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Polyethylene amorphous

Examples of crystalline polymers are nylons, cellulose, linear polyesters, and high-density polyethylene. Amorphous polymers are exemplified by poly(methyl methacrylate), polycarbonates, and low-density polyethylene. The student should think about why these structures promote more or less crystallinity in these examples. [Pg.281]

Figure 13.13. Comparison between partition coefficients values, Kij/p, calculated at 313 K according to equations [13.5] and [13.6] [GIL 10] and the values measured between P = polyethylene (amorphous) and a) F = methanol b)F = ethanol... Figure 13.13. Comparison between partition coefficients values, Kij/p, calculated at 313 K according to equations [13.5] and [13.6] [GIL 10] and the values measured between P = polyethylene (amorphous) and a) F = methanol b)F = ethanol...
Figure 13.14. Partition coefficients, Kip/p, between a water thanol binary mixture and polyethylene (amorphous) at 313 K [GIL 10]. The symbols represent experimental data and the outlined shapes represent calculated values. (Fora color version of this figure, see WWW. iste.co. uk/hamaide/polymers.zip)... Figure 13.14. Partition coefficients, Kip/p, between a water thanol binary mixture and polyethylene (amorphous) at 313 K [GIL 10]. The symbols represent experimental data and the outlined shapes represent calculated values. (Fora color version of this figure, see WWW. iste.co. uk/hamaide/polymers.zip)...
Fig. 6.1. Arrhenius plots of the diffusion constant of oxygen into polyethylene (amorphous and crystalline regions). Several points located at upper left, , marked by a) are based on the results in the paper by Michaels et al. (Ref. Fig. 6.1. Arrhenius plots of the diffusion constant of oxygen into polyethylene (amorphous and crystalline regions). Several points located at upper left, , marked by a) are based on the results in the paper by Michaels et al. (Ref.
The word paracrystalline is used for aramid and gel-spun polyethylene. Amorphous regions are no longer present rather, the discussion is about defects in the crystal regions. Fiber moduli approach theoretical crystal moduli and shrinkage is virtually absent. Indeed, this is a completely different class of materials. [Pg.920]

Figure 4.8 Fraction of amorphous polyethylene as a function of time for crystallizations conducted at indicated temperatures (a) linear time scale and (b) logarithmic scale. Arrows in (b) indicate shifting curves measured at 126 and 130 to 128°C as described in Example 4.4. [Reprinted with permission from R. H. Doremus, B. W. Roberts, and D. Turnbull (Eds.) Growth and Perfection of Crystals, Wiley, New York, 1958.]... Figure 4.8 Fraction of amorphous polyethylene as a function of time for crystallizations conducted at indicated temperatures (a) linear time scale and (b) logarithmic scale. Arrows in (b) indicate shifting curves measured at 126 and 130 to 128°C as described in Example 4.4. [Reprinted with permission from R. H. Doremus, B. W. Roberts, and D. Turnbull (Eds.) Growth and Perfection of Crystals, Wiley, New York, 1958.]...
Docusate Calcium. Dioctyl calcium sulfosuccinate [128-49-4] (calcium salt of l,4-bis(2-ethylhexyl)ester butanedioic acid) (11) is a white amorphous soHd having the characteristic odor of octyl alcohol. It is very slightly soluble in water, and very soluble in alcohol, polyethylene glycol 400, and com oil. It may be prepared directly from dioctyl sodium sulfo succinate dissolved in 2-propanol, by reaction with a methan olic solution of calcium chloride. [Pg.201]

Similarly, the random introduction by copolymerization of stericaHy incompatible repeating unit B into chains of crystalline A reduces the crystalline melting point and degree of crystallinity. If is reduced to T, crystals cannot form. Isotactic polypropylene and linear polyethylene homopolymers are each highly crystalline plastics. However, a random 65% ethylene—35% propylene copolymer of the two, poly(ethylene- (9-prop5lene) is a completely amorphous ethylene—propylene mbber (EPR). On the other hand, block copolymers of the two, poly(ethylene- -prop5iene) of the same overall composition, are highly crystalline. X-ray studies of these materials reveal both the polyethylene lattice and the isotactic polypropylene lattice, as the different blocks crystallize in thek own lattices. [Pg.434]

Polymerization. Supported catalysts are used extensively in olefin polymerization, primarily to manufacture polyethylene and polypropylene. Because propylene can polymerize in a stereoregular manner to produce an isotactic, or crystalline, polymer as well as an atactic, or amorphous, polymer and ethylene caimot, there are large differences in the catalysts used to manufacture polyethylene and polypropylene (see Olefin polymers). [Pg.203]

The properties of elastomeric materials are also greatly iafluenced by the presence of strong interchain, ie, iatermolecular, forces which can result ia the formation of crystalline domains. Thus the elastomeric properties are those of an amorphous material having weak interchain iateractions and hence no crystallisation. At the other extreme of polymer properties are fiber-forming polymers, such as nylon, which when properly oriented lead to the formation of permanent, crystalline fibers. In between these two extremes is a whole range of polymers, from purely amorphous elastomers to partially crystalline plastics, such as polyethylene, polypropylene, polycarbonates, etc. [Pg.466]

There are thus no solvents at room temperature for polyethylene, polypropylene, poly-4 methylpent-l-ene, polyacetals and polytetrafluoroethylene. However, as the temperature is raised and approaches F , the FAS term becomes greater than AH and appropriate solvents become effective. Swelling will, however, occur in the amorphous zones of the polymer in the presence of solvents of similar solubility parameter, even at temperatures well below T. ... [Pg.84]

In the case of crystalline polymers better results are obtained using an amorphous density which can be extrapolated from data above the melting point, or from other sources. In the case of polyethylene the apparent amorphous density is in the range 0.84-0.86 at 25°C. This gives a calculated value of about 8.1 for the solubility parameter which is still slightly higher than observed values obtained by swelling experiments. [Pg.93]


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