Chemistry Reference
In-Depth Information
ness and formed by small Al particles having 22-29 nm grain sizes [18].
Commercial milk and chocolate packaging materials were also investi-
gated.
1.2.2 METHODS
The surface morphology of the films was examined by scanning electron
microscopy. FEI QUANTA FEG-250 SEM was used for this purpose. The
thickness of Al coating on the surface of the films was measured from the
fractured brittle Al layer obtained by stretching the films.
The transmission infrared spectra of the films at 20 °C were taken
with Excalibur DIGILAB FTS 3000 MX type Fourier Transform Infrared
Spectrophotometer with a resolution of 4 cm
-1
. DTGS type detector was
used for all measurements. The transmission spectra of the films were ob-
tained by placing the films in two different positions. The incident infrared
light first strikes to either Al coated or uncoated surface in these posi-
tions. In transmission spectrum the light that passes through the sample
is measured. The grazing angle specular reflectance accessory with 80 °C
(Pike Technologies), in the reflection absorption mode was used to obtain
specular reflectance spectra. Gold-coated glass was used as the reference.
1.3
RESULTS AND DISCUSSION
1.3.1 MORPHOLOGIES OF AL COATINGS
SEM micrographs of the Al coated surfaces of the films were taken to
observe the morphology of the coatings on the films. The Al coating on
the surface of the films were broken by stretching the polymer phase to
observe the thickness of Al coatings.
1.3.1.1
MORPHOLOGY OF COMMERCIAL FILM 1
The commercial polypropylene films were coated with a layer of Al by
physical vapor deposition. The coating thickness was determined from
SEM pictures of commercial film 1 seen in Fig. 1.1a as 32 nm for com-
mercial film 1. The coating had the shape of the polymer layer. There were
