THE INFLUENCE OF PHYSICAL-PROPERTIES OF THE MATERIALS IN CONTACT ON THE ADHESION STRENGTH OF PARTICLES OF SALMETEROL BASE AND SALMETEROL SALTS TO VARIOUS SUBSTRATE MATERIALS

The adhesion force between salmeterol base and a series of chemically related salmeterol salts to various macroscopically flat substrate mat erials has been investigated. The substrates varied in their surface r oughness, surface free energy, and Young's modulus. The results sugges t that the adhesion force of a particulate material to a macroscopical ly hat substrate depends on the physical properties of the substrate s uch as surface roughness, surface free energy and Young's modulus, but there is no universal relationship. The properties of both the partic les and the substrates have to be considered for possible interactions . A knowledge of the Hansen-solubility parameters of the particulate m aterials allows a prediction of rank order of the adhesion strength of particulate materials to a given substrate, but requires a knowledge of similar parameters for the substrate material also. The general rul e is that materials which have, for example, similar hydrogen bonding terms or similar dispersion terms adhere strongly to each other, where as the least adhesion strength will be obtained between materials of d ifferent polarities. However, the rank order of adhesion strength of a given particulate material to various macroscopically flat substrates cannot be predicted theoretically Only the experimental assessment of the adhesion force allows a judgement as to whether or not a substrat e material is the appropriate choice.