Other Plastics

Many plastics are not directly susceptible to microbial attack. This is particularly true of the rigid polymers with few additives. Though some of these plastic formulations do not themselves provide a food source for microbial attack, they are still subject to attack by microbes when exposed to the right combinations of environmental stresses. 

Dirt or debris can adhere to the surface of almost any plastic part, or it can accumulate in micro-cracks caused by heat, light, or mechanical stress. Microorganisms can grow on the debris and produce metabolic products that can stain the plastic and give rise to odors. 

A wide variety of plastic products can benefit from the inclusion of a biocide into the formulation. Table 3 lists the most common applications using biocides. 

This section briefly describes the thermal behaviour and conversion of other plastics, including materials such as PET, that are condensation polymers. As described in Chapter 2, condensation polymers are best depolymerized by chemolysis. However, the knowledge of both their thermal stability and the products derived from their thermal decomposition is of interest because in many cases they are present as contaminants in wastes containing addition polymers. 

The thermal degradation of PET has been studied by Oudhuis et a/.85 using TGA experiments. The DTG curves of PET in argon show a peak around 420 °C whereas 82% of the initial mass is volatilized up to 500 °C. The products released were a complex mixture composed mainly of acetaldehyde, benzoic acid, ethylbenzoate and vinylbenzoate. 

Kaminsky90,92 has reported the product distribution obtained in the fluidized bed pyrolysis of different condensation polymers (polyesters, polyurethanes, polyamides, etc.). Polyester degradation led to 51% of gases, with a high proportion of CO and C02, and 40% of oil rich in benzene, toluene and naphthalene, the formation of water also being detected. On the other hand, polyurethane and polyamide decomposition led to the formation of about 40% gases and 55% oil. In both cases, the gases obtained contained certain amounts of HCN. 

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Other Plastics. A relatively small amount of poly(vinyl chloride) goes into packagiag appHcations and appears in municipal soHd waste (25). 

Other Plastics Uses. The plasticizer range alcohols have a number of other uses in plastics hexanol and 2-ethylhexanol are used as part of the catalyst system in the polymerization of acrylates, ethylene, and propylene (55) the peroxydicarbonate of 2-ethylhexanol is utilized as a polymerization initiator for vinyl chloride various trialkyl phosphites find usage as heat and light stabHizers for plastics organotin derivatives are used as heat stabHizers for PVC octanol improves the compatibHity of calcium carbonate filler in various plastics 2-ethylhexanol is used to make expanded polystyrene beads (56) and acrylate esters serve as pressure sensitive adhesives. 

By far the largest volume synthetic alcohol is 2-ethylexanol [104-76-7] CgH gO, used mainly in production of the poly(vinyl chloride) plasticizer bis(2-ethylhexyl) phthalate [117-81-7], commonly called dioctyl phthalate [117-81-7] or DOP (see Plasticizers). A number of other plasticizer... 

Trimethylolethane trinitrate (metriol trinitrate) is not satisfactory as a plasticizer for nitrocellulose, and must be used with other plasticizers such as metriol triacetate. Mixtures with nitroglycerin tend to improve the mechanical properties of double-base cast propellants at high and low temperatures. Metriol trinitrate has also been used in combination with triethylene glycol dinitrate as a plasticizer for nitrocellulose. Its physical properties are Hsted in Table 7 (118-122). 

Other Films. Although commercially less important than polyethylenes and polypropylenes, a number of other plastic films are in commercial use or development for special appHcations, including ethylene—vinyl acetate, ionomer, and polyacrylonitrile [25014-41-9]. 

Various other diesters, mixed esters, and polyesters of trimethylpentanediol are useful as monomeric or polymeric plasticizers for coatings and plastic film and sheeting (49). They are compatible with, and useful ia, ceUulosics, vinyls, polystyrenes, and some other plastics. 

Lead forms a normal and an acid sulfate and several basic sulfates. Basic and normal lead sulfates ate fundamental components in the operation of lead-sulfuric acid storage batteries. Basic lead sulfates also ate used as pigments and heat stabilizers (qv) in vinyl and certain other plastics. 

Flame and Smoke Retardants. Molybdenum compounds are used extensively as flame retardants (qv) (93,94) in the formulation of halogenated polymers such as PVC, polyolefins, and other plastics elastomers and fabrics. An incentive for the use of molybdenum oxide and other molybdenum smoke and flame retardants is the elimination of the use of arsenic trioxide. Although hydrated inorganics are often used as flame retardants, and thought to work by releasing water of crystallization, anhydrous molybdenum oxides are effective. Presumably the molybdenum oxides rapidly form... 

Uses. Phthabc anhydride is used mainly in plasticizers, unsaturated polyesters, and alkyd resins (qv). PhthaUc plasticizers consume 54% of the phthahc anhydride in the United States (33). The plasticizers (qv) are used mainly with poly(vinyl chloride) to produce flexible sheet such as wallpaper and upholstery fabric from normally rigid polymers. The plasticizers are of two types diesters of the same monohydric alcohol such as dibutyl phthalate, or mixed esters of two monohydric alcohols. The largest-volume plasticizer is di(2-ethylhexyl) phthalate [117-81-7] which is known commercially as dioctyl phthalate (DOP) and is the base to which other plasticizers are compared. The important phthahc acid esters and thek physical properties are Hsted in Table 12. The demand for phthahc acid in plasticizers is naturally tied to the growth of the flexible poly(vinyl chloride) market which is large and has been growing steadily. 

The future for amino resins and plastics seems secure because they can provide quaHties that are not easily obtained in other ways. New developments will probably be in the areas of more highly specialized materials for treating textiles, paper, etc, and for use with other resins in the formulation of surface coatings, where a small amount of an amino resin can significantly increase the value of a more basic material. Additionally, since amino resins contain a large proportion of nitrogen, a widely abundant element, they may be in a better position to compete with other plastics as raw materials based on carbon compounds become more costly. 

Until the 1960s, reclaimed mbber was an important raw material in molded and extmded mbber products, eg, tires, mbber mats, and hard mbber battery cases. With the advent of vinyl, other plastics, and less expensive oil-extended synthetic polymers, reclaimed mbber sales stabilized and decreased. In 1973, the oil embargo and rising energy costs increased costs of the energy-intensive mbber reclaiming process to the point where they matched virgin polymer costs. Increased radial tire production required crack resistance that could not be provided by reclaimed mbber compounds (46). 

Lamination of polymer films, both styrene-based and other polymer types, to styrene-based materials can be carried out during the extmsion process for protection or decorative purposes. For example, an acryUc film can be laminated to ABS sheet during extmsion for protection in outdoor apphcations. Multiple extmsion of styrene-based plastics with one or more other plastics has grown rapidly from the mid-1980s to the mid-1990s. 

PVC Resin Price. PVC resin prices tend to be more stable than other plastics prices, pardy because only about half the molecule is based on hydrocarbon raw material sources. Figure 13 compares PVC prices to other plastics prices Figure 14 illustrates PVC prices over several years. 

The low elastic swell, unique to PVC, results from the presence of the biUion molecule flow units. Other plastics have higher die swell, which... 

Furthermore, it is not tme that other plastics are more environmentally friendly than vinyl. A more recent study compared vinyl to a number of other packaging materials and found that vinyl consumed the least amount of energy, used the lowest level of fossil fuels, consumed the least amount of raw materials, and produced the lowest levels of carbon dioxide of any of the plastics studied (184). In fact, the Norwegian environmental group BeUona has concluded that a generally reduced use of vinyl plastics can lead to a worsening of the environmental situation (185). 

When used alone at low temperatures, diaLkyl thiodipropionates are rather weak antioxidants. However, synergistic mixtures with hindered phenols are highly effective at elevated temperatures and are used extensively to stabilize polyolefins, ABS, impact polystyrene (IPS), and other plastics. 

Phenolics are consumed at roughly half the volume of PVC, and all other plastics are consumed in low volume quantities, mosdy in single apphcation niches, unlike workhorse resins such as PVC, phenoHc, urea—melamine, and polyurethane. More expensive engineering resins have a very limited role in the building materials sector except where specific value-added properties for a premium are justified. Except for the potential role of recycled engineering plastics in certain appHcations, the competitive nature of this market and the emphasis placed on end use economics indicates that commodity plastics will continue to dominate in consumption. The apphcation content of each resin type is noted in Table 2. Comparative prices can be seen in Table 5. The most dynamic growth among important sector resins has been seen with phenoHc, acryUc, polyurethane, LLDPE/LDPE, PVC, and polystyrene. 

Demand for cellulose acetate flake in the United States is projected to decline slightly from 1988 to 1993. Cigarette-filter tow for export is the only market projected to grow. Cellulose acetate for textile fibers is expected to decline, as will flake demand for plastics, with the growth of photographic films somewhat offsetting declining markets in other plastics end uses. 

Diesters. Many of the diester derivatives are commercially important. The diesters are important plasticizers, polymer intermediates, and synthetic lubricants. The diesters of azelaic and sebacic acids are useflil as monomeric plasticizing agents these perform weU at low temperatures and are less water-soluble and less volatile than are diesters of adipic acid. Azelate diesters, eg, di- -hexyl, di(2-ethylhexyl), and dibutyl, are useflil plasticizing agents for poly(vinyl chloride), synthetic mbbers, nitroceUulose, and other derivatized ceUuloses (104). The di-hexyl azelates and dibutyl sebacate are sanctioned by the U.S. Food and Dmg Administration for use in poly(vinyl chloride) films and in other plastics with direct contact to food. The di(2-ethylhexyl) and dibenzyl sebacates are also valuable plasticizers. Monomeric plasticizers have also been prepared from other diacids, notably dodecanedioic, brassyflc, and 8-eth5lhexadecanedioic (88), but these have not enjoyed the commercialization of the sebacic and azelaic diesters. 

Both PET and PBT resin serve some of the same markets as other plastics. Nylon, unsaturated polyester fiber glass, phenoHc, PC, and polyarylate resins sometimes compete for the same molded part. 

FIG. 19-62 New Trilioclcctric. separator for separation of PV C from other plastics. iCovrtesij Carpco, Lnc.)... 

Brush discharges from flexible, intermediate, bulk containers (FIBGs), plastic bags, stretch wrap, or other plastic film... 

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