Plastics bulk methods

Plastic-Plastic Separation Both dry and wet processes can be used to separate one plastic from another in a recycling operation. The most common wet separation methods are based on differences in density between particles of different plastics [1, 2, 10, 49], Density is a bulk property of the plastic. Unfortunately, many factors beyond polymer type affect density. Plastic particles can also show differences in surface properties. Plastic-plastic separation methods based on surface property differences include triboelectric separation [75] (a dry process) and froth flotation [75] (a wet process). Density-based and surface-property-based methods for separating a stream of mixed plastics are covered in the following sections. 

Another method for direct precipitation of cellulose acetate powder suitable for extmsion into plastics is described (90). The reaction solution is precipitated with dilute aqueous acetic acid at 80—85°C in the presence of a coagulant such as isopropyl acetate. The resulting powder particles have a higher bulk density and absorb plasticizers more readily than powders obtained by the usual methods. 

Another method, the emulsion process, was developed in Europe to meet the demand for a resin with small particle size, high bulk density, and low plasticizer absorption properties. These characteristics are especially desirable in making plastisols and organosols, where the resins are dispersed in liquid plasticizers. In this polymerization process, emulsifiers are added, and the solution is agitated to keep the monomer droplets dispersed. The initiators must be water soluble it is usually an inorganic persulfate or an organic hyperperoxide. 

For description of an apparatus used by Philipoff Brodnyan, see Ref 3, and of that used by McKinney et al, see Ref 4 Refs l)E.Meyer K.Tamm, AkustZeitschr 7, 45 50(March 1942), "An Accustic Method for Determining the Dynamic Compressibility and Loss Factor of Elastic Substances 2)C.S. Sandler, NAVORD Rept 1524(Sept 1950), "An Accoustic Technique for Measuring the Effective Dynamic Bulk Modulus of Elasticity and Associated Loss Factor in Rubber and Plastics 3)W.Philipoff J.Brodnyan, JApplPhys 26, 846-9(1955), "Preliminary Results in Measuring Dynamic Compressibilities 4)J. E. McKinney et al, JApplPhys 27, 425-30(1956), "Apparatus for the Direct Determination of the Dynamic Bulk Modulus 5)W.S.Cramer, NAVORD Rept 4380(Sept 1956), "Bulk Compressibility Data on Several Explosives 6)J.Alster, PicArsn, Dover, NJ private communication(1961)... 

In relation to sample preparation, Raman spectra can be obtained from pure complexes in the bulk state, seeing that for better performance the careful grinding of samples is required. Contrary to FTIR spectroscopy, where samples are mixed with mineral oil (Nujol) or KBr pellets, in Raman spectroscopy a pure substance is used. For this reason, the Raman spectroscopy is called a nondestructive measurement method. Additionally, analysis can be carried out through many containers such as glass, Pyrex reaction vessels, plastic containers, and so on. 

The method chosen for segregation and accumulation of wastes destined for incineration depends on the design of incinerator and its waste-feed mechanism, which vary widely. Some incinerators can handle only bulk liquid wastes, whereas others accept solid or packaged wastes such as fiber packs and glass or plastic bottles a few even accept steel cans or drums. 

The top-down approach starts with a bulk material and attempts to break it down into nanoscaled materials through physical methods. Hence, most of these techniques are really forms of fabrication rather than synthesis. For nanostructured bulk phases, including powders, the common methods are milling, devitrification of metallic glass, and severe plastic deformation. For nanocrystalline thin films (films with nanosized crystallites), methods include thermal vaporization (under high vacuum), laser ablation, and sputtering (thermal plasma), all of which were... 

The resin matrix can be either thermosetting or thermoplastic. Thermosetting resins such as epoxy, polyimide, polyester, and phenolic are used in applications where physical properties are important. Polyester and epoxy composites make up the bulk of the thermoset composite market. Of these two, polyesters dominate by far. Reinforced with glass fiber, these are known as fiberglass-reinforced plastics (FRPs). FRPs are molded by layup and spray-up methods or by compression molding either a preform or sheet molding compound (SMC). 

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