Polypropylene, polystyrene, and

Over 70% of the total volume of thermoplastics is accounted for by the commodity resins polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) (PVC) (1) (see Olefin polymers Styrene plastics Vinyl polymers). They are made in a variety of grades and because of their low cost are the first choice for a variety of appHcations. Next in performance and in cost are acryhcs, ceUulosics, and acrylonitrile—butadiene—styrene (ABS) terpolymers (see... 

Resins and plastics such as low-density polyethylene (LDPE), high-density polyethylene (HOPE), linear low-density polyethylene (LLDPE), polypropylene, polystyrene, and polyvinyl chloride (PVC) ... 

Addition polymers, which are also known as chain growth polymers, make up the bulk of polymers that we encounter in everyday life. This class includes polyethylene, polypropylene, polystyrene, and polyvinyl chloride. Addition polymers are created by the sequential addition of monomers to an active site, as shown schematically in Fig. 1.7 for polyethylene. In this example, an unpaired electron, which forms the active site at the growing end of the chain, attacks the double bond of an adjacent ethylene monomer. The ethylene unit is added to the end of the chain and a free radical is regenerated. Under the right conditions, chain extension will proceed via hundreds of such steps until the supply of monomers is exhausted, the free radical is transferred to another chain, or the active site is quenched. The products of addition polymerization can have a wide range of molecular weights, the distribution of which depends on the relative rates of chain grcnvth, chain transfer, and chain termination. 

Typical examples of thermosetting polymers are phenolic and urea-formaldehyde resins, unsaturated polyesters, and epoxy resins. Typical thermoplastics are polyethylene, polypropylene, polystyrene, and poly(vinyl chloride). The thermoplastic or thermosetting character of a polymer... 

Phosphorus Phosphate esters and others (halogenated and nonhalogenated) Polyurethane foams, polyesters, and thermoplastics such as flexible PVC, modified PPO, and cellulosics Also polyethylene, polypropylene, polystyrene, and ethylene/propylene copolymers Akzo Nobel, Albemarle, Amfine Chemical Corp., Amspec Chemical, Bayer, Ciba Specialty Chemical-Melapur, Clariant, Cytec, Daihachi Chemical Industry, Great Lakes, Italmatch Chemicals, Nitroil, Rhodia... 

Another class of secondary antioxidants used in food contact plastics is thioether. The most common examples used in polypropylene, polystyrene and PVC are thiodipropanoic acid, didodecyl ester (DLTDP) and thiodipropanoic acid, dioctadecyl ester (DSTDP). Thioethers react with hydroperoxides to form sulphoxides as shown in Fig. 10.8. 

Figure 11.9 Molecular weight distribution of the waxes derived from the fluidized-bed pyrolysis of high-density polyethylene, low-density polyethylene, polypropylene, polystyrene and polyethylene terephthalate...

Plastic wastes may be the remains of production or post-consumer wastes, the latter being classified as municipal, packaging, agricultural, automotive and electrical. Packaging wastes are the major category [33, 52-54]. These are mainly thermoplastics such as polyethylene, polypropylene, polystyrene and polyvinyl chloride [28, 33, 55-56]. 

Chain branching is a common occurrence during radical polymeri7a-B tions and is not restricted to polyethylene, Polypropylene, polystyrene, and poly(methyl methacrylate) all contain branched chains. Studies have shown 1 that short chain branching occurs about 50 times as often as long-chain ] branching. ... 

HALS exhibit a complex behavior when present in combination with other antioxidants and stabilizers. Effective synergism in both melt and thermal stabilization has been achieved when secondary and tertiary HALS were used in combination with both aromatic and aliphatic phosphites the synergistic optimum depends on the structure of the phosphite. HALS also synergize the action of UV-absorbers, e.g., benzo-triazoles, in different polymers such as polypropylene, polystyrene, and ABS. " ... 

Based on the results shown in table 8.1, it is obvious that during solution analysis of the cracking product of polyethylene and polypropylene, only non-cracked plastics remain completely in the remainder. In contrast to polyethylene and polypropylene, polystyrene and PVC are over 40 wt. % soluble in THF. 

There are many different types of plastics and an even greater number of grades to meet virtually every product requirement. The main economical plastics used in pharmaceutical applications are the economical four i.e. polyethylene, polypropylene, polystyrene and polyvinylchloride. 

Thermal processes are mainly used for the feedstock recycling of addition polymers whereas, as stated in Chapter 2, condensation polymers are preferably depolymerized by reaction with certain chemical agents. The present chapter will deal with the thermal decomposition of polyethylene, polypropylene, polystyrene and polyvinyl chloride, which are the main components of the plastic waste stream (see Chapter 1). Nevertheless, the thermal degradation of some condensation polymers will also be mentioned, because they can appear mixed with polyolefins and other addition polymers in the plastic waste stream. Both the thermal decomposition of individual plastics and of plastic mixtures will be discussed. Likewise, the thermal coprocessing of plastic wastes with other materials (e.g. coal and biomass) will be considered in this chapter. Finally, the thermal degradation of rubber wastes will also be reviewed because in recent years much research effort has been devoted to the recovery of valuable products by the pyrolysis of used tyres. 

U.S. Pat. No. 5,288,772 [75] discloses a cellulose-fiber-reinforced thermoplastic composition for compression molding, where thermoplastic material is polypropylene, or a mixture of polypropylene, polystyrene, and polyethylene (40-90% of plastic by weight), and the cellulosic material (10-60% by weight) was milled scrap newspaper with an initial moisture content of at least 30% by weight. The patentees suggest that lignin present in the cellulosic scrap provides a coherent mass of thermoplastic and cellulosic material. 

Table 15.2. Properties of some commercial, reactor-made polypropylene/polystyrene and polypropylene/acrylic polymer alloys...

Used for optical brightening of PVC, 642 polypropylene, polystyrene, and poly(methyl methacrylate)... 

In blow molding, a tube of molten plastic material, the parison, is extruded over an apparatus called the blow pipe and is then encased in a split mold. Air is injected into this hot section of extruded stock through the blow pipe. The stock is then blown outward, where it foUows the contour of the mold. The part is then cooled, the mold opened, and the molded part ejected. In very heavy sections, carbon dioxide or Uquid nitrogen may be used to hasten the cooling. This process is widely used in molding high- and low-density polyethylene, nylon, polyvinyl chloride (PVC), polypropylene, polystyrene, and polycarbonates. 

Oligomeric bromine-containing ethers on the basis of tetrahromoxylene dihaUdes and tetrahromohi-sphenol-A (molecular weight between 3,000 and 7,000) are useful flame retardants for polypropylene, polystyrene, and ABS. 

These are polymers formed from a single monomer. An example is polyethene (polyethylene), which is made by polymerization of ethene (CH2 CH2). Typically such polymers are formed by addition reactions involving unsaturated molecules. Other similar examples are polypropene (polypropylene), polystyrene, and polytetrafluoroethene (PTFE). Homopolymers may also be made by condensation reactions (as in the case of polyurethane). 

This group of Ziegler-Natta catalysts is stereospecific for the polymerisation of a-olefins and 1,3-dienes the products are mainly isotactic polyolefins (polypropylene, polystyrene, and so on) and 3 5-l,4-polydienes (polybutadiene, polyisoprene, and so on). 

Engineering polymers are defined loosely in Chapter 13 as commodity thermoplastics that are typically flexible and produced in large quantities. The synthetic thermoplastics discussed in this text meet this definition so polyethylene, polypropylene, polystyrene, and polyvinyl chloride all would be classed as engineering polymers. 

Engineering polymers sueh as polyethylene, polypropylene, polystyrene, and polyvinyl ehloride ean be reinforced with liquid crystalline polymers. The stronger, less thermally expansive Uquid... 

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