Polystyrene materials

Isophorone is a solvent for a large number of natural and synthetic polymers, resins, waxes, fats, and oils. Specifically, it is used as a solvent for concentrated vinyl chloride/acetate-based coating systems for metal cans, other metal paints, nitrocellulose finishes, printing inks for plastics, some herbicide and pesticide formulations, and adhesives for plastics, poly(vinyl) chloride and polystyrene materials (Papa and Sherman 1981). Isophorone also is an intermediate in the synthesis of 3, 5-xylenol, 3, 3, 5-trimethylcyclohexanol (Papa and Sherman 1981), and plant growth retardants (Haruta et al. 1974). Of the total production, 45-65% is used in vinyl coatings and inks, 15-25% in agricultural formulations, 15-30% in miscellaneous uses and exports, and 10% as a chemical intermediate (CMA 1981). 

The plasticized polystyrene materials provided by the Koppers Co. Research Department are also appreciated. 

Typical mechanical properties of polystyrene are given in the accompanying table. The long-term load-beanng strength of most polystyrene materials is about one-third of the typical tensile strength given in Table 1. 

The level of unpolymerised residual styrene monomer in commercial grades of polystyrene material has been reduced over the years from 1000 mg/kg (0.1 % w/w) to a target level of 500 mg/kg (0.05 % w/w) by more complete devolatilization after the polymerization step (Brighton 1982). The legal limits for styrene monomer in materials can be much higher (e.g. Australia 2500 mg/kg, AS 2070.3-1992). Hempel and Riidt (1988) carried out a survey of residual volatiles found in polystyrene and polystyrene copolymers whose results are summarized in Table 14-la. 

Table 14-la Survey of volatile substances in polystyrene materials (Hempel and Riidt, 1988). 

Table 14-3 Experimental diffusion coefficients for styrene in polystyrene materials.

Given the initial concentration of styrene residual monomer in the packaging material, the styrene threshold concentration in the product and the desired shelf life of the product one can estimate whether or not a given polystyrene material will cause taints in a given packaging application. 

Bonding of hydrophobic plastic materials to wood to create new wood-plastic (polystyrene) materials with improved mechanical and physical properties that incorporate the desirable features of each constituent is difficult to achieve. This is due to poor interfacial adhesion between the wood and polystyrene components because of their inherent incompatibility. New, well-defined, tailored cellulose-polystyrene graft copolymers have recently been prepared using anionic polymerization techniques. Preliminary bonding studies showed that these graft copolymers can function effectively as compatibi-lizers or interfacial agents to bond hydrophobic plastic (polystyrene) material to wood, evolving into a new class of composites. 

Other typical properties for a 1 Ib/ft (0.016 g/cm ) expanded polystyrene material are... 

In general, pyrolysis of certain hypercrosslinked polystyrene materials at a temperature of about 600°C may result in interesting carbonaceous adsorbing materials with a yield of up to 55-60% within 50-60 min. The products maintain the spherical form of the initial materials and their overall texture, and acquire an exceptional mechanical strength of up to 8 kg per bead. They are basically nanoporous and show size-dependent adsorbing properties [207, 210]. In particular, they efficiently separate mineral ions in accordance with the new frontal ion size exclusion process... 

The intramolecularly hypercrossfinked and toluene-passivated polystyrene material can be precipitated firom the synthesis solution with methanol in the form of a fine, slightly yellow powder. The latter remains soluble in dichloroethane, toluene, chloroform, and dioxane, that is, in the thermodynamically good solvents for the polystyrene precursor, and the solutions remain clear and stable for a long period. 

The present chapter deals with several aspects of adsorption of gases and organic solvent vapors onto Styrosorbs 1 and 2. Most of the adsorption experiments were carried out shortly after the development of hypercrosshnked polystyrene materials. The choice of sorbates was largely dictated by practical needs. Sorption of hydrocarbons and their chloro and fluoro derivatives as well as vapors of organic solvents was thought to be... 

In order to achieve an opposite elution order, having the basic fractions before the acidic fractions (Fig. 12.16), a neutral salt composed of large tetrabutylammonium cations and small iodide anions (9.88 and 6.62 A, respectively) was injected. In this case a typical hypercrossHnked polystyrene material, Styrosorb 2, which is known to have only small nanopores, was used as the sorbent. Indeed, as expected, the large organic cations were totally excluded from the polymer phase, while the smaller... 

Apparent BET surface areas for hypercrosslinked polystyrenic materials can be as high as 2,090 m g in some cases [25] and these materials can be produced as monoliths, powders, suspension polymerized beads, or by surfactant-free emulsion polymerization as spherical particles with diameters of around 500 nm [35]. Some care must be exercised when interpreting gas sorption isotherms for HCPs using sorbates such as nitrogen and argon as they exist in a non-classical [38] physical state and can exhibit unusual swelling characteristics (Fig. 3). 

HCPs have also been produced by the direct polycondensation of small molecule monomers (Fig. 4). Polyxylene networks - for example, produced from dichloroxy-lene (DCX) [21, 31] - are analogous to the Friedel-Crafts linked polystyrene materials described in Sect. 2.1.1 and can exhibit apparent BET surface areas up to 1,431 m"g- [31]. 

The difference in relative permeability of gases through the membranes offers an attractive way for the enrichment of industrial gases. The transport properties of N and O2 through porous polystyrene materials were found to be much higher than through those prepared by bulk polymerization [43]. 

Excellent polymeric particles for SPE are now available commercially. Most of these are cross-linked polystyrene materials, but some polymethacrylate particles are also available. Organic polymers are more stable than siHca materials at alkaline pH values and also tend to have a larger surface area, which enhances their extractive ability. Introduction of -CH2OH or -COCH3 groups into polystyrene resins enhances their ability to extract more polar organic analytes, and also improves mass transport of analytes from the aqueous to the solid phase. A co-polymer of divinylbenzene and vinylpyrrolidone, known as Oasis , is also well suited for SPE of relatively polar analytes. 

Fig. 3.2.2 Refractive index signal from a size exclusion chromatography system for the polystyrene material that was taken from the reactor just before addition of MAA, as well as raw and purified copolymers (Replotted with permission from Wang, 1997)...

S. Reculusa, C. Poncet-Legrand, S. Ra-vaine, C. Mingotaud, E. Duguet, E. Bour-geat-Lami, Syntheses of raspherry-like sflica/polystyrene materials, Chem. 

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