MULTICOMPONENT LATEX IPN MATERIALS .2. DAMPING AND MECHANICAL-BEHAVIOR

The integrals of the linear loss shear modulus vs. temperature (loss a rea, ISI) and Linear tan delta vs. temperature (tan delta area, TA) we re characterized for various core/shell latex particles with synthetic rubber, poly(butadiene-stat-styrene) [P(Bd/S), 90/10], and interpenet rating polymer networks (IPN) as the cores. The IPN cores were compose d of P(Bd/S) (T-g similar or equal to -70 degrees C) and an acrylate b ased copolymer (T-g around 10 degrees C) for potential impact and damp ing improvement in thermoplastics. Poly(styrene-stat-acrylonitrile) (S AN, 72/28) was the shell polymer for all these polymers. Under the sam e loading, for both toughening and damping controls, among the IPN cor e/shell, blend of separate core/shell, and multilayered core/shell pol ymers, the IPN core/shell polymers were the best dampers. However, the other core/shell polymers also showed higher LA values than P(Bd/S)/S AN core/shell polymer. A comparison of LA values via a group contribut ion analysis method was made, the effect of particle morphology and ph ase continuity on damping being studied. Inverted core/shell latex par ticles (glassy polymer SAN was synthesized first) showed much higher L A and TA values than normal core/shell ones (rubbery polymer was synth esized first). Models for maximum LA and TA behavior are proposed. The damping property was essentially controlled by the phase miscibility and morphology of the core/shell latex particles. The LA values for ea ch peak in these multiphase materials provided some indication of the several fractional phase volumes. (C) 1997 John Wiley & Sons, Inc.