Polyethylene
Prepared by :
Sharyan omer
Kazhan abdulla
Shahang ahmed
Dahen Mohamed
Brwa ali
Supervisor : Mr.Bashdar Aziz
Contents
Introduction
Monomer & Polymer structure of polyethylene
Is PE toxic?
What are the Disadvantage of Polyethylene?
How is PE made ?
Different types of polyethylene
Property of polyethylene
Applications
References
Introduction
A light, versatile synthetic resin made from the polymerization of ethylene
It is a thermoplastic polymer with variable crystalline structure and an extremely large range of
application .
Called as poly-“methylene” due to the repeating -CH2 group.
Introduction
--It was the first synthesized by German scientist hans von pechmann,
who prepared it by accident while investigating diazomethane
--Polyethylene is easy to distinguish from other plastics
because they float in water
--Diazomethane (CH2N2)- a strong respiratory irritant,
used as methylating agent for acidic compounds such
as carboxylic acids, phenols, and enols
Monomer structure of polyethylene
Polymer structure of polyethylene
Is PE toxic?
• In solid form, no. In fact, Polyethylene is often used in food handling. It
could be toxic if inhaled and/or absorbed into the skin or eyes as a vapor
or liquid (i.e. during manufacturing processes). Be careful and closely
follow handling instructions for molten polymer in particular.
What are the Disadvantage of Polyethylene?
• Polyethylene is generally more expensive than polypropylene (which can
be used in similar part applications). PE is the second best choice for living
hinges, behind PP at number one.
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
Different types of polyethylene
1. Low density polyethylene (LDPE)
2. High density of polyethylene (HDPE)
3. Linear low density polyethylene (LLDPE)
4. Ultrahigh molecular weight polyethylene (UHMW)
Different types of polyethylene
1. Low density polyethylene (LDPE)
• First polyethylene produced.
• As the name implied, it has a lower density compared to high density
polyethylene
• LDPE has more branching, hence the molecules are less tightly packed
and less crystalline due to the side branches
• LDPE is also frequently used in comsumer packaging, bags, bottles, and
leaners
Different types of polyethylene
2. High density of polyethylene (HDPE)
• It is a polyethylene made from petroleum
• It is sometimes called “alkathene” or “polythene” when used for pipes
• HDPE has little branching, giving it stronger intermolecular forces and
tensile strength Than LDPE
• It is also harder and more opaque and can withstand higher temperatures
Different types of polyethylene
3. Linear low density polyethylene (LLDPE)
• LLDPE is the most flexible type of polyethylene
• It is a blended form of LDPE where the film has much more flexibility, tensile
strength, and more comfortability
• LLDPE is used for films that need a tremendous amount of strength to
absorb impacts without tearing or puncturing
Different types of polyethylene
4. Ultrahigh molecular weight polyethylene (UHMW)
• Also known as high-modulus polyethylene (HMPE) or high performance
polyethylene (HPPE)
• It is odorless, tasteless and nontoxic
• It has extremely long chains , which resuoin a very tough material, with the
highest impact strength of any thermoplastic presently made
schematic
molecular structure
Figure 1 : schematic molecular
structure
A) Low density polyethylene
B) linear low density
polyethylene
C)high density polyethylene
Property of polyethylene
can be divided into mechanical, chemical ,electrical , Optical , thermal
properties
1. Mechanical properties
-Low strength , hardness and rigidity but has high ductility and impact
strength as well as low function.
-it show strong creep under persistent force.
Property of polyethylene
2. thermal properties
• the common commercial grade of medium-and high density
polyethylene the melting point is typically in range of 120c to 180c .
• The melting point LDPE is typically (105 to 115)c.
• - Tempreture vary with the type of polyethylene.
Property of polyethylene
3. chemical properties
• polyethylene consist of nonpolar , saturated, high molecular weight hydrocarbons.
• PE have low moisture absorption
• PE can be brittle when exposed to sunlight ,carbon black is usually used as a
stabilizer.
• PE burns slowly with bile flame having yellow tip and gives off an odor of paraffin.
• Resist acids ,bases ,ester ,alcohol , hydrocarbons. limited resistance to aldehyde.
• Do note react in a room temperature.
Property of polyethylene
4. electrical properties
• PE is a good electrical insulator.
• It reffers good tracking resistance.
Property of polyethylene
5. Optical properties
• PE can vary between almost clear , milky opaque .
Application
• LDPE milk carton, bowls and buckets , squeezable bottles such as ketchup
containers, cable jacketing , flexible water pipes
Application
• HDPE - shopping plastic bags, food backing plastic, crates, dustbin, drums,
detergent bottles, water pipes
Application
• LLDPE food and non food packaging , extrusion applications, garden
products, kitchen accessories, luggage and furniture parts, recreational
products and toys
Application
• UHMW- bulletproof vest , vehicular armor joint and ligament reconstruction
and spinal and maxillofacial implants
References :