Crystalline Density

Density. The density (crystallinity) of catalyticaHy produced PE is primarily determined by the amount of comonomer ( a-olefin) in ethylene copolymer. This amount is easily controlled by varying the relative amounts of ethylene and the comonomer in a polymerization reactor. In contrast, the density of PE produced in free-radical processes is usually controlled by temperature. 

The short side chain branching frequency is inversely proportional to polymer crystallinity. Short branches occur at frequencies of 2—50 per 1000 carbons in chain length their corresponding crystallinity varies from 35 to 75%. Directiy proportional to the polymer density, crystallinity can be calculated by the following formula,... 

Crystallinity and Density. Crystallinity and density of HDPE resins are derivative parameters both depend primarily on the extent of short-chain branching in polymer chains and, to a lesser degree, on molecular weight. The density range for HDPE resins is between 0.960 and 0.941 g/cm. In spite of the fact that UHMWPE is a completely nonbranched ethylene homopolymer, due to its very high molecular weight, it crystallines poorly and has a density of 0.93 g/cm. ... 

Increase in Density (crystallinity) Decrease in Melt Index Basic Properties Unaffected by Density and MI... 

The removal of side products such as EG, A A, CO2, water and oligomers is controlled by the physics of mass transport in the solid state. This mechanism correlates with particle size, density, crystallinity, crystal structure and perfection, and surface conditions, as well as the desorption of the reaction products from... 

One impediment of universally applying PET in the area of packaging is its gas-barrier properties. These can be slightly improved by measures to increase the density (crystallinity) during blow molding, for example, by treatment with ultrasound. Ultrasonic treatment during injection reduces the gas permeability to a certain extent [34],... 

These are exemplified by plastic materials such as plastics, rubbers and elastomers. The material offers some limited resistance to migration but this can occur not only from the surface but also from the interior of the material. The resistance to mass transfer depends on the structure, density, crystallinity, etc., of the material. 

What more could be done to convince the partisans of dualism Colour, solubility, volatility, vapour density, crystalline form, metamorphoses, action upon polarised light, action upon the animal economy, all testified in favour of the theory of substitutions. 

The polyolefins produced by transition metal catalysts are characterized by the absence of large amounts of long- or short-chain branching, which causes variability in density, crystallinity, and melting points. Most catalysts used are heterogeneous but some homogeneous systems are known. A two-step mechanism for catalysis is widely accepted (1) adsorption of the monomer, which may be activated by the configuration established in this step, and (2) insertion of the activated monomer into a metal-carbon bond. 

Which has a greater density, crystalline Si02 or amorphous Si02 Why ... 

Figure 3.1 Density, crystallinity, and polyethylene type scale.

Silica is a material with a low dielectric constant of k—4.0. In order to increase the packing density between multilevel interconnects, new. ultralow-k materials are needed. Because k decreases with decreasing density, crystalline and noncrystalline porous silicas with DK as low as A <2.0 were introduced to replace the current wire insulators in microelectronics for multilayer deviees. Because of their low density, ordered mesoporous materials are used for practical purposes. ... 

Density (crystalline) gcm" Also unstable monoclinic a modification 1.106< > (10)... 

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