RAMAN APPLICATIONS IN POLYMER FILMS FOR REAL - TIME CHARACTERIZATION - Raman Spectroscopy for Soft Matter Applications - page 43

gence provides overall molecular orientation. Limited studies have
reported on the use of off-line polarized Raman spectroscopy to esti-
mate orientation in fi lms [12,14,66] and fi bers [13,67,68] . The detailed
procedure for determining the orientation of the polymer specimens
by polarized Raman spectroscopy was presented by Bower [69] . Later
studies [12,13,67] proposed approaches to simplify the experimental
complexities.
Paradkar et al. [23] demonstrated the use of Raman spectroscopy
for measuring molecular orientation during fi ber spinning of i- PP. They
used the ratio of Raman peaks at 841 and 809 cm − 1 , which is sensitive
to the molecular anisotropy in PP, to estimate a semiquantitative
molecular orientation in the fi ber line for different throughput and
draw ratios. Figure 3.13 shows the real-time ZZ polarized Raman
spectra for PP obtained at three different positions along the fi ber line.
The ratio of the 841- to 809-cm − 1 peak was reported to decrease as the

Near die

3

2.5

Near feed roll

2

1.5

1

Between feed and
draw rolls

0.5

0

600 800 1000 1200 1400

Raman shift (cm -1 )

Figure 3.13 Polarized Raman spectra (ZZ) representing development of molecular
orientation in polypropylene at three different locations in the fi ber-spinning line.
(Reproduced from Paradkar et al. [23].)