Chemistry Reference
In-Depth Information
FIGURE 1.11
Specular Reflection Spectra of chocolate package (1) Polymer surface (2)
Al coated surface.
1.3.4 COMPARISON OF ABSORBANCE VALUES IN
SPECULAR REFLECTANCE SPECTRA OF PACKING MATERIALS
Comparisons of five different films absorbance values are tabulated in
Table 1.1. Base line absorbance values at 920 cm
-1
and maximum absor-
bance values due to polypropylene band at 1450 cm
-1
are reported in the
table. The base line absorbance values of the uncoated and coated surfaces
at 920 cm
-1
are close to each other for all five films. The highest base line
value was observed for magnetron sputtered films. The lowest base line
absorbance was observed for commercial film 1. The absorbance values
of the uncoated polypropylene surface of the five films at 1450 cm
-1
are
close to each other in the range of 0.50-0.77. This peak is due to bend-
ing vibration of the CH
2
groups in polypropylene phase. FTIR light was
reflected by the Al surfaces of the films. The highest reflection and the
lowest absorbance value of −0.08 were observed for commercial film 2.
Commercial film 1 also had a low absorbance value of 0.11 and high level
of reflection. The magnetron sputtered films reflection was not as high as
the commercial films, since its absorbance value at 1450 cm
-1
was 0.36.
The Al coating on this film did not cover the whole surface and there were
polypropylene phase exposed to infrared light. Chocolate packing materi-
als Al coated surface also had low absorbance value, 0.20 indicating that it
also reflected strongly the infrared light. The milk cover Al coated surface
even higher absorbance value 0.44 than other films.
