Polystyrene dynamic moduli

There are plenty of measurements of dynamic modulus of nearly monodisperse polymers starting with pioneering works of Onogi et al. (1970) and Vinogradov et al. (1972a). The more recent examples of the similar dependencies can be found in papers by Baumgaertel et al. (1990, 1992) for polybutadiene and for polystyrene and in paper by Pakula et al. (1996) for polyisoprene. 

Figure 12.14 Polystyrene data dynamic modulus versus temperature for fractions. Numbers on curves are fraction numbers. (Reprinted with permission from Merz, E. H., L. E. Nielsen, and R. Buchdahl Influence of Molecular Weight on the Properties of Polystyrene, Ind. Eng. Qiem., vol. 43, pp. 1396-1401, 1951. Copyright 1951 American Chemical Society.)...

Figure 32 shows the schematic view of a typical isochronal (i.e., fixed deformation frequency) DMA spectra as functions of temperature for an ordinary amorphous polymeric resin, like atactic PMMA or polystyrene. The dynamic storage and loss moduli, E T) and E"(T), measured under a fixed deformation frequency are plotted as functions of temperature T. The dynamic modulus plot is often accompanied with the dissipation factor, tan (5(T). A similar diagram is also obtained for isothermal DMA spectra, where E (o), E (o), and tan (3(co) are plotted as functions of the characteristic experimental time scale, taken as the reciprocal of the deformation frequency co. 

The physical properties of the acid- and ion-containing polymers are quite interesting. The storage moduli vs. temperature behavior (Figure 8) was determined by dynamic mechanical thermal analysis (DMTA) for the PS-PIBMA diblock precursor, the polystyrene diblock ionomer and the poly(styrene)-b-poly(isobutyl methacrylate-co-methacrylic acid) diblock. The last two samples were obtained by the KC>2 hydrolysis approach. It is important to note that these three curves are offset for clarity, i.e. the modulus of the precursor is not necessarily higher than the ionomer. In particular, one should note the same Tg of the polystyrene block before and after ionomer formation, and the extension of the rubbery plateau past 200°C. In contrast, flow occurred in... 

The dynamic viscoelasticity and the thermal behaviour of films of Thermoelastic 125 cast from solutions in four solvents - toluene (T), carbon tetrachloride (C), ethyl acetate (E), and methyl ethyl ketone (M) — have been studied by Miyamato133 The mechanical loss tangent (tan 8) and the storage modulus E dependences exhibit two transitions at —70 °C and 100 °C which have been attributed to onset of motion of polybutadiene and polystyrene segments, respectively. The heights of the polybutadiene peaks on tan 6 curves decrease in the order C > T > E > M, while for polystyrene the order is reversed C < T < E < M. These phenomena have been related to the magnitude of phase separation of the polystyrene and polybutadiene blocks. 

Dynamic Mechanical Properties. Figure 15 shows the temperature dispersion of isochronal complex, dynamic tensile modulus functions at a fixed frequency of 10 Hz for the SBS-PS specimen in unstretched and stretched (330% elongation) states. The two temperature dispersions around — 100° and 90°C in the unstretched state can be assigned to the primary glass-transitions of the polybutadiene and polystyrene domains. In the stretched state, however, these loss peaks are broadened and shifted to around — 80° and 80°C, respectively. In addition, new dispersion, as emphasized by a rapid decrease in E (c 0), appears at around 40°C. The shift of the primary dispersion of polybutadiene matrix toward higher temperature can be explained in terms of decrease of the free volume because of internal stress arisen within the matrix. On the other... 

Figure 13.13 Reduced storage modulus G and dynamic viscosity rj = G /w as functions of reduced frequency uto) for a cylinder-forming polystyrene-polybutadiene-polystyrene triblock copolymer with block molecular weights of 7000-43,000-7000. The curves are time-temperature-shifted to a reference temperature of 138°C the open symbols were obtained in the low-temperature ordered state the closed symbols were obtained in the high-temperature disordered state. (From Gouinlock and Porter 1977, reprinted with permission from the Society of Plastics Engineers.)...

FIGURE 10.19 Dynamic mechanical thermal analysis of a block copolymer of SBR rubber and polystyrene. This illustrates two phases however, owing to the broad loss modulus peak, it may be assumed that some mixing has occurred in the polystyrene phase. (Reprinted from Wetton, R.E. et al., Thermochim. Acta 175, 1, 1991. With permission.)... 

Figure 2. Dynamic Young s modulus E of polystyrene (PS), high impact polystyrene (HIPS), separated gel, and crosslinked poly-butadiene rubber. Data from Ref. 17.

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