Let's talk today about the most popular form of packaging and packaging in our country and, probably, all over the world. These are plastic bags. We learn in more detail their characteristics, purpose, running varieties. We will pay most attention to the classification of this type of packaging.
Sacks, plastic bags
Packaging plastic bags began to be produced in the middle of the last century. They were originally used to pack fruits and bread. Currently, the production of such packaging reaches 4.5 trillion pieces annually!
It consists of a plastic, polyethylene container of a thin polymer base, which is synthesized from ethylene, a gaseous hydrocarbon. Judging by the conditions of the polymerization reaction, the material can be as follows:
- PND (PNED) - is formed in the presence of catalysts at low pressure. Such a bag is more opaque, rustling to the touch.
- LDPE (LDPE) - is obtained under high pressure. The result is a slightly lower density substance. The finished product is transparent, soft, elastic, smooth to a waxy. Another remarkable feature of it is its ability to withstand large loads due to strong intermolecular bonds.
- Packing from linear, medium- density polyethylene, a polyethylene mixture of different types. The final product in its properties occupies a middle position between LDPE and HDPE.
Packaging properties
There are both dense plastic bags and bags of lower density. We highlight their common properties:
- Resistance to chemically active components - acids, fats, alkalis, etc.
- Tensile and tensile strength.
- Preservation of its basic properties even at low temperatures (only at -60 ° C does the material become brittle).
- Non-biodegradability, soaking.
- Non-toxic, which makes it possible to contact even with food contents.
- Availability due to the cheapness of the material.
- Hygiene of polyethylene.
- Impermeability to liquids, gases, which guarantees the protection of contents from undesirable environmental factors.
- Polyethylene is thermoplastic - most of its varieties begin to melt at temperatures above 80-90 ° C. From this, bags of this material are not suitable for storing hot food!
Comparison with other materials
Compare opaque and transparent plastic bags with packaging from a different kind of material.
| Polyethylene | The main advantage is the cheapest packaging material. |
| Cellophane | It is the result of pulp processing. The main disadvantage is that when a small tear appears, it breaks further almost instantly. |
| Paper | The most environmentally friendly packaging. But completely unsuitable for oily or moist contents. |
| Polypropylene | Unlike polyethylene, it is able to withstand higher temperatures. But less resistant to direct sunlight, punctures. Not recommended for sharp products. |
We proceed to the next topic.
Packaging production
How are plastic bags made? The heated polymer mass is extruded through an appropriately sized extruder hole. A certain plastic sleeve is formed , from which packages of the desired variety are formed.
Further, production is divided into the following areas:
- Coiling for subsequent tearing along the perforation line.
- Packing in packs for a certain number of pieces.
- Additional bag design - installation of accessories, handles.
- Drawing images - one-, two-, multi-color.
Types of packages
Modern production of plastic bags involves the release of the following items:
- Packing bags. Transparent, thin, made of different types of polyethylene material. The main purpose is the packaging of piece goods.
- T-shirt packages. They got their name due to the fact that the shape, position of the handles resemble this wardrobe item. The main material is HDPE. Most common in supermarkets because of spaciousness, compactness, ease of carrying.
- Bags with handles. Outwardly similar to bags, they are somewhat more expensive than “shirts”. Material - LDPE, linear polyethylene, blends. The handles are the most diverse - rope, plastic, welt, hinges and so on.
- Bags with clasps, lock.
- Garbage bags, for technical, household needs. Material - polyethylene of all kinds, recyclable materials. Perhaps the presence of tightening tapes, pens.
- Branded packages. Decorated with an image, applying a logo, lettering and so on. An additional way to promote a company, enterprise, other organization.
Classification by type of bottom
Plastic bags are also divided according to the type of bottom:
- Without folds, with a flat seamless bottom. Among the besfaltsevye bags this type is very common. It is the easiest and cheapest option. A seam is observed only on the sides of the bag. The packing of heavy products, objects with sharp edges in such a bag is undesirable. Of all the following, the most unstable when filling.
- Without folds with a bottom having a seam. The most common type. The seam strengthens the bag, which allows it to withstand good weight. The bottom is similar to the edge of the pillowcase. In such a container, it is better not to put wet contents, since water will accumulate at the bottom of the bag.
- With folds, flat seam bottom. Such bags are tear resistant, more dense. The bottom of the plastic bag is flat and welded. Well suited for bulk packaging. Another plus - it has the most presentable appearance.
- With a bottom fold (folds are at the bottom). The main difference between such a package is that the folds are located at the bottom, and not across the entire width of the package. This gives the container stability during filling.
- The bottom is the "star". The shape of such a plastic bag is cylindrical, which allows the weight of the cargo to be distributed evenly over the entire container. A star-shaped bottom seal counteracts leaking wet contents. These are plastic trash bags; they are also widely used in catering establishments.
Plastic bags are produced in a large assortment in Russia and around the world, from various kinds of raw materials. They have both a number of advantages and a number of disadvantages over other types of packaging.