elastomer form is mixed and processed on conventional mbber mills and internal mixers, and can be compression, transfer, or injection molded. The liquid prepolymers are cast using automatic metered casting machines, and the thermoplastic pellets are processed like all thermoplastic materials on traditional plastic equipment. The unique property of the urethanes is ultrahigh abrasion resistance in moderately high Shore A (75—95) durometers. In addition, tear, tensile, and resistance to many oils is very high. The main deficiencies of the urethanes are their resistance to heat over 100°C and that shear and sliding abrasion tend to make the polymers soft and gummy. 

I. Encapsulation. The continuous casting of gel ribbons, with liquid fill material being injected between the gel ribbons using a positive displacement... 

The liquid monomers are suitable for bulk polymerization processes. The reaction can he conducted in a mold (casting, reaction injection molding), continuously on a conveyor (block and panel foam production), or in an extruder (thermoplastic polyurethane elastomers and engineering thermoplastics). Also, spraying of the monomers onto the surface of suitable substrates provides insulation barriers or cross-linked coatings. 

A third construction method involves creating a form in three dimensions by casting. Casting is a technique that requires a mold, into which a material such as plastic, metal, or clay in liquid form is poured or injected. (See Figure 4.3.)... 

Finally, in the reaction injection-molding (RIM) process, low-viscosity reacting monomers or prepolymers are intimately mixed just before being injected into a hot cavity, where they react further and solidify. The RIM process, then, is a variation of the casting process, where highly reactive liquid systems are injected quickly, rather than being allowed to flow by gravity, into complex shape cavities, where they quickly react and solidify. 

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