HDPE vs PETE

[Chewy]

Has anybody worked with PETE 1 plastic? Example Walmart juice containers? I am a bout to melt HDPE 2 into sheets and blocks for a project. I need to make a mold for acrylic. My wife does pens and wants to start in mixing her own acrylic colors. The molds are homemade from commercial HDPE sheet or are available assembled in HDPE or UHMW. The first mold will be 6" square by 1-1/2" high. Looking at the milk jugs and checking You Tube, I decided to recycle the plastic and make my own sheets. The internet recommends the cloudy milk jugs, not the colored versions. Looking farther, I have a large assortment of PETE 1 plastic in the form of jugs. Checking the internet, I can't seem to find any properties on the different plastics, say the difference between HDPE 1 & 4. Just general information and just buy from us.

I have a woodworking and metal working shop so molding and machining are not a problem. Anybody have hands on experience? The molds for the plastic will be whatever scrap I can throw together and I will use the kitchen stove for the trial runs. A long time a go I used to do rubber jewelry molds for wax injecting. Stunk pretty good but a fan took care of that.. The internet says the HDPE does not smell much at all.

Thanks in advance!!!! Charles

 

[DAT510]

HDPE has better "non-stick" properties, is less chemically reactive and is not Hydroscopic (does not absorb water at a molecular level). PET (PETE) is a polyester resin and it does not have the same non-reactive non-stick properties of Polyethylene and IS hydroscopic.

I would recommend HDPE over PET. HDPE is used in chemical bottles (think the original Nalgene bottles) because PE is a very stable molecule, and thus less reactive (thus the non-stick properties) than PET. Also PET needs to be dried using a descant dryer to around a -40C dew point to prevent bubbling/out-gassing of water/steam when melted, which I can't imaging would be good for your molds, as it could make them foamy/porous.

Hope this helped.

 

[RJSakowski]

Check MatWeb for information on plastics and other materials.

Online Materials Information Resource - MatWeb

Material property database with data sheets of thermoplastic and thermoset polymers such as nylon, polycarbonate, polyethylene; metal alloys, aluminum, steel, titanium, nickel, cobalt, and zinc alloys; ceramics, lubricants. Free search tools include mechanical property searches. Comparison and...

www.matweb.com

 

[Latinrascalrg1]

If you have access to a vacuum pump and chamber it would really help with getting solid mold blanks without voids.

 

[middle.road]

Go with the HDPE. Ton of videos (some good) up on YouTube.
Machines easily with sharp tools.
I put it on my 'Wanna-Do' list and started collecting bottles and jugs from friends last spring.
Oops. I now have (3) trash cans full. Thankfully Honey is understanding.
Have some cool colors to play with. Oil and Coolant Jugs come in decent colors. Clean up is a bit of a chore though.
I want(ed) to make up some mallets as gifts for Christmas (now 2020) kind of missed this years gift giving.
Also want to do up some plate. Make up some soft jaws for the vises and such.

 

[Chewy]

My original interest in HDPE was soft jaws, bearings and CHEAP prototypes before machining. Then this came up. Since this is for Wife, I can sit in living room and cut up plastic jugs and use kitchen stove. I am familiar with Delrin from where I worked, but that stuff is expensive.
I do have vacuum pump, compressed air and pressure pots and welding equipment.
THANKS to RJ for link!! I did not know of that site until now! I collect all that reference stuff and try to refer to it before posting here. I am never ceased to be amazed that with all the searching I do that someone here will pop up with an excellent answer.
Thank you all!! Even better you are going to make my wife happy! Charles

PS. The PETE 1 jugs are headed to the recyclers.

 

[RobertB]

PS. The PETE 1 jugs are headed to the recyclers.

Good choice. It has been a long time since I researched this so things may have changed, but PET processing was pretty much not possible at home. Even if you could dry it and melt it, it was not low enough viscosity to pour. It need to be extruded to form anything.