Mold Equipment

We have already noted in an earlier section that treatment of filler with a finishing agent also increases its abrasive attack on the parts of the processing equipment [271], At the same time it has been shown indirectly in [297,298] and directly by microscopic inspection in [294] that a synthesized polymer film remains on the polymerization-modified filler after the processing treatment, that is, there is always a medium which protects the molding equipment from the abrasive attack of the filler. In view of these observations, the polymeric composites with PMF are comparable, in terms of abrasive activity, with unfilled polymers [226, 227],... 

All this marketplace action of the new electronic is targeted to enable customers all over the world to purchase high-quality TPs, other plastic-related materials, molding equipment, tooling, maintenance supplies, packaging materials, and related services. 

The typical TP encapsulation process is an insert injection molding or liquid injection molding operation. The insert, a coil, or an integrated circuit, for example, is placed in a mold equipped with either fixed spider type supports or retractable pins or other features to support it when molten TP is injected. 

Design of injection molding equipment to produce car bumpers made from polymers Designing feedback control systems for bioreactors... 

What measures are taken to protect injection molding equipment while processing polyvinyl chloride ... 

Figure 16.11 Research injection molding equipment. (Courtesy of Du Pont)...

The alkyd molding compounds, depending on the form of the material, may be molded on a wide range of conventional molding equipment. Because of the short time required to cure the compounds, extremely fast molding cycles are possible. 

PVDF resins can be molded by compression, transfer, and injection molding in conventional molding equipment. The mold shrinkage can be as high as 3% due to the semicrystalline nature of PVDF. Molded parts often require annealing at temperatures between 135 and 150°C (275 and 302°F) to increase dimensional stability and release internal stresses.24... 

In injection molding, THV is processed at lower temperatures than other fluo-ropolymers, typically at 200 to 300°C (392 to 572°F) with mold temperatures being 60 to 100°C (140 to 212°F). Generally, standard injection molding equipment is used.34... 

Recently all of the temperature, pressure, and time controls have been replaced with a single microprocessor-based controller. A number of these are available and they allow for complex pressure and temperature curves to be programmed with multiple soaking levels and variables that can be chosen. Built-in memories recall previous programs and cassettes can store them on the shelf. Interfaces can connect with a central host computer for data collection or actual machine setup and supervision. The result is more flexible, more exacting, and easier to control modern molding equipment (Chapter 3). 

SBC can be processed on most conventional blow molding and injection blow molding equipment designed for many other types of polymers with little or no equipment modifications. This includes continuous, accumulator head, or reciprocating screw extrusion blow molding equipment. Bottles made from SBC have been used widely for applications such as honey bears. The SBC will withstand the moderate hot fill temperatures required for this application. 

Thus far, the technology has been used only to paint the bumpers of a two-wheel personal transportation system called Segway. A thin film, when heated it can be molded into shapes that correspond to parts of a car. While the film will be more expensive than paint, the process eliminates the need for paint lines and uses a plant s existing molding equipment. GE Plastics expects to announce its first contract with a carmaker in 2004. 

In many instances, one wishes to produce solid parts so as to maximize the toughness of the product. In some cases, the economics of the busines will not permit the high cost and process sophistication of reaction injection molding equipment. Low-pressure casting is then the process of choice. Casting machine prices are usually 20 to 50% of those of RIM machines. They are typically smaller and simpler machines. They use static or dynamic mixers rather than impingement mix heads. 

All the ordinary extrusion and molding equipment and techniques can be used to process PVDF into different shapes ranging from pipes, fitting, parts, solid rods and sheets, to thin films. Longevity of equipment can be extended using special alloys on the surface that is in contact with molten PVDF, but usually it is not necessary. PVDF based polymers are available commercially in a wide range of melt flow index and with additives to enhance processing or end use properties. However, both homopolymers and copolymers may be shaped from the molten state without extrusion aids or thermal stabilizers. 

PVDF resins are readily molded in conventional compression, transfer and injection molding equipment. Typical molding temperatures in the cylinder and nozzle are 180-240°C for injection types and 50-90°C for molds. As a crystalline polymer, PVDF typically shows relatively high mold shrinkage of about 2-3%, reflecting the high degree of crystallization and the difference between the solid and the molten densities. 

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