This material is one of the most widely used and diverse thermoplastic polymers used in various industries and is obtained from the polymerization of ethylene. It can be produced in a linear or branched form depending on its molecular structure, which creates different types such as HDPE, LDPE, LLDPE and UHMWPE. The melting temperature of polyethylene varies depending on its type, and these differences have a direct impact on the application of polyethylene. By understanding what polyethylene is and how its structure and melting temperature affect its physical and chemical properties, this material can be best used in the production of various products such as pipes, packaging films, industrial parts and sports equipment.
What is polyethylene?
This material is a type of thermoplastic polymer that melts when heated and returns to a solid state when cooled. This material has a variable crystal structure and has different applications depending on its type. Polyethylene, abbreviated as PE, is a lightweight and versatile resin produced through the polymerization process of ethylene and is part of the polyolefin resin family.
In response to what is polyethylene? It must be said that this material is the most widely used plastic in the world, used in the production of transparent nylon food packaging, shopping bags and car fuel tanks. Types of polyethylene include high-density polyethylene (HDPE), low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), each of which has its own characteristics and applications.
The melting point of polyethylene varies depending on the type, but is generally in the range of 115 to 135 degrees Celsius. The material can be spun or spun into synthetic fibers or deformed to have a rubber-like elasticity.
The structure of polyethylene consists of crystalline and amorphous chains, the degree of crystallinity of which can greatly affect the mechanical and chemical properties of the material, and due to these characteristics, the use of polyethylene in various industries is very wide.
Types of polyethylene
This material with a variable melting temperature and different crystal structure, depending on its type, can have a variety of properties and applications. Types of polyethylene, each with its own structure and characteristics, are used in various fields such as packaging, piping, production of strong fibers, and insulation. Understanding what polyethylene is and recognizing the types of polyethylene helps us to use this material in the best way in different industries. In the rest of this article from the Rangin Polymer series, we will examine the types of this material.
Ultra-high molecular weight polyethylene (UHMWPE)
This material has long, linear chains that give it high resistance to impact, abrasion, hardness, and compressive fracture. This type of polyethylene, with difficult processability, is used to produce strong fibers that replace Kevlar in bulletproof vests. Large sheets of UHMWPE can be used as a replacement for ice skating rinks. These applications show what polyethylene is and why it has important applications in certain industries.High Density Polyethylene (HDPE)
High Density Polyethylene (HDPE) is a linear, stiffer, branched polyethylene that has high tensile strength. This type of polyethylene is produced by polymerization at low pressure and temperature. The mechanical properties of HDPE allow it to be used in larger shapes and applications such as sheet materials in tanks and column insulation, and the use of heat welding to join this material is also common.Cross-Linked Polyethylene (PEX or XLPE)
This type of cross-linking (PEX or XLPE) is converted into a thermoset polymer by creating cross-links in the polymer structure, increasing its density and improving its mechanical properties at high temperatures. This type of polyethylene is used in drinking water piping and insulation of medium and high voltage electrical cables. PEX polyethylene is also used in hot water pipes and molded parts.Medium-density polyethylene (MDPE)
This type has higher impact and stress-strain resistance than HDPE and, due to its high chemical resistance, is commonly used in gas pipes and fittings, packaging, carrier bags, and bottle caps.Linear low-density polyethylene (LLDPE)
This polymer is obtained by copolymerizing ethylene with short-chain α-olefins such as 1-butene or 1-hexene and is used to make plastic films such as freezer bags. LLDPE has higher tensile, impact, and puncture resistance than LDPE, and can produce blown films with thinner thicknesses and better strength.Lightweight Low Density Polyethylene (LDPE)
This type is produced under high pressure and temperature, usually using vinyl free radical polymerization, and is used for piping and packaging due to its transparency, flexibility, and expandability. Its chemical resistance is lower than that of HDPE and polypropylene, but it is still resistant to many acids and alkalis.Very light polyethylene (VLDPE)
VLDPE has a linear structure with high levels of short-chain branches and is produced by copolymerization of ethylene with short-chain α-olefins or using metallocene catalysts. It is used in the production of hoses and pipes, ice packs and frozen foods, food packaging, and also as impact modifiers in combination with other polymers.
Applications of polyethylene
Polyethylene, as a thermoplastic polymer with a variable melting temperature and crystal structure, has a wide range of applications in various industries due to its unique properties. Types of polyethylene include different grades, each of which is suitable for the production of different products due to its specific properties.
HDPE, due to its high strength and resistance, is mostly used to produce various types of polyethylene pipes and fittings, polyethylene tanks, plastic parts, bottles, shipping boxes, food storage containers, septic tanks and packaging bags.
LDPE, due to its high flexibility and transparency, is used in the production of various types of plastic parts, polyethylene pipes, polymer sheets, fibers, containers and packaging films, plastic bags and similar products.
MDPE, due to its impact resistance and good mechanical properties, is widely used to make packaging films, protective coatings for metal surfaces, pipes and fittings for pressurized irrigation.
Due to its resistance to stretching and puncture, LLDPE is used in the manufacture of electrical and telecommunications cable sheaths, various protective coatings and films, and plastic parts.
Due to its extraordinary strength, UHMWPE is used in the manufacture of certain parts of industrial machines, special clothing, sturdy sporting goods, bulletproof coatings, and some defense industry equipment.
Other uses of polyethylene include the production of packaging materials, pallets, plastics, packaging strapping, packaging box fasteners, and plastic baskets.
Polyethylene is used in the production of household appliances, for the manufacture of bottles, kitchen utensils, plastic parts for household appliances, and toys.
Melting temperature of polyethylene
The melting point will vary depending on the type and structure of the material, and this difference in melting point has a significant impact on the physical and chemical properties of the material. What is polyethylene and how its structure affects its melting point and properties is a topic that helps to understand the application of polyethylene.
- HDPE has a melting point of around 130-140°C and, due to its linear and crystalline structure, has high strength and toughness, making it suitable for industrial applications such as the production of polyethylene pipes, tanks and plastic parts.
- LDPE has a melting point of around 105-115°C and has a branched structure that makes it softer and more flexible.
- LLDPE has a melting point similar to or slightly higher than LDPE and offers a combination of strength and flexibility due to its linear structure with short branches.
- MDPE has a melting point of around 120-130°C and has properties between HDPE and LDPE.
- UHMWPE has a melting point similar to HDPE, but due to its very long molecular chains, it has special physical properties such as extremely high strength and abrasion resistance. Provides.
Chemical structure of polyethylene
Ethylene (C2H4) is a gaseous hydrocarbon that is usually produced by the cracking of ethane and is a major component of natural gas or can be distilled from petroleum. Ethylene molecules consist of two methylene (CH2) units linked by a double bond between carbon atoms and are represented by the following formula:
In the presence of polymerization catalysts, the double bond of ethylene can be broken and the resulting single bond can be attached to a carbon atom in another ethylene molecule, resulting in a large polymer molecule with a repeating chemical structure. This simple structure, repeated thousands of times in a molecule, is key to the properties of polyethylene.
The structure of basic polyethylene can be modified by adding other elements or chemical groups, such as chlorinated polyethylene and chlorosulfonated polyethylene. In addition, ethylene can be copolymerized with other monomers such as vinyl acetate or propylene to produce a number of ethylene copolymers.
These changes in the structure of polyethylene have significant effects on its physical and chemical properties, resulting in the production of different types of polyethylene with different applications in industries. Understanding what polyethylene is and how its molecular structure can be changed will help us to optimally use this material in different applications.
Summary
As one of the most widely used thermoplastic polymers, polyethylene plays a vital role in various industries with its diversity in structure and melting temperature. A precise understanding of what polyethylene is and the types of polyethylene and their applications will allow us to optimally use this material in the production of various products.From durable pipes and tanks to flexible packaging films, polyethylene’s melting point and molecular structure have a direct impact on the physical and chemical properties of this polymer. Ultimately, this material, with its unique characteristics, has a special place as a basic material in industrial and consumer products.
Frequently Asked Questions
1. What is polyethylene?
This material is a thermoplastic polymer obtained from the polymerization of ethylene and is used in various industries due to its diverse properties.
- How does the structure of polyethylene affect its properties?
- Is polyethylene recyclable?
- Can polyethylene be copolymerized with other monomers?
- How does the melting point of polyethylene affect its properties?
