Polystyrene modelling

R. W. J. Westerhout et al. Kinetics of the low-temperature pyrolysis of polyethene, polypropene, and polystyrene modeling, experimental determination, and comparison with literature models and data. Industrial and Engineering Chemistry Research, 36, 1955-1964 (1997). 

Ceramic shell moulding is a patented process (Replicast ) in which a polystyrene model is covered with a ceramic shell (2-3 mm thickness), based on ethyl silicate and refractory sand. The shell is hardened using ammonia and sintered at 1000 °C. The sintering cures the shell and bums away the polystyrene model. The metal is then poured into the shell. 

Figure 10.25. Plastic and bridle compression failure of polystyrene model particles.

The validity of scaling laws has been tested on several swollen network systems (Table 29.9). Munch et al. [99] studied the concentration dependence of the shear modulus for polystyrene model networks synthesized by copolymerization of styrene and divinylbenzene and swollen to equilibrium in benzene (good solvent for polystyrene). It was found that the modulus obeys a scaling law with equilibrium concentration, similar to that obtained for semidilute polymer solutions. The best fit to the equation G = Brpi yields... 

Swollen Polystyrene Model Networks, Makromol. Chem. 178(2), 485 (1977). Effect of crosslink functionality in styrene block copolymers and IPN-type network formation. 

For sand castings, models made from wood, plastic, and gypsum can be used. For individual castings, polystyrene models have proven themselves due to their easy processing and inexpensive manufacturability. A shrinkage coefficient of 1 to 1.4% has to be taken into account. A casting basin with inserted slag barrier (indirect. 

Gessner, A., Lieske, A., Paulke, B.R., and Muller, R.H. 2003. Functional groups on polystyrene model nanoparticles Influence on protein adsorption. Biomed. Mater. Res. 65A 319-26. 

Peula, J.M. and F.J. de las Nieves. 1993. Adsorption of monomeric bovine serum-albumin on suUbnated polystyrene model colloids. 1. Adsorption-isotherms and effect of the surface-charge density. Colloids and Surfaces A Physicochemical and Engineering Aspects 77 (3) 199-208. 

As further support for the assignments of these resonances to polystyrene termination structures, the ID-NMR spectra of model compounds were collected. In the aliphatic region of the ID-NMR spectrum of poly(2,3-diphenyl-1,4-butylene) (a model compound with H-H/T-T polystyrene model structure), signals were observed in the 48-53 ppm... 

Experimental investigations of the model system of dye molecules adsorbed onto surfaces of polystyrene spheres have finuly established the sensitivity and surface specificity of the SHG method even for particles of micrometre size [117]. The surface sensitivity of die SHG process has been exploited for probing molecular transport across the bilayer in liposomes [118], for measurement of electrostatic potentials at the surface of small particles [119] and for imaging... 

An important step in tire progress of colloid science was tire development of monodisperse polymer latex suspensions in tire 1950s. These are prepared by emulsion polymerization, which is nowadays also carried out industrially on a large scale for many different polymers. Perhaps tire best-studied colloidal model system is tliat of polystyrene (PS) latex [9]. This is prepared with a hydrophilic group (such as sulphate) at tire end of each molecule. In water tliis produces well defined spheres witli a number of end groups at tire surface, which (partly) ionize to... 

As we did in the case of relaxation, we now compare the behavior predicted by the Voigt model—and, for that matter, the Maxwell model—with the behavior of actual polymer samples in a creep experiment. Figure 3.12 shows plots of such experiments for two polymers. The graph is on log-log coordinates and should therefore be compared with Fig. 3.11b. The polymers are polystyrene of molecular weight 6.0 X 10 at a reduced temperature of 100°C and cis-poly-isoprene of molecular weight 6.2 X 10 at a reduced temperature of -30°C. 

In numerous applications of polymeric materials multilayers of films are used. This practice is found in microelectronic, aeronautical, and biomedical applications to name a few. Developing good adhesion between these layers requires interdiffusion of the molecules at the interfaces between the layers over size scales comparable to the molecular diameter (tens of nm). In addition, these interfaces are buried within the specimen. Aside from this practical aspect, interdififlision over short distances holds the key for critically evaluating current theories of polymer difllision. Theories of polymer interdiffusion predict specific shapes for the concentration profile of segments across the interface as a function of time. Interdiffiision studies on bilayered specimen comprised of a layer of polystyrene (PS) on a layer of perdeuterated (PS) d-PS, can be used as a model system that will capture the fundamental physics of the problem. Initially, the bilayer will have a sharp interface, which upon annealing will broaden with time. 

The main results of this miero-mechanical model in the quasi-static regime have been compared with experimental results obtained by placing polystyrene (PS)-polyvinyl pyridine (PVP) diblock copolymers with a short PVP block between PS and PVP homopolymers. The fracture toughness was found to increase linearly with E from that of the bare PS/PVP interface, while the slope of the line increased with the degree of polymerization of the block being pulled out. If the data for the different copolymers were plotted as AG vs. (where... 

We present here a simple experiment, conceived to test both the reptation model and the minor chain model, by Welp et al. [50] and Agrawal et al. [51-53]. Consider the HDH/DHD interface formed with two layers of polystyrene with chain architectures shown in Fig. 5. In one of the layers, the central 50% of the chain is deuterated. This constitutes a triblock copolymer of labeled and normal polystyrene, which is, denoted HDH. In the second layer, the labeling has been reversed so that the two end fractions of the chain are deuterated, denoted by DHD. At temperatures above the glass transition temperature of the polystyrene ( 100°C), the polymer chains begin to interdiffuse across the... 

FIQ. 3 Diffusion coefficient of benzene molecules in benzene-polystyrene mixtures normalized by the diffusion coefficient of neat benzene molecular dynamics results, NMR measurements and prediction by the Mackie-Meares model [26]. 

FIGURE 22.3 Experimental points for polystyrene standards in THF and three OTHdC columns (O, 1.342 fjLm, , 0.862 jum and O, 0.630 tm) with theoretical curves according to the modified BG model. (Reprinted with permission from Ref. 7. Copyright 1986 American Chemical Society.)... 

How does yield stress depend on the size of particles We have mentioned above that increasing the specific surface, i.e. decreasing an average size of particles of one type, causes an increase in yield stress. This fact was observed in many works (for example [14-16]). Clear model experiments the purpose of which was to reveal the role of a particle s size were carried out in work [8], By an example of suspensions of spherical particles in polystyrene melt it was shown that yield stress of equiconcentrated dispersions may change by a hundred of times according to the diameter d of non-... 

Fig. 1 a, b. Projection along the chain axis and side view of models of syndiotactic polystyrene in the a) trans-planar conformation b) s(2/l)2 helical conformation... 

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