Almost everyone by now has at least some familiarity with BPA in plastic, especially if you have kids. For those of you that are not familiar, here is the media narrative on BPA. BPA is an additive that is used in plastic materials. This additive causes horrible health problems but the evil chemical industry won’t remove it and the FDA must be being bought off by the same evil chemical industry to continue to allow its use. In fact the whole obesity epidemic might be the fault of BPA and thus the evil chemical industry.
If you are unaware, there are two sets of test methods that are currently in use for many of the common tests that we see reported on data sheets and certificates of analysis. This has caused a lot of confusion.
To add to the confusion, I have seen many data sheets and certificates of analysis in which data is reported incorrectly. None more than izod impact. There is currently an ASTM method and an ISO method for testing izod impact. Although some data sheets claim that they are, the two test methods used for izod impact are definitely not equivalent. They are two different test methods and there is no way of converting between the two.
As I mentioned in a recent post, after a number of years of searching, I finally found a copy of the Plastics Materials Digest – International Plastics Selector. Before the internet, when I needed to find a material or look up properties, this is how I did it.
The books contain thousands of property data sheets as well an index that allows you to look up materials by trade name and even physical properties.These books were very good. If you needed a polypropylene with tensile strength over 3600 psi, you could find it in the index and then it would refer you to the page where you could find the full data sheet.
The copy that I found happened to be from 1988, the same year that I started in the industry.
I have had a little time to look through the book now and I have a few observations.
Polyethylene was first discovered by accident in a laboratory in 1898. This is a running theme throughout the history of the plastics industry. It was not until 35 years later that the first commercially viable polyethylene was synthesized in 1933 by Imperial Chemical Industries (ICI). The long gap between the initial discovery of a polymer and the commercialization is also a recurring theme in the history of the plastics industry.
Polyethylene is the most commonly used plastic globally. According to Wikipedia, annual production is around 80 million metric tons or 176 billion pounds. It is used in many applications such as film that is used for everything from moisture barrier to grocery bags. It is also used for things like pick-up truck bed liners and tanks of all kinds. In recent years, polyethylene has been used for increasingly demanding applications like automotive fuel tanks, potable water pipe, artificial hip joints and even fiber for bulletproof vests.
Polyethylene’s use in these increasingly demanding applications has been made possible by innovations from the material manufacturers. Unlike TPO, these innovations have not happened at compounders but during the reaction of the polymer. These innovations have brought a dizzying array of new polyethylene materials to the market. A quick look at Matweb shows that there are currently 5534 different grades of polyethylene. I want to break down some of the different types that are now available.