High performance polymers moldings

Crystallization of PCT is relatively rapid, but because of its higher Tg (90 °C) the maximum rate of crystallization occurs at a higher temperature than is typical of other crystalline polymers such as PET (Tg at about 70 °C) or PBT (Tg at about 35 °C). Figure 7.2 compares the crystallization half-times of PET and PCT from both the glass and the melt (data were obtained via DSC measurements). The effect of the higher Tg on the temperature of maximum crystallization rate (i.e. minimum half-time) is most clearly seen in the data from the melt. The basic rapid crystallization rate of PCT allows it to be used as a high-performance injection molding material. 

McNally, D. and Gall, J. S., The history of poly(butylene terephthalate) molding resins, in High Performance Polymers Their Origin and Development, Seymour, R. B. and Kirshenbaum, G. S. (Eds), Elsevier, Amsterdam, 1986, pp. 71-79. 

While the fiber producers were busily expanding their fiber activities, a number of companies were simultaneously trying to adapt poly(ethylene terephthalate) (PET) to molding in much the same way as the nylons had been made to double in brass as molding compound and fiber. This objective has been particularly attractive because the manufacturing capacity for PET in the United States has surpassed 5 billion lbs per year, and all the economy of scale has been obtained to yield high-performance polymers at commodity prices. 

Injection molding is the most common fabrication technique used in the plastics industry, particularly with high-performance polymers. Amorphous resins can be processed over a wide temperature range. 

Polyetherimides were developed as a result of research interests in aromatic nucleophilic displacement chemistry combined with a perceived marketplace need for high performance polymers which could be readily fabricated by standard plastics extrusion and injection molding processes. 

Although low-carbon steels are the most popular, a variety of other materials is also used for bearing cages. Molded nylon, synthetic resin-impregnated fabrics, and bronze/brass are popular in the normal temperature ranges. High-performance polymers, carbon steel, certain stainless steels, and iron-silicon bronze are used for higher temperatures. 

Wen, X., Wang, X., Cai, Z.-Q., Pi, P., Cheng, J., Yang, Z., 2011. Cure kinetics and chemo-rheological behavior of a wind epoxy resin system and its viscoelastic properties reinforced by glass fiber matt with process of vacuum assisted resin transfer molding. High Performance Polymers 23, 477—484. 

A list of materials regarded as high-performance polymers (Table 17.10) overlaps the list of Table 17.9 to some extent, but also includes thermosets such as epoxy, phenolic, and silicone molding resins. As with most molded plastics, high-tanperature performance is enhanced by reinforcement with glass, boron, or carbon or aramid fibers. The thermosets are seldom used without reinforcement. Several are inclnded in Figures 17.6 and 17.7. 

The ECN resins are multifunctional, solid polymers characterized by low ionic and hydrolyzable chlorine impurities, high chemical resistance, and good thermal performance. The ECN resins are widely used as base components in high-performance electronic and structural molding compounds, micro-chip encapsulation, high—temperature adhesives, structural molding powders, etc. 

While polymers with moderately high performance qualities, such as cellulose in wood and cotton have been known for years, these linear polymers could not be extruded or injection molded. However, they were able to withstand the effects of moderately hostile environments. The classic reinforced thermosets could be compression molded and could also be classified as high performance plastics. In contrast, the general purpose thermoplastics, introduced in the 1930 s, were readily extruded and Injection molded but were not useful at boiling water temperatures. 

Polymers with moderately high performance qualities, such as cellulose and cotton and wood have been known for centuries. These linear polymers could not be extruded or injection molded but they did withstand the effects of moderately high hostile environments. 

Polymers and Related Products synthetic resins resin and polymer intermediates resin products adhesives emulsions plasticisers fluorochemi-cals. In general the overseas activities are undertaken by Reichhold Specialty Plastics and Compounds engineering and high performance plastics colourants molded plastic products ... 

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