Cooling Fiber-reinforced, composites

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... 

Curl due to residual stresses is well known in the production of fiber-reinforced composites where uniaxially oriented plies are laminated together to form a sheet. If two such fiber plies are laminated at a relative angle to one another, the sheet will curl just as the LCP film produced by the counter-rotating die. There is no effective way to cause the residual stresses in the LCP film to relax by heating the film, because the orientation in the LCP persists and will not relax to a random state. Near the melt temperature, the LCP film will lie fiat because the stresses are balanced, but upon cooling, no matter how fast or slow, the curl will return. 

In regards to the studies on transcrystalhnity in conventional fiber reinforced composites, their number is vast. A number of issues are related to the formation and growth of TCL [81] crystallinity of the matrix, mismatch of thermal coefficients of the fiber and the matrix, epitaxy between the fiber and the matrix, surface toughness, thermal conductivity, treatment of fiber, etc. Processing conditions such as cooling rate, temperature, and interfacial stress were also found to be important. There are indications that the TC phenomenon is probably too specific for each fiber/matrix system. Nevertheless, it has been recognized that the orientation distribution of the polymer chains in the TCL wUl determine the nature and extent of its effect on the mechanical properties of the composite material [84]. 

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. 

Recently, new compounding methods have been investigated to produce long, natural fiber-reinforced thermoplastic pellets and improve composite mechanical properties [31, 32]. For example, pellets have been formed by melt impregnation of continuous natural fiber yarns by pultrusion followed by cooling and chopping. Another method involves commingling of continuous forms of natural and synthetic fibers that are then heated, consolidated, and chopped. 

The crystallization of isotactic polypropylene (iPP) is affected by many factors, such as macromolecular characteristics [82], crystallization conditions (temperature, cooling rate), and stress (shear, elongational fields) [83-85]. In fiber reinforced iPP matrix composites, the crystalline morphology of the polymer is influenced by the fibers that can act as nucleating agents affecting the crystallization process [86-88]. TranscrystaUinity is a well-known structural feature in pol rmers, which occurs as the result of dense nucleation of the semi-... 

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