Author Topic: A new source of HDPE? (Read 7802 times)

Rand alThor · « **on:** June 08, 2008, 12:31:07 AM »

Hi. I was over at the local recycling center today when I looked at the prices of cashing in per bottle for various materials. I found Plastic number 2 to be HDPE. I thought that milk jugs where plastic type 2 and when I turned one over and looked at the bottom of it-- there it was! A little two in that recycling triangle!

! I was wondering if this could be a goldmine for me because my family goes through a gallon or so of milk every day (six kids under 14 do that

). So I was wondering if I could save the jugs, rinse them, let them dry, and melt them in the oven in, say, a 9 by 13 pan lined with foil (since the oven doesn't go past 500). Would this work? Is the plastic meltable at such low temperatures? Or would it ruin the HDPE? Also, smell would be a big factor, because Mom would have my hide if I stunk up the house for a day. Please respond with any advice you can give me. Thanks,

--The Dragon

airman00 · « **Reply #1 on:** June 08, 2008, 12:41:11 AM »

hey welcome to the forum

what is your experience level in robotics

and heres some helpful info for your question
http://answers.yahoo.com/question/index?qid=20080104132600AAPli43&show=7

Rand alThor · « **Reply #2 on:** June 08, 2008, 04:13:31 PM »

Thanks for the welcome. I have (almost literally) no experience in robotics. I have, however, read pretty much every tutorial on the site, and I plan on starting soon. The only delay is I'm waiting for a catalog from a company that supplies electronic components (www.jameco.com). It should have arrived days ago, but it hasn't, and I want to make sure stuff I order will actually get to me before I spend pretty much all my hard-earned money on them

.

So, to shape the plastic, I'd just have to like put it in a pot of boiling water? If it is a "Smart-alloy," that is. How would I find out if it is, though? I just found an empty jug and on the topwith the expiration date, etc., it says:

JUN 19 A1 PLT#06-10 17:06
FOREMOST

I'm guessing that the "FOREMOST" part is the company name, because it looks like it is on the label.

Could someone (maybe a friendly milkman

) please decipher this for me please?

Also, if melting it releases toxic fumes, I can't go with that. Is there any way to go nontoxic HDPE melting?

I don't need it to be in any particular shape: according to the site (and experience with milk jugs), HDPE is pretty flexable, and some sheets would be fine to me.

Thanks

--The Dragon

airman00 · « **Reply #3 on:** June 08, 2008, 04:25:12 PM »

I have a feeling all of this can be found by google searching

so do some research on google and I am almost certain that you'll find an answer

Jameco is an amazing supplier, they are my favorite!!!

Rand alThor · « **Reply #4 on:** June 08, 2008, 05:04:10 PM »

OK. I'm confused now. Some sites say that HDPE gives off toxic fumes when burned (like that yahoo answers thread and http://www.nt.gov.au/nreta/environment/assessment/register/pointceylon/pdf/Appendices/appendix5.pdf), and some say it doesn't (http://findarticles.com/p/articles/mi_m0UQX/is_7_67/ai_106423171)

So now I'm wondering how toxic the fumes are and whether I can like melt them in a solar cooker out in the desert (I live in the Mojave Desert), or if that would be against regulations. I've heard of people out in the boonies burning their trash and not getting in trouble with anything unless they get in a lawsuit because someone dies because they have asthma. However, If I have to build another solar cooker (I had to for a science project last year), It may just be easier to go looking for those $3 cutting boards in that other post on this site.

I think it'd be cool to get rid of those milk jugs to save some money, but I don't want the EPA to come knocking on my door over a couple of bucks.

Thanks,

The Dragon

pomprocker · « **Reply #5 on:** June 08, 2008, 11:08:51 PM »

get some $3 cutting boards from a hardware store. they are not usually HDPE (polyethelene) but polypropelene. It should still work

Rand alThor · « **Reply #6 on:** June 08, 2008, 11:53:30 PM »

Well, yeah I was thinking that, but I am also on a very tight budget, and if worse comes to worse (meaning I can't really get a straight answer anywhere--*cough cough* --jk

), I'll probably end up cutting the milk jug sides out and gluing them or something like that. I am pretty resourceful-- I am a very accomplished alluminum-foil-smith, after all

.

But seriously, folks, I would much rather find out how to melt them into one piece, rather than buy some cutting boards, because I can't drive, and since gas prices are rocketing, trips into town are getting fewer and fewer, and I can't drive because I'm under 16 and I don't have a motorized trash can(http://www.societyofrobots.com/robotforum/index.php?topic=3857.0, and at the end of Mom's shopping for necessities, e.g. food, all the other five kids are screaming and hungry and crying and it's very hard to convince her to stop by big lots or something like that, if you take my meaning. So most of my shopping has to be at home, online, and I don't think it would be too kind to my pocket book for me to pay shipping for cutting boards I'm just going to mutilate anyway.

AndrewM · « **Reply #7 on:** June 09, 2008, 08:59:49 AM »

Take a look at the "Physical Properties" section here: http://en.wikipedia.org/wiki/Polyethylene
The crystalline structure of polyethylene makes melting and reforming HDPE difficult without adding a chemical reaction to the mix, which in turn increases your costs.

Also beware with polypropelene, as it does not work with 99% of the adhesives on the market (the oily film that is constantly extrudes combined with its incredible chemical resistance). I had to glue about 700 one inch straw pieces together recently

Rand alThor · « **Reply #8 on:** June 09, 2008, 05:44:02 PM »

So what do you suggest for a chemical reaction? Wouldn't just heating it up (perhaps with a solar cooker as mentioned above) to a certain temperature reshape it? I know solar cookers can get like over 200 C.

Again, DOES MELTING HDPE BREAK ANY LAWS AND/OR PRODUCE TOXIC FUMES???!!!!

I'm pretty sure I can figure out a way to melt it if I can do it legally.

bukowski · « **Reply #9 on:** June 09, 2008, 07:22:40 PM »

I can't answer about the local laws in your neighborhood, but here's the MSDS:
http://www.haldiapetrochemicals.com/pdf/new/msds_pdf/HDPE.pdf

Sounds like you would want to do it in a well ventalated space, but it doesn't seem toooooo dangerous...

By the way, too bad about robert jordan, huh?

Rand alThor · « **Reply #10 on:** June 10, 2008, 11:56:42 AM »

Yeah, it is too bad. He was like Mom's favorite author and she got really upset when she found out. She was all depressed for a couple days there, but I think she's gotten over it. I'm reading the books, and they are really good, but I just hope that the ones that are written by his brother (wasn't it?) are just as good.

Anyway, where would you find out laws and/or regulations on HDPE melting for a given area?

paulstreats · « **Reply #11 on:** June 10, 2008, 02:45:15 PM »

I idnt think there were any laws for melting hdpe? Id just make sure that any fumes that might be given off are not affecting anybody else.

In these types of situations i prefer to take the point of view where the law only gets broken if you get caught. (also, even though ignorance isnt an excuse in the eyes of the law

if you get caught just say you didnt realise it was illegal - it is such an obscure point that you would get away with just being told not to do it again....)

Rand alThor · « **Reply #12 on:** June 12, 2008, 12:35:53 AM »

Yeah, laws concerning melting HDPE are just one of those things you don't really think about until you get caught or something... But I'm sure the Feds have got SOME sort of law regarding that. I just looked it up and, heck, they have laws against driving barefooted and playing dominoes on Sunday (whoops...).

Yeah, I guess since there appears to be no law on the subject, I'm gonna have to just carry through with it and hope no one gets upset. I just hope it doesn't make a lot of smoke so someone looks out their window and calls the fire dept. Hahaha. I can imagine the scene: The fire dept. gets an emergency call about the desert being on fire and they get out there and all they find is a solar cooker and some half-melted milk jugs. Hahahahahaha!

P.S. love that avatar, paulstreats. Where'd you get it?

paulstreats · « **Reply #13 on:** June 12, 2008, 02:03:15 AM »

I made it myself, I modelled it off one of the vehicles from the desert planet in star wars!

Rand alThor · « **Reply #14 on:** June 13, 2008, 10:24:38 PM »

Ahh, so that's where it came from...

Anyway, I talked it over with my Mom and she says that burning plastic releases harmful chemicals. Can anyone confirm this with HDPE?

Thanks,

Over and out.

airman00 · « **Reply #15 on:** June 14, 2008, 07:34:40 PM »

http://www.newton.dep.anl.gov/askasci/chem03/chem03082.htm

paulstreats · « **Reply #16 on:** June 14, 2008, 07:45:12 PM »

Theres a big difference between burning plastic and melting plastic.

Many plastics wouldnt be harmful to you, unless you were stupidly inhaling lungfuls of fumes straight off of a plastic fire. They are probably considered more harmful to the environment.

There are exceptions like the pvc above which releases chloride, a form of chlorine which is a poisonous gas.

[disclaimer from angry parents]

But remember if your mom tells you not to do something then you should respect her wishes, or at least respect them in the home that she has worked hard to build up.

[/disclaimer]

[crafty]
If you dont tell somebody what you are planning to do then they cant tell you not to do it.
[/crafty]

Rand alThor · « **Reply #17 on:** June 15, 2008, 03:33:29 PM »

OK. Thanks a LOT. this like completely answers my question. So if I don't want to release carbon monoxide into the wastes of Rosamond, I just have to make sure ther's plenty of oxygen around... Solar powered fan, anyone?

BTW, I found out that the seat to one of these baby toy workbench thingys that we're likely to throw away is HDPE (I looked on the back

), but it's green. Any ideas how to get the pigmentation out? Remember I'm doing this in like a solar cooker, so it'll probably be melted in a pan-shaped object at the bottom.

Thank you SO much!!!

A view of Rosamond...

As you can see, there's lots of open desert space in which I plan to do my melting...

airman00 · « **Reply #18 on:** June 15, 2008, 03:50:32 PM »

now the pigmentation might be toxic

why does it matter what color it is? Just paint it over with your color of choice.

paulstreats · « **Reply #19 on:** June 15, 2008, 04:54:38 PM »

I dont thing that the pigment is easily removed (i reckon that you have to melt it to a liquid then the plastics/pigments will seperate and form layers).

When you talk about melting hdpe, do you mean like melt it to a liquid or melt it until its pliable? many people melt it until its pliable (there are a lot of examples on instructables.com) which will let you easily mould it. But i think to melt it to a liquid state will require others chemicals aswell to hold its composition together.

If you are melting it either until pliable or to a liquid, its important to do it almost scientifically on your first go. So set your oven/heater at its lowest temperature and wait for 20 minutes then check to see if the hdpe is how you want it. If not set the temperature up a notch and wait for 20 minutes and then check it. and so.....

Its important to do it like this because then you will not risk ruining your hdpe and you can better control its mouldablility, like knowing what temperature and for how long it takes to bend a sheet, knowing what temperature and how long it takes to model it as if it was modelling dough etc...

Remember to use gloves, the hdpe will be hot hot hot

Rand alThor · « **Reply #20 on:** June 15, 2008, 11:49:58 PM »

When I talk about melting HDPE, I don't really care how hot it is as long as it forms sheets at the bottom of a pan/the cooker at the end of the process

. I don't think it being pliable would really help things, cause you know, I'm talking about milk jugs as my primary source of HDPE.

And I think there might be a little confusion as to what I mean when I say "solar cooker." I mean basically a cardboard box with aluminum foil on the inside. Of course it would be more effiecient and complicated then that, but I don't really think I can control the temperature in there

.

Quote from: airman00 on June 15, 2008, 03:50:32 PM

now the pigmentation might be toxic

why does it matter what color it is? Just paint it over with your color of choice.

It matters because it is the most UGLY shade of green in the world. (And the main perpose of my robots isn't to make everyone puke, either -jk)

How do I show an attached file, anyway? (I have a picture of the shade attached. I hope it works)

Rand alThor · « **Reply #21 on:** June 16, 2008, 12:13:33 AM »

Well, I guess it worked.

airman00 · « **Reply #22 on:** June 16, 2008, 07:13:58 AM »

just paint over it, problem solve

Rand alThor · « **Reply #23 on:** June 19, 2008, 11:39:06 AM »

I just got my soldering iron yesterday, and it says it gets up to 700F. So could I use this to melt the milk jugs? It'd be easier than building a solar cooker and draging things out to the desert every day at noon.

Thanks,

The Dragon.

Trumpkin · « **Reply #24 on:** June 19, 2008, 03:32:15 PM »

not unless you want a messed up soldering iron tip.

Rand alThor · « **Reply #25 on:** June 19, 2008, 09:25:51 PM »

Ahh, I guess you're right. But how about a planning-to-never-use-again-for-any-other-purpose-than-melting-milk-jugs-hot-glue-gun? Or would a "Smelting pot" heated by a disassembled hot glue gun work better?

P.S. The stupid spell cheker didn't know what a planning-to-never-use-again-for-any-other-purpose-than-melting-milk-jugs-hot-glue-gun was. Didn't even have any suggestions.

lol.

JonHylands · « **Reply #26 on:** June 20, 2008, 08:20:38 AM »

I think you're wasting your time here. Don't bother with milk jugs - save your money and buy a cheap plastic breadboard, or just use plywood. Lots of people build robots from wood, and its a lot easier to work with than any plastic...

- Jon