Reticulating adhesive

Applications such as the noise attenuation panels that line engine inlets and exhausts require a special form of high temperature adhesive known as a reticulating adhesive. These bond honeycomb sandwich assemblies have inner facesheets with numerous small holes (Fig. 13). The holes and underlying honeycomb core... 

Reticulating Adhesive - Usually applied to unsupported film adhesives (i.e. with no textile carrier) where, during cure at higher temperatures, surface tension pulls the softened adhesive back to form fillets at corners. This property is useful when bonding face skins to honeycomb core materials. 

At the same time, natural adhesives such as casein glues, animal glue and polysaccharide gums have gradually been replaced by synthetic adhesives vinyl thermoplastic adhesives [poly(vinyl acetate)], adhesives obtained by reticulation in situ of two components (as epoxy resins), represent very important materials in this field. 

The big question is whether the seemingly ideal properties of a reticulated foam will be maintained when we start to change the chemistry (for cell adhesion, extraction, etc.). Changes in the polyol or isocyanate will inevitably affect its physical properties. A balance of chemical activity would have to be established. In many cases, this balance will degrade the desirable properties. An answer is the recent development of a composite of a chemistry designed according to desirable chemical features grafted to a reticulated scaffold. " Such a composite was developed and patented and it will be cited as an example for several applications. 

FIGURE 6.5 CeU adhesion on a hydrophilic polyurethane-grafted reticulated foam imbibed with fibronectin. 

It was hypothesized that the imbibed fibronectin may have been washed out by the medium, and this could have affected adhesion in sections of the disc. To eliminate this possibility, samples of the composite were made with gelatin dissolved in the aqueous phase. They were then emulsified with the hydrophilic prepolymer and applied to the reticulated foam. The result was covalent bonding of some of the protein into the polymer backbone, thus making it immune to washout. Figure 6.6 reports counts of endothelial cells cultured on this formulation and effects of sterilization method compared to controls without gelatin. 

These characteristics indicate in particular that one can improve the adhesion between the brush or the pseudo-brush and the elastomer by decreasing the number of monomers between crosslinks, Nc. This result, which is a direct consequence of the de Gennes analogy between a network and a melt (see Sect. 4.1), cannot be correct for too small values of Nc, that is for too highly reticulated networks. For pseudo-brushes, it has been conjectured [107] that Eqs. (20) and (21)... 

Bacterial Adhesion. Bacteria often adhere to interfaces and the resulting biofilms can cause a nuisance on ship hulls, to water reticulation and hydro-electric pipelines and in heat exchangers... 

Adhesives for Film Reticulation," SAMPE, "Materials Review-75", 7, 10/14-16/1975, Albuquerque, NM... 

If the melt viscosity is too high, the polymer will not flow into the substrate and an inadequate bond results if too low, strike through or sfiike back can occur, resulting in a stiff substrate and a bond starved of adhesive. Thermal stability must be adequate should the polymer be kept molten in the application for long periods. The physical form is important for example, a discontinuous coating is preferred in some applications to give products with a soft handle, and the ability to form reticulated films is therefore a consideration. 

Trent 900 In the construction of the blocker doors for the Trent 900, Redux 322 is first reticulated onto the pre-cured and perforated carbon skin. This is then bonded directly to the honeycomb. Finally, uncured carbon prepreg skins are cobonded onto the honeycomb to complete the sandwich panel. (Note It is accepted that reticulation of the adhesive film onto the perforated skin gives better acoustic deadening properties than if the adhesive were to be reticulated onto the core. However, both methods are used, depending on the engine.)... 

CFM 56 Here both aluminium and carbon reinforced composite sandwich panel constructions are used. An aluminium bondment forms the inner structure of the acoustic panel. Perforated, Redux 119 primed skins are bonded to aluminium honeycomb, Redux 319 film adhesive having first been reticulated onto the core. The outer structure is a conventional bondment of a carbon reinforced composite skin bonded to the core. 

Embraer 145 The air intakes comprise conventionally constructed acoustic sandwich panels where pretreated and primed perforated aluminium skins are bonded to aluminium honeycomb, Redux 319 film adhesive having first been reticulated onto the core. 

Reticulated structural film adhesive Surfacing film... 

Of all the current civil engines. Rolls Royce s Trent 7(X) does have high temperature requirements. The IFS of the thrust reversers has to operate for considerable periods of time at elevated temperatures (> 140-150°C). The component manufacturers, Hurel-Hispano, believe that this is asking too much of an epoxy adhesive and hence a Cytec-Fiberite BMI film adhesive (FM-2550) is used to bond this structure. Here the BMI adhesive is reticulated onto phosphoric acid anodised aluminium honeycomb. The core is then bonded directly onto pre-cured carbon-reinforced BMI laminates to form a sandwich structure, one of the skins being perforated to produce an acoustic panel , which helps reduce engine noise. 

Kapton tape is the most appreciated with respect to the high temperature resistance of Kapton, intensively used as dielectric insulator of solar cell panels. The Kapton tape is associated with acrylic or fully reticulated silicon adhesives outgassing is the driving factor for the choice of the adhesive part of the tape, the unwanted event being the bubbling between the tape and the adherend under vacuum. 

ZrB -SiC based foams have been produced using aqueous slurry prepared at 48 vol% solid stabilized with Dolapix PC33 (1.5 wt%). Polyacrylic acid at a high molecular weight (200000 Da) was added to the slurry to ease the wetting and adhesion of the slip on the templates. The templates were commercially available PU ester reticulate foams and cellulose sponges. 

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