Sunday, December 26, 2010

Nylon Used

The adhesion of nylon, especially to metal, when used by the hot melt technique can be substantially increased by using a thermosetting phenol formaldehyde resin in association with it. This combination of nylon and a phenolic resin is not included in the section dealing with two polymer adhesives, because very little phenolic resin is used (it may as low as one percent) and the quantity of phenolic resin is to small to modify the physical properties of the nylon except at the adherent interface, where it increses adhesion perhaps merely by facilitating wetting.

The most efficient way of using a nylon/PF adhesive system is to "prime" the face of each adherend with a thin coating of phenolic resin (a thick coating reduces adhesion), evaporate the solvent, and interpose a thin film of the sufficient to melt the nylon and for sufficient time to cure the phenolic resin. In the use of a soluble nylon such as N-alkoxy methylpolyamide, a solution containing both the nylon and the phenolic resin can be made and applied in the normal way.

Unlike the phenolic/acetal and phenolic/nitrile rubber adhesives, the nylon must reach a minimum (threshold) temperature for satisfactory bonding. These threshold temperature are important because, being substantially crystalline the nylons have definite melting points which must be reached - preferably slightly exceeded - to ensure adhesion. These melting points are high, especially in the case of the more useful types such as nylon II (melting point 185 oC, nylon 610 (220 oC) and nylon 6/6 (260 oC).