Description
What is Polymers PE?
Polymers PE:Polyethylene or polythene is a type of polyolefin. It is often abbreviated as PE. The chemical formula of PE is (C2H4)n. It is lightweight, durable, and one of the most commonly produced plastic. Used for frozen food bags, bottles, cereal liners, yogurt containers, etc.
Look around you, all plastics with recycling codes 2 and 4 are made of PE. These plastics come with different crystalline structures.
Molecular Structure of PE
How is PE made?
Polyethylene is made from the polymerization of ethylene (or ethene) monomer. The PE chains are produced by addition or radical polymerization. The possible synthesis methods are:
- Ziegler-Natta Polymerization and
- Metallocene catalysis
What are the common types of Polymers PE?
Depending on its density and branching, different PE grades can have very different performance from one another.
PE grades are therefore classified as follows.
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- Branched Versions
- Low-density polyethylene (LDPE)
- Linear low-density polyethylene (LLDPE)
- Branched Versions
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- Linear Versions
- High-density polyethylene (HDPE)
- Ultra-high-molecular-weight polyethylene (UHMWPE)
- Linear Versions
- Cross-linked polyethylene (PEX or XLPE)
Additionally, other types of PE are also available such as:
- Medium-density polyethylene (MDPE)
- Ultra low-density polyethylene (ULDPE)
- High-molecular-weight polyethylene (HMWPE)
- Metallocene polyethylene (mPE)
- Chlorinated polyethylene (CPE)
What are the applications of HDPE?
Excellent combination of properties makes HDPE an ideal material in diverse applications across industries. Some of the major uses of
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- Packaging Applications – HDPE is used in several packaging applications including crates, trays, bottles for milk and fruit juices, caps for food packaging, jerry cans, drums, industrial bulk containers etc. In such applications HDPE provides the end product a reasonable impact strength.
- Consumer Goods – Low cost and easy processability make HDPE a material of choice in several household/consumer goods like garbage containers, housewares, ice boxes, toys etc.
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- Fibers and Textiles – Thanks to its high tensile strength, HDPE is widely used for agricultural applications, such as in ropes, fishing and sport nets, nets as well as industrial and decorative fabrics.
Other applications of HDPE include pipes and fittings (pipes for gas, water, sewage, drainage, sea outfalls, industrial application, cable protection, steel pipe coating, large inspection chambers and manholes for pipe sewage etc.) due to its excellent resistance to chemical and hydrolysis, automotive – fuel tanks, wiring & cables – sheeting of energy, telecommunication cables.
What is low density polyethylene (LDPE)?
Low-density Polyethylene (LDPE) is a semi-rigid polymer with low crystallinity (~50-60%). The LDPE is composed of 4,000-40,000 carbon atoms, with many short branches. Compared to HDPE, it has a higher degree of short and long side-chain branching. The chemical structure of LDPE is:
Polymers PEHow is LDPE manufactured?
LDPE is produced at high pressure (1000-3000 bar) and temperature (80-300°C). It is derived via the free radical polymerization process.
Two basic processes to produce LDPE:
- Stirred autoclave reactor
- Tubular reactor
The tubular reactor has been gaining preference over the autoclave route due to its higher ethylene conversion rates.
What are the properties of LDPE?
- LDPE Melting point: 105 to 115°C
- Density of LDPE: 0.910–0.940 g/cm3
- Chemical resistance of LDPE:
- Good resistance to alcohols, dilute alkalis and acids
- Limited resistance to aliphatic and aromatic hydrocarbons, mineral oils, oxidizing agents and halogenated hydrocarbons
- Temperature resistance up to 80°C continuously and 95°C for shorter times.
- Low cost polymer with good processability
- High impact strength at low temperature, good weatherability
- Excellent electrical insulating properties
- Very low water absorption
- FDA compliant
- Transparent in thin film form
What are the disadvantages of LDPE?
The presence of more branching in polymer chain brings certain drawbacks to LDPE performance. Such as:
- Susceptible to stress cracking
- Low strength, stiffness and maximum service temperature. This limits its usage in applications requiring extreme temperatures.
- High gas permeability, particularly carbon dioxide
- Poor UV resistance
- Highly flammable
- High-frequency welding and joining impossible
To overcome these challenges, several LDPE grades have been developed with improved properties such as UV stabilized, high strength, antiblocking, etc. Check out LDPE grades here »
Tip: Do not forget to use “Key Features” filter to explore other optimized grades of LDPE
What are the applications of LDPE?
LDPE uses majorly revolve around manufacturing containers, dispensing bottles, wash bottles, tubing, plastic bags for computer components, and various molded laboratory equipments. The most popular application of LDPE is plastic bags.
- Packaging – Thanks to its low cost and good flexibility, LDPE is used in packaging industry for pharmaceutical and squeeze bottles, caps and closures, tamper evident, liners, trash bags, films for food packaging (frozen, dry goods, etc.), laminations etc.
- Pipes and Fittings – LDPE is used to manufacture water pipes and hoses for the pipes and fittings industry due to its plasticity and low water absorption.
Other applications include consumer goods – housewares, flexible toys, agricultural films, wiring & cables – sub-conductor insulators, cable jacketing.
What is linear low-density polyethylene (LLDPE)?
The structure of linear low-density polyethylene (LLDPE) has a linear backbone with short and uniform branches (unlike longer branches of LDPE). These short branches are able slide against each other upon elongation without becoming entangled like LPDE. It is structurally similar to LDPE.
How is LLDPE manufactured?
LLDPE is produced by the polymerization of ethylene (or ethane monomer) with:
- 1-butene, and
- smaller amounts of 1-hexene and 1-octene.
This process occurs using Ziegler-Natta or metallocene catalysts. In the present-day scenario, LLDPE has been quite successful in replacing LDPE thanks to the below-mentioned properties.
What are properties of LLDPE?
- Very flexible with high impact strength
- Translucent and natural milky color
- Excellent for mild and strong buffers, good chemical resistance
- Good water vapor and alcohol barrier properties
- Good stress crack and impact resistance
Some grades are designed for your specific requirements like good processability, antiblocking, antioxidant, etc. Check out LLDPE grades here »
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