The Best of Polypropylene Films

In the packaging bags we use daily and in industrial production, polypropylene (PP) film is particularly important because of its excellent performance. Cast polypropylene film (CPP) and biaxially oriented polypropylene film (BOPP) are the two most commonly used PP films. They each have their own strengths and are very useful in different places. Many industries cannot do without them.

Cast polypropylene film (CPP)

Production process

The birth of CPP film is due to the ingenious technology of cast process. Specifically, the polypropylene raw material is heated to a molten state, and then the molten raw material is evenly extruded through an extruder so that it is spread flat on a cooling roller. Under the rapid cooling of the cooling roller, the molten polypropylene is quickly shaped, thus forming the CPP film we see. This process is relatively direct, but it gives CPP film a series of unique properties. ​

Performance and application

One of the most striking features of CPP film is its super strong tear and puncture resistance. This is like putting on a solid "armor" for the product. In the packaging process of the product, it can resist the pulling and collision that may occur during the packaging process; in the transportation of the product, it can also stick to its post and protect the internal products from damage in the face of complex situations such as bumps and squeezing; even in the storage stage, it can effectively prevent damage caused by stacking, friction, etc. For this reason, it is particularly reliable when packaging heavy items or products that need to be transported over long distances and face complex logistics environments. ​

High transparency is another "magic weapon" that CPP film has won favor in the packaging field. When CPP film is used to package products, its crystal clear characteristics make the appearance, color and other details of the internal products clearly visible. For food, consumers can directly see the freshness of the food; for cosmetics, they can clearly appreciate the exquisite packaging of the product; for stationery, they can also know its style at a glance. This good display greatly enhances the product's attractiveness to consumers and adds a lot of points to the product in market competition. ​

In terms of heat resistance, CPP film also has a good performance. It can maintain a stable shape and performance under high temperature environment, which makes it play an important role in heat-sealed packaging. For example, when sealing and packaging some cooked food and baked food, high-temperature heat sealing is required to ensure the sealing of the packaging.

At this time, CPP film can withstand the high temperature during the heat sealing process, and will not deform or break, ensuring the quality of the packaging. At the same time, this also gives it a place in some industrial applications that require high-temperature treatment, such as temporary packaging or protection of some industrial parts. ​

CPP film also has excellent moisture-proof and air-proof properties. This is undoubtedly a great boon for products that are sensitive to humidity and gas. Foods such as biscuits and potato chips will lose their crispy taste once they are damp, and CPP film can effectively block the intrusion of external moisture and extend their shelf life; for some electronic components, humidity and harmful gases may affect their performance or even cause damage, and the air-barrier and moisture-proof ability of CPP film can provide them with reliable protection. ​

However, CPP film also has the characteristic of high water vapor permeability. In some cases, this seems to be a disadvantage, such as it is not applicable to products that need to be strictly isolated from water vapor. But everything has two sides. In some special packaging scenarios, this feature can play a positive role. Take fresh fruits and vegetables as an example.

If the packaging material is completely airtight, the water vapor generated by the breathing of fruits and vegetables will condense into water droplets inside the packaging, which can easily cause the fruits and vegetables to rot. The moderate water vapor permeability of CPP film can allow some water vapor to be discharged, avoiding excessive condensation, thereby better maintaining the freshness of fruits and vegetables. ​

Biaxially oriented polypropylene film (BOPP)​

Production process​

Unlike CPP film, the birth of BOPP film has undergone a more complex stretching process. It is to stretch the polypropylene film first in the longitudinal direction and then in the transverse direction. Through these two stretchings, the molecular chains inside the film are orderly oriented in both the longitudinal and transverse directions. This directional arrangement of molecular chains is like optimizing and reorganizing the structure of the material, thus bringing a series of excellent properties to BOPP film.​

Performance and Application​

After biaxial stretching, the tensile strength and stiffness of BOPP film are significantly improved. This means that it can withstand greater tension and pressure without breaking or deforming easily, and its mechanical properties are excellent. During the packaging process, whether it is traction during machine packaging or pulling during manual packaging, BOPP film can maintain good integrity, greatly reducing the loss during the packaging process.

At the same time, its high stiffness makes the film have good stiffness, which is easier to shape during packaging operations, and is also convenient for stacking and storing products, saving storage space and improving storage efficiency. ​

BOPP film also performs well in temperature adaptability

It can maintain good puncture performance and flexibility and crack resistance in a wide temperature range. Whether in the cold winter when the ambient temperature is low, or in the hot summer when the temperature is high, BOPP film will not become fragile and easy to break due to drastic changes in temperature.

This feature allows it to adapt to environmental changes in different regions and seasons, and its application range has been greatly expanded. From the cold north to the hot south, from indoors to outdoors, it can be seen.​

The excellent gloss and high transparency make BOPP film a "weapon" for improving product quality. Its surface gloss can make the packaging look more refined and high-end, while its high transparency can clearly show the charm of the internal products.

When BOPP film is used to package some high-end gifts and luxury goods, it can make the products more attractive and leave a good first impression on consumers. In some industries that focus on brand image and product texture, such as high-end cosmetics, precious tobacco and alcohol, this advantage of BOPP film has been fully utilized. ​

The diversity of BOPP film is also an important reason for its wide application. It can be made into various types such as glossy, transparent, opaque, matte or metallized according to different needs.

Glossy and transparent BOPP films are suitable for scenes that need to fully display the original appearance of the product; opaque BOPP films can provide good light-shielding properties to protect products that are sensitive to light, such as certain medicines and chemical raw materials; matte BOPP films have a low-key and soft texture, giving people an elegant feeling, suitable for some products that pursue a simple style of packaging; metallized BOPP films have both good barrier properties and decorative effects. 

Their metallic texture can improve the grade of the product, and at the same time, it can effectively block oxygen, moisture and light, extending the shelf life of the product. They are widely used in the packaging of food, cigarettes and other products. ​

In addition, BOPP film's high efficiency in blocking oxygen and moisture makes it outstanding in ensuring product quality. Oxygen and moisture are the main causes of many product deterioration, such as food deterioration due to oxidation and mold due to moisture; medicines will be affected by moisture and affect their efficacy.

BOPP film can act as a solid barrier to effectively block the intrusion of oxygen and moisture, provide a stable storage environment for products, and significantly extend the shelf life of products. This is also an important reason why it is widely used in the food, pharmaceutical and other industries. ​

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