Polyethylene Silica

The first physically interpenetrating nanocomposite between polyethylene (PE) and silica (the simplest and most common organic and 

Instead of blending them either by dispersing silica powders as fillers within PE, which is a well-developed technology with many applications, or by polymerizing ethylene within the pores of modified9 or unmodified silica,10 now the nanometric physical blending 

The key to the successful preparation of this new composite is the identification of a surfactant, PE-b-PEG, that is capable of stabilizing the emulsion and promoting the dissolution of the PE. Then submicrometre particles of low-density PE silica and high-density PE silica are synthesized by carrying out a silica sol-gel polycondensation process within emulsion droplets of TEOS-dissolved PE, at elevated temperatures (78 and 130°C for low- and high-density PE, respectively). 

Molecular sol-gel encapsulation adds value because, once entrapped in a sol-gel matrix, molecules retain their basic physical and chemical properties that define the practical value of those molecules, but encapsulation also expands the properties conferring a whole new set 

Silica-Based Materials for Advanced Chemical Applications By Mario Pagliaro Mario Pagliaro 2009 

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Tian et al. [56] have studied poly(G-caprolactone)-silica and Sengupta et al. [57] have investigated nylon 66-silica hybrid systems and have observed that the phase separation started when Si/H20 mole ratio is increased above 2 and the resultant hybrid films become opaque. Gao [11] has reported similar observations on sol-gel-derived ionomeric polyethylene-silica system. A wide range of literatures is not available on this topic of mbber-silica hybrid nanocomposites, though Bandyopadhyay et al. [34,35] have reported the hybrid formation with different TEOS/H2O mole ratios from ACM and ENR and also demonstrated detailed structure-property correlation in these systems. The hybrids have been prepared with 1 1, 1 2, 1 4, 1 6, 1 8, and 1 10 TEOS/H2O mole ratios. Figure 3.14 shows the morphology of the ACM-silica hybrid composites prepared from different TEOS/H2O mole ratios. 

Materials that are used most frequently are polyethylene, silica, and aluminum foil. Polyethylene satisfies requirements 2 and 3 listed above, but it has low resistance to radiation and temperature. It becomes brittle after exposure to a fluence of 10 -10 neutrons/m. Polyethylene tubes of different diameters are routinely used in radiation laboratories. The tubes can be easily cleaned and sealed. Silica containers are not as useful as polyethylene because they are not as pure, they become radioactive, and sealing is more complicated. Aluminum foil is useful for packaging solids, but it becomes radioactive through Al(n, y) Al and Al(n, a) Na reactions. The second reaction is more troublesome than the first because the half-life of Na is the 15 h, whereas the half-life of A1 is only 2.3 min. 

Reddy, C. S. and Das, C. K. 2006. Thermal and dynamic mechanical properties of low density polyethylene-silica nanocomposites Effect of zinc-ion coating on nanosilica. Polymers and Polymer Composites 14 281-290. 

Lau KY, Vaughan AS, Chen G, Hosier IL, Holt AF (2013) Absorption current behaviour of polyethylene/silica nanocomposites. Dielectrics 2013(10-12) 24-25 Lee Y, Porter RS (1987) Double-melting behavior of poly(ether ether ketone). Macromolecules 20 1336-1341... 

Fig. 7 Polyethylene silica composite from in situ polymerization on MAO-coated silica nanoparticles...

Crystallization process is an important consideration in selection of an antiblocking agent for polyethylene. Silica antiblocking agents do not interfere with the crystallization process, but talcs may affect the crystallization process of polyethylene to a large extent. " ... 

Polyethylene glycol 4000 alcohols, amines stabilization and enhancement spray solution, 50% in methanol, best results on silica gel [271]... 

The reagent can be employed on silica gel, kieselguhr and Si 50 000 layers (also when they are impregnated with polyethylene glycol [1]) and on cellulose layers. 

TLC plates Silica gel 60 (Merck) impregnated by dipping once in a 10% solution of polyethylene glycol 1000 in methanol. 

High-density polyethylene (HDPE) is produced by a low-pressure process in a fluid-bed reactor. Catalysts used for HDPE are either of the Zieglar-type (a complex of A1(C2H5)3 and a-TiCl4) or silica-alumina impregnated with a metal oxide such as chromium oxide or molybdenum oxide. 

The term polyethylene separator is somewhat misleading, since this separator consists mainly of agglomerates of precipitated silica, held within a network of extremely long-chained, ultrahigh-molecular weight polyethylene molecules. The raw materials, precipitated silica (Si02 — about 60 percent), ultrahigh-... 

It has been outlined by several authors that the single macromolecule may be irreversibly bound because of the large number of weakly interacting segments. The first papers on the construction of polymer-coated silica adsorbents involved the physical adsorption of water-soluble polymers. Polyethylene oxides [28, 29] and poly-/V-vinylpyrrolidone [30] are examples of the stationary phases of this type. 

The same research group proved the applicability of PEO-silicas to the separation of ribonucleic acids and studied how the log k vs m slopes are affected by the molecular weight of polyethylene oxide, the type of salt used in eluent... 

Large yields of polymer seem to be obtained only when polymerization proceeds on the outer catalyst surface, because the transport of high molecular polyethylene from catalyst pores is impossible (112). The working part of the specific surface of the catalyst can be expected to increase with diminishing strength of links between catalyst particles (112). Therefore, to obtain a highly active catalyst a support with large pore volume should be used (e.g. silica with pore volume >1.5 cm8/g). 

This comprehensive article supplies details of a new catalytic process for the degradation of municipal waste plastics in a glass reactor. The degradation of plastics was carried out at atmospheric pressure and 410 degrees C in batch and continuous feed operation. The waste plastics and simulated mixed plastics are composed of polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene, and polyethylene terephthalate. In the study, the degradation rate and yield of fuel oil recovery promoted by the use of silica alumina catalysts are compared with the non-catalytic thermal degradation. 9 refs. lAPAN... 

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. 

A polyethylene-coated (PEE) silica column was used with water-methanol eluents to achieve the separation and retention of 27 pesticides.40 The retention times of 33 commercial pesticides were determined on an octadecyl (ODS)-derivatized alumina column using water-methanol eluents and compared with retention properties on an ODS-silica column packing.41 More recently, RP-HPLC was used in combination with diode array detection for the identification and quantification of 77 pesticides (acidic, basic, and neutral) in groundwater samples.42... 

Forgacs, E. and Cserhati, T., Use of principal component analysis for studying the separation of pesticides on polyethylene-coated silica columns, J.Chro-matogr. A, 797, 33-39, 1998. 

Capillary electrophoretic separations are performed in small diameter tubes, made of Teflon, polyethylene, and other materials. The most frequently used material is fused silica. Fused silica capillaries are relatively inexpensive and are available in different internal and external diameters. An important advantage of a fused silica capillary is that the inner surface can be modified easily by either chemical or physical means. The chemistry of the silica surface is well established due to the popularity of silica surfaces in gas chromatography (GC) and liquid chromatography (LC). In capillary electrophoresis, the silica surface is responsible for the EOF. Using surface modification techniques, the zeta potential and correspondingly the EOF can be varied or eliminated. Column fabrication has been done on microchips.13... 

In an attempt to formulate an anhydrous, but water-soluble, semisolid base for potential ophthalmic use, five bases were studied [279]. The nonaqueous portion of the base was either glycerin or polyethylene glycols in high concentrations. The matrix used to form the phases included silica, Gantrez AN-139, and Carbopol 940. Eye irritation results were not reported, but the authors studied representative bases from that research report and found them to be quite irritating in rabbit eyes. The irritation is believed to be primarily due to the high concentration of the polyols used as vehicles. 

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