Many plastic bags are shaped essentially like two identically-sized rectangular plastic sheets fused together on three of the sides, with one side left for the opening. This type of shape allows for rather simple, economic manufacturing and compact storage of the bags before use. Polyethylene is an economicalplastic so it is commonly used for disposable bags. Plastic bags can be made having various colors, including translucent or even transparent in some cases. Bags made of HDPE (High Density Polyethylene) are typically not see-through or are translucent, but not fully transparent. Bags made out of LDPE (Low Density Polyethylene) can be quite clear, but are still usually not as totally transparent as other plastics.
Although there was a time when plastic bags were not available and people made do, they are a more convenient and more sanitary way of handling rubbish and are widely used today. Plastic rubbish bags are fairly lightweight and are particularly useful for messy or wet rubbish as is commonly the case with food leavings and also useful for wrapping up rubbish to minimize odor. Plastic bags are often used for lining litter or waste containers or bins. This serves to keep the container sanitary by avoiding container contact with the rubbish. After the bag in the container is filled with litter, the bag can be conveniently pulled out by its edges, closed, and tied.
Plastic bags for rubbish or litter are normally sold in a numer of sizes at grocery and many other stores in packets of almost a dozen to several dozen. The size and thickness of the bags are often specified on the packet, as well as the number of bags. The simple rectagularly-shaped bags come with twist ties in the packet to be used for closure once the bag is filled. Perhaps ten years ago or so, rubbish bags with draw strings have been introduced. The draw strings can be conveniently pulled to close up the bag after it is filled with litter. Most commonly, the rather soft, flexible plastic used to make rubbish bags is LDPE (Low Density Polyethylene) or, for strength, LLDPE (Linear Low Density Polyethylene). HDPE (High Density Polyethylene) has been used in some cases which gives a more crinkly (less soft) texture or feel.
The largest size plastic bags commonly available to the general consumer are lawn and leaf bags for yard waste. Since plastic bags are usually not biodegradable, some localities require special large paper bags for disposal of yardwaste. The next largest size commonly available to the general consumer is a rubbish can size made to be suitable lining rubbish containers. This size is very commonly used for disposal of rubbish. Other large sizes are often used in business and institutions. Tall kitchen rubbish size is another somewhat smaller size routinely available to consumers for lining kitchen rubbish containers. Then there are even smaller sizes available for lining wastebaskets.
Economical disposable plastic bags for bagging purchases at grocery stores or supermarkets are usually made of HDPE.
Smaller plastic bags are commercially available for containing and storing food items and can be used for holding other items as well. A company that started making them years ago called them baggies and since then this name has become commonly used generically for such small bags. These kinds of bags are commonly made of LDPE. Another brand name that has been used in connection with such food bags is ziploc which refers to the zipper-like sealing mechanism on one side (edge) of the bag. Such simple sealing mechanisms made in one piece with the plastic of the bag are common on food plastic bags. There is generally no need to make rubbish bags see-through, but other types of storage bags, such as for food, are commonly clear so the user can easily identify what is inside. Simple, economical, soft, thin-walled, transparent plastic bags without sealing mechanisms are usually available without charge at grocery stores for bagging produce such as fruits and vegetables. Twist ties or tying the opening end of the bag in a knot can close up such bags.
Since they are economical and convenient, plastic bags of various sizes are also widely used for commercial packaging applications. Small, usually clear, plastics bags are used for containing small items or goods, especially small parts which would otherwise be easily lost. Often such bags are sealed, stapled, or taped shut until they are torn or cut open by the consumer. Plastic linings similar to plastic bags are commonly used inside cardboard boxes or other harder containers, especially for holding powder or granular material.
Polyethylene Definition (used for packing bags)
|The above article is licensed under the GNU Free Documentation License. From Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/plastic_bag). 12/23/05|