Mechanical behavior, dynamic blending

Short fiber reinforcement of TPEs has recently opened up a new era in the field of polymer technology. Vajrasthira et al. [22] studied the fiber-matrix interactions in short aramid fiber-reinforced thermoplastic polyurethane (TPU) composites. Campbell and Goettler [23] reported the reinforcement of TPE matrix by Santoweb fibers, whereas Akhtar et al. [24] reported the reinforcement of a TPE matrix by short silk fiber. The reinforcement of thermoplastic co-polyester and TPU by short aramid fiber was reported by Watson and Prances [25]. Roy and coworkers [26-28] studied the rheological, hysteresis, mechanical, and dynamic mechanical behavior of short carbon fiber-filled styrene-isoprene-styrene (SIS) block copolymers and TPEs derived from NR and high-density polyethylene (HOPE) blends. 

Fig. 21. Dynamic mechanical behavior of miscible, amorphous PEEK/polyimide (BTDA-Bis P) blends (composition in wt%)...

CavaiDe, J.Y., Perez, J., Jourdan, C., and Johari, G.P. (1987) Dynamic mechanical behavior of poly(vmyl-methyl ether)-poly (styrene) blends. J. Pdym. Sci. B Polym. Phys., 25 (9), 1847-1858. 

Cimmino, S., DiPace, E., Karasz, F.E., Martuscelli, E. and Silvestre, C. (1993) Isotactic polypropylene/hydrogenated oligo(cyclopentadiene) blends Phase diagram and dynamic-mechanical behavior of extruded isotropic films. Polymer, 34, 972-976. 

The similarity in morphology of four blends can be proved by the DMA investigation. In Fig. 24 elastic modulus and tan 8 of four blends are presented. The dynamic-mechanical behavior of the investigated blends does not differ from each other. It was found that CNTs mainly reside in the polar NBR and non-polar NR but not in weak polar SBR. Such unusual localization of CNTs in ternary SBR/NBR/NR can be explained by taking into consideration the presence of... 

Regarding PEN nanocomposites, Si02-based systems have been developed since 2004 by Ahn, Kim, and Lee (2004), who surface-modified silica nanoparticles to improve their dispersion in the polymer during melt blending in an internal mixer. They reported on the increase of the elastic modulus and elongation at break at low nanoparticle content (0.4%wt). On the same nanocomposite system, Kim et al. showed an increase of several chemical-physical properties (thermal stability, dynamic mechanical behavior, and crystallization kinetics) after nanoparticle addition, and also a fourfold gain in the elastic modulus above the glass... 

Abstract The miscibility behavior in blends of polyethersulfone (Victrex PES) with the polyimide PI 2080, (the condensation product of 3,3, 4,4 -benzophenone tetracarboxylic dianhydride [BDTA] and a 4 1 mixture of 2,4-toluene diisocyanate and 4,4 -diphenylmethane diisocyanate) or with the polyimide XU 218 (the condensation product of BDTA and 5(6)-amino-l-(4 -aminophenyl)-l,3,3 -trimethylindane) was investigated using differential scanning calorimetry, dynamic mechanical analysis and thcmiogravimetric analysis. The effects of solvents (dimethylacetamide, tetramethylene sulfone, dimethyl sulfoxide and l-methyl-2-pyrrolidone) on miscibility were studied and one solvent, tetramethylene sulfone was found to have a plasticizing effect. In the absence of solvent, the equilibrium phase boundary for these blends was in the experimentally inaccessable region below the Tg-composition line. The phase boundary at zero solvent concentration was obtained by extrapolation using data collected in the presence of the plasticizer. 

DMPPO and polystyrene form compatible blends. The two components are miscible in all proportions (59). Reported dynamic—mechanical results that indicate the presence of two phases in some blends apparendy are caused by incomplete mixing (60). Transition behavior of thoroughly mixed blends indicates that the polymers are truly compatible on a segmental level (61). CompatibiUty may be attributed to a %— % interaction between the aromatic rings of the two polymers sufficient to produce a negative heat of mixing. However, the forces are very small, ie, = ca40 J/mol (9.6 cal/g), and any... 

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