Processes

Ways of recycling different plastics

High Density Poly Ethylene

HDPE Also known as #2, this is the plastic used to make milk jugs and detergent bottles. The initials stand for High Density Poly Ethylene which designates a denser form of polyethylene that is almost as dense as water. Most milk jugs are a translucent white and do not contain any pigment. This type of HDPE is called natural since that is it's natural color, and it is the most valuable because it can be made into any color when it is recycled. Other products are often packed in brightly colored bottles which are mixed together at recycling plants into mixed color or rainbow bales. Most of this material is later dyed black after it is processed.

Recycling HDPE is a pretty simple process. The bales are broken apart and ground into small flakes about 3/8 ths of an inch ( 1 CM ). These flakes are then washed and floated to remove any heavy (Sinkable) contaminants. This cleaned flake is then dried in a stream of hot air and may be boxed and sold in that form. More sophisticated plastic plants may reheat these flakes, add pigment to change the color and run the material through a pelletizer. This equipment forms little beads of plastic that can then be reused in injection molding presses to create new products.

Some common end uses for recycled HDPE are plastic pipes, lumber, flower pots, trash cans, or formed back into non food application bottles.

Relatively low in value, we purchased HDPE between $.06 and $.15 US per pound in 2001

Low Density Poly Ethylene

LDPE plastic is actually Low Density Poly Ethylene. It is chemically similar to HDPE but it is less dense and more flexible. Most polyethylene film is made from LDPE which you often see as plastic bags and grocery sacks. This scrap may be clear or pigmented and it is hand sorted and baled at recycling processing plants.

Recycling LDPE is very similar to HDPE except special grinders are used to handle the thin films. The films are often washed and repelletized or used directly to make new products. Some end uses for recycled LDPE are plastic trash bags and grocery sacks, plastic tubing, agricultural film, and plastic lumber.

Relatively low in value, we purchased LDPE between $.01 and $.15US per pound in 2001

Poly Ethylene Terepthalate

PET or #1 is a resin called Poly Ethylene Terepthalate. It is a form of polyester or Mylar that is extremely tough and useful. Soft drink and water bottles are made from this resin as are many plastic jars and clamshell packages ( like cookie containers or trays) .

Recycling PET is similar to the process for polyethylene. Bottles may be color sorted and are ground up and washed. Unlike polyethylene, PET sinks in the wash water while the plastic caps and labels are floated off. The clean flake is dried and often repelletized.

Recycled PET has many uses and there are well established market for this useful resin. By far, the largest usage is in textiles. Carpet companies can often use 100% recycled resin to manufacture polyester carpets in a variety of colors and textures. PET is also spun like cotton candy to make fiber filling for pillows, quilts and jackets. PET can also be rolled into clear sheets or ribbon for VCR and audio cassettes. In addition a substantial quantity goes back into the bottle market.

PET prices vary widely with supply and we paid between $.06 and $.17 US per pound in 2001.