Adhesive gap-filling

Fillers (calcium carbonate, calcium sulfate, aluminum oxide, bentonites, wood flour) increase the solid content of the dispersion. They are added up to 50%, based on PVAc. The purpose of the addition is the reduction of the penetration depth, provision of thixotropic behavior of the adhesive, gap filling properties and the reduction of the costs. Disadvantage can be the increase of the white point and a possible higher tool wear. 

Adhesive, gap-filling—An adhesive subject to low shrinkage in setting,... 

Solvent-borne adhesives. Although the NR polymer is inherently tacky, tack-ifying resins are generally added to improve bonding to polar surfaces. Because the solids content in these adhesives is lower than 35 wt%, they are not suitable for gap filling. The quick-grab (cements) adhesives are particular because they contain about 65 wt% rubber, and set within a few seconds under finger pressure. 

EP adhesives come as fabric- or glass-supported films, pastes, and viscous liquids [208,212]. They are often supplied in solvent. The pastes are most useful in situations where gap filling is required [208]. A wide variety of epoxies are available. Some of the producers are Bloomingdale, Shell (EponICI [formerly Hysol] (Hysol ), CIBA-Geigy (Araldite )i 3M (Scotch Weld ), and Amicom (Uniset ). There are many more. 

Since real surfaces are not smooth or perfectly flat and most epoxy adhesives are viscoelastic fluids, it is necessary to understand the effects of surface roughness on joint strength. A viscous liquid can appear to spread over a solid surface and yet leave many gas pockets or voids in small surface pores and crevices. Even if the liquid does spread spontaneously over the solid, there is no certainty that it will have sufficient time to fill in all the voids and displace the air. The gap-filling mechanism is generally competing with the setting mechanism of the liquid. 

Check pretreatment process use clean solvent and wiping rags. Wiping rags must not be made from synthetic fiber. Make sure cleaned parts are not touched before bonding. Cover stored parts to prevent dust from settling on them Replace resin. Check solids content. Clean resin tank Check for distortion correct or discard distorted components. If distorted components must be used, try adhesive with better gap-filling properties... 

D 3931 Test Method for Determining Strength of Gap Filling Adhesive Bonds in... 

The fourth research category mentioned in the NFPA review relates to enhancing the performance of established natural adhesives for wood bonding to provide durability equivalent to that of the synthetics. This is especially desirable where natural adhesives presently offer significant performance advantages over synthetics in terms of fast hot-press times, short-cycle cold cure, or improved gap-filling properties. Specific examples would include ... 

Straight casein lumber laminating adhesives for their superior open and closed beam assembly time tolerance and gap-filling properties. 

The addition of thickening agents to paints, pharmaceutical products and adhesives has many functions and the most important is for flow behaviour, gap filling and wetting ability for paints and adhesives. They are added at variable concentrations to pharmaceutical... 

Surfaces must be flat the low viscosity adhesive system has poor gap-filling properties Potential (and actual) toxicity problems, due to monomers and activators. 

Products classified as first generation are still on the market and are sold primarily for bonding thermoplastics. They provide excellent gap filling characteristics, rapid cure and adhesion, and are generally stronger than the substrates themselves. 

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