The viscoe-lastic be havior of the samples was determined by
oscillatory tests evaluating the elastic modulus G 0 and the viscous
modulus G00 (Kealy, 2006). The tangent of phase shift or phase angle
(tan d ¼ G00/G0) was also evaluated. All measurements were made in
duplicate at 20 C in a Haake RS 800 oscillatory rheo meter equipped
with a temperature control sensor DC 50 using parallel plates
35 mm(PP 35/S), with a gap between plates of 1.5 mm. The surfaces
of both upper and lower plates were serrated to remove the possibility
of slip at the boundary.