Chemistry Reference
In-Depth Information
The high cost and scarcity of landfill space for the creation of new ones
have influenced the development of alternative techniques for waste dis-
posal. The impact of plastics is even more serious when plastics are disposed
of improperly and dispersed in the environment. This has led to techniques
for recycling and incineration and these techniques have been more usually
practiced.
According to Christiana Figueres, the Executive Secretary of the United
Nations Framework Convention on Climate Change (UNFCCC), in a state-
ment issued in Bonn, Germany, where the UNFCCC was held in May 2013,
the concentration of carbon dioxide (CO
2
) in the atmosphere surpassed 400
parts per million (ppm) for the first time, leaving the planet in a ''danger
zone''. Statements like these, ineffective policies for the treatment of solid
waste and a very low recycling rate, make the population more concerned
about the environment. In this context, the use of materials with environ-
mental appeal has been well regarded.
The properties required for plastic packaging depend mainly on the
changes shown by the product and the conditions where it is stored. For
food packaging applications, bioplastics should: (i) have good sensory
properties, a gas and mechanical barrier; (ii) have sucient biochemical,
physical-chemical and microbiological stability; (iii) be free of toxic waste
and be safe for consumption; (iv) have simple manufacturing technology;
(v) not pollute; (vi) have good availability and low cost (raw material and
process).
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The main natural biomaterials for bioplastics are proteins, cellulose de-
rivatives, alginates, pectins, starch and other polysaccharides. The solubility
in water of the polysaccharide film is advantageous in situations where the
film is consumed with the product, resulting in little change in the food's
sensory properties.
24
Edible films based on proteins, polysaccharides or
lipids minimize special care with the final package and increase food
quality.
25
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9.2.5.1 Methods for Obtaining Plastic Products
Various methods are used in plastic product manufacture, but the four main
ones are extrusion, injection, blow and rotational.
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According to Smith,
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the extrusion process has many advantages such as
versatility, high quality of product, low production cost, the formation of
products with different geometric shapes and no formation or release of
euents. This process can be divided into three stages: pre-extrusion, ex-
trusion and post-extrusion, where the equipment for the first and last steps
depends on the type of material to be used, while in the extrusion step,
processing conditions may vary.
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The greatest technique for converting thermoplastics is injection molding
and is widely used for bottle and jar production, as well as production of
caps and dispensers.
12
Various plastic accessories are also manufactured
using this technique.
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