Dynamic thermomechanical property

Dr. Riew has presented more than 50 technical papers and holds more than 25 patents on emulsion polymers, hydrophilic polymers, synthesis and application of telechelic polymers, and toughened plastics for adhesives and composites. His latest research is in the synthesis, characterization, and performance evaluation of impact modifiers for thermosets and engineering thermoplastics. His research interests include correlating polymer chemistry and physics, morphology, engineering, and static and dynamic thermomechanical properties to the failure mechanisms of toughened plastics. 

Hydrogen bonds were also responsible for blending of chitosan and cellulose [147]. The mechanical and dynamic thermomechanical properties of the material appear to be dominated by cellulose. The reduced rate of water vapor transport through the blend appears suitable for wound dressings, providing an optimal moisture environment of the wound by preventing excessive dehydration. The blend demonstrated effective antimicrobial activity against E. coli and S. aureus. 

The static mechanical and dynamic thermomechanical properties of the nanocomposites in the glassy state remain almost the same as those of the pristine PI, while a significant reinforcement effect is observed in the rubbery state above the main relaxation at 7. ... 

The dynamic mechanical properties of VDC—VC copolymers have been studied in detail. The incorporation of VC units in the polymer results in a drop in dynamic modulus because of the reduction in crystallinity. However, the glass-transition temperature is raised therefore, the softening effect observed at room temperature is accompanied by increased brittleness at lower temperatures. These copolymers are normally plasticized in order to avoid this. Small amounts of plasticizer (2—10 wt %) depress T significantly without loss of strength at room temperature. At higher levels of VC, the T of the copolymer is above room temperature and the modulus rises again. A minimum in modulus or maximum in softness is usually observed in copolymers in which T is above room temperature. A thermomechanical analysis of VDC—AN (acrylonitrile) and VDC—MMA (methyl methacrylate) copolymer systems shows a minimum in softening point at 79.4 and 68.1 mol % VDC, respectively (86). 

Thermal and thermomechanical analyses44 are very important for determining die upper and lower usage temperature of polymeric materials as well as showing how they behave between diose temperature extremes. An especially useful thermal technique for polyurethanes is dynamic mechanical analysis (DMA).45 Uiis is used to study dynamic viscoelastic properties and measures die ability to... 

Dynamic properties are more relevant than the more usual quasi-static stress-strain tests for any application where the dynamic response is important. For example, the dynamic modulus at low strain may not undergo the same proportionate change as the quasi-static tensile modulus. Dynamic properties are not measured as frequently as they should be simply because of high apparatus costs. However, the introduction of dynamic thermomechanical analysis (DMTA) has greatly widened the availability of dynamic property measurement. 

The term water dynamics indicates the mobility of the plasticizing diluent and a theoretical approach to understanding how to control the water movement in glassforming food systems. The term glass dynamics deals with the time and temperature dependence of relationships among composition, structure, and thermomechanical properties, as well as the functional behavior of food systems. 

Bikiaris, D. N. and Karayannidis, G. P., Dynamic thermomechanical and tensile properties of chain-extended PET, J. Appl. Polym. ScL, 70, 797 (1998). 

Plastics - Thermomechanical analysis (TMA) - Determination of linear thermal expansion coefficient and glass transition temperature Plastics - Thermomechanical analysis (TMA) - Determination of softening temperature Plastics - Determination of dynamic mechanical properties -General principles Plastics - Dynamic mechanical analysis - Determination of glass transition temperature Plastics - Dynamic mechanical analysis - Calibration... 

Static and dynamic thermomechanical analysis of the commercial polymer separators (PP and PE) were made to understand their properties (Love, 2011). Anisotropic separators manufactured from a dry process showed limited tensile performance in the transverse direction. The separators prepared from a wet process displayed a uniform and biaxial structure and nearly showed identical mechanical strength on both directions. It was also found that small losses in mechanical integrity were observed after the separators were exposed to various electrolytes. 

Crystallinity of PLA has a strong impact on its mechanical properties. Suryanegara et al. have prepared PLA/MFC nanocomposites in both fully amorphous and crystallized states. The tensile modulus and strength of pristine PLA were improved with an increase of MFC content in both amorphous and crystallized states. Dynamic mechanical analysis (DMA) has been used to study the effect of MFC reinforcement on the thermomechanical properties of PLA in both states and the results are shown in Figure 9.5. In the amorphous state, the storage modulus of pristine PLA below Tg is almost constant at around 3 GPa. Above Tg, the modulus drops to 4 MPa at 80 °C, and then increases to 200 MPa at 100 °C owing to the cold... 

The experimental determination of thermomechanical properties and the evaluation of related quantities offers a substantial test of theoretical calculations and computer simulations of mixed liquid systems. Furthermore, thermodynamic investigations of viscous flow are seen to give supplementary information on the dynamics of molecular aggregates, and in some cases, when water is the cosolvent polyaggregates are arranged in a supra-clusters organization. 

Trends similar to those for the tensile properties can be observed in the thermomechanical properties of these nanocomposites. In Figure 4.6 we compare the dynamic mechanical response of a homo-PET with that of its nanocomposites at 3 wt% MMT (melt-processed with alkylammonium, 2MTL8, and alkylimidazolium, Cie-imidaz, montmorillonites). It is clear that the storage moduli of the nanocomposites are higher than that of the unfilled PET... 

I. N. Sim, and S. O. Han, Effect on modified nanoclay on dynamic mechanical and thermomechanical properties of natural fiber/polypropylene biocomposites. / Adhes. Sci. Technol. 27,1313 (2013). 

To investigate the two-phase nature and low-temperature properties of PAS, dynamic thermomechanical spectra were obtained. The dynamic me-... 

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