TIME-DEPENDENT ADHESION INDUCED PHENOMENA - THE FLOW OF A COMPLIANT SLICONE-POLYESTER COPOLYMER SUBSTRATE AVER RIGID MICROMETER SIZE GOLD AND POLYSTYRENE PARTICLES

A polyester-polydimethylsiloxane block copolymer substrate (Young's modulus of approximately 9.2 x 10(6)N/m(2)) was observed by SEM to gradually creep over higher modulus gold and polystyrene micrometer sized particles in contact with its surface. The particle/substrate and particle/particle interfaces were examined shortly after particle deposition and again at various intervals up to a month later. SEM micrographs clearly showed an increase in the size of the contact menisci with time (for periods up to approximately two weeks) at both sets of interfaces. After only one week the gold particles appeared to be completely encapsulated by the substrate. These time-dependent observations confirm the plastic deformation mechanism proposed previously to explain similar observations on micrometer- and submicrometer-sized glass, polystyrene, and poly-vinylidene fluoride beads contacting the same substrate (L.P. DeMejo, D.S. Rimai, J. Chen, and R.C. Bowen, J. Adhesion 39, 61 (1992)).