
Single -layer plastic film often cannot fully meet the requirements of
protecting goods, beautifying goods, and adapting to processing. So there is a
more ideal packaging material with the same or different packaging materials of
two or more layers of more ideals. This composite material overcomes the
shortcomings of a single material and obtains the excellent performance that a
single material does not have. At present, composite materials have accounted
for the main position in food packaging bags.
Basic structure of composite materials:
Generally speaking, the outer material of the composite packaging materials
should be high melting points, good thermal resistance, not easy to scratch,
grinding hair, good printing performance, and good optical properties.
Carbonate, nylon, polyester, polypropylene, etc.
The inner materials should have the performance of heat -sealing, adhesive,
odorless, oil -resistant, water -resistant, water -resistant, chemical resistant
and other performance, such as polypropylene, polyethylene, polytinyl chloride
and other heat -resistant plastic materials.
The middle layer of composite materials above the three layers usually use
materials such as obstructive gas and water and water, and high mechanical
strength, such as aluminum foil, polytaline, glass paper, paper, polyethylene,
etc.
The adhesive is coated between the layer and the layer. Generally, solvent
-based thermosettic polyurethane adhesives are used between the outer layer and
the middle material. The outer layer requires high adhesion strength, simple
process, and low cost. The inner layer requires high temperature resistance,
high peeling strength, and tastelessness. It does not affect the nutritional
content of food, and can maintain the color and fragrance of food.
In recent years, it has developed a layer of coating agent evenly on the
surface of the substrate thin film to improve the gas, oil resistance and
chemical stability of the packaging materials, so that it is applicable to a
variety of food packaging. Commonly used coating agents include polytatochloride
resin and polypropylene-polytatrodeline. The coating method is single -sided and
double -sided coating.
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