LLDPE (Linear Low-Density Polyethylene): Production, Price and its Properties
What is LLDPE (Linear Low- Density Polyethylene)?
Linear low-density polyethylene is a kind of linear polymer which was first produced by DuPont in 1959 in Canada, with a number of short branches formed by copolymerization of ethylene with different long chains of olefins. It is like a part of the poly-olefins family which has some structural differences from conventional LDPE (Low-density polyethylene).
This polymer has established itself as the third prominent player of polyethylene business along with LDPE and HDPE. In 2016 it held 3% of the share of the global polyethylene market and the world per capita consumption of linear low-density polyethylene market was around 4-5 Kg per person.
The linear property of the polymer results from the difference in the manufacturing processes of linear density polyethylene and low-density polyethylene.
Usually, linear low-density polyethylene polymers are produced at comparatively lower temperatures and pressures by the co-polymerization of ethylene and higher alpha-olefins such as Butene, Hexene or Octene. Their difference in the co-polymerization process also results in a difference of molecular weight distribution of LDPE and linear low-density polyethylene resins, as these polymers have narrower molecular weight distribution than LDPE polymers.
It exhibits higher tensile strength, impact and pressure resistance as compared to the conventional LDPE polymers which make linear low-density polymers suitable for a wide range of applications and uses.
Linear low-density polyethylene resins are used primarily as films for bags and sheets or in the packaging industry. It is also used in the manufacturing of other goods such as toys, lids, buckets, plastic containers, bubble wraps and composite films.
LLDPE Pricing Trend
Production of LLDPE
Linear low-density polyethylene is a polymer with the density greater than 965 kg/m, usually produced at low temperatures. It is produced by the addition of olefins (butene, hexene or octene) during the polymerization process of ethylene.
Poly-olefins are used in the production of linear low-density polyethylene resins as these monomers contain a reactive double bond. These monomers are used accordingly to control the density and physical properties of the resin produced according to their user’s demand. It is produced by using two major techniques which are:
In this process, linear low-density polyethylene resins are produced at relatively low temperatures (70-110° C) along with low pressure (1-5 MPA) within a saturated form of hydrocarbon medium.
During the process of polymerization, the polymer forms a suspension or mobile slurry. Further, the reaction medium is removed and the polymer is separated from the hydrocarbon inert medium.
The powder obtained as a result of this process is further mixed with stabilizers and extruded in pellets forms. These linear low-density polyethylene pellets can be further used in production of end- segment plastic products.
Gas phase polymerization
In this process, a gas phase reactor is used which, is a kind of fluidized bed of dry polymer particles. These resin particles are maintained is gas reactor by stirring or passing ethylene gas at high speed.
In this gas reactor ethylene along with co-monomer are fed at the base of fluid bed into which later catalyst is injected. In this gas, the reactor pressure is relatively low (up to 2 MPA) and the temperature maintained is around 70 to 110° Celsius.
Finally, the molted form of polymers is mixed with the stabilizers and extruded in form of linera low-density pellets. These pellets are further used in the production of plastic products.
The gas phase polymerization process is better than Solution Polymerization in terms of the operational cost involved, temperature maintenance in the process and ease of flexibility during the production of polymers.
World Production Capacity of LLDPE
The production of polyethylene in 2016 was 103 million tons. Linear low-density polyethylene occupied a share of 34% in total polyethylene production. The production capacity for linear low-density polyethylene was for 35.1 million tons.China was the leading region where most of the production capacity was added in the recent years.
Production Capacity of LLDPE by Region
The Asian region has the highest share of production capacity for linear low-density polyethylene in 2016 It accounted for 45% of the production share globally. China was the leading country in the production of the polymer. The Asian region has shown a signification growth rate in production capacity from past 5 years.
The second leading region producing the polymer is North America accounting for 21% of the global production. It is followed by Middle-East producing 17% of the polymer.
Market Analysis of Linear Low-Density Polyethylene
Linear low-density polyethylene is a kind of linear polymer having a considerable amount of branches. It is widely used for applications such as injection molding, rotational molding, wires, sheets, pipes, and conduits. These are further used for producing goods of end-user industries such as packaging, agriculture, construction, automotive, household, marine, and toys etc.
The linear low-density polyethylene global market is anticipated to witness stable growth in the coming years, as there has been a continuous increase in linear low-density polyethylene capacity additions planned worldwide and constantly rising demand for the product.
The market for linear-low density polyethylene is primarily driven by growing population and increasing demand for food which, contributes towards the growth of linear low-density polyethylene market in food packaging. There has been a tremendous amount of growth in market demand due to the replacement of much low-density polyethylene good with linear density polyethylene.
Films are the largest sector of linear low-density polyethylene market contributing to more than 70% share of the market demand. Demand for films (agricultural films, stretch films, lamination, heavy duty sack and personal care film etc.) are majorly driving the demand for linear-low density polyethylene market.
Growth in major end-user industries such as construction and packaging is also expected as the key factors driving the market demand for next few years. Increase usage in coating and packaging of medical products is expected to provide new growth opportunities in the market demand.
North America has been the largest consumer of linear- low-density polyethylene which is further followed by Asian-Pacific regions. Other emerging economies such as Canada, Brazil, and China are also anticipated to have a high demand for linear low-density plastics in the forecasted period.
Government environmental regulations regarding the usage of plastics may result in hampering the growth of the market. Availability of substitutes and their pricing may also affect the demand in the global market.
The linear low-density polyethylene market is dominated by players such as Borealis, Braskem SA, Chevron Phillip Chemical Co., DuPont, ExxonMobil Chemical, INEOS Group, Nova Chemicals, and The Dow Chemical Company.
Properties of Linear Low-Density Polyethylene
These resins prove to be basic building blocks for films and packaging industry, offering balanced stiffness and toughness as desired by the product. The balance between characteristics, physical and chemical properties of linear low-density material make them the ideal resin for packaging of consumables, heavy duty shipping sacks, films (collation shrink films and stretch films etc) and also for producing containers and closures.
Basic properties offered by the polymer are:
- They offer higher tensile strength, high impact, and high puncture resistance.
- Linear low-density polyethylene materials are very flexible and usually elongate themselves under stress conditions.
- These polymers can be easily used to produce thin films as they have good environmental stress cracking resistance.
- Linear low-density plastics are strongly chemical resistant along with having good electrical properties.
- They have higher mechanical and improved sealing properties.
- It has a transparent and glossy appearance which provides good finishing to the final products.
- Linear low-density polymers have low production and transformation costs.
Physical Properties of Linear Low-Density Resins:
- Tensile strength is 30 MPA and notched impact strength is 06+ kJ/m
- Density is 916 g/cm³
- Maximum operating temperature is 50 °C
- Linear expansion offered 20×10−5/°C
- Water absorption level is usually 01%
- Melting Temp. Range of polymer is 120 to 160 °C
Uses of Linear Low-Density Polyethylene Polymers
The application segment of linear low-density polyethylene has witnessed high growth in recent years. The popularity of this polymer in producing end segment plastic products is increasing due to its properties such as high tensile strength, superior impact and puncture resistance than its competitors.
It is used on a large scale for producing plastic films and wraps. Strong toughness offered by linear low-density material has opened up its uses in new application areas such as automotive, construction, household and agricultural sectors. Some of the major end-use applications are:
Linear low-density polyethylene is widely used for producing a plastic film for a variety of uses. It is used to manufacture film in two ways which are:
Blow Film Extrusion
In this process linear low-density polyethylene blow film resins are processed on smooth barrel extruders, length of these barrels can range from 24:1 to 30:1. As it is not easy to measure the bubble diameter so, it is calculated from the flat lay width which is between 2:1 and 3:5:1 ratio.
Due to the narrow molecular weight distribution of the linear low-density polyethylene resins, the films are required to be extruded between wide range gaps of 90 mils to 110 mils. If the die gap is too narrow for resins, the film can be subjected to melt and fracture and if the gap is too wide there can be stability issues in the film produced.
Certain improvements in the properties can be made while producing these films by this process through adjusting the linear low-density polyethylene frost line height (FLH). As by lowering the level of FLH while production better mechanical properties and film clarity can be obtained.
Extruder and Die Temperature Settings
In this process, linear low-density polyethylene films are produced at different temperature setting in different zones of the extruder to enhance the properties of linear low-density polyethylene films.
This process is used for producing films according to the requirement of application and usage. Approximately temperature at which linear low-density polyethylene resins are melted in extruder range from 390°F (200°C) to 450°F (230°C).
Properties of Linear Low-Density Films
- It is very flexible, mostly ranging from 0.5 mil thick up to 40 mil in flexible sheeting forms.
- Linear low-density polyethylene films are natural milky color and translucent in appearance.
- They have high chemical and impact strength along with good water absorption quality.
- Linear low-density polyethylene films offer excellent impact and stress crack resistance
- They usually have density of 93 g/cm3
Linear low-density films are used widely in a variety of industries such as construction, agriculture, and surface protection applications, covers of all sorts, tarps and much more. Example of films being manufactured is stretch films, agricultural films, lamination films and collation shrink films etc.
Linear low-density polyethylene has certain properties like excellent stress crack resistance, flexibility, durability and low cost which make them completely suitable for tubing industry. Linear low-density plastics are widely used in tubing which includes chemical exposure, aging, high vibration connections, connecting to barb type fittings and with other compression fittings.
Linear low-density tubing can easily withstand 500 and more hours of exposure to different solutions and chemicals. They can even resist cracking when used with compression or push to connect fittings.
Benefits of Linear Low-Density Polyethylene Tubes
- Greater tensile strength and high burst pressure.
- They offer Superior stress and crack resistance.
- These tubes have excellent high puncture resistance.
- Linear low-density polyethylene tubing is highly impermeable to gasses and moisture.
- They have superior dielectric properties.
- Lightweight, Durable and Economical.
- Available in different colors such as black, gray, red, green, blue, yellow, orange, clear, and purple.
Physical properties of Linear Low-Density Polyethylene Tubing
- Temperature Range for these Tubing: -40°F to 150°F (-40°C to 66°C)
- Vacuum Rating: to 28” Hg
- Diameter Tolerance of these Tubes: ±0.004”
- Tube Markings: FW specifications
- Working Pressure: 3:1 safety factor
These tubings are applicable to be used with food and beverage, medical, and pharmaceutical applications.
Like HDPE (High-density Polyethylene) and LDPE (Low-density polyethylene), the linear low-density polyethylene materials are also used widely for producing different Poly bags applicable to a variety of uses.
Industrial poly bags are often made from these materials as they offer high resistance towards breakage and puncturing under stressful or any other extreme conditions. These plastic bags are used as grocery bags, bags used in clothing stores, heavy-duty sack bags, shopping bags or huge waste disposal bags.
These Poly bags are very flexible with high impact and tensile strength, scratch-free and durable. As linear low-density polyethylene is a low-cost material and easily available so, these poly bags are more economical as compared to others.
They have a shiny appearance and can be recycled to use again. Now day’s linear low-density plastic bags are largely produced using recycled linear density polyethylene materials.
Linear low-density polyethylene liners or the linear low-density polyethylene polymer geo-membranes are required for a variety of applications due to their strength, flexibility, and durability. Their thickness may vary from .5, .75, 1.0, 1.5, 2.0 and 2.5 mm (20, 30, 40, 60, 80 and 100 mils) and rolls of linear low-density liners are usually 23 feet wide and vary in length depending on the thickness of the geo-membrane.
Linear low-density material is an ideal choice for producing plastic liners due to following reasons:
- These geo-membranes offer a high degree of flexibility. Greater flexibility is useful as it provides increased conformance to subsidence and differential settlement.
- They are strongly UV and chemical resistant.
- These liners have high puncture resistance and more durable as compared to its competitors.
- These liners are available in two different surface colors- the white and black color used according to their demand.
Applications of Linear Low-Density Polyethylene Liners
They are used for number of applications such as
- It is used as linings in Lagoons, Canal, Tanks, and Ponds (Retention ponds, Agricultural ponds etc).
- Linear low-density polyethylene liners are widely used for landfill caps and closures.
- These geo-membranes are used for mining heap leach pads.
- The liners are also used for treating raw water of reservoirs, waste water and also used as portable water reservoirs.
- It is used as the secondary contaminant for above ground storage tanks and Floating covers for water reservoirs.
Difference among HDPE, LDPE, and LLDPE
High-Density Polyethylene (HDPE), Low-Density Polyethylene (LDPE), and Linear Low-Density Polyethylene all of them are a different kind of polyethylene polymers used in end segment markets for producing plastic products.
They all have certain properties which make them applicable to a variety of different uses. The major difference between these resins is on the basis of their cellular structure or the molecular bond with each other which depicts how tightly they are formed.
Which is the most flexible of them all?
Linear Low-Density Polyethylene is the most flexible form of plastic used. It is a more refined form of LDPE which has more flexibility, tensile strength, and conformability. It is widely used for sheets and films due to their strong and suitable properties. It is extensively used as liners for ponds and canals.
Which is the most common of all?
Low-density polyethylene is the most common type of plastic used. It is very flexible and is mostly from 0.5 mil thick to 40 mil. It is widely used in agriculture, construction, containers and lids, sheeting etc.
Which is the least commonly used of all?
Medium density polyethylene (MDPE) is the least commonly used form of polyethylene for sheeting. Though it is stronger than LDPE and has better chemical resistance than LDPE when MDPE has to be blended with LDPE to achieve stronger and flexible end product.
Which is toughest of all?
High-Density Polyethylene is the strongest and toughest form of Polyethylene. It has maximum chemical resistance and comparatively is less flexible than other forms of polyethylene plastic resins. HDPE materials have the maximum level of UV resistance which adds to their quality of toughness.
Difference on the basis of Properties:
|Flexibility||Very flexible||Flexible||Flexible, but more rigid than LDPE|
|Color||Natural Milky color and translucent||Natural milky and translucent||Naturally milky white, can be both translucent & opaque|
|Impact Strength||Very High||High||Good|
|Chemical Resistance||Excellent||Good||Very Good|
|Water Vapor & Gas Barrier||Good water and gas barrier both||Good water vapor resistance but poor gas resistance||Good water vapor and poor gas resistance|
|Stress Crack||High-stress crack resistance||Good stress crack resistance||Good stress crack resistance|
|Impact Resistance||Excellent||Very Good||Good|
|Polymer Chains||Significant number of short branches||Excessive branching or polymer chains||Minimal branching of polymer chains|
|Density||0.93 g/cm3||0.910–0.940 g/cm3||0.963 g/cm3|
Advantages and Disadvantages of LLDPE
Linear Low-Density Polyethylene is the most common form of used polyethylene for producing sheets, bags, and containers. It is chosen over other forms of polyethylene resins as it offers following benefits:
- These materials offer high flexibility and longevity.
- It has a good level of resistance to UV rays and chemicals.
- Linear low-density plastics are highly punctured resistant.
- Linear low-density polyethylene materials have solid mechanical properties and lower maintenance.
- They have high tensile strength.
- It is an excellent environment and stress crack resistant material.
As Linear, low-density polyethylene is a refined form of Low-density polyethylene and is widely used a form of polyethylene but it has certain limitations such as:
- It is less glossy as compared to linear low-density polyethylene.
- Temperature range of heat sealing is less in these materials.
- As compared to LDPE it does not offer ease of flexibility in the processing phase.
Recycling of LLDPE
LLDPE is recycled into new products on a large scale to reduce plastic pollution from the environment. It is also recycled like LDPE or any other form of plastic by segregating the linear low-density plastic from the waste and then melting it to form recycled plastic pellets. It is generally identified by the recycling code 4.
Linear low-density plastic is converted into the recycled black material which is further used to produce new plastic products such as bags, containers, plastic sheets and used for packaging also.