This document summarizes research on the rheology of nylon 11 clay nanocomposites. It discusses the history and properties of nylon, characteristics of neat nylon and nanocomposites under steady shear, the effect of shear rate and temperature on viscosity, and the Cox-Merz rule for correlating shear stress and dynamic viscosity. Figures and equations are included to illustrate key concepts.

1. Rheology of Nylon 11/Clay Nanocomposites SITI NORAINI BT KAWAEED 0724126 NUR NADIAH AJMAN 0727574 NOR SUHAILA NOR SAIDI 0727830 SITI KHADIJAH ABDUL RAHMAN 0720050

2. HISTORY OF NYLON(POLYAMIDES) Nylon was the first truly synthetic fiber to be commercialized (1939). Nylon was developed in the 1930s by scientists at Du Pont, headed by an American chemist Wallace Hume Caruthers (1896-1937). Nylons are semi-crystalline polymers.

3. GENERAL CHARACTERISTIC NYLON high melting points. good mechanical properties. strength and ductility. excellent resistance to solvents. Fatigue and abrasion.

4. Figure 1 Steady shear viscosity versus shear rate for neat PA11 and its clay nanocomposites at 210°C.

5. SHEAR RATE The steady shear viscosity as a function of shear rate for PA11 and its nanocomposites is shown in Figure 1 as a function of clay loading. Each flow curve displays a similar profile with shear rate independent viscosity at lower shear rates and shear thinning at higher shear rates. the viscosities increase with increasing the clay loading.

6. Shear rate(cont.) Then, the slope of ŋ versus γ on a log-log plot in the power-law region is (n1), where n is called non-Newtonian index. Then, the critical shear rate (γc) is defined as the onset point of shear-thinning transition and is approximately equal to the inverse of t1 (or the longest relaxation time). the addition of clay renders the transition from the Newtonian plateau region to shear-thinning region occurring at lower critical shear rate with increasing the clay concentration.

7. Viscosity At high temperature, viscosity is slightly lower than at lower temperature. At higher temperature, the greater average kinetic energy of the molecules more easily overcome the attractive forces between molecules. It has been reported that the viscosity of the confined melts is greater than that of bulk chain. The large viscosity of confined melts is believed to arise from an “immobilized hydrodynamic layer” near the wall having a thickness of the order of radius of gyration of the polymer chains.

8. shear stress (τ) Cox-Merz rule (named by type-II) correlates the first derivative of shear stress (τ) with respect to strain, that is, the so called “consistency,” with the imaginary part of the dynamic viscosity with the following expression: