  There is increasing necessity for low background active materials as
ton-scale, rare-event and cryogenic detectors are developed.
Poly(ethylene-2,6-naphthalate) (PEN) has been considered for these applications
because of its robust structural characteristics, and its scintillation light
in the blue wavelength region. Radioluminescent properties of PEN have been
measured to aid in the evaluation of this material. In this article we present
a measurement of PEN's quenching factor using three different neutron sources;
neutrons emitted from spontaneous fission in \cf, neutrons generated from a DD
generator, and neutrons emitted from the \Can and the \Lipn nuclear reactions.
The fission source used time-of-flight to determine the neutron energy, and the
neutron energy from the nuclear reactions was defined using thin targets and
reaction kinematics. The Birk's factor and scintillation efficiency were found
to be $kB = 0.12 \pm 0.01$ mm MeV$^{-1}$ and $S = 1.31\pm0.09$ MeV$_{ee}$
MeV$^{-1}$ from a simultaneous analysis of the data obtained from the three
different sources. With these parameters, it is possible to evaluate PEN as a
viable material for large-scale, low background physics experiments.
