Polystyrene economic development

Economic Development. In terms of output, polystyrene experienced a dramatic development in the postwar years. Whereas in 1940 world production was under 10,000 tons per year, by 1950 consumption in the western world had risen to 138,000 tons. The U.S.A. alone accounted for 85% of this. In 1960 550,000 tons and in 1970 2.1 million tons were used. 

FIGURE 5.97 Effect of plastic type (polyethylene o, polypropylene A, polystyrene X) and wood loading levels on properties of wood plastic composites. (After Chelsea Center for Recycling and Economic Development (CCRED), 2000. Technical Report 19, An Investigation of the Potential to Expand the Manufacture of Recycled Wood Plastic Composite Products in Massachusetts, Univ. of Massachusetts, Massachusetts.)... 

The second large-scale process was the batch mass suspension process. Monsanto did the pioneer work on this (41). In this process, prepolymerization is carried out in bulk and main polymerization in suspension the latter is taken to conversions of over 99%. In contrast to the continuous mass process, peroxide starters are used in order to achieve a high conversion at tolerable reaction times. Figure 3 shows a basic flow diagram of such a plant. A detailed discussion of advantages and disadvantages of the two processes can be found in R. Bishop s monograph published in 1971 (42), and it is continued in a paper by Simon and Chappelear in 1979 (43). It was a decisive factor for the economic success of impact polystyrene that these processes had been completely developed and mastered in theory and practice. 

The first move in this direction was to improve the weatherability of impact-resistant polystyrene. Because polybutadiene, the most widely used rubber in impact-resistant polystyrene, is unsaturated, it is sensitive to photooxidation, and impact-resistant polystyrene is therefore not suitable for outdoor applications. A saturated rubber might be able to help here. In the ABS sector this has been successfully tried out with acrylate rubber (77) and EPDM (78, 79), and the latter has also been used in impact-resistant polystyrene (80, 81) This development has elicited satisfactory responses only in certain areas and more work still has to be done. For instance, attempts have been made to improve resistance to weathering by using silicone rubber (82 ). This approach is effective, but economic factors still stand in its way. Further impetus may also be expected from stabilizer research. Hindered secondary amines (83), to which considerable attention has recently been paid, are a first step in this direction. 

I PA could always be made by direct hydration, but the severe operating conditions (high pressures and temperatures) and puny yields had always limited the economic enthusiasm for the process. Then catalysis research paid off with the development of a sulfonated polystyrene cationic exchange resin catalyst, a mouthful in itself. The breakthrough permitted reduced pressures and temperatures without loss of yield. The catalyst works in the vapor phase, the liquid phase, and the mixed phase. 

In this study, Raman spectroscopy and pattern-recognition techniques were used to develop a potential method to differentiate common household plastics by type [87-89], which is crucial to ensure the economic viability of recycling. The test data consisted of 188 Raman spectra of six common household plastics high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), and polyvinylchloride... 

With the fast developments in the plastic industry, some of the lesser known plastics will either find future usage or already be used for devices, general medical instruments and apparatus or as implant aids. Certain plastics now involve alloys, i.e. mixtures of thermoplastics, and thermoplastic and thermoset resins. Improvements in what were the economic five plastics, i.e. polyethylenes, polypropylenes, polyvinylchlorides, polystyrenes and polyesters, are constantly occurring. Use of metallocene catalysts is likely to produce plastics of a controlled chain length. 

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. 

In 1943, polystyrene could not be economically produced on a commercial basis. However, the shortage of natural rubber from the South Pacific because of World War II (3) led to the increased demand and the development of styrene-butadiene rubber (SBR) in the United States during the 1940 s. Thus, styrene was produced by many producers. 

Due to the influence of environmental considerations, plastics recycling is a growing economic activity. The need to open up new channels for discarded packaging has stimulated the recycling of plastics to produce new packaging materials. Such technical processes are being developed for the most widely used polymers polyolefins, polystyrene (PS), polyvinyl chloride (PVC) and PET. 

The proper choice of resin is important for the efficient and economical preparation of a peptide. The first resin to be used by Merrifield in the 1960s was polystyrene and this efficient type of resin is still widely used today [3]. Over the years, a limited number of resins, which contain polyethylene glycol (PEG) linked to polystyrene, have been developed. Also, resins made solely from PEG and a cross-linker have become commercially available. However, companies which specialize in reagents for solid-phase peptide synthesis tend to use their own names for resins and linkers as well as... 

Many reformers are now part of integrated petrochemical complexes and produce aromatics (benzene, toluene and xylenes or BTX) to feed into chemical processes for polystyrene, polyesters and other commodity chemicals. As such, it is important to consider how models can help in optimizing the BTX operation. Model developers and users must also be aware that complete BTX operation may not be the most profitable reformer operation scenario. Economic analyses are required to justify changes from a gasoline-producing to a BTX-producing scenario. 

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