Polyethylene And Polypropylene: Simple, Safe And Strong Plastics

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POLYETHYLENE and POLYPROPYLENE: Simple, Safe and Strong Plastics

Elsie David Association of Petrochemical Manufacturers of the Philippines 25-Jul-08

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POLYETHYLENE is among the simplest man-made polymers.

• With the simple ethylene monomer

we can make polyethylene,

which can also be drawn as

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H

H

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Properties of the Alkane [ H-(CH2)n-H ] Series No. of Carbons State and Properties of in Chain Material

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Use Dependent on Chain Length

1–4

Simple gas

LPG for cooking

5 – 11

Simple liquid

Gasoline

9 – 16

Medium viscosity liquid

Kerosene

16 – 25

High viscosity liquid

Oil and grease

25 – 50

Simple solid

1000 – 3000

Tough plastic solid

Paraffin wax candles PE bottles and containers

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POLYPROPYLENE is also among the simplest man-made polymers.

• With the simple propylene monomer

we can make polypropylene,

which can also be drawn as

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H

H

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STRICTLY SPEAKING...

and

H

H

is homopolymer polyethylene

H

H

is homopolymer polypropylene.

• A homopolymer consists of only one type of repeating unit (monomer). • Sometimes there are two types of repeating units, the monomer (major) and the comonomer (minor). 25-Jul-08

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A Gas Phase PE/PP Manufacturing Process... PURIFICATION

REACTION

RESIN DEGASSING

Raw Materials

VENT RECOVERY

Gases

PRODUCT SILOS Resin

EXTRUSION AND ADDITIVE ADDITION

Additives

To Packaging

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• PE and PP resins are simple to manufacture.

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• PE and PP resins are simple to convert into useful articles.

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• PE and PP are simple to design into finished products. End use: Cost Properties Aesthetics

Conversion Process PE / PP Resin

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• Polyethylene and polypropylene:

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•

have simple structures

•

are simple to manufacture as resins

•

are simple to convert into useful articles

•

are simple to design into finished products

•

are simple to recycle

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• Their behavior beyond normal use conditions is easy and simple to predict. Decomposition Degradation

Temperature 25-Jul-08

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PE and PP are safe plastics.

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•PE and PP are safe to use for food packaging.

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• PE and PP are safe to use for drinking water pipes.

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• PE and PP are safe to use for storing our food.

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• PE and PP are safe to use for grooming and hygienic purposes.

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• HDPE is safe to use for detergents, bleach and lubricants packaging.

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• PE and PP are safe to use in our homes.

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• PE and PP have thousands of other safe uses in our everyday lives.

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SIMPLE...

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SAFE... • PE and PP articles are safe to use for drinking water pipes, for food storage and packaging, and for packing household and industrial chemicals. • Evalene PE and PP resins are acceptable for food contact applications based on the Philippine Bureau of Food and Drug’s requirements (based on US FDA 21CFR177.1520).

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STRONG... • PE and PP resins can be made stiff and strong for pallets, crates, pipes, furniture, appliance parts, ropes, bottles and grocery bags.

• The key to PE and PP stiffness and strength is chain length and crystallinity. 25-Jul-08

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Polyethylene Crystalline Structures

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PE Density and Crystallinity

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High-Density Polyethylene (HDPE) • Density: 0.941 to 0.965 g/cm3 • 70 – 95% crystalline • A strong, relatively opaque form of PE with a dense structure. • Characterized by stiffness, strength/toughness, resistance to chemicals and moisture.

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Low Density Polyethylene (LDPE) / Linear Low Density Polyethylene (LLDPE) LDPE • LDPE Density: 0.910 to 0.930 g/cm3 • LLDPE Density: 0.915 to 0.926 g/cm3 • Characterized by flexibility, toughness, tear resistance, drop impact resistance. • Low seal temperature.

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Polypropylene (PP)

• Density is constant at around 0.900 g/cm3. • Characterized by strength/toughness, resistance to chemicals, resistance to heat, barrier to moisture.

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HDPE

LLDPE / LDPE

PP

Simple to make and convert

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Safe

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Strong

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Recyclable

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9 Excellent tear/drop resistance

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