What type of plactic to use?

[pingwin77]

I'm in the middle of designing a new item to help with my home brewing and need some help. I want to mold the part out of plastic but I have no idea what kind to use. This will be in contact with the wort so it need to be sanitized and not have any large porous areas to harbor bacteria. Does anyone have any suggestions?

 

[WVBeerBaron]

Most food grade storage containers are made from PET (polyethylene terephthalate) or HDPE (high density polyethylene). My homebrew buckets are HDPE. Hope this helps.

 

[IrregularPulse]

+1 to HDPE and I can't wait to see what you're making.

 

[arturo7]

How much heat will does the part need to handle?

What type of stress?

 

[AiredAle]

You say you are molding the item. So you want a recommendation on the type of Food Grade plastic to use. This depends on use temperatures and your mechanical strength needs. You have a range of available plastics, HDPE, PVC, PP, PET to name a few. Each has a use temperature range, a liquid resistance range, and widely varying mechanical and physical properties. We need more info to be more helpful.

 

[pingwin77]

There is no real stress, tension or pressure going into the part. It just needs to be durable so it doesn't break if dropped and a good material to just be able to dunk in some sanitizer. As long as those 2 needs are met then it pretty much comes down to the cost. I'll post more info about the project in a few days. I have a few things I need to take care of before then, but HBT will be the first to see it.

 

[AiredAle]

Based on your description, polypropylene would be my choice. If you are going to have a mold made for your part, then the molding cost will greatly outweight the raw material cost, unless you are going into the business of selling your part.

 

[pingwin77]

The goal will be to sell this once I get it made. I had the first prototype created and all the preliminary test passed with water. Since it was made out of machining plastic, I decided to not use it with actual wort since I have no idea what kind of chemicals may leach out into my wort. The guy that made my first part is working on the next revision and using a peek plastic. This way I can test it with actual wort since the characteristics vary some from water. My only issue is that he is doing on his free time so it is taking a bit longer than I had hoped, but for free, I'm not complaining too much.

The first batch of parts will be machine since the cost of an injection mold is so damn high. If the demand for the part is great enough, which I am anticipating, I will convert it over later. I am still looking for a site to provide bulk machining stock of HDPE. I think that will be the most cost effective material to use and still provide all the critical requirements. If you happen to know of a good distributor, pass the info on and I'll toss you a free part once they are ready to go.

 

[Revvy]

ooooohhhh could this be the unbreakable plastic hydrometer we've all been dreaming about but noone's come up with?

I hope I hope.

 

[pingwin77]

Wrong part of the brewing process, but a great idea to start thinking about. I will add it to my list of brewing inventions.

 

[Bobby_M]

I'm also looking forward to seeing what it is because well, most of the "inventions" that have made their way through here solve a problem that doesn't exist ;-)