Transcript DAY 31: MECHANICAL BEHAVIOR: HANDS ON. Cold work and annealing mean different things for polymers.  Play around with some polymers.

DAY 31: MECHANICAL BEHAVIOR:
HANDS ON.
Cold work and annealing mean different things
for polymers.
 Play around with some polymers. Observe the
effects of different strain ratess.

STRESS STRAIN CURVE - THERMOPLASTIC
Neck propagates
Neck starts at yield
DRAWING AND ANNEALING
Drawing, or Cold Work. Take advantage of the
increased strength and stiffness caused by the
orientation of the chains. This can actually be
used as a final step in manufacturing polymers
as it is in metals. Note: drawing just imparts
strength / stiffness in one direction! How is this
different from CW in metals?
 Annealing. (1) If the material is already drawn,
it has much the same effect of softening as in
metals. BUT (2) If the material is not drawn it
can impart strength and stiffness (at least in
some polymers) by enhancing crystallinity.

POLYMER BEHAVIOR – HANDS ON
Qualitatively examine the effect of strain rate on
some polymers.
 You will be given 3 polymers:
1. Construction plastic
2. Silly Putty
3. Wire Tie
 Try to pull on these with different strain rates.
See what happens. Could you predict how
increasing the temperature would affect these
polymers?
 What happens in the microstructure to produce
the behavior?
