Polymer bonding aids

Although not strictly used as prime structural adhesives, polymer latices or dispersions have been included here because of their increasing use as aids to bonding in the patch repair of spalled concrete. They usually take the form of a polymer-cement slurry which is applied to the moistened and prepared concrete surface. In general, the repair mortar must then be applied before a film 

Before discussing the various forms of polymers which may be encountered it is pertinent to describe briefly the basic structure of water-based polymer dispersions(ll). The starting point is a monomer which forms droplets in water. Aqueous surfactants are adsorbed at the droplet surface to stabilise the emulsion before an initiator is added to cause polymerisation under controlled conditions of pressure, temperature and stirring rate. The latex is thus an aqueous dispersion of small discrete polymer particles to which is added a range of additives, such as coalescents, anti-foaming agents, bacteriocide and anti-oxidants, to improve shelf life and properties related to its end use. 

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Where it is considered essential to apply a granolithic topping onto an existing concrete substrate the danger of de-bonding can be much reduced by the use of polymer-based bonding aid. Two types of bonding aid are commonly used ... 

All the herein-described hyperbranched polymers are constructed from triple-bond building blocks and are expected to show unique properties due to their novel -conjugated structures. Investigation and understanding of the advanced functional properties of the new polymers will aid their development from macromolecules of academic curiosity to materials of technological value. 

Use Bonding agents, polymer process aids, catalysts, blowing agent activators, corrosion inhibitors, dispersing agents. 

Ceraplast n. Any reinforced thermoplastic, particularly polyethylene, containing ceramic or mineral particles that have been dispersed in the polymer melt to their ultimate size (no agglomerates) and completely enveloped in resin. Bonding of the envelope to the filler particles and the matrix polymer is aided by the addition of a small percentage of reactive monomer or resin precursor. It is believed that, in the extremely thin transition envelope, there is a smooth gradient of modulus from that of the particulate material to that of the polymer. The mechanical properties of cera-plasts are superior to those in which the same fillers have been conventionally incorporated. 

Sprayed or trowelled concrete with or without admixtures or bonding aids. Polymer Modified Cement Concrete. Epoxide Resin Mortar. 

Polymer modification imparts a wide range of performance improvements to ceramic tile mortar adhesives, including improved bond strength, water resistance, flexibility, impact strength, freeze-thaw resistance, improved mix workability. Polymers also aid in promoting adhesion to difficult substrates such as plywood and vitreous tiles (porcelain). 

Gelatin stmctures have been studied with the aid of an electron microscope (23). The stmcture of the gel is a combination of fine and coarse interchain networks the ratio depends on the temperature during the polymer-polymer and polymer-solvent interaction lea ding to bond formation. The rigidity of the gel is approximately proportional to the square of the gelatin concentration. Crystallites, indicated by x-ray diffraction pattern, are beUeved to be at the junctions of the polypeptide chains (24). 

Bonding Agents. These materials are generally only used in wire cable coat compounds. They are basically organic complexes of cobalt and cobalt—boron. In wire coat compounds they are used at very low levels of active cobalt to aid in the copper sulfide complex formation that is the primary adherance stmcture. The copper sulfide stmcture builds up at the brass mbber interface through copper in the brass and sulfur from the compound. The dendrites of copper sulfide formed entrap the polymer chains before the compound is vulcanized thus hoi ding the mbber firmly to the wire. 

Olefin metathesis (olefin disproportionation) is the reaction of two alkenes in which the redistribution of the olelinic bonds takes place with the aid of transition metal catalysts (Scheme 7.7). The reaction proceeds with an intermediate formation of a metallacyclobutene. This may either break down to provide two new olefins, or open up to generate a metal alkylidene species which -by multiple alkene insertion- may lead to formation of alkylidenes with a polymeric moiety [21]. Ring-opening metathesis polymerization (ROMP) is the reaction of cyclic olefins in which backbone-unsaturated polymers are obtained. The driving force of this process is obviously in the relief of the ring strain of the monomers. 

The versatility of Ziegler-Natta catalysis is shown in the polymerization of butadiene. Polybutadiene may have either a 1,2 or 1,4 configuration. The 1,4 polymer has a double bond as part of the main chain and this can be atactic, isotactic, or syndiotactic. Thus many different polybutadienes can be made and all of them have been made with the aid of Ziegler-Natta catalysts. 

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