Uniaxial thermoplastic polymers

Tong, L., White, J.R. Photo-oxidation of thermoplastics in bending and in uniaxial compression. Polym. Degiad. Stab. 53, 381-396 (1996)... 

Roetting O, Hinrichsen G (1994) Blends of thermotropic liquid crystalline and thermoplastic polymers a short review. Adv Polym Technol 13(l) 57-64 Roth D, Thomas L (1989) Why LCP film. In Abstracts of papers of the American Chemical Society, vol 198, p 3-CMEC. American Chemical Society, Washington, DC Rudko O (2002) Liquid crystalline polymers. Uniaxial-biaxial nematic phase transition Scott CE, Macosko CW (1995) Morphology development during the initial stages of polymer-polymer blcmding. Polymer 36(3) 461-470... 

In practice polymeric materials are often subjected to mechanical loads. Therefore, it is essential to know how polymers respond to the mechanical load. Figure 1.3 presents the common behavior of thermoplastic polymers under uniaxial deformation. On the stress(a)-strain(e) curve four regions [7] can be distinguished in region I the material shows an elastic behavior. In this region the material is characterized by its Young s modulus of elasticity. In region II the material yields. The slope of... 

Section II B of Chapter 2 gave a description of the uniaxial deformation behavior of an unoriented thermoplastic polymer. It was indicated that — depending on experimental and material parameters - failure could occur at any of the different stages of a tensile loading process ... 

Orientation A process of drawing or stretching of as-spun synthetic fibers or hot thermoplastic films to orient polymer molecules in the direction of stretching. The fibers are drawn uniaxially and the films are stretched either uniaxially or biaxially (usually longitudinally or longitudinally and transversely, respectively). Oriented fibers and films have enhanced mechanical properties. The films will shrink in the direction of stretching, when reheated to the temperature of stretching. 

Under static loading conditions where either the stress or strain is keeping constant polymer materials (especially thermoplastics) show non-linear viscoelastic deformation behaviour to appear as retardation (creep) or relaxation. Long-term investigations to analyse creep or relaxation can be accomplished at flexural, indentation, or uniaxial tensile or compression loading as a function of time and loading level as well as environmental conditions such as temperature, media etc. (see [13Gre], p. 171 - 183). 

Fillers are mainly used for reasons of economy, but in many cases they also improve some properties of the polymer. The most important fillers for polymers are minerals such as talc, chalk and china clay. Filler content generally used with plastics is up to 60 wt%. The most common practice is to feed the filler downstream into the melt by means of a twin-screw side feeder (Figure 6.3). It is well-known that thermoplastic melts with high loadings of small particles such as calcium carbonate, carbon black and titanium dioxide give both yield values in shear flow [58, 59], and uniaxial extension [60, 61]. 

The rotary clamp consisting of a pair of gears is a basic construction element for the design of various types of extensional rheometers for polymer melts described earlier. The fact that the design is amenable for use in uniaxial and biaxial extensional rheometry has been shown by Meissner et al. [77]. Other biaxial extensiometers for molten thermoplastics have also been described [78,79] by other researchers. 

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