Each year when teaching polarization phenomena and the Triboelectric Series in a unit on electrostatics, I would balance some rods (2–3 ft in length) made from wood, aluminum, PVC, and Plexiglas on an inverted watch glass and demonstrate to the class how a party balloon rubbed with fake rabbit fur (charging the balloon negative) would always attract the uncharged rods, causing them to rotate towards the balloon (see Fig. 1). The fact that a charged object always attracts a neutral object due to the induced dipole in the latter is a great way to test if something is in fact charged. Surprisingly, the PVC pipe would usually, but not always, repel the charged balloon and rotate away! Repulsion means that neither of the objects are electrically neutral. In a separate test, after rubbing together a Plexiglas rod with a polyethylene grocery bag (making the rod positively charged and the bag negatively charged), the PVC usually attracts the rod. With the help of a student as part of his senior project, I finally decided to investigate further the source of the negative charge that exists on PVC. Specifically, is it nothing more than static charge that builds up on the pipe from unavoidable contact with its surroundings, or is it somehow intrinsic to the manufacturing process?

2.
Klinger Educational Products
, http://www.klingereducational.com/. The electrometer sells for $350.
3.
Formufit Furniture Grade PVC, http://www.formufit.com/ ; JM Eagle, http://www.jmeagle.com/ ; Charlotte Pipe, http://www.charlottepipe.com/ ; Genova, http://www.genovaproducts.com/plumbing.htm; the CPVC pipe was from an unknown manufacturer.
4.
Chul-Hyun
Park
 et al, “
PVC removal from mixed plastics by triboelectrostatic separation
,”
J. Hazard. Mater.
144
(
1–2
),
470
477
(
2007
).
5
Gunter
Luttgens
,
Electrostatic Hazards
(
Burlington
,
Elsevier Sciences
,
1997
).
6.
Private conversation, Mike Buchanan, Valencia Pipe Company, http://www.valenciapipe.com.
7
R.
Chabay
and
B.
Sherwood
,
Matter & Interactions
, 3rd ed. (
Wiley
,
2011
) and private communication, B. Sherwood.
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.