Ask A Scientist© Environmental Science Archive

Author:     nieslanik
Text:       I am a high school student studying recycling. I have noticed 
different numbers on the bottom of some plastics. Our town will only recycle 
those with a 1 or a 2. What is the difference between all these codes?

Response #: 1 of 1
Author:     Eric Dallman
Text:       The reason for the difference in codes is that there are different 
types of plastic. The codes are usually placed inside the recycling symbol, 
and the letter abbreviation for the type of plastic is usually placed 
underneath the symbol. You will find 6 codes corresponding to the following 
letter codes and types of plastic: 1: PETE, polyethyl tetraethylenei 2: HDPE, 
high density polyethylene; 3: V, vinyl (PVC?) (this one I am not certain of); 
4: LDPE, low density polyethylene; 5: PP, polypropylene; 6: PS, polystyrene 
(found as plastic or foam). Your town is only equipped to recycle polyethylene 
(the density does not matter) so they only accept codes 2 and 4. Each type of 
plastic is a different chemical with different properties so they generally 
are not combined during recycling. PETA (1) is a tough, somewhat bendable 
plastic commonly found in 2 liter pop bottles. Polyethylene (2 ~ 4) is a good 
general purpose plastic. HDPE (2) is suitable for milk jugs, nonpressurized 
bottles and plastic cups. LDPE (4) is used to make "stretchy" type plastic for 
plastic wrap and bags such as those from Jewel (crinkly K-Mart bags are HDPE). 
(3) is a hard plastic that resists oils and petroleum distillates. Much of 
automotive products and oil based cleansers require the use of V. HDPE will 
eventually be attacked by certain chemicals that V will not. PP (5) is 
generally harder than HDPE, but tends to be brittle. It is the material found 
in sour cream and yogurt containers. PS is a plastic frequently used to make 
disposable cups. It is .used either in its plastic form, or made into foam. 
Polystyrene foam, a trademarked product, is a type of PS. Another reason your town 
does not except anything but 2 and 4 plastic for recycling is the typical 
contents of the containers. 2 and 4 are usually only accepted if they 
contained food products. Most communities do not want HDPE bottles that 
contained chemicals because the chemicals, if not completely washed out, may 
still be present in the recycled product (or ruin the process). 3 plastic, for 
example, is used in most household situations, to hold chemicals. By taking 2 
and 4 plastic, the community gets a large percentage of the plastic suitable 
for recycling. For more specific information on your particular community, 
contact your local recycling center or a large recycling center such as the 
Lyons branch of BFI (708-442-1110).