Commercial foamed plastics polystyrene

Foamed plastics (qv) were developed in Europe and the United States in the mid-to-late 1930s. In the mid-1940s, extmded foamed polystyrene (XEPS) was produced commercially, foUowed by polyurethanes and expanded (molded) polystyrene (EPS) which were manufactured from beads (1,2). In response to the requirement for more fire-resistant ceUular plastics, polyisocyanurate foams and modified urethanes containing additives were developed in the late 1960s urea—formaldehyde, phenoHc, and other foams were also used in Europe at this time. 

While unaffected by water, styrofoam is dissolved by many organic solvents and is unsuitable for high-temperature applications because its heat-distortion temperature is around 77°C. Molded styrofoam objects are produced commercially from expandable polystyrene beads, but this process does not appear attractive for laboratory applications because polyurethane foams are much easier to foam in place. However, extruded polystyrene foam is available in slabs and boards which may be sawed, carved, or sanded into desired shapes and may be cemented. It is generally undesirable to join expanded polystyrene parts with cements that contain solvents which will dissolve the plastic and thus cause collapse of the cellular structure. This excludes from use a large number of cements which contain volatile aromatic hydrocarbons, ketones, or esters. Some suitable cements are room-temperature-vulcanizing silicone rubber (see below) and solvent-free epoxy cements. When a strong bond is not necessary, polyvinyl-acetate emulsion (Elmer s Glue-All) will work. 

Styrenic polymer foams have been commercially accepted in a wide variety of applications since the 1940s [1,4]. The total usage of polystyrene foams in the United States rose from about 4.10 x 105 metric tons in 1982 to an estimated 5.35 x 105 metric tons in 1987. It is expected to grow at a rate of 3-4% for the next several years [5]. For example, a recent Fredonia report on foamed plastics estimates that the 2008 volume will be 10.77 x 105 metric tons [6]. 

What are the trends in the polymeric foam industry The production of foamed plastics on the basis of high polymers will continue to expand mainly utilizing common raw materials (polystyrene, poly(vinyl chloride), polyolefins and synthetic resins). Apart from that, one should expect a strong increase in the commercial pro-... 

Unique Properties of Foamed Plastics Structural Features of Foamed Plastics Leading Commercial Polymers Polyurethane Polystyrene Poly(vinyl chloride)... 

Foams can be made with both thermoplastic and thermosetting plastics. The well known commercial thermoplastic foams are polystyrene, PVC, polyethylene, polypropylene, ABS copolymer, cellulose acetate. The thermosetting plastics which may be mentioned, among others, are phenol-formaldehyde, urea-formaldehyde, polyurethane, epoxy, and silicone. The methods of manufacture of some of these polymeric foams are given below. 

Polystyrene (PS) is prepared by the polymerization of styrene (CeHs—CH=CH2), also known as vinylbenzene. Commercial PS is mostly of the atactic variety and is therefore amorphous. The polymer, on decomposition, unzips and forms the monomer with some benzene and toluene. Its major defects are poor stability to weather exposure, turning yellow and crazing in sunlight. In spite of these drawbacks and its brittleness it has found wide use as molded containers, Uds, bottles, electronic cabinets. As a foamed plastic it is used in packaging and insulation. The thermal conductivity of the expanded PS foam is about 0.03 Wm K The foam can absorb aromatic hydrocarbons usually found in the exhaust of automobiles and buses, causing the foam to disintegrate after long periods of normal exposure to a polluted environment. 

Potential uses for photodegradable polymers, such as ethylene-carbon monoxide and Ecolyte polystyrene and poly(ethylene terephthalate), will exist wherever plastics littering occurs. It has been estimated that almost a billion pounds of plastics find their way into the world s waterways annually [35]. Because E-CO and foamed plastics float and are photodegradable when in water, there should be commercial opportunities for them in marine packaging, fishing gear, and similar applications. 

Commercial Construction. The same attributes desirable on residential constmction appHcations hold for commercial constmction as weU but insulation quaHty, permanence, moisture insensitivity, and resistance to free2e—thaw cycling in the presence of water are of greater significance. For this reason ceUular plastics have greater appHcation here. Both polystyrene and polyurethane foams are highly desirable roof insulations in commercial as in residential constmction. 

Polystyrene, the familiar crystal-clear brittle plastic used to make disposable drinking glasses and, when foamed, the lightweight white cups for hot drinks, is usually made by free-radical polymerization. Commercially an initiator is not used because polymerization begins spontaneously at elevated temperatures. At lower temperatures a variety of initiators could be used (e.g., 2,2 -azobis-(2-methylpropionitrile) which was used in the free-... 

Special collection systems are generally provided for large-scale or commercial postconsumer applications such as for agricultural films, chemical containers, automotive parts, carpets, and polystyrene foam packaging. Since most of the plastic is collected as multimaterial or in commingled forms, the collected plastic waste has to be sorted, separated, and cleaned, and most of this is done at material recovery facilities (MRFs). 

Mechanical testing on the foam is performed to measure the compressive stress and the resiliency. The results from diese tests are shown in table 2, in which the properties of extruded polystyrene foam (XPS) and commercial starch-based loose-frll foams (Eco-foam and Mater-Bi) together with EPS loose-fill foam (Pelaspan Pac) are added for conq>arison. The values of XPS are obtained from tests on typical XPS retail packaging trays. The table shows that the compressive stress reached with potato starch foam is comparable with that of XPS. Through the cell structure of the potato starch foam (high cell density, very small cells) a good resiliency can be obtained, although pure starch plastics exhibit brittle fracture behavior. This brittle fracture still is present on the microscopic scale of the individual cells but due to the cell density, the foam exhibits resiliency on macroscopic scale. 

Polystyrene is an aromatic polymer made from styrene, an aromatic monomer which is commercially manufactured from petroleum. Polystyrene is commonly injection moulded or extruded while expanded polystyrene is either extruded or moulded in a special process. Solid polystyrene is used in disposable cutlery, plastic models, CD and DVD cases, etc. Foamed polystyrene is mainly used for packing materials, insulation, foam drink cups, etc. Polystyrene foams are good thermal insulators and therefore used as building insulation materials such as in structural insulated panel building systems. They are also used for non-weight-bearing architectural structures. The information on OPF-polystyrene composites is limited. 

The first cellular synthetic plastic was an unwanted cellular phenol-formaldehyde resin produced by early workers in this field. The elimination of cell formation in these resins, as given by Baekeland in his 1909 heat and pressure patent (2), is generally considered the birth of the plastics industry. The first commercial cellular polymer was sponge rubber, introduced between 1910 and 1920 (3). Most plastic polymers can be foamed. However, a relative few have commercial significance, such as polystyrene, polyolefins, poly(vinyl chloride), polyimides, and polyurethanes. 

Application of food extruders gives much better results in processing of starch-based materials than conventional plastic extruders due to the plant origin of the biopolymer. Most of the experimental works which apply extmsion-cooking for the production of starchy loose-fill foams started in the Department of Food Process Eng., Lublin University of Life Sciences in 2012. Their objective is to achieve commercially acceptable biodegradable products based on locally produced potato, corn- and wheat starch, which can replace popular expanded polystyrene loose-fill foam products. Results of the first phase of this study are presented in their work (Mitrus and Moscicki 2014). 

Apart from the reprocessors of post consumer plastics, other companies have continued to specialize in waste plastics from industrial and commercial operations. The recycling of plastic pallet wrap is expanding across the country. Used electrical wire and cable is being reprocessed primarily for the recovery of metals however a number of specialized operations recycle the cable insulators, polyethylene and polyvinyl chloride. Similarly a few facilities exist to recycle waste automotive trim and foam polystyrene packaging. A considerable effort is being expended to find applications for plastic auto shredder residue which is the by product of the automobile recycling industry which currently recovers metals from end of life automobiles. At present viable applications are still understudy and current residues continue to be landfilled. 

PVC and polyurethane constitute together the majority of expanded plastics, but expanded polystyrene packaging is also important because it has excellent protective qualities for the transport of delicate articles, and is widely used in the catering industry. Crosslinked polyethylene foams are also important and there are several other commercially successful varieties. 

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