Types of packaging for flexible packaging

There are two main types of flexible packaging, namely stretch wrap packaging and various bag packaging. Stretch wrap packaging is composed of plastic film that has not yet formed a packaging shape, which is simply wrapped around one or more products to be packaged and fixed in place in some form. Plastic bags are made into a certain shape before or at the same time as the product is placed inside. The most common method is to heat seal the plastic edges to form this shape.
1) Stretch wrapping packaging
One of the biggest applications of plastic film in packaging is stretch wrap packaging, which bundles the goods on a pallet together to make them one and enter circulation. The most commonly used plastic film is low-density polyethylene, which is stretched when wrapped around products and trays, usually in a spiral shape. After wrapping, cut the film and stick the film head to the goods, usually self-adhesive. After the stretching force is released, the film attempts to return to its unstretched size, generating a restraining force that acts on the goods, binding them and keeping them stationary during circulation.
In addition to bundling, stretch wrap packaging can also prevent goods from getting damp, falling dust, and wearing out. Stretch wrap packaging can also provide this protective effect for a single variety of goods, and can also bundle goods with a load capacity of less than one pallet together.
Although stretch wrap packaging is conceptually simple, its structure is quite complex. For each layer of stretch wrap packaging, the ideal result is to stick to the underlying layer, but it is not desirable for adjacent goods that may shrink to stick to each other or to other objects in contact with them. Therefore, stretch wrap packaging may have multiple layers of structure, with adhesive added to the inner layer to enhance bonding. In addition to LLDPE, low-density polyethylene, polyvinyl chloride, ethylene vinyl acetate copolymer, and other polymers are also used as stretch wrap films.
2) Shrink packaging
Shrinkage packaging is an alternative to bundling, stretching, and wrapping packaging. When the shrink wrap is exposed to a heat source, the originally aligned (oriented) molecules attempt to recover to a lower energy, unstretched random coil structure, preventing the film from returning to its unstretched size. The force exerted by the material on the product binds the goods together.
Stretch wrap packaging is more common than shrink wrap packaging for bundling goods on pallets, as it requires less energy and is more economical. Shrinkage packaging is more commonly used as bundling packaging to bundle two or several products (the same or different) together, rather than a whole pallet of goods.
Shrink wrap is often used for product protection rather than bundling, applied to everything from meat to toys. It can be designed to form a tight shell around the entire product, effectively preventing dirt, moisture, and wear. Usually, before the film tightly shrinks into the product in the shrink drying oven, it is first made into a loose bag. LDPE and LLDPE are commonly used materials for shrink film. The usage of PVC and PP is relatively low, and the same applies to some special films.
2. Bags, large bags, and sealed bags
Production bags, large bags, and sealed bags are the process of sealing two or more edges of plastic film together to form a cavity for holding products. In most applications, the opening is then sealed in order to completely encapsulate the product with packaging material. Sometimes, one side of the shopping bag is left open.
The words' bag ',' sack ', and' pouch 'may be confused. Some authors believe that 'big bag' is larger than 'bag', but both refer to packaging with an open top, while 'sealed bag' is much smaller, referring to fully sealed packaging. But these definitions do not match the widespread use of this word, as they are often used interchangeably in practical applications.
Common sealed bags include pillow shaped bags, three sided sealed bags, and four sided sealed bags. Pillow shaped bags are made of plastic film into cylindrical shapes, and then the edges are sealed together. The sealed edges become the back seam of the finished packaging. Pinch and seal the bottom end of the cylinder, insert the product, and then add a top seam. The packaging of the product looks like a pillow - hence the name.
As the name suggests, the production of a three sided sealed bag involves folding the film into a rectangle and sealing the three unfolded edges together. Sometimes, the fourth edge is also sealed to increase strength. The four sided sealed bag is made of two thin films, with all edges sealed together. Therefore, the four sided sealed bag does not need to be rectangular. Unlike pillow shaped bags and three sided sealed bags, different plastic films can be used for the front and back of the four sided sealed bag.
Any type of sealed bag formed can be expanded with corner braces to increase its capacity without increasing its width or height.
Sealed bags can be used alone or together with other packaging for product circulation and/or distribution. A very common packaging structure is box lined bag packaging, which involves placing sealed bags in folded cardboard boxes or corrugated boxes.
The material of the bag can be all plastic film itself, or it can be a multi-layer material containing paper and/or aluminum foil. Paper can be used to increase the strength, hardness, printability, and apparent density of flexible packaging. Aluminum foil can be added to enhance its resistance to oxygen, water vapor, odors, fragrances, and other penetrating substances.
In the past few years, upright bags have increasingly replaced cardboard boxes and bottles, with designs including corner braces and specially shaped bottom plates that can stand upright on retailers' shelves.
3. Production of sealed bags
There are two main ways to package with bags, large bags, and sealed bags: as prefabricated bags or for use in molding filling sealing production. In the production of Forming Filling Sealing (FFS), the substrate (usually pre printed if applicable) is added to a horizontal or vertical FFS machine, made into a bag, and then the product is packed and finally sealed. If prefabricated bags are used, they should be made into bags first, leaving a mouth to hold the product inside. Put the product into a bag in another production and then seal the bag.
From an economic perspective, for large-scale production, forming filling sealing usually has advantages. If the production is low or the materials are difficult to seal or there are quality control issues, then generally speaking, purchasing prefabricated bags is more economical.
4. Opening and resealing properties
A long-standing drawback of flexible packaging is the difficulty in providing bags that are easy to use, easy to open and reseal. In the past few years, several innovative technologies have significantly improved the above-mentioned performance of packaging.
The most common method to open products in flexible packaging is to cut or tear open the opening of the packaging bag, or peel off a seam. For some products, such as breakfast cereals packaged in inner bags, this issue is the most complained about by consumers. Sealing is generally not easy to peel off, often by cutting the bag along the edges, causing cereal products to spill into the box. It is almost impossible to seal the bag again to maintain the freshness of the product. Some soft packaging uses zipper sealing and often comes with tear strips for easy initial opening. Other packaging also has a resealable flap, usually located at the seams.
For liquid products, some packaging has threaded outlets and comes with a standard nut. The outlet can be located at the top and bottom of the bag, depending on the size of the product and packaging. In the lined bag packaging of the box, the outer cardboard box has a folding lid. When opened, pull the outlet out of the folding lid. For disposable beverage packaging, it is generally accompanied by a straw (the straw has its own packaging to prevent dirt contamination, sticking to one side of the beverage bag), and a point is specified on the packaging to improve the packaging for easy straw penetration.