Plastic containers: polystyrene

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. 

To complete the assembly of a cell, the interleaved electrode groups are bolted to a cov er and the cover is sealed to a container. Originally, nickel-plated steel was the predominant material for cell containers but, more recently plastic containers have been used for a considerable proportion of pocket nickel-cadmium cells. Polyethylene, high impact polystyrene, and a copolymer of propylene and ethylene have been the most widely used 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. 

Recycling polymers is one way to minimize the disposal problem, but not much recycling occurs at present. Only about 25% of the plastic made in the United States is recycled each year, compared with 55% of the aluminum and 40% of the paper. A major obstacle to recycling plastics is the great variation in the composition of polymeric material. Polyethylene and polystyrene have different properties, and a mixture of the two is inferior to either. Recyclers must either separate different types of plastics or process the recycled material for less specialized uses. Manufacturers label plastic containers with numbers that indicate their polymer type and make it easier to recycle these materials. Table 13-5 shows the recycling number scheme. 

Styrene co-butadiene is a rubbery amorphous polymer with a glass transition temperature well below room temperature. Polystyrene co-butadiene is an important component of several commercial families of plastic that contain polystyrene blocks. 

I. Toluene behaves as a plasticizer for polystyrene. Estimate the 7"A value of a polystyrene containing 20 vol c/( toluene,... 

By far the most studied PolyHIPE system is the styrene/divinylbenzene (DVB) material. This was the main subject of Barby and Haq s patent to Unilever in 1982 [128], HIPEs of an aqueous phase in a mixture of styrene, DVB and nonionic surfactant were prepared. Both water-soluble (e.g. potassium persulphate) and oil-soluble (2,2 -azo-bis-isobutyronitrile, AIBN) initiators were employed, and polymerisation was carried out by heating the emulsion in a sealed plastic container, typically for 24 hours at 50°C. This yielded a solid, crosslinked, monolithic polymer material, with the aqueous dispersed phase retained inside the porous microstructure. On exhaustive extraction of the material in a Soxhlet with a lower alcohol, followed by drying in vacuo, a low-density polystyrene foam was produced, with a permanent, macroporous, open-cellular structure of very high porosity (Fig. 11). 

Butadiene is used primarily in the production of synthetic rubbers, including styrene-butadiene rubber (SBR), polybutadiene nibber (BR), styrene-butadiene latex (SBL), chloroprene rubber (CR) and nitrile rubber (NR). Important plastics containing butadiene as a monomeric component are shock-resistant polystyrene, a two-phase system consisting of polystyrene and polybutadiene ABS polymers consisting of acrylonitrile, butadiene and styrene and a copolymer of methyl methacrylate, butadiene and styrene (MBS), which is used as a modifier for poly(vinyl chloride). It is also used as an intermediate in the production of chloroprene, adiponitrile and other basic petrochemicals. The worldwide use pattern for butadiene in 1981 was as follows (%) SBR + SBL, 56 BR, 22 CR, 6 NR, 4 ABS, 4 hexamethylenediamine, 4 other, 4. The use pattern for butadiene in the United States in 1995 was (%) SBR, 31 BR, 24 SBL, 13 CR, 4 ABS, 5 NR, 2 adiponitrile, 12 and other, 9 (Anon., 1996b). 

Over the years letterpress printing has declined into niche markets, two of which are the printing of plastic self-adhesive labels on narrow-web rotary-offset letterpress machines that are fitted with UV drying and the common-impression rotary-offset letterpress and UV-curing on mandrel of plastic containers such as yoghurt tubs and toothpaste tubes. In uses such as these the most common self-adhesive plastic is PVC and the most usual for tubs and tubes are polystyrene, PVC, ABS, and polypropylene. 

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. 

When plastics are recycled, the various types must be separated from one another. To aid in the separation, many states require manufacturers to include a recycling symbol on their products to indicate the type of plastic. You are probably familiar with these symbols, which are found on the bottom of plastic containers. The symbols consist of three arrows around one of seven numbers an abbreviation below the symbol indicates the type of polymer from which the container is made. The lower the number in the middle of the symbol, the greater is the ease with which the material can be recycled 1 (PET) stands for poly(ethylene terephthalate), 2 (HDPE) for high-density polyethylene, 3 (V) for poly(vinyl chloride), 4 (LDPE) for low-density polyethylene, 5 (PP) for polypropylene, 6 (PS) for polystyrene, and 7 for all other plastics. 

Polyethylene is used for milk, food, and detergent bottles. Polypropylene is used for outdoor carpeting for home and sports stadia. Polyfvinyl chloride) is used for home siding and plastic pipe. Polystyrene is used for hot drinking cups and fast-food containers. Polytetrafluoroethylene is used for nonstick cookware. Polymerization of these and other alkenes on an industrial scale is responsible for producing over 50 billion lb per year of plastic and elastomer products in the United States. 

Alternative container Polystyrene or similar plastic beaker/container... 

Water samples for analysis by ion chromatography should be collected in plastic containers, such as polytetra-fluoroethylene (PTFE), polypropylene (PP), polystyrene (PS), or high-density polyethylene (HOPE). Glass bottles can contribute ionic contamination when performing trace analysis. Polyvinylchloride (PVC) should absolutely be avoided. 

Styrene can also be homopolymerized to produce polystyrene (Sec. 22.2). This material is one of the most versatile plastics ever invented. For example, it can be molded into rigid cases for radios and batteries or formulated in a more flexible form useful in the manufacture of toys and all kinds of containers. Polystyrene can also be produced in the form of a lightweight foam known as Styrofoam . This foam is used for insulation in buildings and is molded into ice chests and disposable cups for hot and cold drinks. 

Stock solution of dimethylglyoxime Final concentration 0.01 or 0.1 mol/L, is prepared either in methanol or in 0.5mol/L sodium hydroxide solution. The methanolic solution can best be stored in a suitable glass vial as plastic containers, including polystyrene, tend to release plasticizers. 

Environmental impacts of sustainable plastic containers can be determined with the LCA information and the definitions of sustainable plastics. The sustainable plastic containers can be made of recycled plastic or biobased plastics. The end-of-life for the plastic is either recycled or composted. Thus, polystyrene is not considered because sufficient recycled plastic is not available. As a comparison, virgin PET is evaluated for LCA. Recycled PET and biobased PLA can be compared for clear sustainable plastic containers. The LCA information from Madival et al. 2009 is used as a starting point. Then, WARM model from ERA is... 

The elements are inserted into cell containers of plastic or stainless steel. Plastic containers are made from polystyrene, polypropylene, or flame-retardant plastics. Important advantages of plastic containers over steel containers are that they allow visual control of the electrolyte level and they require no protection against corrosion. Also, they have lower weight and they can be more closely packed in the battery. The main drawbacks are that they are more sensitive to high temperatures and they require somewhat more space than steel containers. A plastic-bonded plate cell in a plastic container is shown in Fig. 26.3. 

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