The Society of the Plastics Industry is probably an organization that you don’t know much about. Aside from supporting the plastics’ industry, they are responsible for setting up a resin identification coding system. This system is something you come into contact with every time you drink water or soda in plastic bottles or use a plastic product. Search around on the plastic and you will find a number which is surrounded by arrows. This number is a resin code which identifies what type of plastic you are holding.
In many parts of the country, items with a number one or number two are the only types accepted for municipal recycling programs. The number one indicates items that are made from the polymer polyethylene terephthalate or PET which includes soft drink bottles and water bottles. Biaxially oriented PET film is known more commonly as Mylar, and this is used for thin, flexible food packaging and other products. Thermoforming is used to create these products, which begin, as a large sheet of thin plastic. Heat is applied, and the plastic is formed to a mold, then cooled and trimmed to create a finished product.
When the number on your plastic is a two, this is plastic that has been created with high-density polyethylene. Many products, including grocery bags, milk jugs and containers for food storage are made using this polymer, which is sometimes called HDPE plastic. This type of plastic is also used from some toy items, such as hula hoops, and even used in some reconstructive surgeries.
The number three is used as a resin code to identify products made from polyvinyl chloride, which is commonly known as PVC. PVC is often used to create pipes and used in construction, but this plastic also is used to make plastic bottles that hold cleaners or other non-edible products and even used to create many toys. LDPE or low-density polyethylene is identified using a number four, and this plastic is often used in science labs because it is not affected by liquids that are acids, alcohols or bases. In addition, every time you buy a six-pack of beer or soft drinks, those flexible plastic rings are made from LDPE.
While it might not seem like diapers and carpet have much in common, both contain a bit of resin number five, which is polypropylene. This is a durable polymer which is also used to make bottle tops, such as flip tops on ketchup or salad dressing, as well as furniture. Because it is fairly heat resistant it can be used in laboratories, as well. Polystyrene is yet another type of polymer, and it is marked with resin code six and is often known by the brand name of Styrofoam. But generic versions of this polymer are used to create a variety of containers and cups, as well as packing peanuts that keep items safe in parcels during transit.
A seven is a number used for a miscellaneous category that includes items with a variety of different plastics in them, as well as plastics such as nylon and acrylic. There is no eight yet designated, but the number nine is used to identify products made from acrylonitrile butadiene styrene, also known as ABS. This type of thermoplastic is used to make a variety of interesting products, most notably Lego bricks.
Lenna Stockwell likes writing about how stuff is made. For further information about plastic thermoforming or to find out more about custom plastic packaging, please visit the Indepak site now.
Understanding The Numbering System On Plastic Products
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