Differences between Roll Film and Ready – to – use Bags in Packaging
Differences between Roll Film and Ready – to – use Bags
Application Scenarios of Plastic Films in Laminated Bags
In the structure of laminated bags, plastic films play a crucial role. Different types of plastic films, with their unique material characteristics, are suitable for a wide variety of application scenarios.
Polyethylene (PE) Films
Low – Density Polyethylene (LDPE)
LDPE films are extremely soft, as smooth as silk, and have excellent flexibility. They can be easily bent in various ways and are very difficult to crack during the bending process. This outstanding flexibility enables LDPE films, when used as the inner – layer material of laminated bags, to perfectly fit the shape of food. Whether it is the irregular shape of gummy candies or the soft and deformable texture of pastries, LDPE films can tightly wrap around them, providing close – fitting protection for food. In terms of moisture – proof performance, LDPE films perform excellently. Like a loyal guard, it can effectively block the invasion of external water vapor and maintain a dry environment inside the package. For foods that are extremely sensitive to humidity, such as biscuits and potato chips, the moisture – proof function of LDPE films is a key factor in ensuring their crispy taste and stable quality. In addition, LDPE films also have excellent heat – sealing performance. In a specific temperature environment, it can quickly heat – seal with itself or other materials to form a firm and tight sealing effect, effectively preventing food leakage and external pollution. In daily food packaging, in the laminated bags of small – packaged snacks we commonly see, such as individually packaged gummy candies and small breads, the inner layer mostly uses LDPE films, precisely taking advantage of its softness, moisture – proof and easy – heat – sealing characteristics.
High – Density Polyethylene (HDPE)
Compared with LDPE, the strength of HDPE films has been significantly improved. It has good rigidity and excellent wear resistance, and can withstand a certain degree of extrusion and friction without being easily damaged. This high strength enables HDPE films to enhance the overall protective performance in laminated bags, just like putting a solid armor on the package. The density characteristics of HDPE endow it with good barrier performance. It has a certain ability to block small molecules such as oxygen and nitrogen, which can effectively delay the oxidation and deterioration process of food and extend the shelf – life of food. In terms of appearance, HDPE films have relatively lower transparency than LDPE, but the surface is smooth and flat. In practical applications, HDPE films are often selected for the packaging of large – package grains and beans. For example, in the 5 – kg rice packaging bag, the outer layer usually uses HDPE film. On the one hand, it uses its high strength to withstand the friction and extrusion during handling and storage, protecting the inner – layer packaging and rice from damage; on the other hand, the certain barrier property of HDPE also helps to further prevent moisture and insects, ensuring the stable quality of rice during long – term storage.
Polypropylene (PP) Films
PP films have high transparency, which makes them have obvious advantages in application scenarios that require product appearance display. When used in laminated bags, it can clearly show the color and shape of the food inside the package, allowing consumers to intuitively see the quality of the food, greatly enhancing the attractiveness of the product. For example, in the packaging of dried fruits and candies, PP films can perfectly present the bright colors of dried fruits and the delicate shapes of candies, stimulating consumers’ desire to buy. PP films have good stiffness, enabling laminated bags to have a certain shape – retaining ability and not being easily deformed. Even if they are subjected to a certain external force extrusion during transportation and storage, they can still maintain a relatively regular appearance, improving the overall aesthetics of the package. PP has strong chemical stability and strong corrosion resistance to acids and alkalis. This characteristic makes it suitable for packaging some foods with slight corrosion, such as some acidic fruit gummy candies. In addition, PP films also have good heat resistance and can maintain stable performance in a certain high – temperature environment. They are suitable for food packaging that has undergone high – temperature sterilization treatment. For example, some high – temperature cooking bags often use PP films as part of the laminated bag to ensure that the package will not deform or be damaged during the high – temperature sterilization process, while ensuring the safety and quality of the food.
Polyethylene Terephthalate (PET) Films
PET films have excellent mechanical properties, with high tensile strength and tear resistance, and can effectively resist external pulling and puncturing, providing reliable protection for the food inside the package. When facing the touch of sharp objects or the bumps during transportation, PET films can rely on their strong mechanical properties to ensure the integrity of the food packaging and prevent the food from being damaged. Its barrier performance is also excellent, with significant barrier effects on oxygen and water vapor, which can greatly delay the oxidation and moisture – absorption deterioration of food. For foods with extremely high freshness requirements, such as coffee and tea, the barrier performance of PET films is the key to extending their shelf – life and maintaining their flavor and quality. Coffee is prone to oxidation due to contact with oxygen, losing its original aroma and taste, and tea is extremely sensitive to humidity and prone to mildew after being damp. PET films can effectively block oxygen and water vapor, providing a stable storage environment for coffee and tea. PET films also have relatively prominent heat resistance and can withstand high temperatures. They are widely used in food packaging that requires high – temperature processing or high – temperature storage. At the same time, the good printability of PET films makes it possible to print beautiful patterns and texts on the surface of laminated bags, helping to enhance the brand image of products. In the market, the laminated bag packaging of many high – end chocolates and health products often uses PET films, taking advantage of its high performance to protect products and displaying brand charm through beautiful printing.