LDPE (Low-Density Polyethylene): Production, Price and its Properties

 

What is LDPE (Low-density Polyethylene)?

LDPE (Low-density Polyethylene) is the most common form of polyethylene used. The resins are much more than just being general purpose polyethylene resins. They prove to be a valuable product of polyethylene family which has excellent combining superior clarity and with stiffness and density.

The resins also offer excellent packaging applications on grounds of aesthetics, strength, tear resistance, printability, and elasticity. These thermoplastics can be easily processed on high-speed lines to be used as films, coatings or for lamination purpose.

 

LDPE Resin Price

 

LDPE Production Process

The two common process used in the production of low-density polyethylene polymer is (1) Tubular Process (2) Autoclave Process. Both these process use free radical chemistry.

Low-density polyethylene is manufactured by the process of the polymerization of ethylene at very high temperatures in a tubular reactor. In this tubular reactor, high-pressure polymerization allows further copolymerization of ethylene with polar co-monomers.

The tubular process has an advantage over autoclave process. The tubular lines are more cost efficient with lesser power consumption. Globally tubular process occupy a major share in low-density polyethylene production technology.

The resins find their basic usage in producing general purpose and high-performance applications, including blow and cast film, extrusion and coating, film and sheets, rotational and injection molding and other applications. The other typical applications of the thermoplastic include consumer bags, liners, overwraps, lamination films, agricultural films, extrusion coatings, caps and closures, toys and a variety of many other durable plastic products used in daily lives. They are even used in molded laboratory apparatus such as for manufacturing pipette washing equipment, bags, tanks and general purpose tubing.

Major Low Density Polyethylene Manufacturing Plants

 

World Production Capacity of LDPE


The global production capacity of polyethylene polymer in 2016 was 103 million tons. The production capacity of low-density polyethylene occupied a share 20.9% in global polyethylene production. The production of low-density polyethylene in 2016 was 20.9 million tons.

The major low-density polyethylene production regions were Europe and Asia accounting around 28-29% each. The other leading was North America with 17% of the production share.

 

History of Low-Density Polyethylene Resins

It is a resin made from monomer ethylene. It was the first grade of polyethylene produced by the Imperial Chemical Industries (ICI) in the year 1933. The resin was produced by using a very high-pressure process termed as free radical polymerization. Even today the thermoplastics are produced by using the same method. These resins are available in a wide range of flexibilities depending on their production process.  Despite high competition among the polymers it retains its importance as a good plastic grade in the market.

 

Properties of Low-Density Polyethylene

Physical Properties

Low-Density Polyethylene is the most commonly used grade of polyethylene. The thermoplastics offer a wide range of usage due to their properties which make them applicable to a variety of products.

It is a high molecular weight polyolefin material. Like all another polyolefin low-density polyethylene is also non-toxic, non-contaminating and high quality of break resistance. It is lighter than water, chemically inert and insolvent at room temperatures.

Generally, it has a milky white translucent appearance with a combination of a flexible material and unique flow properties, which proves its suitability for plastic film applications. Though the resins have high ductility but still have low tensile strength usually, when they are exposed to light and oxygen they lose their strength and tear resistance.

The product of this resins is widely used in different ends segment industries such as construction, automotive, packaging, and others. The polymers are given preference over other grades of polyethylene due to their differential properties which are:

  • The resins can be tough and flexible according to their demand usage.
  • It can be transparent or even translucent and have a waxy surface.
  • They are semi-rigid, tough and waterproof.
  • They have a low melting point and also provide good moisture barrier properties.
  • These thermoplastics provide stable electrical properties and good chemical resistance
  • The plastics can be easily processed by low-cost methods.

Basic Physical properties of Low-Density Polyethylene

Tensile strength 0.20 – 0.40 N/mm2 and impact strength no break

Thermal Coefficient of expansion 100 – 220*10.6

Max Cont Use Temperature 65 ° Celsius

Density 0.917 – 0.930 g/cm3

Resistance towards Chemicals

  • Excellent resistance (no attack / no chemical reaction) to dilute and concentrated acids, alkalis, alcohols, bases, and esters.
  • It offers good resistance (minor attack / very low chemical reactivity) towards Oils and Greases, Aldehydes and Ketones.
  • Limited resistance (moderate attack / significant chemical reaction, suitable for short-term use only) for different kind of hydrocarbons such as Aliphatic hydrocarbons, Aromatic hydrocarbons, and Halogenated hydrocarbons. Even for oxidizing agents and mineral oils.

The resins have strength, rigidity and both chemical along with temperature resistance which makes them applicable for producing a variety of goods in different segments. Products made from low-density polyethylene are durable and their vast usage can be easily depicted in plastic products used in our daily lives such as bags, toys, films, laboratory apparatus, toys etc.

 

Uses of Low-Density Polyethylene

Low-Density Polyethylene is a widely used polymer for manufacturing of various containers, wash bottles, dispensing bottles, tubing, plastic bags and a variety of molded laboratory apparatus. The plastics are used in very large quantities due to their properties which make them applicable for a variety of end segment products. Basic Applications of the thermoplastics are:

 

Low-Density Polyethylene Pipe

Low-density polyethylene pipe (poly pipe) is the most commonly used pipe for domestic and chemical irrigation purpose. These pipes are used in irrigation basically to deliver from source to micro-pipe. They are highly suitable for installing above grounds and as they are not very flexible so connectors can be used to direct supply pipes. Barbed connectors are used with the pipes as they provide a tight and free seal which helps to prevent leakage and easily withstand water pressure.

Specifications of LDPE Pipe

  • The pipes do not react at room temperatures outside the high oxidation factors.
  • These pipes have a defined range from 0.910 to 0.940 g/cm3
  • Low-density polyethylene pipes can continuously withstand at 80° C and 95° C.
  • The pipes are completely translucent or opaque in appearance and highly break resistant.

Physical Properties of the Pipe

  • The pipe can withstand the maximum temperature of 176 ° F (80 ° C) and the lowest temperature of 248° F (120° C).
  • Melting point of the pipes is 248 ° F (120 ° C)
  • Tensile strength: 1700 psi (11.7 MPA)
  • Density: 0.92 g / cm3
  • They have poor UV resistance.
  • They are translucent with excellent flexibility.

Areas of Applications

The pipes can be used for a wide range of applications ranging from sprinkler irrigation, drip irrigation, drainage system, agricultural piping and other irrigation systems. These pipes are used with the full flow having nylon insert fittings such as couplings, elbow tees, and adaptors.

Installation of Low-Density Polyethylene Pipes

The pipes and fittings can be installed very easily with simple equipment. All fittings and already internally fitted pipes are warmed up before insertion of a fitting. Further pipe is secured with clamping it down on the pipe to be installed with a heated screw type clamp. As a measure, warm screw clamps should be protected if they are being used in the area of high humidity and exposed to chemicals. These pipes can be buried in the ground or installed above the ground.

 

LDPE Film and Sheets

 Low-Density Polyethylene was the first polyethylene to be developed and is known for its toughness and flexibility, with relatively heat resistance and temperature impact. These features make them applicable to be produced in form of films and sheets which can be further utilized to produce other plastic products. This material is one of the fastest growing plastics used today mainly for film applications apart from being also suitable for injection, blow and rotational molding.

Properties of Low Density Polyethylene Films and Sheets

  • The sheets are translucent and shrinkable.
  • They are heat and chemical resistant.
  • The sheets can be easily welded by plastic welder
  • They are not UV stabilizes
  • These films are conductive films and can be easily colored.
  • They offer ease of sealability which means they can be easily heat sealed.
  • The films and sheets are flexible, lightweight and economical.
Physical properties –    
  • Density: 0.92
  • Forming temperature: 245°F
  • Temperature range: 0°F – 140°F
  • Tensile Strength (PSI) 1600
  • Ultimate Elongation 600%
  • Meet FDA standards

Application of LDPE Film and Sheets

  • Packaging industry– Use in food packaging and textile packaging. Films and sheets are commonly used for the production of produce bags, brad bags, trash bags, garment bags, grocery sacks and shipping bags etc in the packaging industry.
  • Industrial- Used to produce tapes, sealants, gaskets, photographic protection, liners, piping system, composites, automotive parts, shrink films, pallet stretch, greenhouse coverings, tanks, and containers etc.
  • Medical– Used for Transdermals, Hydrogels and in wound care or for packaging of medicines.

 

Low-Density Polyethylene Bags

The bags or flat poly bags are the most commonly used bags in the packaging industry and are easily affordable. These bags are simple to use and provide an easy way to protect any item. These bags are available in three categories; Standard flat poly bags, Crystal clear poly flat bags, and Heavy duty poly flat bags. Each of these bags offers different qualities and features and are applicable according to their properties required for usage.

The bags are now days widely produced from recycled low-density polyethylene plastic materials which are more economical and environment-friendly way of using these bags in the packaging industry.

 

Other Uses of Low Density Polyethylene

It is used for different products in a variety of different forms such as playground slides, plastic wraps, military tents, trays, cartons, packaging of computer hardware (optical drives, hard disk drives, and screen cards etc), as a layer of aluminum foil and many others.

 

Advantages and Disadvantages of LDPE

Low-Density Polyethylene is used in the production of a variety of end segment market products such as pipes and tube, carry bags, films, and sheets, packaging of goods and others. It offers strong chemical and temperature resistance and easy flow which make the resin applicable for pipes and sheets. It is a commonly used form of polyethylene grade as it offers following benefits:

  • They have low specific gravity and high impact strength.
  • It is strongly chemical and temperature resistant which enhances the durability of the products.
  • It is highly water resistant to low density.
  • The plastics can be easily reused as liners or shopping bags.
  • The resin can also be a source of energy when it is burned for heating buildings.
  • It is break resistant which is useful in the production of long-term use products.

Though the thermoplastics are the maximum used grades of polyethylene which is applicable to a variety of plastic products used in daily lives, these resins still offer certain limitations such as:

  • They have poor heat resistance for some products.
  • High coefficient of thermal expansion provides a limitation in the production of low-density polyethylene products.
  • The thermoplastics offer poor weathering resistance.
  • The resins are often subjected to stress cracking.
  • It is a kind of PE grade which has difficulty in bonding
  • The plastics have hazardous environmental effects such as landfill sites destroy green spaces and it is made from nonrenewable resources such as crude oil which exerts stress on resources.
  • A lot of energy is wasted to produce this kind of plastics.

 

Difference between LDPE and HDPE

Properties

Structure

Flexibility

Color

Impact Strength

Low-Density Polyethylene

 It structure consists of lot of branching and is less dense

It is very flexible

Natural milky and translucent color

It has very high impact strength

High-Density Polyethylene

It has less branch and is denser

It is more rigid than low-density polyethylene

Milky white and semi-translucent

It has good impact strength

 

 

Recycling of LDPE

The plastics are used to create a variety of plastic products ranging from medical supplies, household to film and sheets. The resin offers increased pliability and decreased strength which makes it an ideal material for the packaging industry in form of plastic bags and milk cartons etc. This widespread use of the plastics result in recycling of the material in large quantities.

 

Purpose of Recycling

It is the commonly used in large quantities which can have a hazardous impact on health and environment if not recycled. It is produced from crude oil which is a non-renewable resource and creates pressure on it. When the plastic is not recycled it is dumped as landfill which consumes green spaces.

Identification of Materials for Recycling

Plastics produced carry an identification number ranging from one to seven which indicate how these materials have to be recycled. It can be identified by a recycling symbol which comprises of a triangle with the three arrows on the outer side, carrying number 4 in the middle of the triangle. Usually, this triangle mark can be seen near the list of ingredients on the package or on the plastic container itself.

Considering Materials to be Recycled

A large variety of plastic products may have number 4 recycling symbol but the plastics are most commonly found in bottled water packaging. The thermoplastics are commonly used in thin and soft form after recycling so products such as shopping bags, milk cartons, and garbage bags can be considered to be produced from a recycled form of low-density polyethylene plastics.

Reducing Pollution from Low-Density Polyethylene Usage

The polymer recycling centers are available almost everywhere so dropping of the plastic products at these centers weekly may also reduce pollution and increase recycling of the material. For packaging or carrying, goods preference can be given to plastic bags made from recycled material.

Recycling Process

The products available in recycling centers are melted by a heating process to eliminate contaminants. While the plastics are heated they turn from solid to gummy liquid and finally to the fluid as heating temperature is further increased. The melting point of LDPE is around 115°celsius which allows a process of ‘float- and- sink’ to separate low-density polyethylene polymer from other polymer materials. The separation process is carried out in a tank using water. As the recycling process ends the polymer liquid material are converted in form of plastic sheets which are sold to manufacturers to produce recycled materials.

Uses of Recycled Low-Density Polyethylene

The recycled form of low-density polyethylene plastics can be further used to produce plastic products such as Grocery bags, toys, Lids, Refuse bags, carpets and many other products used in daily lives.