Polystyrene unfilled

The preferred morphology of these rubber modified amorphous thermoplastics is the distribution of distinct rubber particles unfilled or filled in an isotropic matrix of the basic polymer. This was shown to be the case for rubber modified polystyrene and for ABS-type polymers. 

For the unfilled polystyrene melt at low elongational rates a constant value of Tjg is achieved given by three times the zero shear viscosity according to Trou-... 

It was found that the total fraction of the free-volume in the system increases with increasing concentration of the polymeric filler. The temperature dependence of fg for the epoxy matrix was calculated on the supposition that free-volume is an additive value of the constituent components and using the temperature dependence of the fractional free-volume of polystyrene. It was found that with increasing filler concentration the fractional free-volume becomes greater than for pure epoxy resin. Since the fraction of the free-volume increases with increasing total surface area of the filler, it may be supposed that this effect is associated with the surface layers of polymer. It was found that the rate of free-volume expansion in a filled system is higher than in an unfilled one, which means that the expansivity of the free-volume... 

Fig. 2. Dimensionless ratio AsM/fa] for various polymers. Open circles, polyisobutylene 148). Upright triangles, poly(raethyl methacrylate) 40, 47, 5V, 59). Inverted triangles, polyvinyl acetate (62, 233). Squares, polystyrene 35,71, 73,148,206,208). Filled circles, atactic polypropylene 138). Crosses, linear polyethylene 26,152,256), The unfilled points were selected as specially reliable in 1957 by Orofino and...

In general, plastics are superior to elastomers in radiation resistance but are inferior to metals and ceramics. The materials that will respond satisfactorily in the range of 1010 and 1011 erg per gram are glass and asbestos-filled phenolics, certain epoxies, polyurethane, polystyrene, mineral-filled polyesters, silicone, and furane. The next group of plastics in order of radiation resistance includes polyethylene, melamine, urea formaldehyde, unfilled phenolic, and silicone resins. Those materials that have poor radiation resistance include methyl methacrylate, unfilled polyesters, cellulosics, polyamides, and fluorocarbons. 

FKuR also introduced Biograde 200C in 2005, an unfilled cellulose blend with high stiffness and transparency for cast film and injection moulding. The material can also be blow moulded into bottles and thermoformed into cups and trays. Injection moulded Biograde 200C exhibits properties comparable to polystyrene, but with the addition of barrier performance comparable to PLA. It consists of 100% renewable resources, but does not contain starch. 

Polystyrene (PS) is another polymer which can be degradated to the monomer. The required pyrolysis temperature is higher than in the case of PMMA as feedstock. The experiments were carried out in the fluidized-bed reactor (see Figure 24.1) between 515 and 540°C and with different fluidizing gas flows (Table 24.7). The molecular weight of the unfilled PS was 225 000. 

In contrast to observations in polystyrene, we do not observe permanent bands our specimens exhibit no residual birefringence upon release from stress. Neither do we observe crazing before failure. However, the specimens do whiten just before failure when viewed edge-on, and this whitening disappears within a few seconds after fracture occurs. We think the oscillations in intensity we observe are likely to be due to incipient shear deformation which disappears after specimen failure. Unpublished results of other workers are reported (see References 11 and 14 in the present Reference 12) to be consistent with the idea that such bands should be difficult to observe in PMMA and in polycarbonate because of their lower draw ratios compared to polystyrene. Studies of an unfilled epoxy polymer (14) in cyclic tensile deformation indicate that shear bands do not remain after removal of stress until a threshold amplitude of deformation is exceeded. 

FIGURE 1.7 Plots of viscomelric branching parameter, g, versus branch functionahty, p, for star chains on a simple cubic lattice (unfilled circles), together with experimental data for star polymers in theta solvents , polystyrene in cyclohexane , polyisoprene in dioxane. Solid and dashed lines represent calculated values via Eqs. (1.70) and (1.71), respectively. (Adapted... 

Materials for sintering and melting are plastics, metals, or ceramics. Plastics may be unfilled or filled with glass or aluminum spheres or egg-shaped geometries to improve properties like durability and thermal resistance. Also nanoscale particles are used. Unfilled plastics are mostly commodities like semicrystalline polyamides from the PAl 1 or PA12 type or amorphous plastics like polystyrene (PS). Engineering plastics like PEEK are available. 

Fig. 7.16. h(Y) determined from the procedure explained in Fig. 7.15. Filled circles represent polystyrene of molecular weight 8.42 xlO and the unfilled circles of 4.48 x 10 . Directions of pips indicate concentrations which range from 0.02 g cm to 0.08 g cm. The solid curve rqnesents the theoretical value (eqn (7.131)), and the dashed curve the result of the independent alignment approximation (eqn 7.187). Reproduced from ref. 69.

FIGURE 12.8. The depression of Tg of a polystyrene by dissolution in toluene, xis the weight fraction of toluene. Filled circles represent dilatometric determinations and unfilled circles were obtained by means of differential thermal analysis, DTA. The crosses represent the results of Jenckel and Heusch [56]. (From Braun and Kovacs by permission, [58].)... 

Clearly, the combinations of resins and fillers and the resulting property variations are endless (see Fig. 6-2). The point is that each combination is in fact a new material with its own trade-offs. Some properties will be improved, others unchanged, and still others diminished from those of the basic unfilled plastic. In this chapter there is no relationship, direct or implied, between any plastic in terms of the space given it and its performance or the size of its market. The largest consumption of these plastics is low-density polyethylene (LDPE) formulations, at about 25 percent weightwise, followed by high-density polyethylene (HDPE), then polypropylene, polyvinyl chloride, and polystyrene. These together total about two-thirds of all plastic consumption. 

Figure 9.4 shows the extensional viscosity vs. time curves for unfilled polystyrene melt at different extensional rates. It was found [19] that the extensional viscosity may tend to become constant at very low deformaticm rates, but become unbounded at higher and higher deformation rates. With filler concentration at low loading levels of 5 and 10% of carbon black filler, it weis fotmd [19] that the plots resembled those in Figure 9.4. However, at higher filler concentrations, constant extensional viscosities were achieved with time and these values were found to decrease with increasing extensional rate as shown in Figures 9.5 ctnd 9.6 for 20 and 25 vol% carbon black loading.

Figure 9.4 Variation of extensionai viscosity with time at different extensionai rates for unfilled polystyrene melt at 170°C. (Reprinted from Ref. 19 with kind permission from Society of Plastics Engineers Inc., Connecticut, USA.)...

Figure 9.11 shows the effect of surface treatment on extensional viscosity for 30% calcium carbonate filled polystyrene [27]. The data are presented in two forms, namely steady state extensional viscosity vs. extensional rate in Figure 9.11(a) and steady state extensional viscosity vs. tensile stress in Figure 9.11(b). Irrespective of the type of data representation, it is seen that surface treated calcium carbonate reduces the level of extensional viscosity and brings it closer to that of the unfilled polymer. The yield stress value is reduced considerably though the values of the ratio of yield stress in extension to that of shear is still maintained nearer to the von Mises value of 1.73 as can be seen from Table 9.1. Surface treatment tends to modify the forces of particle-particle interaction and hence show reduced yield stress values due to lowering of the interaction forces [2,27]. 

Plastics Available are unfilled and filled (with aluminum or glass pellets) semicrystalline polymers of the type PA 11 or PA 12 (Polyamide) and amorphous polymers of the type of polystyrene (PS). 

---