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A Closer Look

How to Sort Plastic Bottles for Recycling
lastic containers are made of different a. Polyethylene terephthalate (PET)
Ptypes of plastic resins; some are suit- b. Large soft-drink bottles, salad dressing
able for recycling and others are not. How bottles
1
do you know which are suitable and how to
c. Frequently recycled
sort them? Most plastic containers have a
code stamped on the bottom. The code is a
number in the recycling arrow logo, some-
times appearing with some letters. Here is a. High-density polyethylene (HDPE)
what the numbers and letters mean in terms b. Milk jugs, detergent and bleach
of (a) the plastic, (b) how it is used, and 2 bottles, others
(c) if it is usually recycled or not. c. Frequently recycled

a. Polyvinyl chloride (PVC or PV)
3 b. Shampoos, hair conditioners, others
c. Rarely recycled

a. Low-density polyethylene (LDPE)
4 b. Plastic wrap, laundry and trash bags
c. Rarely recycled but often reused

a. Polypropylene (PP)
5 b. Food containers
c. Rarely recycled

a. Polystyrene (PS)
6 b. Styrofoam cups, burger boxes, plates
c. Occasionally recycled

a. Mixed resins
b. Catsup squeeze bottles, other squeeze
7 bottles
c. Rarely recycled

Polyethylene is a familiar thermoplastic polymer used polyethylene near the melting point is rolled in alternating
for vegetable bags, dry cleaning bags, grocery bags, and plas- perpendicular directions or expanded and compressed as it is
tic squeeze bottles. Polyethylene is a polymer produced by a cooled, the polyethylene molecules become ordered in a way
polymerization reaction of ethylene, which is derived from that improves the rigidity and tensile strength. This change in
petroleum. Polyethylene was invented just before World War II the microstructure produces high-density polyethylene with a
and was used as an electrical insulating material during the superior rigidity and tensile strength compared to low-density
war. Today, many variations of polyethylene are produced by polyethylene. High-density polyethylene is used in milk jugs,
different reaction conditions or by the substitution of one or as liners in screw-on jar tops, in bottle caps, and as a material
more hydrogen atoms in the ethylene molecule. When soft for toys.

316 CHAPTER 12 Organic Chemistry 12-18