How is PE plastic wrap made?

PE plastic wrap, also known as polyethylene plastic wrap, is a widely used product in various industries, from food packaging to industrial applications. As a supplier of PE plastic wrap, I'm often asked about how this versatile product is made. In this blog post, I'll take you through the detailed process of manufacturing PE plastic wrap.

Raw Materials

The primary raw material for PE plastic wrap is polyethylene, a thermoplastic polymer derived from petroleum or natural gas. There are different types of polyethylene, but the two most commonly used for plastic wrap are low - density polyethylene (LDPE) and linear low - density polyethylene (LLDPE).

LDPE is known for its high flexibility, transparency, and excellent sealing properties. It has a more branched molecular structure, which gives it a lower density compared to other polyethylenes. LLDPE, on the other hand, has a linear molecular structure with short branches. It offers higher tensile strength and puncture resistance than LDPE. In many cases, a blend of LDPE and LLDPE is used to achieve the desired combination of properties for the plastic wrap.

Polymerization

The first step in making PE plastic wrap is the polymerization of ethylene monomers. Ethylene is a gaseous hydrocarbon that can be obtained from the cracking of petroleum or natural gas. There are two main methods of polymerization used to produce polyethylene:

High - Pressure Polymerization

This method is used to produce LDPE. Ethylene gas is subjected to high pressures (up to 3000 atmospheres) and temperatures (around 100 - 300°C) in the presence of a free - radical initiator, such as an organic peroxide. The high pressure and temperature cause the ethylene molecules to react with each other, forming long - chain polymers. The resulting LDPE has a highly branched structure, which contributes to its flexibility and transparency.

Low - Pressure Polymerization

This method is used to produce LLDPE. It typically involves the use of a catalyst, such as a Ziegler - Natta or metallocene catalyst. The reaction takes place at lower pressures (around 1 - 100 atmospheres) and temperatures (around 50 - 100°C). The catalyst helps to control the polymerization process, resulting in a polymer with a more linear structure and short branches.

Extrusion

Once the polyethylene resin is produced, it is ready for the extrusion process. Extrusion is a manufacturing process in which the resin is melted and forced through a die to form a continuous shape.

Melting

The polyethylene resin is first fed into a hopper, which then feeds the resin into an extruder. The extruder consists of a heated barrel with a rotating screw inside. As the screw rotates, it moves the resin along the barrel, and the heat from the barrel melts the resin. The temperature in the extruder is carefully controlled to ensure that the resin is melted evenly without degrading.

Die

The melted resin is then forced through a die, which is a specially designed tool that gives the plastic its shape. For PE plastic wrap, a circular die is commonly used to produce a tubular film. The die has a small gap through which the melted resin is extruded, forming a thin tube of plastic.

Cooling

As the plastic tube emerges from the die, it is cooled rapidly to solidify it. This is usually done by blowing air or water onto the tube. The cooling process is crucial as it affects the physical properties of the plastic wrap, such as its clarity and strength.

Blown Film Process

The blown film process is a common method used to produce PE plastic wrap. After the plastic tube is extruded, it is further processed in the following steps:

Inflation

Air is blown into the center of the plastic tube, causing it to expand like a balloon. This inflation process increases the diameter of the tube and reduces its thickness, resulting in a thin film. The ratio of the final diameter of the tube to its initial diameter is called the blow - up ratio, which can be adjusted to control the thickness and width of the plastic wrap.

Collapsing

Once the desired thickness and width are achieved, the inflated tube is collapsed between a pair of nip rollers. These rollers flatten the tube into a double - layer film.

Trimming and Winding

The flattened film is then trimmed to remove any uneven edges. Finally, the film is wound onto large rolls, which can be further processed or sold directly to customers.

Additives

In some cases, additives are added to the polyethylene resin during the manufacturing process to enhance the properties of the plastic wrap.

Anti - fog Agents

Anti - fog agents are used to prevent the formation of fog on the surface of the plastic wrap when it comes into contact with moisture. This is particularly important for food packaging applications, as fog can reduce the visibility of the product inside the wrap. You can learn more about Anti - fog PE Cling Flm on our website.

Slip Agents

Slip agents are added to reduce the friction between the layers of the plastic wrap, making it easier to unwind and use. They also prevent the wrap from sticking to itself during storage and handling.

UV Stabilizers

UV stabilizers are used to protect the plastic wrap from the harmful effects of ultraviolet radiation. This is important for outdoor applications or products that are exposed to sunlight for extended periods.

Quality Control

Quality control is an essential part of the manufacturing process to ensure that the PE plastic wrap meets the required standards. Various tests are conducted at different stages of production, including:

Thickness Measurement

The thickness of the plastic wrap is measured using a thickness gauge. This ensures that the wrap has a consistent thickness throughout, which is important for its performance.

Tensile Strength Testing

Tensile strength testing is used to determine the maximum amount of stress that the plastic wrap can withstand before breaking. This test helps to ensure that the wrap is strong enough to hold the product without tearing.

Seal Strength Testing

Seal strength testing is conducted to evaluate the strength of the seals made with the plastic wrap. This is important for food packaging applications, as a weak seal can lead to product spoilage.

Applications

PE plastic wrap has a wide range of applications, including:

Food Packaging

PE plastic wrap is commonly used to wrap food products, such as fruits, vegetables, meats, and cheeses. It helps to keep the food fresh by preventing the loss of moisture and the entry of air and bacteria. You can explore our PE Fruit Film for more information on food - specific applications.

Industrial Packaging

In the industrial sector, PE plastic wrap is used to protect products during storage and transportation. It can be used to wrap machinery, equipment, and other large items to prevent damage from dust, moisture, and scratches.

Household Use

PE plastic wrap is a staple in many households for covering leftovers, storing food in the refrigerator, and wrapping sandwiches and snacks.

Conclusion

As a supplier of PE plastic wrap, I'm proud to be part of an industry that produces a versatile and useful product. The manufacturing process of PE plastic wrap involves several steps, from polymerization to extrusion and blown film processing. Each step is carefully controlled to ensure the quality and performance of the final product. Whether you're looking for PE Wrapping Film for food packaging or industrial applications, we have the expertise and experience to meet your needs.

If you're interested in purchasing PE plastic wrap for your business, we'd love to have a discussion with you. Contact us to start a procurement negotiation and find the best solution for your packaging requirements.

References

• "Plastics Technology Handbook" by Charles A. Harper
• "Polymer Science and Technology" by Donald R. Paul and Christopher B. Bucknall
• "Blown Film Extrusion" by John L. Throne