HDPE is formed in long, straight chains. These
chains can line up parallel to one another and
can be packed tightly, giving this polymer high
density. The linear molecules in HDPE are closely
aligned, so the intermolecular forces among
them are relatively strong. As a result, HDPE is a
sturdy plastic, making it a good choice for plastic
Recycling plastic bags
Recycling plastics, in general, is commonplace, but recycling plastic bags is not. The main
problem is that plastic bags tend to get caught in
the sorting machinery, causing time-consuming
and costly shutdowns. So the only way to recycle
plastic bags is to collect and process them separately from other recyclable materials.
Many stores—such as Walmart, Target,
and Whole Foods—have labeled boxes placed
at entrances for the collection of plastic
bags and products made of
plastic film, including bread
bags, wrap for water bottles,
food-storage bags, and plas-
tic cereal-box liners.
There is a new recycling
symbol for plastic bags and
products made of plastic film
(see symbol, left).
Plastic bags that are
deposited in appropri-
ate recycling bins can be
made into different types of
products. Two of the most
common products are new plastic bags and
To make new plastic bags, the recycled
plastic bags are cleaned, melted, and re-
formed into small plastic pellets. These pellets
can then be made into new plastic bags. For
instance, as part of its Bag-2-Bag program,
the company Novolex™ manufactures plastic
bags by using plastic pellets from recycled
bags (Fig. 2). As of 2014, 33% of the plastic
material used to make the bags in this pro-
gram was recycled. The company’s goal is to
make that percentage higher in the future.
Another common use for recycled plastic
bags is composite lumber. While traditional
lumber is made from trees, composite lum-
ber is made from a mixture of sawdust and
plastic. The plastic and sawdust are combined
and heated into a soft, flexible material that
is shaped into boards, which are then cooled
and cut to the designated length.
Composite lumber is often used for deck
material in the same way that traditional lumber is used. It has the look of traditional lumber, is durable, and requires little maintenance.
The company Trex ® uses 400 million pounds
of plastic bags and films per year to make its
These recycling efforts are steadily improving, as the amount of recycled plastic bags
and films has increased by 74% between 2005
and 2015, leading to a variety of new plastic
products, such as plastic lumber, new plastic
film, and lawn and garden products.
Tullo, A. H. Breaking the Plastic Bag Habit.
Chemical & Engineering News, 92(37), pp 12–17,
Sept 15, 2014.
Barclay, E. How Plastic in the Ocean Is
Contaminating Your Seafood. National Public
Radio, Dec 13, 2013: http://www.npr.org/sections/
[accessed Feb 2017].
Kathy De Antonis is a science writer who lives in
Old Saybrook, Conn. Her latest ChemMatters
article, “Sports Supplements: Helpful or Harmful?”
appeared in the October/November 2013 issue.
Figure 2. Plastic bags are recycled in a multistep process. Shown here are the five steps used
by the company Novolex™ to recycle plastic bags.
Abby Goldberg, Grayslake, Ill., stands with her Bag Monster
made of 300 plastic bags, which is the average number of
bags used by U.S. residents per year.
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