Bonds wetting

NR adhesives can be divided in two types wet bonding and dry bonding. Wet bonding adhesives are applied on substrates in a fluid state, the bond being formed by drying. The dry bonding NR adhesives are pressure-sensitive adhesives because the bond is created under pressure. 

One-sided bonding (wet bonding) In this procedure, the adhesive is applied to one adherend only. This is recommendable for bonding of solvent-permeable, respectively, absorbent materials (leather, textiles, wood products). In this case, complete solvent evaporation is not required. 

Dry zAX-trans- and 13-c/5-retinals show no fluorescence in dry alkane solvents when at low concentration, but do so when hydrogen-bonded (wet) or in sufficiently high concentration to be present as dimeric aggregates/ Solid films of all-tran5-, 9-cis-, and 13-cw-retinal are fluorescent at room temperature. 

Wetting - The spreading out (and sometimes absorption) of a fluid onto (or into) a surface. In adhesive bonding, wetting occurs when the surface... 

A two part epoxy for structurally demanding applications, offering a fast cure, excellent resistance to vibration or impact loading. Particularly suitable for bonding wet-lay, SMC or BMC components. 

The primary particles produced after dispersion are subdivided into smaller units by milling or comminution (a process that requires rupture of bonds). Wet milling can be achieved using ball mills, bead mills (ceramic balls or beads are normally used to avoid contamination) or colloid mills. Again the milling conditions must be adjusted to prevent heat and/or foam formation. The role of the dispersing agent (surfactant) in... 

Structured fibre Needlefelts, bonded, wet-laid (paper) spun (spun bonded, melt blown)... 

The first industrial hardboard was developed by W. Mason in the mid-1920s he found that a mat of wet fiber pressed in a hot press would produce a self-bonded flat panel with good strength, durabiUty, and stabiUty. The product was patented in 1928, trademarked as Masonite, and commercial production began. Over time several other processes for producing hardboards have been developed from modifications of the original process. Brief descriptions of these processes foUow and a flow chart of the process is shown in Figure 5. 

A higher density sol—gel abrasive, produced by the introduction of seed crystaUites formed by wet-milling with high alumina media or by introduction of submicrometer a-alumina particles, was patented (28) and designated Norton SG. The microstmcture of this abrasive consists of submicrometer a-alumina crystals (Fig. 1) and its bulk density approaches that of fused alumina. Norton SG has proven to be an exceptional performer in coated and bonded abrasive products it was awarded the 1989 ASM Engineering Materials Achievement Award (29). 

The mounting cup (ferrule for botde valves) mechanically joins the valve to the container. The mounting cup may be made from a variety of materials, but is typically tin-plated steel coated on the underside. It contains the gasket which provides the seal. Soft gasketing material is appHed wet and bonded in place or, more frequently in larger cans, cut mbber, polyethylene, or polypropylene gaskets are used. 

The crystal stmcture of PPT is pseudo-orthorhombic (essentially monoclinic) with a = 0.785/nm b = 0.515/nm c (fiber axis) = 1.28/nm and d = 90°. The molecules are arranged in parallel hydrogen-bonded sheets. There are two chains in a unit cell and the theoretical crystal density is 1.48 g/cm. The observed fiber density is 1.45 g/cm. An interesting property of the dry jet-wet spun fibers is the lateral crystalline order. Based on electron microscopy studies of peeled sections of Kevlar-49, the supramolecular stmcture consists of radially oriented crystaUites. The fiber contains a pleated stmcture along the fiber axis, with a periodicity of 500—600 nm. 

---