Polyethylene general

The time required to produce a desired barrier improvement, varies with the type of polymer, its degree of crystallinity and the particular penetrant being considered. For example, a gasoline container or gas tank fabricated of polyethylene generally requires a degree of sulfonation equivalent to about 0.1 mg to 1 mg S03 per cm2. 

There are several kinds of polyethylene (LDPE, LLDPE, HDPE, UHMWPE), which are synthesized with different molecular weights and chain architectures. LDPE and LLDPE refer to low-density polyethylene and linear low-density polyethylene, respectively. These polyethylenes generally have branched and linear chain architectures, respectively, each with a molecular weight of typically less than 50,000 g/mol. 

Acrylonitrile-butadiene-styrene terpolymer and low-density polyethylene generally cannot meet the fatigue endurance, dimensional stability, and heat and creep resistance requirements of precision gears. Such polymers are most often found in basic low-load or low-speed gears. 

Spherulites of aliphatic hydrocarbon polymers such as polyethylene generally have their molecular chains with the highest refractive index oriented perpendicular to the radial growth direction. This is the case with the polypropylene spherulites shown in Fig. 2.9a, which were crystallized at 140 °C and consequently contain very few cross-hatched lamellae, so in this respect they are like polyethylene spherulites. The lower refractive index in this view is radial in direction, giving a yellow colour where the radius is parallel to the slow direction of the tint plate these are therefore termed negative spherulites. 

Here only a few of the highlights of the extensive study will be mentioned for the simplest case of equal A and B site hard-core diameters, and an equimolar mixture of chains of N sites each (< =i). The A chain aspect ratio is fixed at approximately 1.3, which is representative of a polymer such as polyethylene. Thus, the structural asymmetry variable = 2(rg - r )/(rg -I- F ) < 0 for most experimental polyolefin mixtures since unbranched polyethylene generally has the largest aspect ratio of the saturated hydrocarbon polymers. Figure 17 shows spinodal phase boundaries based on Eq. (4.5) for two reduced densities representative of a dense melt and concentrated solution (as studied by simulation). There are several important features. ... 

Provides good adhesion to a variety of substances including aluminum, stainless steel, tin plated steel, and polyethylene (general Properties ... 

The thermal analysis of polyethylene generally involves heating or cooling a sample at a controlled rate while monitoring some of its physical characteristics. 

Laboratory tests indicated that gamma radiation treatment and cross-linking using triaHylcyanurate or acetylene produced a flexible recycled plastic from mixtures of polyethylene, polypropylene, general-purpose polystyrene, and high impact grade PS (62). 

Fluoroboric acid and some fluoroborate solutions are shipped as corrosive material, generally in polyethylene-lined steel pads and dmms or in rigid nonretumable polyethylene containers. Acid spills should be neutralized with lime or soda ash. 

Cheese products generally must be maintained under refrigeration using closed flexible plastic, or plastic cups or tubs for packaging. Ice cream packaging is generally minimal, ie, lacquered or polyethylene extmsion-coated paper-board cartons, molded plastic tubs, or spinal wound composite paperboard tubs or cartons. 

Margarine and butter contain fat plus water and water-soluble ingredients, eg, salt and milk soHds that impart flavor and color to the product. Generally these products are distributed at refrigerated temperatures to retain their quaHty. Greaseproof packaging, such as polyethylene-coated paperboard, aluminum foil/paper, parchment paper wraps, and polypropylene tubs, is used for butter and margarine (see Dairy substitutes). 

A variety of cellular plastics exists for use as thermal iasulation as basic materials and products, or as thermal iasulation systems ia combination with other materials (see Foamed plastics). Polystyrenes, polyisocyanurates (which include polyurethanes), and phenoHcs are most commonly available for general use, however, there is increasing use of other types including polyethylenes, polyimides, melamines, and poly(vinyl chlorides) for specific appHcations. 

Multiple chent studies have proliferated on a world basis since the first generally recognized study of this type done in 1952 on polyethylene by the Roger Wdhams organization. There are directories of available multiple cHent studies that can direct the researcher to a source, eg, FINDex—The FirectoTy of Market Research Keports, Studies, and Surveys. Multiple chent studies can have budgets of 50,000 to 250,000 and can require the equivalent of several work years by the researchers. 

The use of steam is generally limited to polypropyleae and polyethylene fusion because impractical pressures are required to reach the temperature levels, eg, >200° C, required for bonding polyesters. In general, greater temperature control is required for area bonding polypropylene than for other polymers because the temperature difference between the matrix and biader fibers can be only 3°C (26). 

One of the early popular low power research and training reactors was the AGN-201, suppHed by Aerojet General Nuclear. This is a homogeneous sohd fuel reactor, consisting of a mixture of polyethylene and uranium at 20% enrichment in The core 235U... 

Polyethylene (PE) is a genetic name for a large family of semicrystalline polymers used mostiy as commodity plastics. PE resins are linear polymers with ethylene molecules as the main building block they are produced either in radical polymerization reactions at high pressures or in catalytic polymerization reactions. Most PE molecules contain branches in thek chains. In very general terms, PE stmcture can be represented by the following formula ... 

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