I’m sure that, at some time, you must have pondered this question. Having spent the first twenty years of my roto career selling the stuff, lots of molders have asked me that question, along with – “why can’t you guys develop something with better properties than PE?”
I should immediately declare an interest: I love PE. It paid for my three kids to get through university and it bought me my first house. However, even an ardent PE fan like me has to admit that PE has its limitations. Sometimes it’s not stiff enough, it scratches really easily, you can’t paint it, it goes seriously floppy at temperatures above 100°F and it doesn’t contain gasoline very well.
So why is our industry totally addicted to it?
Largely because there doesn’t seem to be that much else around that could replace PE and what polymers there are all have snags and limitations.
When I met with the ARM Education Committee last Fall, in New Orleans, they felt that a serious review was in order. Specifically, they felt that we should gather together what we already know about polymers that are rotomoldable and that aren’t called PE, PP or PVC. In a wider discussion, it became apparent that there is quite a bit of collective wisdom out there about alternative rotomoldable polymers. The Committee gave me the job of collecting it together and writing down on paper what we already know.
The list of rotomoldable polymers (ie not PE, PP or PVC) that we identified for consideration is as follows:
- Polyamide 6 (Nylon)
- Polyamide 11
- Polyamide 12
- Polyoxymethylene (Acetal)
- TPC-ET thermoplastic elastomer (Hytrel)
Over the next few months I’ll be publishing blogs on what we know so far about various rotomoldable alternative polymers. At the end of each blog, I’ll invite interested readers to add to our existing knowledge, by a response to the blog in the comment section. If you know anything about a particular polymer and, in particular, if you have practical experience of molding it, I really would encourage you to join in the discussion. That way, we can all learn.
Once this process has gathered up all the available collective wisdom, we’ll publish it in a more permanent format. In this way, we can gain a better understanding of where we are currently. Hopefully then we can use this knowledge to work out strategies to encourage potential suppliers to provide us with alternatives to polyethylene that are both technically and commercially viable.
Here’s a couple of initial questions, to get you all started: Have we missed anything off the list that should be seriously considered? If so, what should be added? Do you have any knowledge and / or experience of any of these polymers that you could share with us right away? Please leave a reply with your feedback.
Dr Nick Henwood serves as the Technical Director for the Association of Rotational Molders. He has 25 years-plus experience in rotomolding, specializing in the fields of materials development and process control. He operates as a consultant, researcher and educator through his own company, Rotomotive Limited, based in UK.