Polymer-modified types

Of the several types of the polymer-modified mortars and concretes used for various construction applications, latex-modified mortar and concrete are by far the most widely used materials. Latex-modified mortar and concrete are prepared by mixing a latex, either in a dispersed liquid or as a redispersible powder form with fresh cement mortar and concrete mixtures. The polymers are usually added to the mixing water just as other chemical admixtures, at a dosage of 5-20% by weight of cement. Polymer latexes are stable dispersions of very small (0.05-5 pm in diameter) polymer particles in water and are produced by emulsion polymerization. Natural rubber latex and epoxy latex are exceptions in that the former is tapped from rubber trees and the latter is produced by emulsifying an epoxy resin in water by the use of surfactants [87]. 

If the surface of a metal or carbon electrode is covered with a layer of some functional material, the electrode often shows characteristics that are completely different from those of the bare electrode. Electrodes of this sort are generally called modified electrodes [9] and various types have been developed. Some have a mono-molecular layer that is prepared by chemical bonding (chemical modification). Some have a polymer coat that is prepared either by dipping the bare electrode in a solution of the polymer, by evaporating the solvent (ethanol, acetone, etc.) of the polymer solution placed on the electrode surface, or by electrolytic polymerization of the monomer in solution. The polymers of the polymer-modified electrodes are either conducting polymers, redox polymers, or ion-exchange polymers, and can perform various functions. The applications of modified electrodes are really limit-... 

If the hydrolyses in silane precursor-polymer systems are carried out using relatively large amounts of the silane, then the silica generated can become the continuous phase, with the elastomeric polysiloxane dispersed in it.12 14 136-143 Again, a variety of ceramic components and polymeric components have been studied. The resultant composite is a polymer-modified glass or ceramic, frequently of very good transparency. Although its thermal stability will be inferior to that of the ceramic component itself, there are many applications for ceramic-type materials where this is not a serious problem. 

FIGURE 22. Types of metal-containing polymers. (Modified from Ref. 61a.)... 

If the chronoamperometric response of a - polymer-modified electrode is measured alone - in contact with inert - supporting electrolyte - Cottrell-type response can be obtained usually for thick films only, because at short times (f < 0.1-1 ms) the potential is not established while, at longer times (t > 10-100 ms), the finite diffusion conditions will prevail and / exponentially decreases with time. Another complication that may arise is the dependence of D on the potential in the case of - conducting polymer films [vi]. 

The type of process used also indicates the addition of polymer modifiers. Blow-molding requires that the polymer flows easily, while retaining good cohesive strength when molten, to avoid tears and voids. Melt flow modifiers are typically used for this purpose and include fatty acid esters, oleoamides, and adipates. Compounds of this type often also serve to prevent blocking (adhesion of one side of a bag to the other). 

Polymer modified lightweight cement mortar Pull-out adhesion strength (MPa) Failure type... 

Fig. 3 Formation of the core-shell type hydrogel nanoparticles by electrostatic interactions. The anionic solution which contains core polymer is introduced as a mist into a cationic solution of shell polymer. (Modified from Ref. l)...

The Ru(bpy)3 /guanine reaction can be carried out in solution, as well as many different types of electrode surfaces. It was originally developed using DNA physically adsorbed to ITO, but has also been applied to DNA attached to carbon nanotubes and polymer-modified electrodes. As long as the DNA-electrode linkage can tolerate potentials up to -1.3 V (the oxidation potential of Ru(bpy)3 ) the assay should be feasible at virtually any interface. 

As we said above, various types of modifiers, chemicals, and additives are compounded with the base resin or polymer material before processing. The compounding is usually done by the materials manufacturer however, this is also performed by a group within the polymer industry. Such companies buy the base resin from the materials manufacturer and then compound it specially for resale to the processor. The processor may also buy the base polymer, modifiers, chemicals, and additives for in-house compounding. 

Several types of polymer-modified mortars and concretes, i.e., latex-redispersible polymer powder-, water-soluble polymer-, liquid resin-, and monomer-modified mortars and concretes, are produced by using the polymers and monomers shown in Fig. 2.1. Of th, the latex-modified mortar and concrete are by far the most widely used cement modifiers. 

Drainage pavements coated with polymer-modified paste containing photocatalyst (ana-tase-type titanium dioxide) (which effectively decompose car exhaust gases with nitrogen oxides on road surfaces by the action of the photocatalyst and prevent air pollution) Special semiflexible pavements with water retentivity, executed by grouting the voids of open-graded asphalt concrete with polymer-modified paste containing superabsorbent polymers to prevent a heat island phenomenon in urban areas... 

Y. Ohama Improvements in properties of vinyl acetate-type polymer-modified mortars, in Proceedings of the 13th Japan Congress on Materials Research, The Society of Materials Science, Japan, Kyoto (1970), pp.212-215. 

Y. Ohama and S. Matsumoto Effect of type of powdered antifoamer on properties of polymer-modified mortars using redispersible polymer powders with powdered shrinkage-reducing agent, in Proceedings of the 4th Asia Symposium on Polymers in Concrete, Kangwon National University, Chuncheon, Korea (2003), pp.81-87. 

Y. Ohama, M. Ota and H. Tatematsu Properties of polymer-modified mortars using redispersible polymer powders with nitrite-type hydrocalumite (in Japanese). Cement Science and Concrete Technology No.59/2005 (2006), pp.461-468. 

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