Processing of Polystyrene

An advantage of the matching densities of the two zones or phases is that there is little warping and generally good dimensional stability. 

Property ASTM method Units Unfilled 30% glass filled 30% glass filled and impact modified 

There has also been some interest in melt blending with polyamides to increase the toughness but at some sacrifice to dimensional stability and moisture resistance. 

Polystyrene and closely related thermoplasties such as the ABS polymers may be proeessed by sueh techniques as injection moulding, extrusion and blow moulding. Of less importance is the processing in latex and solution form and the 

The negligible water absorption avoids the need for predrying granules. The low specific heat (compared with polyethylene) enables the polymer to be rapidly heated in injection cylinders, which therefore have a higher plasticising capacity with polystyrene than with polyethylene. The setting-up rates in the injection moulds are also faster than with the polyolefins so that faster cycles are also possible. 

Although it is not difficult to make injection mouldings from polystyrene which appear to be satisfactory on visual examination it is another matter to produce mouldings free from internal stresses. This problem is common to injection mouldings of all polymers but is particularly serious with such rigid amorphous thermoplastics as polystyrene. 

---

Copolymers of acrylonitrile and vinylidene chloride have been used for many years to produce films of low gas permeability, often as a coating on another material. Styrene-acrylonitrile with styrene as the predominant free monomer (SAN polymers) has also been available for a long time. In the 1970s materials were produced which aimed to provide a compromise between the very low gas permeability of poly(vinylidene chloride) and poly(acrylonitrile) with the processability of polystyrene or SAN polymers (discussed more fully in Chapter 16). These became known as nitrile resins. 

Furusawa and Yamamoto [16] studied the adsorption process of polystyrene samples (M ranging from 16700 to 2xl06) with narrow molecular weight distribution (Mw/M = 1.01-1.07) at the -conditions (cyclohexane, 35 °C). Controlled pore glass with pore diameter of 1000 A was used as an adsorbent. 

Determine the cycle time of an injection-molding process of polystyrene at the following conditions. How can you decrease flow time Cooling time Dead time ... 

Additives are commonly used in the processing of polystyrene to enhance or to gain additional properties of polystyrenes. What are the common additives used in polystyrenes and why are they used ... 

At intermediate expansion levels, expanded droplets (balloons) have been observed by Reverchon et al. [18]. Spherical balloons were also observed by Dixon et al. [25] during the processing of polystyrene. Different nucleation structures can appear and different kinds of balloons have been observed. For example, during the precipitation of samarium acetate, empty shells of solute with a continuous surface were observed [18]. This is explained by the solute precipitation, which starts at the supercritical fluid-liquid interface and then propagates inside the liquid attracting the solute toward the separation surface. This mechanism results in the formation of hollow spherical structures [17]. 

Polytrifluorostyrene n. A clear, thermoplastic material introduced in 1965 and said to combine the oxidation resistance of poly-tetrafluoroethylene with the mechanical and electrical properties and ease of processing of polystyrene, but still not commercially available in 1992. 

The effect of increasing humidity was studied during the electrospinning process of polystyrene (PS) nanofibers. It was reported that increasing humidity ended up with formation of nanofibers with superficial circular pores (Fig. 6). Moreover, extra humidity led to those pores coherence (Casper et al. 2004). 

Jang J and Pai k H (2002) In situ sol-gel process of polystyrene/silica hybrid materials effect of silane-coupling agent, J Appl Polym Sci 85 2074. 

D. R. Bauer, J. I. Brauman, and R. Pecora. Depolarized Rayieigh spectroscopy studies of relaxation processes of polystyrenes in solution. Macromolecules, 8 (1975), 443 51. 

---