  The timing characteristics of scintillators must be understood in order to
determine which applications they are appropriate for. Polyethylene naphthalate
(PEN) and polyethylene teraphthalate (PET) are common plastics with uncommon
scintillation properties. Here, we report the timing characteristics of PEN and
PET, determined by exciting them with 120 GeV protons. The test beam was
provided by Fermi National Accelerator Laboratory, and the scintillators were
tested at the Fermilab Test Beam Facility. PEN and PET are found to have
dominant decay constants of 34.91 ns and 6.78 ns, respectively.
