90
4
two parallel plates—one of which is moving relative to the other.
The flow is driven by virtue of a viscous drag force acting on the
fluid and the applied pressure gradient parallel to the plates [5]. The
extension of the polymer occurs in all three directions in PEF, as
shown in . Fig. 4.6a.
Strong stretching occurs in one direction, while contraction
occurs equally in the other two directions in USF, as shown in
. Fig. 4.6b. In BSF, the stretching of the polymer occurs in two
directions, as in the cases of the blown film shown in . Fig. 4.6c.
Normal stresses occur due to the nature of the fluid, but shear
flow occurs due to the flow of fluid.
4.2 Rheology Aspects of a Polymeric Matrix
Since thermoplastics tend to have high molecular weights as well
as a greater molecular weight distribution, it is evident that the
nature of the polymer will be different from Newtonian behaviour. The polymer chains are inherently in an entangled state,
which is by far the inertial state of the system. Application of shear
at defined rates leads to disentanglement of the polymer melt.
Elongated polymeric
chains
Entangled polymeric
chains
. Fig. 4.5 Elongational flow
a
b
Contraction
Elongation
c
. Fig. 4.6 Schematic presentation of a PEF, b USF, and c BSF
Chapter 4 · Rheology in Processing of Polymeric Composites
4
two parallel plates—one of which is moving relative to the other.
The flow is driven by virtue of a viscous drag force acting on the
fluid and the applied pressure gradient parallel to the plates [5]. The
extension of the polymer occurs in all three directions in PEF, as
shown in . Fig. 4.6a.
Strong stretching occurs in one direction, while contraction
occurs equally in the other two directions in USF, as shown in
. Fig. 4.6b. In BSF, the stretching of the polymer occurs in two
directions, as in the cases of the blown film shown in . Fig. 4.6c.
Normal stresses occur due to the nature of the fluid, but shear
flow occurs due to the flow of fluid.
4.2 Rheology Aspects of a Polymeric Matrix
Since thermoplastics tend to have high molecular weights as well
as a greater molecular weight distribution, it is evident that the
nature of the polymer will be different from Newtonian behaviour. The polymer chains are inherently in an entangled state,
which is by far the inertial state of the system. Application of shear
at defined rates leads to disentanglement of the polymer melt.
Elongated polymeric
chains
Entangled polymeric
chains
. Fig. 4.5 Elongational flow
a
b
Contraction
Elongation
c
. Fig. 4.6 Schematic presentation of a PEF, b USF, and c BSF
Chapter 4 · Rheology in Processing of Polymeric Composites