368 Chapter 9

Table 9.1 The Big Six

Polymer Recycle Symbol Monomer Properties of Polymer Uses of Polymer

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

Translucent if not pigmented. Soft and flexible. Unreactive to acids and bases. Strong and tough.

Bags, films, sheets, bubble wrap, toys, wire insulation.

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

Similar to LDPE. More rigid, tougher, slightly more dense.

Opaque milk, juice, detergent, and shampoo bottles. Buckets, crates, and fencing.

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

Variable. Rigid if not softened with a plasticizer. Clear and shiny, but often pigmented. Resistant to most chemicals, including oils, acids, and bases.

Rigid: Plumbing pipe, house siding, charge cards, hotel room keys. Softened: Garden hoses, waterproof boots, shower curtains, IV tubing.

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

Variable. “Crystal” form transparent, sparkling, somewhat brittle. “Expandable” form lightweight foam. Both forms rigid and degraded in many organic solvents.

“Crystal” form: Food wrap, CD cases, transparent cups. “Expandable” form: Foam cups, insulated containers, food packaging trays, egg cartons, packaging peanuts.

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

Opaque, very tough, good weatherability. High melting point. Resistant to oils.

Bottle caps. Yogurt, cream, and margarine containers. Carpeting, casual furniture, luggage.

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

HDPE

LDPE

Polyethylene

2

Polyethylene

3

Polyvinyl chloride

PVC, or V

6

PS

Polystyrene

5

PP

Polypropylene

1

PETE,or PET

Polyethyleneterephthalate

4

Ethylene

Ethylene

Vinyl chloride

Styrene

Propylene

Terephthalic acid

Ethylene glycol

C C

HH

HH

C C

HH

HH

C C

HH

ClH

C C

HH

CH3H

C C

HH

H

C

O

OH

C

O

HO

OHHO CH2CH2

Transparent, strong, shatter-resistant. Impervious to acids and atmospheric gases. Most costly of the six.

Soft-drink bottles, clear food containers, beverage glasses, fleece fabrics, carpet yarns, fiber-fill insulation.

Note: The structures of the first five monomers differ only by the atoms show in blue.

Table 9.1 also lists properties of these six polymers. All are solids that can be colored with pigments. All are also insoluble in water, although some degrade or soften in the presence of hydrocarbons, fats, and oils. All are thermoplastic polymers, mean-ing that with heat, they can be melted and reshaped over and over again. However, they exhibit a range of melting points depending on the route by which they were manufactured. Of the Big Six, polyethylene has the lowest melting point, with LDPE and HDPE melting at about 120 °C and 130 °C, respectively. In contrast, polypropylene (PP) melts at 160–170 °C. Depending on the arrangement of their molecules, polymers have varying degrees of strength. At the microscopic level, the molecules in some parts of the polymer may have an orderly repeating pattern, such as one would find in a crystalline solid (Figure 9.8). In these crystalline regions, the long polymer molecules

In contrast to thermoplastics, some plastics are thermosetting. These solidify

or “set” irreversibly with heat. Examples include rubber-soled footwear and

antique Bakelite ovenware.

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