Polyethylene

If you have ever looked at the ingredients list on any of your favourite mascaras, tampons, squeeze bottles, trash bags, or orthopedic goods you have probably come across polyethylene. (1)

Polyethylene is basically the photo-bomber of anything plastic. It is composed of ethylene molecules (CH2=CH2) which have been bonded together through the process of polymerization. (1) During polymerization the double bond between the carbon atoms is broken which allows another carbon to attach to one of the carbon atoms of the first ethylene molecule. (1) If it’s a little unclear just think of two friends holding both of each others hands. When they let go with one hand it frees them up to hold onto someone else’s. This continues to happen until you have a chain of people holding hands which is similar to a polyethylene chain, with the people’s joint arms representing the carbon bonds.

The chain length and side branches of polyethylene are the key factors in determining what type of plastic it will be used to make. Longer polyethylene molecules with no branches are generally used to make sturdier products such as pipes. (1) Shorter molecules with branches tend to end up used in films or thinner plastics. (1)

In regards to any danger being related to polyethylene’s presence in the products around your home, it’s negligible. It would take an oral dose of more than 2 g/kg in order to kill a rat. (2) A 145 g oral dose would be needed to kill a 165 lbs person at the same ratio. Even though polyethylene in harmless it can still cause some irritation should it get into your rabbit’s eyes, but there is no conclusive evidence of it being harmful to humans. (2)

Something you may not know about polyethylene is that is was discovered accidentally twice. It was only two years after it’s re-discovery that J.C. Swallow and M.W. Perrin figured out a way to produce it commercially. (1) Unfortunately; it was difficult to produce polyethylene of standard quality and the companies making it were facing financial ruin. That was until Wham-O began to produce hula-hoops out of the lower quality products. (1) This saved the industry while scientists fiddled around trying to produce a more consistent polyethylene by way of a more efficient reaction involving catalysts. (1)

References

1)     Polyethylene. (2006). In N. Schlager, J. Weisblatt, & D. E. Newton (Eds.), Chemical Compounds (Vol. 2, pp. 579-582)

2)     Final report on safety assessment of polyethylene. (2007) International Journal of Toxicology. Retrieved Oct. 22, 2015, from http://toxnet.nlm.nih.gov/cgi-bin/sis/search2/f?./temp/~odtn3q:1

3) Wikipedia. Polyethylene. Retrieved October 30, 2015 from https://upload.wikimedia.org/wikipedia/commons/5/55/Polyethylene_balls1.jpg