⁠Film blowing machine is a machine that heats and melts plastic particles and then blows them into a film. There are many types of film blowing machines, including PE film blowing machine, POF film blowing machine, PP film blowing machine and so on. PE film blowing machine should be the most widely used machine. Today we will explain the common raw materials of PE film blowing machine. The most common raw materials for PE film blowing machines are: HDPE, LDPE, LLDPE, MPE.

    Usually what we call polyethylene is actually a general term for a large class of ethylene homopolymers and copolymers. According to the difference in molecular structure and density, polyethylene is roughly divided into three types: low-density polyethylene, high-density polyethylene, and linear low-density polyethylene. Although ethylene plastomers and elastomers are also in the large polyethylene category, because their properties are far from common polyethylene resins, most of the time they will be discussed separately. Even the three most common types of polyethylene have different characteristics. Let's sort it out carefully for everyone below.

Low-density polyethylene

    Low-density polyethylene, abbreviated as LDPE, is the earliest commercially produced polyethylene variety. In the 1930s, it was first commercialized by ICI. Low-density polyethylene is a homopolymer synthesized by free radical polymerization of ethylene monomer under extremely high pressure. Due to the high pressure in the reactor, it is also called "high pressure polyethylene" in China. Although there is only one monomer, ethylene, the low-density polyethylene molecule has a highly branched structure due to the severe reaction conditions. A large number of long-chain branched structures make it have very good extrusion properties and melt strength. Also subject to the violent reaction process, there are few conditions that can be controlled in the reaction, so the density range of low-density polyethylene is very narrow. The density of common low-density polyethylene is mostly between 0.915 and 0.930. The melting point of most low-density polyethylene is around 105 degrees.

High-density polyethylene
    High-density polyethylene, the English abbreviation HDPE, is the first type of polyethylene synthesized by a catalyst. The first commercial production was in the 1950s. Due to the introduction of the catalyst, the reaction conditions are not so harsh. The polymerization reaction can be carried out under lower pressure, so it is also called "low pressure polyethylene" in China. Also due to the role of the catalyst, the polymerization process can proceed in a gentle and orderly manner. Thereby, a regular single-chain structure is obtained without any long chain branches. During the polymerization process, only a small amount of comonomer (butene or hexene) is added, or even no comonomer, so there are very few short-chain branched structures on the molecule of HDPE. This makes it have a high degree of crystallinity, and also a higher density. Nowadays, polyethylene with a density exceeding 0.940 is generally referred to as high-density polyethylene. Of course, most of the typical high-density polyethylene has a density of 0.950 or higher, and the melting point is also above 130 degrees. High crystallinity brings good stiffness and water vapor barrier properties to high-density polyethylene, but also greatly reduces its transparency and gloss.

Linear Low Density Polyethylene
    With the development of polymerization technology, in the 1970s, the Ziegler-Natta catalyst was used to successfully develop linear low density polyethylene (LLDPE). As the name suggests, linear low-density polyethylene is characterized by a linear single-stranded structure and a lower density. The most common linear low-density polyethylene has a density around 0.920. But in fact, the density of linear low-density polyethylene can be well regulated by controlling the content of comonomers in the polymerization. In theory, any density between 0.855 and 0.960 can be produced. However, the common specifications are between 0.915 and 0.940. Due to the different comonomers, linear low-density polyethylene can be divided into four-carbon linear (butene copolymer), six-carbon linear (hexene copolymer) and eight-carbon linear (octene copolymer). Generally speaking, the larger the comonomer, the better the physical properties. However, most of the linear low-density polyethylene produced in China is still four-carbon linear. Six-carbon and eight-carbon linear low-density polyethylene still mainly depends on imports.

Metallocene polyethylene
    Metallocene catalysts were invented and used in the commercial production of polyethylene in the 1990s. The polyethylene obtained by metallocene catalyzed polymerization is called metallocene polyethylene. Strictly speaking, it is actually a linear low-density polyethylene. However, because the metallocene catalyst controls the molecular structure more accurately, the metallocene polyethylene can provide very excellent toughness and heat sealing performance. At the same time, products with a wider density range can also be produced. From elastomers to low-temperature sealing plastomers, the most common density of 0.920 and even medium and high density, they can all be produced by metallocene technology.

    According to the different characteristics of the film blowing material, our specific requirements in the film blowing process are also different. For example, the heating temperature and blow-up ratio are different, and the die heads used are more different. Shanghai Duxia Industry and Trade Co., Ltd. is a factory specializing in the production of film blowing machines, plastic bag making machines, printing machines, plastic recycling and granulating machines. We not only provide customers with high-quality machines, but also provide customers with corresponding technologies in the production process. Guidance and support. If you need any of the above machines, please leave your information, our sales will contact you as soon as possible, and welcome your inquiry.

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