Beads, manufacture

In contrast, sites located on the northern Channel islands produced as much as 150,000 pieces of bead manufacturing refuse and hundreds of production blanks from a single cubic meter of excavation (18, 20, 36, 37). As well, a tradition of specialized bead making tools, including micro-blade drills and anvils, is documented on the northern Channel Islands (16). Nothing comparable to this level and regularity of production is evident at archaeological sites in central and northern California. 

X powder and beads manufactured from the powder were obtained from Lancaster Syntheses, U. K. The characteristics of the H-ZSM-5 samples studied are given in Table 1. 

Contract and manufacturing services for the pharmaceutical industry, includes wet granulation, direct compression, fluid bed processing, film coating, encapsulation, bead manufacture, mixing/blending, etc.)... 

Ku CC, Joshi YM, Bergum JS, Jain NB. Bead manufacture by extrusion/spheronization—a statistical design for process optimization. Drug Dev Ind Pharm 1993 19 1505-1519. 

Ethylene and tetrafluoroethylene are copolymerized in aqueous, nonaqueous, or mixed medium with free-radical initiators. The polymer is isolated and converted into extmded cubes, powders, and beads, or a dispersion. This family of products is manufactured by Du Pont, Hoechst, Daikin, Asahi Glass, and Ausimont and sold under the trade names of Tefzel, Hostaflon ET, Neoflon EP, Aflon COP, and Halon ET, respectively. 

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. 

Mechanical Properties and Structural Performance. As a result of the manufacturing process, some cellular plastics have an elongated cell shape and thus exhibit anisotropy in mechanical, thermal, and expansion properties (35,36). Efforts are underway to develop manufacturing techniques that reduce such anisotropy and its effects. In general, higher strengths occur for the paraHel-to-rise direction than in the perpendicular-to-rise orientation. Properties of these materials show variabiUty due to specimen form and position in the bulk material and to uncertainty in the axes with respect to direction of foam rise. Expanded and molded bead products exhibit Httie anisotropy. 

Manufacture of ion-exchange resins has traditionaHy been a batch process. Significant progress was made more recentiy in the development of a continuous process for the manufacture of copolymer beads. However, as of this writing (ca 1994) is it not used by aH manufacturers. Moreover, those companies having continuous processing capabiHties do not use it for aH ion-exchange products. 

A Gaussian distribution of particle size is the result of copolymer manufactured by suspension polymerization. A jetting process produces beads with more uniform particle size. The uniformity coefficient is a numerical method of indicating closeness of all beads to the same size. 

As manufactured, most resias have a Gaussian-Hke distributioa of particle size. Very few are as small as 0.3 mm or as large as 1.0 mm. Most are betweea 0.5—0.8 mm. A backwash before usiag aew resia is common practice to assure uniform flow during the adsorption and regeneration steps. The backwash eliminates air pockets that may have formed while filling the column and sorts the beads such that the smaller sizes are at the top of the bed and... 

C Q—C g-ethoxylated quaternaries surfactants for coating polystyrene beads in the manufacture of lightweight concrete 17... 

Sodium orthosihcates are produced by blending ASM and NaOH beads or by fusion and grinding as in the direct manufacture of ASM. The relationships of these processes are shown in Figure 6. 

Use of the peUetted converter, developed and used by General Motors starting in 1975, has declined since 1980. The advantage of the peUetted converter, which consists of a packed bed of small spherical beads about 3 mm in diameter, is that the pellets were less cosdy to manufacture than the monolithic honeycomb. Disadvantages were the peUetted converter had 2 to 3 times more weight and volume, took longer to heat up, and was more susceptible to attrition and loss of catalyst in use. The monolithic honeycomb can be mounted in any orientation, whereas the peUetted converter had to be downflow. AdditionaUy, the pressure drop of the monolithic honeycomb is one-half to one-quarter that of a similar function peUetted converter. 

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