Polystyrene dynamic mechanical

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... 

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... 

A reversible succession of order-order and order-disorder transition was observed for a poly(ethylene-a/f-propylene)- -poly(ethylene-co-butylene)-b-polystyrene terpolymer, which shows at room temperature non-hexagonally packed PS cylinders. Upon heating, this system reorganizes to a hexagonally packed one, and at higher temperatures dynamic-mechanical analysis indicates the transition to the disordered state [73],... 

Frederick, J.E., Tschoegl,N.W., Ferry.J.D. Dynamic mechanical properties of dilute polystyrene solutions dependence on molecular weight, concentration, and solvent. J. Phys. Chem. 68,1974-1982 (1964). 

Holmes,L.A., Kusamizu,K., Osaki,K., Ferry.J.D. Dynamic mechanical properties of moderately concentrated polystyrene solutions. J. Polymer Sci. Pt. A-2 9, 2009-2021 (1971). 

The dielectric relaxation of bulk mixtures of poly(2jS-di-methylphenylene oxide) and atactic polystyrene has been measured as a function of sample composition, frequency, and temperature. The results are compared with earlier dynamic mechanical and (differential scanning) calorimetric studies of the same samples. It is concluded that the polymers are miscible but probably not at a segmental level. A detailed analysis suggests that the particular samples investigated may be considered in terms of a continuous phase-dispersed phase concept, in which the former is a PS-rich and the latter a PPO-rich material, except for the sample containing 75% PPO-25% PS in which the converse is postulated. 

Abbreviations DMA, dynamic mechanical analysis DSC, differential scanning calorimetry He, helium PE, polyethylene PMMA, polymethylmethacrylate PP, polypropylene PS, polystyrene St-bend, steel disc with topography similar to that of pipe bend St-sb, steel disc with sandblasted surface... 

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... 

Electron micrographs of compositions D and E are shown in Figures 9 and 10. It is evident that in E polybutadiene is the continuous phase (with some rubber in the polystyrene domains) while D represents a transition from lamellar to polybutadiene-continuous morphology. Again the dynamic mechanical data (Table II) are consistent with these obser-... 

In Figure 21.8, a softening temperature for the polystyrene endblock is shown as a function of endblock molecular weight (ranging from about 6000 to 30000). The softening temperature is characterized as the onset of test specimen creep (in a small-strain dynamic mechanical test in tensile mode), the creep point occurring when strain extension becomes considerable in order to maintain the appropriate stress level to continue the test. This softening temperature lies below the measured Tg, and it is an indication of the... 

Dynamic Mechanical Behaviour of Atactic Polystyrene, High-impact Polystyrene and Other Styrenic Polymers... 

This chapter discusses the dynamic mechanical properties of polystyrene, styrene copolymers, rubber-modified polystyrene and rubber-modified styrene copolymers. In polystyrene, the experimental relaxation spectrum and its probable molecular origins are reviewed further the effects on the relaxations caused by polymer structure (e.g. tacticity, molecular weight, substituents and crosslinking) and additives (e.g. plasticizers, antioxidants, UV stabilizers, flame retardants and colorants) are assessed. The main relaxation behaviour of styrene copolymers is presented and some of the effects of random copolymerization on secondary mechanical relaxation processes are illustrated on styrene-co-acrylonitrile and styrene-co-methacrylic acid. Finally, in rubber-modified polystyrene and styrene copolymers, it is shown how dynamic mechanical spectroscopy can help in the characterization of rubber phase morphology through the analysis of its main relaxation loss peak. 

EFFECT OF POLYMER STRUCTURE AND ADDITIVES ON THE DYNAMIC MECHANICAL SPECTROSCOPY OF POLYSTYRENE... 

The dynamic mechanical loss spectrum of polystyrene, in common with the spectra of most polymers, shows a small number of discrete loss peaks which are best resolved by a low-frequency test, preferably at or below 1 Hz. Figure... 

Figure 28.1 Schematic idealized plot of the dynamic mechanical spectrum of linear, amorphous, atactic polystyrene...

In rubber-modified polystyrenes, the rubber is dispersed in the polystyrene matrix in the form of discrete particles. The two-phase nature of rubber-modified polystyrene was first suggested by Buchdahl and Nielsen [47] based on data on dynamic mechanical properties obtained with a torsion pendulum. The existence of two prominent loss peaks led to this conclusion, one at low temperatures which is due to the a relaxation of the rubber (e.g. 193 K for polybutadiene) and one at high temperatures which is due to the a relaxation of the matrix (e.g. 373 K for polystyrene). Later, microscopy provided proof of the existence of the rubber phase as a discrete dispersed phase in polystyrene [48]. 

Dynamic mechanical characterization of rubber-modified polystyrenes or styrene copolymers can reveal some of the variables in the structure of the rubber phase. The tan<5 peak at lower temperature, which can be considered as representative of the rubber a relaxation, was shown to be affected by the volume fraction of the rubbery phase, , in both HIPS [54] and ABS [55]. 

In this work we used polystyrene-based ionomers.-Since there is no crystallinity in this type of ionomer, only the effect of ionic interactions has been observed. Eisenberg et al. reported that for styrene-methacrylic acid ionomers, the position of the high inflection point in the stress relaxation master curve could be approximately predicted from the classical theory of rubber elasticity, assuming that each ion pah-acts as a crosslink up to ca. 6 mol %. Above 6 mol %, the deviation of data points from the calculated curve is very large. For sulfonated polystyrene ionomers, the inflection point in stress relaxation master curves and the rubbery plateau region in dynamic mechanical data seemed to follow the classical rubber theory at low ion content. Therefore, it is generally concluded that polystyrene-based ionomers with low ion content show a crosslinking effect due to multiplet formation. More... 

Figure 9.18 gives one more example of how interaction affects dynamic mechanical properties. Two polymers were tested with various concentrations of alumina. Polystyrene was almost unaffected by various concentrations of filler. Sulfonated polystyrene interacts more strongly with its filler than polystyrene which contributes to increase in Tg." ... 

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