RAMAN SCATTERING THEORY AND ELEMENTS OF RAMAN INSTRUMENTATION - Raman Spectroscopy for Soft Matter Applications - page 24

1200

1000

800

600

400

200

0

4

2

Crystalline
contribution
(Lorentz)

0

-2

-4

-6

-8

Amorphous
contribution
(Gauss)

-10

-12

-14

0 2 4 6 8 10 12

Strain (%)

Figure 2.11 Comparison of the strain dependency of the crystalline and amorphous
low-frequency Raman contributions with the stress-strain tensile curve for polyeth-
ylene-terephthalate (PET) fi bers. (Adapted from Colomban, Ph., Herrera-Ramirez,
J.-M., Paquin, R., Marcellan, A., Bunsell, A. [2006]. Eng. Fract. Mech. , 73[16],
2463-2475.)

amorphous matrix, whereas nanocrystallites are only slightly com-
pressed by Poisson's effect.
In PA fi bers, both the amorphous and crystalline moieties accom-
modate the stress because the nanostructure puts them “in series”.
Wave number-strain curves thus start with a plateau that corresponds
to the disentanglement of the polymer chains (viscoelastic regime) and
wave numbers start downshifting as soon as “knots” block this process
(elastic regime) [40] .

REFERENCES

1. Brillouin , L. (1922). Diffusion of light and X-rays by a transparent homo-

geneous body. The infl uence of thermal agitation. Ann. Phys. (Paris) , 1 7 ,
88 .
Smekal A. ( 1923 ). The quantum theory of dispersion . Naturwissenschaften ,
11 , 873 .

2.