High-density polyethylene /isotactic

Although very similar to high-density polyethylene, isotactic polypropylene differs from the former in a number of respects of which the following are among the most important ... 

Doroudiani S, Park CB, Kortschot MT (1998) Processing and characterization of micro-cellular foamed high-density polyethylene/isotactic polypropylene blends. Polym Eng Sci 38 1205-1215... 

Second 1950 1965 High-density polyethylene, isotactic polypropylene, polycarbonate, polysulfones, linear polyesters, synthetic rubbers Improved mechanical strength... 

Glycidyl methacrylate High density polyethylene Isotactic copolymer of styrene and p-methyl styrene Isotactic poly(ethyl methacrylate) Isotactic poly(methyl methacrylate) Isotactic polystyrene Low density polyethylene Linear low density polyethylene Maleic anhydride Poly(4-methyl pentene) Random copolymer of phenyl ether and phenyl ketone... 

Various metal complex systems of Ziegler type are widely applied within industry for the production of high-density polyethylene, isotactic polypropylene, 1,4-c/s-and 1,4- rans-polymers of isoprene and 1,2-poly butadiene, and many other types of copolymers, such as ones based on ethylene and propylene, which could not be produced earlier based on traditional methods of synthesis. 

Zhang, C., Yi, X.S., YuL H., Asai, S., and Sumita, M. (1998) Selective localization and double percolation of short carbon fiber filled polymer blends high-density polyethylene/isotactic polypropylene. Mater. Lett., 36, 186. 

The second generation of polymers was introduced during 1950—65 and includes a number of engineering plastics such as high-density polyethylene, isotactic polypropylene, polycarbonates, polyurethanes, epoxy resins, polysulphones and aromatic polyesters, also used for films and fibres. New rubber materials, acrylic fibres made of polyacrylonitrile and latex paint were also introduced. 

The majority of spunbonded fabrics are based on isotactic polypropylene and polyester (Table 1). Small quantities are made from nylon-6,6 and a growing percentage from high density polyethylene. Table 3 illustrates the basic characteristics of fibers made from different base polymers. Although some interest has been seen in the use of linear low density polyethylene (LLDPE) as a base polymer, largely because of potential increases in the softness of the final fabric (9), economic factors continue to favor polypropylene (see OlefinPOLYMERS, POLYPROPYLENE). 

Blends of isobutylene polymers with thermoplastic resins are used for toughening these compounds. High density polyethylene and isotactic polypropylene are often modified with 5 to 30 wt % polyisobutylene. At higher elastomer concentration the blends of butyl-type polymers with polyolefins become more mbbery in nature, and these compositions are used as thermoplastic elastomers (98). In some cases, a halobutyl phase is cross-linked as it is dispersed in the polyolefin to produce a highly elastic compound that is processible in thermoplastic mol ding equipment (99) (see Elastomers, synthetic-thermoplastic). ... 

The metal catalyzed production of polyolefins such as high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and polypropylene (PP) has grown into an enormous industry. Heterogeneous transition metal catalysts are used for the vast majority of PE and all of the PP production. These catalysts fall generally within two broad classes. Most commercial PP is isotactic and is produced with a catalyst based on a combination of titanium chloride and alkylaluminum chlorides. HDPE and LLDPE are produced with either a titanium catalyst or one based on chromium supported on silica. Most commercial titanium-based PE catalysts are supported on MgCl2. 

Voids within a sample are a major cause of internal haze. We see the effect of voiding when we stretch polymers, such as high density polyethylene and isotactic polypropylene, that have distinct yield points and clearly defined necks (as discussed earlier in this chapter). The... 

AFM Atomic force microscopy aPP Atactic polypropylene DSC Differential scanning calorimetry HDPE High-density polyethylene iPP Isotactic polypropylene LLDPE Linear low-density polyethylene MD Microdomain ODT Order-disorder transition PB Poly(butadiene)... 

The hydrogenated copolymers of poly(butadiene-poly(isoprene) have been milled with 30% isotactic polypropylene and high density polyethylene. These thermoplastic elastomers (TPR s) showed excellent physical properties (illustrated in Table VIII). 

Hydrogenated diblock Poly(.butadiene)-Poly(isoprene) filled with isotact i c polypropylene and high density polyethylene. 

The data from this table illustrate the semicompatibility of the phase between isotactic polypropylene and the high density polyethylene with block copolymer without gross interference in the domain structure or the crystalline phases that exist in these TPR s. 

Table I shows the production of different kinds of polyolefins [high-density polyethylene (HDPE), low-density polyethylene (LDPE), isotactic polypropylene (PP), and linear low-density polyethylene (LLDPE)] (6). Apart from LDPE (discovered by workers at ICI), which has a highly branched structure and is produced in free radical reactions at ethylene pressures of 1000-3000 bar (1 bar = 105 Pa), the other polyolefins are synthesized at far lower pressures and in the presence of catalysts (7).

Figure 4 shows that the orientation of the two chains follow similar paths. The similarity suggests that the local environment is very much the same for both blend constituents. In contrast, a phase-separated binary mixture of polymer segments will exhibit a different orientation for each component. For example, high-density polyethylene and isotactic polypropylene form multiphase systems when blended together (16). When the incompatible blends are deformed, the component which constitutes the continuous phase always orients to a higher degree than... 

Isotactic polypropylene Atactic polystyrene Low density polyethylene High density polyethylene A soft polyurethane Nylon 6... 

The melting temperature for PAN is extremely high as compared, e. g., with that of isotactic polystyrene (230 °C) or high density polyethylene (137—140 °C). Generally, a high melting point, T , can be caused by a high heat of fusion, AHf, and/or by a low entropy of fusion, ASf ... 

The phase diagram of polyolefins and hydrocarbon diluents is exemplified for high-density polyethylene in Figure 1. When the polymer-diluent mixture is heated, dissolution of the semicrystalline polymer takes place along the borderline 1 (turbidity curve) [43, 44], This line depends on the polymer (e. g., polyethylene, isotactic polypropylene), average chain length, and copolymer composition. 

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