Cooling Fiber-reinforcement

Crystalline polymers undergo a discontinuous decrease in volume when cooled through (Fig. 4). This can lead to nonuniform shrinkage and warping in molded objects. On the other hand, it also causes the polymer to "lock on" to reinforcing fibers, eg, glass (qv), so that crystalline thermoplastics benefit much more than amorphous thermoplastics from fiber reinforcement. 

Fiber reinforcement of polymers allows us to use them in engineering applications that were previously off limits, We use fiber reinforced injection moldings in many under-the-hood automotive applications, such as rocker box covers and front end modules, which support the radiator, cooling fan, and hood latch, that are subjected to a wide range of temperatures. 

Fig. 2.18 illustrates the nature of the intensity profiles in pure polyetheretherke-tone (PEEK) and carbon fiber reinforced PEEK composites in the transmission and reflection modes, respectively. The quenched amorphous and slowly cooled crystalline components from PEEK can be separated. The three prominent diffraction peaks from the crystalline components in Fig. 2.18(a) correspond to the three uniform rings which can be detected in X-ray photographs. In contrast, no clearly measurable signal is identified from the PEEK amorphous phase independent of the carbon fiber content. 

Many other parameters may be involved depending on the method of processing. Such orientation not only occurs when processing from a solution or a melt but may also occur by inducing strain in the material. Glass fiber reinforced polyamide-6 was subjected to such a strain. Heated specimens were extended under controlled strain and cooled under extension. Hencky strain was calculated from the following equation ... 

Ablative cooling has been used in a number of liquid propellant engines. The materials employed are generally of an oriented fiber reinforced resin. 

Hazardous Decomp. Prods. CO, hydrocarbons heated to decomp., emits acrid smoke and fumes Storage Keep tightly closed in cool place Uses Reactive diluent for epoxy resins for solv.-free coating systems, laminating resins, fiber-reinforced composites stabilizer for chlorinated hydrocarbons thickener for paints and varnishes Manuf./Distrib. Aldrich Fluka Raschig... 

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