Chemistry Reference
In-Depth Information
ABSTRACT
Polymer films coated with a thin layer of aluminum or aluminum oxide
are extensively used in food packing as heat shields. The infrared rays
were not transmitted through the films and were reflected protecting the
contents from the harmful effects of infrared light. The quantitative mea-
surement of the film thickness and infrared light reflection and absorption
capacities of aluminum coated films used as packing materials were pos-
sible using infrared spectroscopy.
1.1 INTRODUCTION
The protection from harmful effects caused by infrared radiation on foods
can be made by using infrared shielding packing materials. Nano-oxides
with the surface effect, small size effect, quantum size effect, macroscop-
ic quantum tunneling effect and other special properties can be used in
preparation of infrared shielding coating, absorbing coatings, conductive
coatings, insulation coatings and so on [1].
Polymer coatings on the surfaces are very easily degraded because of
the infrared light. The life of the polymer coating could be extended if they
are coated with an infrared light reflecting or absorbing layer. Aluminum
coatings were used for this purpose in many applications [h2]. Alumi-
num oxide coating on polymers is also used for protection of the polymer
layer. Covalent bonds are responsible for adhesion of aluminum oxide to
polymer surface. Nano Al
2
O
3
particles have a wide absorption band in the
infrared band and they have been used widely in the paint, military, sci-
entific and industrial application [2]. Resonance absorption of the infrared
radiation may take place at extremely thin metal coatings by reducing the
overall temperature of the heat shield [3].
Polymer surfaces are modified by plasma techniques for interfacial
enhancement [4-10]. Au, Ag, Pd, Cu and Ni were coated on poly (meth-
ylmethacrylate) (PMMA) by barrel technique [11]. Coating of Al alloys
on PET was compared with Ti layer under Al alloys [12]. Thin Aluminum
oxide coatings have been deposited on various uncoated papers, polymer-
coated papers and plain polymer films using atomic layer deposition tech-
nique [13]. The isotactic polypropylene (iPP) and Al composite is widely
used as television cable electromagnetic shielding materials [14]. The
reflection of infrared light depends on geometry of the surface of alumi-
