Polystyrene, hard plastics

Styrene-butadiene-styrene (SBS) block copolymers are adequate raw materials to produce thermoplastic mbbers (TRs). SBS contains butadiene—soft and elastic—and styrene— hard and tough—domains. Because the styrene domains act as cross-links, vulcanization is not necessary to provide dimensional stability. TRs generally contain polystyrene (to impart hardness), plasticizers, fillers, and antioxidants processing oils can also be added. Due to their nature, TR soles show low surface energy, and to reach proper adhesion a surface modification is always needed. 

Another type of rubber that is used frequently is thermoplastic rubber. Components are fabricated in a process that is similar to that used for common hard plastics, such as polyethylene or polystyrene, but the final product is an elastic material with properties otherwise equivalent to those of thermoset rubbers. No chemical reactions are involved in the processing of a thermoplastic rubber. The fabrication process consists of heating the rubber compound until it liquefies, injecting the liquid into a mold, cooling the mold, and finally removing the closure from the mold. The process is reversible. Closures can be remelted and remolded into different shapes or sizes as desired. 

Polystyrene (flame Nemours Koppers Hard plastic 25.2 B... 

A rather unusual test is to tap the plastic firmly with a fingernail. If the sound is metallic, the plastic is likely to contain polystyrene. Hardness is another property that can be roughly tested with a fingernail applied to the underside of an object. Plastics which can be marked with a fingernail include polyethylene, polypropylene, plasticised PVC and polyurethane other types are not affected. 

Although the dynamic mechanical properties and the stress-strain behavior iV of block copolymers have been studied extensively, very little creep data are available on these materials (1-17). A number of block copolymers are now commercially available as thermoplastic elastomers to replace crosslinked rubber formulations and other plastics (16). For applications in which the finished object must bear loads for extended periods of time, it is important to know how these new materials compare with conventional crosslinked rubbers and more rigid plastics in dimensional stability or creep behavior. The creep of five commercial block polymers was measured as a function of temperature and molding conditions. Four of the polymers had crystalline hard blocks, and one had a glassy polystyrene hard block. The soft blocks were various kinds of elastomeric materials. The creep of the block polymers was also compared with that of a normal, crosslinked natural rubber and crystalline poly(tetra-methylene terephthalate) (PTMT). 

About two-thirds of all the styrene produced in the United States is used in the manufacture of polystyrene. Polystyrene is a clear, colorless, hard plastic that is easily molded and made into a foam known as styrofoam. It is used in the insulation of electrical wires and devices, in containers for hot and cold foods and drinks, and for the insulation of buildings. 

Figure 3.19 Vickers hardness of crosslinked PABA in comparison with other materials, a functionally graded polymer composite with 45 % SiC b heat treated crosslinked PABA c common hard plastics including PVC, PMMA, polycarbonate, polystyrene and acetal d heat treated polyaniline (polyaniline). (Reprinted with permission from Chemistry of Materials, 17, 3803. Copyright (2005) American Chemical Society.)...

One other polymeric material that was once used in capacitor manufacturing but which fell from favour many years ago, largely because of its toxicity and the general demise of paper capacitors, is polyvinyl carbazole. This material is worthy of mention if only because of more recent interests in its monomer s properties as a component for plasma developable resist systems.Polyvinyl carbazole is a hard plastic with a structure related to polystyrene, the difference being the presence of a carbazole group in place of a phenyl group... 

You will be familiar with many common, everyday polymers, such as polyethylene plastic grocery bags or the polystyrene used for hard plastics and packing foams. These molecules have a linear chain structure with... 

Hard plastic toys Polystyrene cc Krlymers DecaBDE PBDEs 34.3 mg/kg (median) 53 mg/kg (median) Chen et al. (2009) Chen et al. (2009)... 

Polystyrene is a transparent hard plastic with a tendency to brittleness which can lead to cracking under stress. Coloured versions are also available as with other types of polymer. Toughened or high impact grades have been developed to overcome the cracking problem - more will be said about these later. Polystyrene is an easy material to join using suitable solvent-based adhesives capable of softening the surface. 

Plastics. Vehicles in offset inks for plastics (polyethylene, polystyrene, vinyl) are based on hard drying oleoresinous varnishes which sometimes are diluted with hydrocarbon solvents. Letterset inks for polystyrene employ vehicles of somewhat more polar nature. Polyester or other synthetic resins (acryhc) dissolved in glycol ethers and/or esters are used in some of the older inks. Uv inks are widely used for decoration of these preformed plastic containers. 

Adhesives, Coatings, and Sealants. Eor these appHcations, styrenic block copolymers must be compounded with resins and oils (Table 10) to obtain the desired properties (56—58). Materials compatible with the elastomer segments soften the final product and give tack, whereas materials compatible with the polystyrene segments impart hardness. The latter are usually styrenic resins with relatively high softening points. Materials with low softening points are to be avoided, as are aromatic oils, since they plasticize the polystyrene domains and reduce the upper service temperature of the final products. 

With plastics there is a certain temperature, called the glass transition temperature, Tg, below which the material behaves like glass i.e. it is hard and rigid. As can be seen from Table 1.8 the value for Tg for a particular plastic is not necessarily a low temperature. This immediately helps to explain some of the differences which we observe in plastics. For example, at room temperature polystyrene and acrylic are below their respective Tg values and hence we observe these materials in their glassy state. Note, however, that in contrast, at room temperature, polyethylene is above its glass transition temperature and so we observe a very flexible matoial. When cooled below its Tg it then becomes a hard, brittle solid. Plastics can have several transitions. 

However, they do more than merely replace. They are lighter than metals, less brittle than glass, tougher than wood, less permeable than paper, more resistant than ceramics, and more decorative than cardboard. Plastics, and polystyrene as one of them, have secured their own firm place in the modern world and it is hard to imagine life without them. 

Substitute for Conventional Vulcanized Rubbers, For this application, the products are processed by techniques and equipment developed for conventional thermoplastics, ie, injection molding, extrusion, etc. The S—B—S and S—EB—S polymers are preferred (small amounts of S—EP—S are also used). To obtain a satisfactory balance of properties, they must be compounded with oils, fillers, or other polymers compounding reduces costs. Compounding ingredients and their effects on properties are given in Table 8. Oils with high aromatic content should be avoided because they plasticize the polystyrene domains. Polystyrene is often used as an ingredient in S—B—S-based compounds it makes the products harder and improves their processibility. In S—EB—S-based compounds, crystalline polyolefins such as polypropylene and polyethylene are preferred. Some work has been reported on blends of liquid polysiloxanes with S—EB—S block copolymers. The products are primarily intended for medical and pharmaceutical-type applications and hardnesses as low as 5 on the Shore A scale have been reported (53). 

The most difficult recyclates are the MSW, which usually consists of more or less dirty plastics of various types and sources. According to one report [15] the plastic portion of MSW contains typically 50% PE (mainly low density polyethylene, LDPE), 8-14% polypropylene (PP), 15% polystyrene (PS), 10% polyvinylchloride (PVC) and 5% polyethylene terephthalate (PET), and 5% other polymers, while the hard packaging fraction consists of approx. 60% of PP and HDPE [16]. 

PS (polystyrene) Styrofoam, used in take-out containers, meat and bakery trays, and, in its hard form, clear take-out containers and some plastic cutlery and cups Avoid it leaches chemicals into food, some of which can disrupt normal hormonal functioning. 

Sodium softeners are used to treated RO influent water to remove soluble hardness (calcium, magnesium, barium, and strontium) that can form scale on RO membranes. Once known as sodium zeolite softeners, zeolites have been replaced with synthetic plastic resin beads. For sodium softeners, these resin beads are strongly acidic cation (SAC) polystyrene resin in the sodium form. The active group is benzene sulfonic acid, in the sodium, not free acid, form. Figure 8.12 shows styrene-divinylbenzene gel cation resin. Equation 8.4 shows the softening reaction for calcium exchange ... 

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