Adhesion Performance

Adhesion Life. A second key factor in determining the durabHity of a sealant is the abHity of the sealant to adhere to the substrate through its lifetime. A sealant may have exceHent resistance to uv effects, but if it has poor adhesion performance and faHs adhesively, it is of Httie use. The same can be said of a sealant with superior adhesion characteristics but poor resistance to uv. Either situation results in a short performance life. 

Another way to determine durabHity is to find successfuHy sealed, existing field instaHations. Sealant manufacturers often have case histories of successful instaHations. Adhesion performance can vary widely with sealant type, substrate type, and cleaning method. Eor this reason, it is important to understand the sealant s sensitivity to cleaning practices. Often with difficult-to-adhere substrates, a primer is used. Sealant manufacturers can provide recommendations as to which substrates require primers, what type of primers should be used, and how they should be appHed. 

Numerous reports of comparable levels of success in correlating adhesion performance with the Scatchard-Hildebrand solubility parameters can be found in the literature [116,120-127], but failures of this approach have also been documented [128-132J. Particularly revealing are cases in which failure was attributed to the inability of the Scatchard-Hildebrand solubility parameter to adequately account for donor-acceptor (acid-base) interactions [130,132]. Useful reviews of the use of solubility parameters for choosing block copolymer compatibilizers have been prepared by Ohm [133] and by Gaylord [134]. General reviews of the use of solubility parameters in polymer science have been given by Barton [135], Van Krevelen [114], and Hansen [136]. 

Tackifiers and modifiers are generally added to improve the adhesive performance of synthetic elastomers. All resins added to an adhesive formulation modify their properties (viscosity, open time, tack) and therefore these resins are also called... 

However, other properties are very important in adhesive performance, such as the solubility, the compatibility, the chemical and thermal stability, the viscosity, and the molecular weight and molecular weight distribution. 

With rubber base adhesives, it is necessary to prevent their properties from changing during service life. Oxidative changes induced by thermal, ozone exposure and UV light can dramatically affect service life of rubber base adhesives. More precisely, the rubber and the resin are quite susceptible to oxidative degradation. Environmental and physical factors exert detrimental effects on rubber base adhesive performance. These effects can be mitigated by the incorporation of low levels of stabilizers during the fabrication process of the adhesive. 

NR adhesives perform adequately under peeling stresses. The peel strength can vary from a few N/m in PSA formulations to substrate tear in vulcanized compounds used in hose, belting and tire products. 

A detailed study of adhesion or design of the adhesive performance of a silicone adherent material requires that all possible mechanisms of adhesion be evaluated. The following section focuses on the mechanisms of adhesion that affect Go-... 

Because they are acrylic monomers, alkyl cyanoacrylate esters still require the addition of radical polymerization inhibitors, such as hydroquinone or hindered phenols, to prevent radically induced polymerization over time [3j. Since basic initiation of alkyl cyanoacrylate monomers is the predominant polymerization mechanism, large quantities of free radical inhibitors can be added, with little or no effect on adhesive performance. 

Eagland, D. (1988), Adhesives and adhesive performance The silent background, Endeavour 12,183-191. 

Adhesive Performance of Surface-Activated Polyolefin Surfaces with Respect to Reinforcement Resins... 

Polyester cloth-backed flat PP sheets (fleece-backed sheets) are normally used to manufacture large reservoirs for liquid containment purposes. Typically, such reservoirs are reinforced on the outside with fiberglass. The polyester mat backing serves as an adhesion key between the PP and the fiberglass resin. Fluorine surface activation can be used as a substitute for the fleece-backed material at a considerable cost-saving. Table 16.12 shows a comparison between the adhesive performance of the materials with two polyester resins. 

Composition of Surface Film and Adhesion of UVC Lacquer. As the deadhesion of UVC lacquer has occurred at the interface between the substrate and lacquer (or in the oil film), both chromium oxide and oil film affect the adhesion performance. From this standpoint, the adhesion of the UVC lacquer is summarized in Fig. 9. When chromium oxide is hydrated to a high degree or surface oil is oxidized to a greater level, the adhesion of the UVC lacquer does not deteriorate. 

Compound 9, which Is not detectably rehydrated by water or attacked by simple alcohols, Is also converted In high yield to cyclic acetals H at 70 C, pointing again to the significant thermodynamic driving force of cyclic acetal formation. This strongly favored acetal reaction Is one explanation for the excellent adhesion performance of this system on cellulosics and glass. 

Moon SH, Chiche A, Forster AM, Zhang WH, Stafford CM (2005) Evaluation of temperature-dependent adhesive performance via combinatorial probe tack measurements. Rev Sci lustrum 76 062210... 

The objectives of the extender-filler in glue mixes are to improve the adhesive performance, to help control the mix viscosity and to conserve the phenolic and urea adhesives. These fillers and extenders serve specific needs in these glue mixes. They extend the resin solution from its original non-volatile state to lower levels, such as 26 percent resin solids in the mix. They also function as a means of maintaining the very low resin molecular weight and size molecules on the surface when they are applied to the veneer to prevent over-penetration prior to hot press pressure and temperature which gels the resin to a permanently set condition. 

High adhesive performance at low molecular weight and viscosity was achieved using [PS-fo-P(ethylene/butylene)]2PI2 and [PS-b-P(ethylene/buty-... 

Yoon TH, McGrath JE (1992) Enhanced adhesive performance of thermoplastic po-ly(imide siloxane) segmented copolymer with peek-graphite composites by gas plasma treatment. High Perform Polym 4(4) 203... 

Yoon TH, Arnold CA, McGrath JE (1989) Titanium 6/4 single lap shear adhesive performance of polyimide homopolymers and poly(siloxane imide) segmented copolymers. Mater Res Soc Symp Proc 153 (Interfaces Polym Met Ceram) 211... 

One of the disadvantages of CTBN-epoxy adhesives has been their high viscosity, which limits additional formulation options. Recently new adducts, such as EPON 58003 and RSM-2577 from Resolution Performance Products LLC, have been introduced which have significantly lower viscosities.19 In addition, lower concentrations of these new CBTN-epoxy adducts are generally required to achieve equivalent adhesive performance. 

Table 14.4 presents formulation information for bisphenol A and polyfunctional epoxy resin emulsions that are cured with an aliphatic amidoamine curing agent. Adhesive performance data are also provided for substrates common to the automotive industry. Both formulas are based on a 1 1 epoxy-amine stoichiometry and they are reduced to 45 percent nonvolatiles with water. The working life of each system is several hours at room temperature. 

For elevated-temperature cures, however, dicyandiamide and melamine curing reactions have been shown to be beneficial in epoxy-based adhesives when used on copper substrates. These epoxy adhesives perform about as well in copper joints as in aluminum or steel joints. The formulations show significantly increased time to adhesive failure on either bare or alkaline permanganate-treated copper.30... 

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