RHEOLOGICAL BEHAVIOR OF 2-PHASE AND 3-PHASE FIBER SUSPENSIONS

The theology of two polyamide 6.6 systems filled with long glass fiber s, as well as that of a three-phase polyamide 6.6-glass fiber-gas bubb le system, was studied using capillary rheometry. To investigate the i nfluence of fiber concentration, the shear and extensional viscosities were determined for both 30 and 40 vol% fiber filled suspensions as w ell as for the base polymer. Comparison revealed a modest increase in both the shear and extensional viscosities with increased fiber fracti on. The shear viscosities, eta(s), of both suspensions are shown to be close to one order of magnitude greater than the base matrix fluid vi scosity, eta. However, the extensional viscosities, eta(E), of the sus pensions are determined to be approximately four orders of magnitude g reater than the shear viscosity of the matrix fluid for strain rates f rom 10(0) s(-1) to 10(2) s(-1). The addition of a gas bubble phase to the neat polymer and polymer-fiber suspensions was accomplished throug h the decomposition of various percentages of an azodicarbonamide blow ing agent. The presence of gas bubbles resulted in reduced shear and e xtensional viscosities for both the neat and fiber-filled polyamide wi th greater reductions observed for the neat polyamide. Greater viscosi ty reductions were observed as the blowing agent concentration was inc reased.