MatSE443 (previously PLMSE 406):
Introduction to the Materials Science of Polymers
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All paragraph and pages numbers refer to the primary text (Painter & Coleman) Study Guide (chapter 11)
This is the most important chapter of the
course
Concepts that you must know:
Understand the concepts of stress, strain, modulus and viscosity and
have a broad feel for the strength, stiffness and toughness of polymers
relative to other materials.
Sketch the form of the stress-strain plots obtained from various
general classes of polymers (elastomers, glassy polymers, semi-crystalline
polymers, etc.).
Appreciate how variations in temperature and/or the
introduction of plasticizers can affect the shape of the stress-strain
plot.
Understand the definitions of the following materials properties:
strength, toughness, modulus, and enlongation-at-break and know how to
estimate from the stress-strain graph
Understand yielding phenomena in polymers.
Describe the basic properties of polymer melts, the concept of
entanglement, reptation, and the dependence melt viscosity on molecular
weight
Understand the nature of viscoelasticity, particularly creep and
stress relaxation
Describe the time-temperature superposition principle and the WLF
equation.
Exercises:
*Go through the material that describe the following two
graphs: and make sure you can identify the various
regions (A-D), understand how to derive properties (e.g. modulus, strength,
Tg or Tm, etc) from such graphs
Interactive Module:
You need the
latest plugin
(Flash Player version 6) (which can be obtained free from here)
The files are extremely small (typically half a minute with a modem) and
can be run directly from this web-page.
After reading the help window, close it. Move the curves of the left
panel towards the right (the first -red- one is immobilized) until they
appear to overlap into a continuous curve. Notice the shift factors -right
panel- while you move each curve. Click the "WLF on" button to see how well
you shifted each curve. Comment on the log(a_T) shift factors and the
amount of time you displaced each curve.
*Move the reference temperature slider and comment on the time scale
movements. Also comment on what short of timescales of experiments are
needed o measure the whole curve at this reference temperature.
Hit the "help" button to reveal at what temperatures each curve was
measured. Close the help window, pick another Ts from the temperatures
in the bottom left side. Repeat all the curve shifting, and comment on the
shift factors. What do positive vs. negative values of the log(a_T)
mean ?
