Chemistry Reference
In-Depth Information
TABLE 1.1
Absorbance Values of Specular Reflectance Spectra of Uncoated and Al
Coated Surfaces of Packing Materials
Type of film
Absorbance at 1450 cm
-1
Absorbance at 920 cm
-1
Uncoated
surface
Al Coated
Surface
Uncoated
Surface
Al Coated
Surface
Commercial film 1
0.50
0.11
0.12
0.11
Commercial film 2
0.66
-0.08
-0.03
-0.07
Magnetron sputtered film
0.60
0.36
0.29
0.28
Chocolate packing
0.77
0.20
0.69
0.18
Milk Cover
0.75
0.44
0.63
0.38
1.4 CONCLUSIONS
Infrared spectroscopy is an efficient tool for measuring the thickness of
thin polymer films and their ability to absorb or reflect infrared lights.
The thicknesses of the commercial films coated with aluminum were
determined to be 16 and 19 µm for film 1 and 2. The aluminum-coated
surface of the commercial films had the ability of reflecting the infrared
rays, which strike. They can be used efficiently as infrared light shields for
the materials inside their packing. The Al coatings obtained by chemical
vapor deposition were 32 nm and 185 nm for commercial film 1 and 2,
respectively. The coatings were more perfect than the coating obtained by
magnetron sputtered cast film. The Al coating of the cast film was more
brittle, and there were uncoated polypropylene regions and the infrared
light was only partially filtered. Thus it was a less efficient infrared shield
compared to commercial films. The magnetron sputtering method needs
more investigation for optimum results. The chocolate and milk packing
materials Al coated surfaces reflected the infrared light better than their
other surfaces. They were also good infrared light protectors. However,
milk-packing material Al surface was also coated with another polymer
layer either for esthetic or safety reasons or since it was used in contact
with milk.
