Polyurethane Rails attempt - SUCCESS!

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Re: So, who want's PU rails?

Chris
A quick google suggests that Hyrdroxyl groups and possibly any water in the bamboo (some part of the sap I guess) react during the chemical process the PU goes through to act as a foaming agent or modify the chemical reaction... I think that might be the problem...

Chemistry bit
http://www1.chem.leeds.ac.uk/delights/texts/expt_31.html

Bamboo bit
http://www.emeraldinsight.com/journals.htm?articleid=1776195
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Re: So, who want's PU rails?

downunder
Indeed Chris.

Thanks for the links. As per my post from the above :

"Moisture. 0.2% moisture content in the materials will cause the polyurethane to foam. By foam I mean like house insulation foam."

Why am I so stubborn?!

Coz of this on minute 1.54:

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Re: So, who want's PU rails?

Chris
They are probably using a modifed PU with something to stop the foaming, a controlled environment and possibly a different type of wood i.e. paulownia by the looks of the rest of the site.

You may find because of the structure of bamboo it holds the water and resin longer
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Re: So, who want's PU rails?

downunder
This post was updated on .
To answer bending question, yes, it can be bend after slight heating with a torch (slight pigment sedimentation at the bottom of container):



It stays in this shape rock solid. The above color is actually a fluorescent orange!

A few samples for the experiment. Vivid colors, but gone after curing:





Cut two samples in half to see if any traces of air bubbles. Not visible with a naked eyes. Also slightly bent sample with compression after heating:



Now the foaming:



Extreme samples:



The next experiment with this samples is epoxy bonding. Sanding first, etc...
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Re: So, who want's PU rails?

Chris
Slightly off topic,

What is the manufacturer of the pigment? Is it an epoxy specific pigment? Where did you get it from?

I only ask as all I can find here in the UK is plain red, blue, cream etc...
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Re: So, who want's PU rails?

downunder
This post was updated on .
I am selling this fluorescent powder pigments Chris:) As well as other stuff on the Market thread. PM me if you want some.

It is a PU pigment. Works well with epoxy.

P.S.

Smooth-On has got many pigments:

http://www.smooth-on.com/index.php?cPath=1255

http://www.smooth-on.com/a95/SO-Strong%3D-%26-Ignite%3D-Now-in-a-9-Pack-Sampler!/article_info.html


I have the Smooth-Cast 327 (20mins life, 325 is 3min) on backorder. Will be interesting to try with.
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Re: So, who want's PU rails?

downunder
This post was updated on .
Today I've poured some PU into the perspex channel. I used a wax and hair spray as release agent and did not leave it for long before PU. Now thinking that a hair spray has got water in it:((( That might foam.

Also poured PU into the sealed "rails" on a bamboo leftover. Will report back the results.
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Re: So, who want's PU rails?

downunder
Already seeing the results:) 2 hours curing time.

The longitudinal cut rails (in a wood grain direction), is a way much better than orthogonal (ie on a tips).

Of course, the perspex foamed coz of moisture comming for a hair spray (my mistake). Will use a wax only for next attempt.
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Re: So, who want's PU rails?

downunder
This post was updated on .
I might have a winner!

The winning card is to pour at the last moment after degassing.

On the left side is my second attempt (a lot of bubbles, and a bottom foamed).

On the right side my third attempt:



Sooooo much better.

So what I've done?

I degassed this baby like hell. The pot time is 18-20 minutes and I degassed for like 17 minutes.  You can see how is bubbling in a vacuum pot on a FULL vacuum.




The problem with PU is if you slightly disturb the resin it will bubble like no other! Inside the vacuum!

I recon, this disturbance is our enemy. When pouring it's is next to impossible to avoid it. End see how it works:



Than in the last moment, I poured it also in the perspex cast:



And now this is the result. My pre made rails:)



Almost no air bubbles at all

De casted after 1 hour. 5 hours latter the rails are not too flexible, quite strong.

To conclude: you need to work with fast resins like 2mins pot life. The best would be even shorter life, since will have no tome to introduce air in it.

For a longer pot life, don't stress, just degas it for a minute or two before a pot life. Than pour on epoxy sealed rails.

This will minimise any air bubbles. It is also what big boys are doing, using ultra fast resins (Dan's tip).

Now, let's build on that!
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Re: So, who want's PU rails?

mattma
Administrator
Great experimenting and well done on cracking the code.

Did dan mention why they were using PU in production boards? I hear people talk about it being cheaper but that doesn't seem to be the case in Australia. Maybe the high price is only an issue in the Australian market?

Cheers
Matt
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Re: So, who want's PU rails?

downunder
Thanks Matt.

It is still wip, will test FG bonding soon. The above 0.84kg PU is $30 only. In Perth.

The PU doesn't fade so much by my experiment, and it is light. Lighter than epoxy I think. Not brittle. Heat formable. Easy to sand and machine.

Might be relatively better for the environment. The epoxy has almost top carbon footprint.

I like it so far. Will see in a due course.

D.
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Re: So, who want's PU rails?

downunder
Today I rebooted and back to my projects! Hurrah!

So, back to the rails. I have some samples from quite some time ago and in due for bonding with epoxy.

But first wanted to see how is it machining and if there are any air bubbles. Router (Dremel, mid speed), works great, orbital sander excellent.

Not many bubbles, big makro:



This sample is 2x40cm 5mm tick bamboo, rail about 4.5mm deep.

This was made by pouring PU at last minutes of pot life. Till than was in a full vac, taken out just before pouring.

As seen, not visible bubbles. The PU is hard, but it is possible to imprint with a nail on the edge only.
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Re: So, who want's PU rails?

Chris
What is the pot life of this one then? I've seen some here in the UK with about 5min potlife at a reasonable cost so thinking of going that way
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Re: So, who want's PU rails?

downunder
20 mins this one.

On 1/19/14, Chris [via BoardBuilders Forum]
<[hidden email]> wrote:

>
>
> What is the pot life of this one then? I've seen some here in the UK with
> about 5min potlife at a reasonable cost so thinking of going that way
>
>
>
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Re: So, who want's PU rails?

downunder
In reply to this post by downunder
downunder wrote
Thanks Matt.

It is still wip, will test FG bonding soon.

Testing FG bonding now....Testing bonding with two different top sheets as well.
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Re: So, who want's PU rails?

downunder
Awesome results...
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Re: So, who want's PU rails?

Chris
oooh do tell, what topsheets are you trying?
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Re: So, who want's PU rails?

downunder
Scorp Duraclear corona treated gloss and Crown Durasurf mat.

http://www.socrep.com/ang/products/ski/index.html


On 1/22/14, Chris [via BoardBuilders Forum]
<[hidden email]> wrote:

>
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> oooh do tell, what topsheets are you trying?
>
>
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> _______________________________________________
> If you reply to this email, your message will be added to the discussion
> below:
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Re: So, who want's PU rails?

downunder
My pressure chamber for a pre made PU rails.

The aluminium mold will go in with a PU and all pumped up to 40psi.



Wish me luck

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Re: So, who want's PU rails?

mattma
Administrator
Hey Downunder. Looks like you doing so awesome experiments!!!

What is the idea of increasing the pressure in this set up?
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