Reactive elements adhesion

The reactive hotmelt adhesives retain a high level of flexibility and dynamic load-bearing capacities even after crossUnking and are used to join plastics to one another as well as to wood (furniture industry), glass (construction industry), aluminum (sandwich elements), and painted surfaces. Typical applications include window casement sheathing, foil laminations, clip fasteners, bookbinding, textile... 

At 1200 °C and 1300 °C, incorporation of a reactive element in Fe3Al as an oxide dispersion is more effective in improving scale adhesion than a comparable elemental addition. It is proposed that this is due to strengthening of the substrate. 

High reactivity elements (RE e.g., cerium, yttrium, zirconium, hafnium) are sometimes added to the Fe-Cr-Al matrix these help the formation of the alumina protective layer that is, they speed up the transition from the less to the more stable crystallographic lattices [5,6] and increase its adhesion to the substrate. Secondly this action is assisted by the precipitation of "pegs" made up by fhe oxides of fhe reactive elemenfs (RE), partially immersed both in the substrate and in the scale of continuous superficial oxide [6]. However, fhe same authors state that the formation of fhe pegs is nof vital for the resistance to the scaling off of fhe layers of superficial oxide. It is important to note that its crystallographic type is a-Al203, which is much more effective than the 5, y, or 9 types. 

Single-component solventless reactive liquid adhesives where the diisocyanate group is the key bonding element in a prepolymer base. 

Y ions into an aluminide ((3-NiAl) on a nickel-base alloy and confirm that while initially the implanted reactive element effectively imparts increased scale adhesion, both in air and oxygen at 1000 -1200 C, the beneficial influence is not long lasting. They attributed this loss to the influence of the substrate Ni-base superalloy, since lasting benefits of reduced rates of oxidation and improved scale adherence were maintained when Y was implanted into bulk 3-NiAl (Jedlinski and Mrowec 1987). 

The reader is directed to three comprehensive reviews and a conference publication, dealing with the reactive-element effects on oxidation Whittle and Stringer (1980), Stott and Wood (1987), Moon and Bennett (1989) and Lang (1989), thus only a broad summary of proposed mechanisms, classified as either chemical, physical or mechanical effects is presented here. These may be further, or even alternatively, sub-divided into effects relating to (i) initial oxidation, (ii) growth-rate, (iii) scale adhesion, or (iv) cracking. 

Hou, P.Y., and J. Stringer, 1988, Ion-implantation of Reactive Elements in Improving Adhesion of Thermally Grown Chromia Scales Report LBL -25031, April 1988 (Lawrence Berkeley Laboratory, Berkeley, CA). 

Strawbridge A and Hou P Y (1994), The Role of Reactive Elements in Oxide Scale Adhesion, Mater High Temp, 12, 177-181. 

Hou P Y, Stringer J, The effect of reactive element additions on the selective oxidation, growth and adhesion of chromia scales . Mater Sci Eng A, 1995, 202, 1-10... 

Lees D G, On the reasons for the effects of dispersions of stable oxides and additions of reactive elements on the adhesion and growth-mechanisms of chromia and alumina scales - the sulfur effect , OxidMet, 1987, 27(1-2), 75-81... 

Additions of reactive elements (RE), such as Y, Hf and Zr, to MCrAlY bond coats enhance the oxide adhesion. Y and Hf promote the formation of... 

Conceivably, many compounds of inorganic elements have chemical reactivity that could contribute to improved adhesion to mineral surfaces. A fairly wide range of compounds, not restricted to any particular group in the periodic table, have been proposed as coupling agents as is shown in the following list ... 

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