Gap-filling properties

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. 

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... 

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. 

Recently, copper plating has found an important new application in metallizing interconnects on semiconductor wafers3. Here, a specially designed and dedicated tool is used to plate well-defined disk-shaped silicon wafers. A very uniform copper layer must be electrodeposited with excellent gap-fill properties onto a resistive seed layer through contacts along the circumference of the wafer. The new process poses numerous critical challenges ... 

The monosilic acid thus formed condenses to form a concentrated solution on the surface of the substrate. It is the fluidity of the solution that provides the planarizing and gap-filling properties. Subsequent polymerization (Eq. 5.12) and dehydration (Eq. 5.13) provides the eventual Si02 layer. 

Total impregnation. The infusion of consolidant becomes necessary when the original fabric is degraded to the point of being dissociated to an amorphic substance. While acrylic and vinyl resins are preferable for their solvency after polymerization, cross-linking epoxides and polyesters may be necessary for their cohesive and gap-filling properties. 

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

As mentioned previously, neat pMDI does not have gap filling capability for wood bonding because of its low viscosity and propensity for deep penetration. Consequently, neat pMDI is not used for applications such as plywood, laminated veneer lumber, etc. However, gap filling properties may be achieved by modifying pMDI with a wide variety of difunctional or polyfunctional polyols. Viscosity and NCO content are easily tailored to meet many application requirements. 

Adhesive, foaming—An adhesive designed to foam in situ, after application, in order to provide extensive gap-filling properties. 

The parts to be bonded should be unstressed and, if necessary, annealed. The surfaces should be smooth, mate well, and have tight tolerances. Although bodied cements will provide gap filling properties, they should not be considered a final solution for poorly matched parts. 

Methylene chloride is a very fast solvent cement for polycarbonate. This solvent is recommended only for temperature chmate zones and on small areas. A mixture of 60 percent methylene chloride and 40 percent ethylene chloride is slower drying and the most common solvent cement used. Ethylene chloride is recommended in very hot climates. These solvents can be bodied with 1 to 5 percent polycarbonate resin where gap filling properties are important. A pressure of 200 psi is recommended. 

Some recent patents that relate to this work include the reaction products of isocyanates with polyamines or polyols, and special urethane acrylates for high-temperature service or gap-filling properties. ... 

A thixotropic two component epoxy assembly adhesive for application by trowel or roller, with good gap filling properties and offering a long open time. 

PVC adhesives, usually consisting of solutions of post-chlorinated PVC in methylene chloride, are used in the case of inorganic acids as flow-through media in PVC pipe because of their better chemical resistance. Since PVC adhesives have no gap-filling properties a special application technique is required. This priming method is little used today. 

Numerous industrial and domestic applications requiring Instant bonding for metals, plastics, rubbers, wood, glass and ceramics. Widely used for the precision assembly of small mechanical and electrical components, i.e. small bond areas. Special grades are available for bonding difficult materials (porous, polyethylene, some elastomers, etc.). Gel products with improved gap filling properties are also available. 

Manufacturers Comments RT cure. Coverage 0.09 - 0.25 kg.nr Manufacturers Comments RT cure. Non-slumping filled adhesive with excellent gap-filling properties. Also exists in fast-cure (PD7962PA) and slow cure (1186A) versions. 74% Non-volatiles. ... 

The major part of the market for ceramic tile adhesives is held by formulations based on a filled polyvinyl acetate latex, but natural rubber latex is still used as a base, particularly where the adhesive is to perform under damp conditions. Formulations II and III give examples. Tile adhesives need to be stiffer than most other applications, and this effect is provided by the clay filler, which also reduces material costs and imparts gap filling properties. Cost may be further reduced by increasing the level of clay to 250 pphr, although performance will be reduced. The resin serves to improve bond strength and water resistance. 

Fillers. Apart from carbon black, fillers do not play a large part in the formulation of solution adhesives. Small additions of clay or whiting are sometimes used to control viscosity, but usually this is achieved by solvent blending. An exception to this is the traditional use of zinc oxide in surgical plasters and tapes and of whitings or clays where there is a need for some gap-filling property. Solvent adhesives are not, in essence, good gap fillers, however. 

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