Blown Film Process -Ruihang plastics machinery

15/09/2025

Q: What kind of additives are antioxidants used in blown film? What role do antioxidants play? How do you choose the right antioxidant?

A: Antioxidants are a very useful additive used in blown film production. Those of us working in blown film have all encountered the problem of blown film aging and yellowing, or even yellowing and aging after a period of storage. How can this problem be solved? This is where antioxidants come in. These additives are commonly used in high-end film products. Properly used, they can effectively improve the physical properties of blown film.
1. First, what are antioxidants? While this article focuses primarily on blown film, antioxidants are actually widely used in plastic products.
2. Simply put, antioxidants are a class of chemical substances that, when added in small amounts to PE, can delay or inhibit the oxidative degradation of plastics. They prevent material aging by capturing free radicals and decomposing hydroperoxides, thus extending the service life of blown film products. Therefore, they are also called "antioxidants." In the blown film process, antioxidants effectively prevent molecular chain breakage caused by thermal oxidation during high-temperature extrusion and film blowing, thereby preventing problems such as decreased mechanical properties, yellowing, and the appearance of "crystal points." They are particularly suitable for film products that require weather resistance and transparency. 3. Now that we have a general understanding of the concept of antioxidants, let's discuss their classification. Antioxidants are categorized into amine antioxidants, phenolic antioxidants, phosphite antioxidants, sulfur-containing antioxidants, biological antioxidants, and compound antioxidants. Each type of antioxidant has its own advantages and specific applications, so we will not discuss them one by one.
4. From the above introduction, you can see that despite their relatively simple functions, antioxidants are actually classified into a very specialized category. So how do we choose the right antioxidant? We need to consider the following principles. First, compatibility. PE material is non-polar, while antioxidant molecules have varying degrees of non-polarity, so compatibility between the two can be challenging. Therefore, it is important to select an antioxidant with good compatibility. Second, migration resistance. Especially for thicker products, since most oxidative degradation occurs at the surface, the antioxidant must be able to continuously migrate from the interior of the film to the outside without causing precipitation. Secondly, stability refers to both the molecular stability of the antioxidant itself and ensuring that it does not react with other additives, thereby affecting the quality of the finished product. Of course, for products that come into contact with food, there are also safety and environmental considerations.
5. Choosing the right antioxidant and the appropriate dosage can be done by consulting the antioxidant manufacturer. Understanding the concept, classification, and selection principles of antioxidants will make communication with them much easier.

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02/09/2025

Concept, principle and related functions of PPA additives for blown film
Q: PPA is a crucial additive used in blown film production. Many people have likely used it as a rheological agent, especially in high-pressure blown film production, where it's often described as a panacea. But what exactly is PPA? What is its mechanism of action? What are the benefits of PPA?

A：First, let's discuss what PPA is. Specifically, PPA is a type of modified plastic processing additive primarily composed of a fluorinated polymer. It's typically formulated as a masterbatch using LLDPE as a carrier resin. It's suitable for blown film processing of polyolefin resins, including high-pressure, linear, metallocene, and low-pressure materials. Its core function is to improve melt flow, reduce processing defects, and enhance film quality and production efficiency. Furthermore, this additive complies with food safety standards.
So, what is the mechanism of action of PPA? Generally speaking, PPA molecules are composed of polar functional groups and non-polar polymer segments. During extrusion, the polar functional groups in the PPA molecule tend to migrate toward the metal surface, forming a directional lubricating film through van der Waals forces or chemical adsorption, effectively reducing the friction coefficient between the melt and the metal layer. Understanding the principles of PPA makes it easier to understand the role this additive plays.
First, PPA rheology additives can reduce extrusion pressure, especially at the die, effectively eliminating melt fracture during the blown LLDPE and MLLDPE film production process. Melt fracture, also known as "sharkskin," can severely impact the product's appearance. By reducing the friction between the melt and the die, adding PPA also helps delay die buildup. Furthermore, the reduced extrusion pressure allows for a narrower die gap, resulting in better film balance.

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19/08/2025

Q: What is corona breakdown? What problems will occur with the thin film after corona breakdown? How to avoid corona breakdown?
A: 1. What is corona breakdown? How to avoid corona breakdown? Corona breakdown can have some adverse effects on our thin film products, seriously affecting the quality of the film. So what is corona breakdown? The so-called corona breakdown refers to the phenomenon of corona discharge occurring on non corona surfaces. Of course, some people also refer to the phenomenon of micro pores or damage on the surface of thin films caused by high-energy discharge during corona treatment due to excessive local electric field or improper process parameters as corona breakdown. The corona breakdown referred to here refers to the phenomenon of corona values appearing on the opposite side of the corona surface, which can have adverse effects on the printing and heat sealing of films. For example, when processing bags with such films, poor heat sealing may occur due to corona on the back, and the blown film roll may cause adhesion and ink back adhesion during unwinding and unwinding. Even films with corona breakdown may experience a decrease in ink adhesion due to insufficient surface tension of the film. How does the phenomenon of corona breakdown occur? How to avoid corona breakdown? Let's have a detailed discussion. First of all, we need to know that the principle of corona machine generating corona is actually a high-voltage discharge phenomenon, which ionizes the air. The ozone generated by ionization acts on the surface of the film to produce certain polar molecules. At the same time, high-frequency corona can also make the surface of the film rough, thereby increasing the surface tension and producing good auxiliary properties, thus obtaining satisfactory printing effects. However, if there is an air isolation gap between the interlayer of the film or the film and the corona roller during corona treatment, the air in the gap will also be ionized, causing corona on the back of the film. It should be pointed out that in the process of blowing the film, due to the difficulty of clamping the clamping roller, there will be more corona when the film passes through the corona roller. The living folds, So the film is more prone to corona breakdown.
3. What causes corona breakdown during the blown film process? If the exhaust of the film is not thorough during the blowing process, there are too many active folds, there are too many foreign objects on the guide roller causing gaps between the film and the corona roller, or the surface of the corona roller is uneven and damaged, this problem may occur. Therefore, when corona breakdown occurs, the above factors must be carefully investigated. In order to avoid the occurrence of corona breakdown phenomenon, we need to pay attention to the above factors, regularly check whether there is any damage on the surface of the traction roller and corona roller, ensure the cleanliness of these roller surfaces, adjust the tension of the film appropriately during the film blowing process, and avoid wrinkles. By paying attention to these aspects, corona breakdown can be avoided to the greatest extent possible.

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12/08/2025

💡Part 2 Forms and classifications of corona treatment

🔹Corona treatment is carried out in three stages according to different needs: film online corona treatment; film post-processing line corona treatment; and a combination of the two for two treatments.
🔹In-line corona treatment of film production, commonly known as hot film treatment, is the most common form of treatment. Because the treatment occurs before the polymer molecules have fully crystallized, the treatment is highly effective. However, it is generally only suitable for films that will undergo immediate further processing (such as printing, coating, or lamination). The corona treatment device is typically located after the film cooling and shaping section and before the winder.
🔹The quality of corona treatment, commonly known as cold film treatment, in post-processing film processing is also affected by the film's twisting time. If the film is stored for a long time after production, a large amount of precipitated additives will adhere to the film surface, reducing the quality of the film after corona treatment. Furthermore, it is important to consider whether the sparks generated by the corona treatment may ignite the solvents used. Corona treatment equipment is generally installed before the printing (or coating, or laminating) equipment.
🔹The second method is a combination of the two, where the film is first treated on the production line and then treated a second time on the film's post-processing line. This is suitable for films with poor quality from the first treatment, or films that have been stored for a long time after the first treatment and the treatment effect has faded a lot.
🔹Depending on the film's usage requirements, corona treatment can be divided into single-sided or double-sided corona treatment. For high-speed cast film production lines, some also use multiple sets of electrodes to meet the surface tension requirements of the plastic film's later processing.

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11/08/2025

🔥Corona treatment is a crucial film processing technique. Simply put, it involves applying a high-frequency voltage to the surface of plastic film, enhancing its adhesion and facilitating subsequent processing steps such as printing, coating, and lamination. Below, we will introduce the methods and processes of corona treatment, as well as the factors that contribute to its failure.
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📌Part 1: The principle of corona treatment

08/08/2025

POE Introduction

02/08/2025

How can you fix the yellowing problem encountered during film blowing, especially with LDPE film? Our video details the causes and solutions!

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25/07/2025