Methods of Manufacturing Plastic
Compared to metals, plastics are lighter, more flexible and more economical to produce. Thanks to advances in engineering plastics are being made stronger making them useful in more applications. Metal parts are typically made through subtractive machining, which consists of a milling spindle cutting away excess material until a part is formed. Plastic, on the other hand, is typically melted and formed. There are several manufacturing processes deployed to do so.
Plastic is a synthetic material made by man, and can take many forms. In its smallest form it is a polymer, a large molecule chain of repeating structural units. Most of these molecules in the chain are familiar to you already, for example, carbon and oxygen. When these chains are linked together they form synthetic solids, otherwise known as the plastic. There are two types of plastics, thermoplastics and thermosetting polymers. When it comes to plastic bags, we are talking about the thermoplastics. These thermoplastics can be formed and heated and then this process repeated infinitely. Speaking of types of plastic, another useful term to know in regards to it is 'polyethelene.' Most plastic bags are made of either high or low density polyethelene.
The Manufacturing Process
In order to make plastic bags the raw materials need to be present. The key ingredients are petroleum and natural gas. These components are heated, broken apart, and then recombined with other additives. These additives have a variety of purposes; adding color, providing fire resistance, or simply protection from degrading in the future. The tangible material of this manufacturing process looks like small pellets. Once the pellets are made they are combined in a process known as extrusion. Extrusion is the action of pushing the materials through a template in order to make, in this case, plastic bags. Remember that polyethelene is a type of thermoplastic, this means that during the process of extrusion the plastic is heated in order for it to be formed into its finished shape. Once the plastic is heated it is blown through a tube into the appropriate shape (a bag) and then cooled using blown air. The plastic bags are then rolled along so that they can be flattened and cut into the desired size.
Characteristics of Plastic Bags
The material used to produce plastic bags has several characteristics which makes it desirable as a packaging source. It is resistant to moisture and chemicals. It is also lightweight, though during the manufacturing process there are numerous ways to vary its thickness according to the needs of the manufacturer. Plastic is also a very durable material.
The End Product
Once the manufacturing process is complete, and the plastic bag has been colored, cut, and created to the desired specifications it is shipped all over the world. Chances are not only is your supper resting in a plastic bag as you carry it home, part of the food contents are packaged in the very same type of polyethelene plastic.