Network in situ

Murugesan, S. Mark, J. E. Beaucage, G. Structure-Property Relationships for Poly(dimethylsiloxane) Networks In Situ Filled Using Titanium 2-Ethylhexoxide and Zirconium n-Butoxide. In Synthesis and Properties of Silicones and Silicone-Modified Materials-, Glarson, S. J., Fitzgerald, J. J., Owen, M. J., Smith, S. D., Van Dyke, M. E., Eds. ACS Symposium Series 838 American Chemical Society Washington,... 

Geary J.R., Nijak, G.J. and Talley, J.W. 2008. Networked in-situ water monitoring, 6th National Monitoring Conference, Atlantic City, New Jersey. 

There have been numerous experiments carried out on various polymer networks in situ filled with silica in uniaxial extension [3,14,15,17,19-21,67,68]. In fact, the... 

It is well known that the pyrolysis of polyolefin was a free radical chain reaction through (3-scission of polymer chains, whereas the free radicals produced in turn speeded up the degradation of polymers. Many scientists have reported that the Qo fullerene molecule has high reactivity to free radicals one Ceo molecule can trap from 1 to 34 free radicals [30], Based on these viscoelastic measurements, it was reasonable to conclude that Ceo was Ukely to trap macromolecular free radicals (PP radicals) and other free radicals such as hydrogen and hydroxyl radicals created from the decomposition of PP at elevated temperatures and form cross-linked networks in situ. On the other hand, the radical-trapping effect of Ceo also provided partial PP radicals more time to recombine, which resulted in a remarkable increase in both storage modulus and complex viscosity of nanocomposites. 

Generally, the degradation of polymers is thought to be a free radical chain reaction through (3-scission of polymer chains. Ceo, described as a radical sponge [30], has high reactivity toward free radicals, in that it has 30 carbon-carbon double bonds and can trap more than 34 free radicals [30, 36-38], Thus, Ceo can trap the macromolecular or any other radicals created by the pyrolysis of polymers and then form a gelled ball network in situ. The network can increase the melt viscosity and consequently slow the combustion of polymeric materials. Thus, in another sense, Ceo naay be considered to be a gas phase flame retardant. 

Polymers also are used to improve volumetric sweep efficiency in reservoirs that are fractured or have considerable permeability variation. In this application, commonly called in-situ permeability modification, the polymer is crosslinked in situ to form a gel network. In-situ gelation reduces the permeability in the region contacted by the polymer. By selection of chemical systems, treatments... 

Reactive adhesives are those liquid materials that are ciued (or cross-linked) into a solid network in situ. For example, epoxy adhesives consist of two components, one of which is a prepolymer formed by the reaction of an excess of epichlorohydrin with bisphenol-A, as follows [14] ... 

Miscibility or compatibility provided by the compatibilizer or TLCP itself can affect the dimensional stability of in situ composites. The feature of ultra-high modulus and low viscosity melt of a nematic liquid crystalline polymer is suitable to induce greater dimensional stability in the composites. For drawn amorphous polymers, if the formed articles are exposed to sufficiently high temperatures, the extended chains are retracted by the entropic driving force of the stretched backbone, similar to the contraction of the stretched rubber network [61,62]. The presence of filler in the extruded articles significantly reduces the total extent of recoil. This can be attributed to the orientation of the fibers in the direction of drawing, which may act as a constraint for a certain amount of polymeric material surrounding them. 

This process is highly suitable for rubbers with poor solubility. In this process, the rubber sheet is soaked in TEOS or quite often in TEOS-solvent mixture and the in situ sUica generation is conducted by either acid or base catalysis. The sol-gel reaction is normally carried out at room temperature. Kohjiya et al. [29-31] have reported various nonpolar mbber-silica hybrid nanocomposites based on this technique. The network density of the rubber influences the swelling behavior and hence controls the silica formation. It is very likely that there has been a graded silica concentration from surface to the bulk due to limited swelling of the rubber. This process has been predominantly used to prepare ionomer-inorganic hybrids by Siuzdak et al. [48-50]. 

Fine silica network is visible in the in situ silica-filled rubber composite synthesized from 50 wt% of TEOS, producing almost 15 wt% of sdica. On the other hand, addition of only 10 wt% of precipitated silica externally gives distinct aggregations. 

Nieto, JL Baselga, J Hernandez-Fuentes, I Llorente, MA Pierola, IF, Polyacrylamide Networks. Kinetic and Structural Studies by High Field Hl-NMR with Polymerization in Situ, European Journal of Polymers 23, 551, 1987. 

In situ, pectins may form a 3-D network based on different mechanisms of interaction they piay an important role on cohesion of cell walls but also in recognition reaction [2, 3]. 

Our approach, to achieve a high dispersion of the metal compound while the oxide network is formed, is to employ metal complexes of the type LnM[X(CH2)3Si(OR)3]y in the sol-gel process [2]. The metal ions then cannot aggregate because of complexation, and the metal complexes cannot leach because they are linked to the oxidic support. These complexes are formed in situ on reaction of silanes of the type X(CH2)nSi(OR)3 with suitable metal salts. 

The crosslinking efficiency of many peroxide-initiated free radicals is low. These labile radicals can be converted to more stable radicals by contact in situ with polyfunctional monomers to form a three-dimensional network. Crosslinking efficiency is thus increased by some 20%. In addition, these materials act as plasticisers during processing and in some cases also act as hardening agents. 

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