Plastics. Also polyethylene

Waterproof. Waterproofing barrier systems may be either hot- or cold-appHed. The hot-appHed generaUy involve a bituminous material such as asphalt used in conjunction with a reinforcing fabric such as roofing felt, cotton, or glass cloth. Cold-appHed can be bituminous or elastomeric materials either in Hquid or sheet form, with or without fabric reinforcement. Liquid elastomeric treatments include neoprene, polyurethanes, and blends of these or epoxies with bituminous materials. Among the commonly used precured elastomeric sheet materials are neoprene, polyisobutylene, EPDM mbber, and plasticized PVC. Polyethylene and PVC films and nonwoven plastic or glass fabric coated with bituminous materials also find use (78). Because these... 

Weathering. This generally occurs as a result of the combined effect of water absorption and exposure to ultra-violet radiation (u-v). Absorption of water can have a plasticizing action on plastics which increases flexibility but ultimately (on elimination of the water) results in embrittlement, while u-v causes breakdown of the bonds in the polymer chain. The result is general deterioration of physical properties. A loss of colour or clarity (or both) may also occur. Absorption of water reduces dimensional stability of moulded articles. Most thermoplastics, in particular cellulose derivatives, are affected, and also polyethylene, PVC, and nylons. 

Reactive compatibilization is also carried out by adding a monomer which in the presence of a catalyst can react with one or both phases providing a graft copolymer in situ that acts as a compatibilizer. Beaty and coworkers added methyl methacrylate and peroxide to waste plastics (containing polyethylene [PE], polypropylene [PP], PS, and poly(ethylene terephthalate) [PET]). The graft copolymer formed in situ homogenized the blend very effectively [19]. 

The commodity thermoplastics are the most-used plastics in this sector, accounting for 95% of all thermoplastic packaging. Polyolefins are the most important, accounting for more than 65% of the total plastic weight. Polyethylene terephthalate, polystyrene and PVC are also commonly used. 

Chrome yellow pigments stabilized with a large amount of silicate play a major role in the production of colored plastics (e.g., PVC, polyethylene, or polyesters) with high temperature resistance. Incorporation into plastics also improves their chemical resistance to alkali, acid, sulfur dioxide, and hydrogen sulfide. 

At curbside many communities are collecting aluminum and tin cans, glass bottles, newspaper and plastic bottles. High-density polyethylene (HOPE) and polyethylene terephthalate (PET) are the most commonly recycled plastic bottles. Some areas that have a market for other plastics also pick them up for recycling. Sorting is done to some degree by the resident, the collector, and the reprocessor. 

The recycling of plastics also contributes to energy efficiency. Soft drink bottles made from polyethylene terephthalate reached a recycling rate of 41% in the U.S. in 1995 (19). Recycling is becoming widespread, and many studies are in progress to develop new and improved recycling practices. 

Polymers— large molecules made up of repeating units of smaller molecules called monomers— include such biologically important compounds as proteins and carbohydrates. They also include such industrially important plastics as polyethylene, poly(vinyl chloride) (PVC), and polystyrene. 

It has generally been observed that urethane systems, which are cured on the surface of some low energy materials, are also free from adhering to them, i.e. they are self-releasing. Materials which show this characteristic relative to urethanes in a very effective way include at least three different types of plastics polytetrafluoroethylene, polyethylene, and polypropylene. These materials all have a defined critical surface tension sc less than about 30 dynes/cm. Assuming that this value is near, the liquid vapor surface tension lv value of an effective IMR urethane systems, then the work of adhesion as given by Equation 4 is as follows ... 

Thermoplastics may be further subdivided into two broad categories on the basis of their cost and suitable end uses. Commodity plastics are typified by high volume production, good properties, and low resin cost. The four major commodity plastics are polyethylene, polypropylene, poly(vinyl chloride), and polystyrene. Their adequate properties and low cost have led to the extensive use of these plastics in packaging applications where they are very competitive with paper, steel, and glass. They are also used for some less demanding applications as components of durable goods (Table 22.1). 

The development of plastics also reflects economic history. Restrictions on imported latex, wool, silk and other natural materials to Europe during the Second World War resulted in the rapid development of alternative synthetic plastics. Table 1 shows that between 1935 and 1945, many new polymers were introduced including polyethylene, polyamides, poly(methyl methacrylate), polyurethanes, poly(vinyl chloride) (PVC), silicones, epoxies, polytetrafluoro-ethylene and polystyrene. Polyethylene was incorporated into radar systems while PVC replaced the limited stocks of natural rubber as cable insulation. 

The largest single use of ethylene glycol today is in the manufacture of a plastic called polyethylene terephthalate (PET). PET s primary application is in the manufacture of plastic bottles, an application that accounts for about a third of all the ethylene glycol made in the United States. Large amounts of PET are also used in the manufacture of polyester fibers and films. Some additional uses of the compound include ... 

Chlorine occurs in plastics such as PVC, chlorinated polyethylene, and rubber hydrochloride. Some plasticizers also contain chlorine. Flame-proofing agents often contain chlorine or bromine. 

Plastics are polymeric solids that can be formed into various shapes, usually by the application of heat and pressure. There are several types of plastics. Thermoplastics can be reshaped. For example, plastic milk containers are made from the thermoplastic polymer polyethylene. These containers can be melted down and the polymer recycled for some other use. In contrast, a thermosetting plastic (also called a thermoset) is shaped through irreversible chemical processes and, therefore, cannot be reshaped readily. Another type of plastic is the elastomer, which is a material that exhibits... 

One of the most important polymers to be studied is polyethylene. It is the simplest of the polyolefins, those polymers consisting only of carbon and hydrogen, and polymerized through a double bond. Because of its simple structure, it has served as a model polymer in many laboratories. Also polyethylene s great commercial importance as a crystalline plastic has made the results immediately usable. It has been investigated both in the bulk and in the single-crystal state. 

The most difficult-to-bond plastics family is polytetrafluoroethylene and the other fluori-nated polymers which are the Teflon-like materials. The widespread use of these polymers as coatings for cookware is, of course, based on this property of nonsticking. The conventional methods of etching which can be useful with other difificult-to-bond plastics, like polyethylene and polypropylene, simply do not work on these fluorinated polymer surfaces. Instead the surfaces must be treated with an exotic mixture of metallic sodium and naphthalene in tetrahydrofuran.( 37,i38) More recently, ionized gases (plasma treatment) have also been used successfully. Once treated the surfaces become bondable using conventional two-part liquid... 

Starch-based plastics can be classified as compostable if the additives are also biodegradable under industrial compost environment conditions. Starch can be an additive for petroleum-based plastics like polyethylene, polypropylene, polyurethane, and polyester. However, these starch-filled petroleum-based plastics are not included in this book since they would not biodegrade under industrial composting conditions and would not be recyclable with commercial mechanical recycling operations. 

Plastic materials have become basic and indispensable in our life. To protect against contamination and conserve them, food products are distributed in different plastic packages bags, bottles, boxes, etc. that contain all kinds of edible products liquid (water, milk, cold beverages) or solid (fruit, meat, fish, frozen foods, etc.). The group of commercial plastics, also termed commodity plastics, consists of the most used polymers in terms of volume and number of applications. They are mainly polystyrene (PS), polypropylene (PP), high-and low-density polyethylene (HDPE, LDPE), polyethylene terephthalate (PET) and, in lower proportion, polycarbonate (PC) [71. 

Nucleating agent, cell-control These agents promote symmetrical, cohesive expansion of cells within foamed polyurethane and polystyrene plastics also to a limited extent in polyethylene and polypropylene plastics. 

Polyolefin plastic Also called olefin, olefinic plastics or olefinic resins. They represent a very large class of carbon-chain TPs and elastomers. The most important are polyethylenes and polypropylenes. They all have extensive use in many different forms and applications. 

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