Adhesive polyaddition

Adhesive-Coated Material. The addition of an adhesive-coated material [335] to proppants decreases the flowback of the particulates. Such adhesive-coated materials can be inorganic or organic fibers, flakes, and the like. The adhesive-coated material interacts mechanically with the proppant particles to prevent the flowback of particulates to the wellbore. The consolidation of a proppant also may occur via a polyurethane coating, which will slowly polymerize after the fracturing treatment because of a polyaddition process [1856]. 

Results are presented of experiments undertaken by Gaiker in the manufacture of sandwich panels containing foam cores based on PETP recycled by a solid state polyaddition process developed by M G Ricerche. Panels were produced with glass fibre-reinforced unsaturated polyester and epoxy resin skins, and allthermoplastic panels with PE, PP, PS and glass fibre-reinforced PETP skins were also produced. EVA hot melt adhesives and thermoset adhesives were evaluated in bonding glass fibre-reinforced PETP skins to the foam cores. Data are presented for the mechanical properties of the structures studied. 

The polyaddition reaction is the most commonly used type of reaction for the cure of epoxy resins. The curing agents used in this type of reaction have an active hydrogen compound, and they include amines, amides, and mercaptans. With this reaction mechanism, the most important curing agents for adhesives are primary and secondary amines containing at least three active hydrogen atoms and various di- or polyfunctional carboxylic acids and their anhydrides. 

The catalyst does not make up part of the final epoxy network structure or have a significant effect on the final properties of the cured resin. Thus, the final cured properties of the epoxy system are primarily due to the nature of the epoxy resin alone. Homopolymerization normally provides better heat and environmental resistance than polyaddition reactions. However, it also provides a more rigidly cured system, so that toughening agents or flexibilizers must often be used. In adhesive systems, homopolymerization reactions are generally utilized for heat cured, one-component formulations. 

Polyisocyanates are very reactive compounds and produce various polymers such as fibers, resins, elastomers, foams, coatings and adhesives by the reaction of polyaddition, polycondensation or stepwise polymerization. 

These two different monomers A and B with their respective reactive epoxy and amine groups can, according to the schematic in Figure 4.1, combine by a chemical reaction, they add according to the scheme A + B + A + B +. .. to the macromolecules that develop the hard (cured) adhesive layer. From this kind of polymer development the term polyaddition typical for this kind of reaction is derived. 

Since several reactive groups may exist at the respective monomer molecules A and B, net-like linked polymer molecules with thermoset adhesive layer properties occur in polyaddition. Due to the various selection possibilities regarding the chemical structure of the components A and B, curing behavior can be influenced as well. Differences are made between ... 

For the application of the two-component epoxy polyaddition adhesives described here, it is important to observe the mixing ratio indicated on the packaging (Section 3.1.2). 

The PUR (or PU) adhesives also cure according to the described mechanism of polyaddition. The reactive group at the molecules of resin component A has the following chemical structure and is called an isocyanate group ... 

Regarding their curing reaction these adhesive systems differ considerably from the described epoxy and polyurethane adhesives that are characterized by the principle of polyaddition. 

Apart from polyaddition and polymerization adhesives, a third kind of adhesive that shows a special reaction mechanism during the curing process exists. They should be mentioned for the sake of completeness, although they are less important compared to the systems mentioned so far. Their characteristic is the fact that a byproduct arises in the formation of the polymers from the monomers, which has to be considered in curing. The central molecule of these adhesives is formaldehyde... 

Hardener Adhesive component, triggering the chemical setting of an adhesive by polymerization, polycondensation or polyaddition, added or admixed to the adhesive resin, often also called second component . 

Polycondensation In contrast to polyaddition and polymerization adhesives, a byproduct, for example, water, develops during curing. Apart from the application of heat, adequate pressurizing of the adherends is required (see autoclave). 

Polymer Chemical compound consisting of monomers or prepolymers developed by polyaddition, polycondensation or polymerization, usually in solid state. In cured condition, adhesives generally consist of polymers. 

The aspects relevant to the use of rosin as such, or one of the derivatives arising from its appropriate chemical modification as monomer or comonomer [12-14], have to do with the synthesis of a variety of materials based on polycondensations and polyaddition reactions of structures bearing such moieties as primary amines, maleimides, epoxies, alkenyls and, of course, carboxylic acids. These polymers find applications in paper sizing, adhesion and tack, emulsification, coatings, drug delivery and printing inks. 

Diisocyanates are an important class of chemicals of commercial interest, which are frequently used in the manufacture of indoor materials. such as adhesives, coatings, foams and rubbers (Ulrich, 1989). In some types of particle board, the diisocyanates have replaced formaldehyde. Isocyanates are characterized by the electrophilic -N=C=0 group, which can easily react with molecules containing hydroxy groups, such as water or alcohols. On hydrolysis with water, primary amines are formed, while a reaction with alcohols leads to carbamates (urethanes). Polyurethane (PUR) products are then obtained from a polyaddition of diisocyanate and diol components. Compounds commonly used in industrial surface technology are 4,4 -diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI). The diisocyanate monomers are known as respiratory sensitizers and cause irritation of eyes, skin and mucous membrane. Therefore, polyisocyanates such as HDI-biuret and HDI-isocyanurate with a monomer content <0.5 % are used for industrial applications, and isocyanate monomers will not achieve high concentrations in ambient air. Nevertheless, it is desirable to measure even trace emissions from materials in private dwellings. 

Polyurethane bulk and thin-film samples are prepared from a two-part PU adhesive formed by polyaddition of Bayer Desmodur CD (89% diphenylmethane-4,4 -diisocyanate 1 with 11% uretoneimine triisocyanate 2 as additive) with a polyol mixture of Bayer Desmophen 2060BD (linear poly(propylene ether) diol... 

Epoxy resins [1] are duroplastics. Polyaddition initially produces an essentially linear macromolecule that still possesses numerous OH groups. This addition product is either placed in a mold or applied to surfaces in liquid form. This is followed by chemical curing, and this process often involves heat application. Because of their reliable adhesion to metallic substrates, epoxy resins are excellent primer coats for automobile paints and can also be used as metal adhesives. A further important field of application is electronics, where they serve as structural... 

Adhesives and sealants are manufactured from a variety of polymers. Their selection and their combinations used impact solvent selection. Most solvent systems are designed to optimize the solubility of the primary polymer. Adhesives can be divided into ones which bond by chemical reaction and ones which bond due to physical processes. Chemically reactive adhesives are further divided into three more categories for those that bond through polymerization, polyaddition, or polycondensation. Physically bonding adhesives include pressure sensitive and contact adhesives, melt, or solution adhesives, and plastisols. Polymerization adhesives are composed of cyanoacrylates (no solvents), anaerobic adhesives (do not contain solvents but require primers for plastics and some metals which are solutions of copper naphthenate), UV-curable adhesives (solvent-free compositions of polyurethanes and epoxy), rubber modified adhesives (variety solvents discussed below). 

Polyaddition adhesives include epoxy and polyurethane polymers which can either be 100% solids, water-based, reactive or non-reactive hot melts or contain solvents mostly to regulate viscosity. Typical solvents include methyl ethyl ketone, acetone, mineral spirits, toluene, and xylene. Polycondensation adhesives include phenol-formaldehyde resin, polyamides, polyesters, silicones and polyimides. With the exception of polyesters (which require ethanol and N-methylpyrrolidone as solvents) and polyimides (which require... 

PUU with PC group introducing during polyaddition Platelet adhesion [96]... 

Curing the setting of an adhesive by chemical reaction (polymerization, polycondensation, polyaddition). 

Formation and Cross-linking of the Adhesive film by Polyaddition. 

Before setting, reactive adhesives consist predominantly of reactive low molecular mass monomers and/or oligomers that, during curing, are converted by chemical reactions into high molecular mass, often three-dimensionally cross-linked polymers. Reactive adhesives can be divided into polymerization, polyaddition, and polycondensation adhesives. Vulcanizing reactive adhesives are a special group. 

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