Solution-applied polymer adhesive

There are relatively few investigations into the physical and chemical nature of the interaction. A solution-applied polymer adhesive will lose its solvent on setting, so the bond line will be mostly air filled, while a dispersion will fill more of the bond line, and a reaction-type adhesive will completely fill the bond line, but with some shrinkage (Figure 5.8). 

It is an industrial polymerization technique, wherein a monomer is dissolved in a nonreactive solvent that contains a catalyst. In this method, both the monomer and the resulting polymer are soluble in the solvent. The heat released during the reaction is absorbed by the solvent and thus reduces the reaction rate. Once the maximum or desired conversion is reached, excess solvent is to be removed in order to obtain the pure polymer. The products obtained by this method are relatively low molecular weights because of the possibility of chain transfer. This process is suitable for the production of wet polymers since the removal of excess solvent is difficult and also the solvent is occluded and firmly traps the polymer. Therefore, this polymerization technique is applied when solutions of polymers are required (for ready-made use) for technical applications such as lacquers, adhesives, and surface coatings. 

A reactive adhesive is used by applying the adhesive (polymer solution) to one of the surfaces to be bonded and the activator frequently insolution is applied in a thin film to the opposing surface. In some types of reactive adhesives the two films may be left open and unbonded for many hours without adverse effects on the resulting bond (9). ... 

When M < Me, the role of entanglements is no longer present and Eqns. 2 and 3 cannot be used since Gie = 0 at Me. However, the Nail solution applies for weak interfaces (see Eqn. 3 in Polymer-polymer adhesion models) and the chain segments simply pullout at fracture such that (Gic-Gq) M, where Gq is the surface energy term, and we obtain. 

This class of adhesives consists of solutions of polymers, resins and where applicable, other additives in organic solvents. They have low to moderate viscosities, with solid content ranging from 15% to 40% in weight, corresponding to a solvent content of 60-85%. They are applied as PSA or contact adhesives. 

In order to have efficient transfer, the substrate materials should have stronger adhesion to the assembled material (in this case PANi) than that to the template substrate (e.g. silicon wafer). In addition, the substrate materials should be fluid-like, such as concentrated polymeric solutions or polymer melts, so that the normal force can be applied uniformly across the contact area. 

Another major area of use is in the field of adhesives. The main attractions of the material are the absence of a need for mastication, easy solvation of the polymer, which is supplied in a crumb form, the production of low-viscosity solutions and high joint strength. In conjunction with aromatic resins they are used for contact adhesives whilst with aliphatic resin additives they are used for permanently tacky pressure-sensitive adhesives. In addition to being applied from solution they may be applied as a hot melt. 

One of the most common rubber adhesives are the contact adhesives. These adhesives are bonded by a diffusion process in which the adhesive is applied to both surfaces to be joined. To achieve optimum diffusion of polymer chains, two requirements are necessary (1) a high wettability of the adhesive by the smooth or rough substrate surfaces (2) adequate viscosity (in general rheological properties) of the adhesive to penetrate into the voids and roughness of the substrate surfaces. Both requirements can be easily achieved in liquid adhesives. Once the adhesive solution is applied on the surface of the substrate, spontaneous or forced evaporation of the solvent or water must be produced to obtain a dry adhesive film. In most cases, the dry-contact adhesive film contains residual solvent (about 5-10 wt%), which usually acts as a plasticizer. The time necessary... 

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