Polycaprolactone - Make Your Own Kite Fittings
Polycaprolactone - Make Your Own Kite Fittings
I asked around on several kite forums about whether anyone worked with Polycaprolactone - brand names InstaMorph, ShapeLock, Friendly Plastic, Polymorph, InstaLock, Plastimake (AU) - to make fittings? Only one person responded and stated they had used it to make some end caps, but no fittings. As no one seems to have really used the material (at least no one willing to speak up over a 2 week period), I decided to order up some samples and do my own testing.
This material has been around for a while. It has a melting point of only 60 deg C /160 deg F - so you put it in hot water and then mold it by hand (or form). It can be remelted and reused over and over. It can be colored with a number of different inks. The cooled product was reported to be akin to plastic injection molded nylon.
Here it is in a homemade KAP fitting I found pictured on the internet.
The Friendly Plastic brand seems to be used in a lot of jewelry. And comes in a pretty amazing variety of colors.
So I decided to get started with the testing even though I only have 3 products.
Shapelock - Friendly Plastic (in pellet form) - instaMorph. I went for the smallest amounts I could get. Shapelock mails out 1.4 oz for just $4.59 shipping. Friendly Plastic's smallest amount is 1.4 oz - $6.59 (free shipping with Amazon Prime or $11.99 shipping from the maker Amaco (ouch)). Instamorph $9.99 for 6 oz (free shipping with Amazon Prime).
I did a quick weigh in to see if any of the companies shorted me on product and none of them did.
Products all appeared about the same. The Shapelock pellets were the larges. The Friendly Plastic had the most stringy tails. InstaMorph were the most uniform.
For testing purposes I decided to use a silicone Maoi ice cube tray. I wanted to see how the material took the shapes of the mold.
I filled up 3 sections of the mold to the rim to measure the same volume of each product. I wanted to be able to address the shrinkage question so I kept each amount even.
So on to the melting. Because only some of the products discuss melting in the oven, and because microwaves can vary, I followed the directions to the letter for hot water melting. For Shapelock the water was 150 deg F, for Friendly Plastic the water was 120 deg F, and for InstaMorph the water was 160 deg F. When the material is melted it turns clear and is ready to kneed together. At their specified temperatures only the InstaMorph started to melt.
So with the water at 160 deg F I reheated the Shapelock and Friendly Plastic and they began melting.
When the material is only partly melted it is partly clear. This is the Friendly Plastic partially melted - it kneeded together but still needed to melt some more.
It took about 3 water changes to melt the material fully. After kneeding the above partially melted Friendly Plastic together so that it was not loose pellets I just dropped it into the water on the stove - that led to much quicker melting.
I took each fully melted sample and kneaded it and then pressed it into the Maoi mold by hand. After placing all 3 in the molds I ran them under cold water to cool them quickly. I squeezed the Friendly Plastic Maoi out too quickly and squished its face - so it went back in the pan of water on the stove to reheat - and then back in the mold. Here it is in the center - still hot - while the other two have cooled and thus are white again.
Note the volume in the mold. I believe that the reduction is just the elimination of the spaces between the pellets.
After they were fully cooled all 3 Maoi came out of their molds.
Each product took the mold shape and details very well. The lines were crisp and defined.
I could not bend or break any of the 3 by hand.
It took placing a Maoi in the vice to do anything. This one bent - but did not tear or break - at the thinnest point of the mold. When I took it out it went back to the original position - with a crease in it.
I decided to try a couple more pieces with the Instamorph. After melting 1 oz of material I kneeded it into a ball. The more the material is worked and folded the more effort it takes to get the fold lines and/or air bubbles out of the material. If you are patient and careful you can get these out. It helps to put the piece back in the pan of hot water periodically to keep it melted.
I then cut out a star with a cookie cutter. The cookie cutter pressed through the plastic with some effort and pushed down the top edges but it did cut out the shape. The pieces outside the cutter went back into the pot to remelt and reuse.
Because the cutter pressed down on the edges and created a bulge in the center, I hand pressed the center of the top side back down and up against the walls of the cutter. When cooled this showed up as an uneven top.
I used a belt sander to smooth this down. The temperature apparently got just to the melting point as the edges showed some melt.
Cutting the material with the cookie cutter was possible - but it distorted the top of the shape significantly. If I was going to use a one again for the shape - I would simply press the material down into it.
I also tried making a 4" cylinder from the InstaMorph. I worked the material and rolled it on the counter. Back into the water in the pan on the stove to remelt it and keep it workable. Rolling it on the counter got a good clean cylinder.
I drilled out the ends with my standard drill to accept two carbon spars. The tailings can go right back into the pot to be remelted.
I could not bend it or get any significant deflection by hand.
Putting in two 32.5" carbon spars and bending them to a full half circle the cylinder deflected some but not much. I have this in the window frame now and will report back on its status after 24 hours.
Based on the workability of this material and these intial tests, I am very impressed with this material and I think it may be fantastic for fittings. Shaping it appropriately is easy because the material can continuously be remelted and reworked. And if you aren't satisfied - melt it and start over. It seems to be slightly flexible - definitely not brittle - but plenty strong for fittings.
I would not use this material to make fittings that can be bought on the market. The plastic in injection molding is probably a little stronger and there is no need to make a detailed mold. I also think standard ferrules are stronger and lighter out of metal. But for a custom fitting, or to replace a broken fitting, this material may be just the ticket.
Re: Polycaprolactone - Make Your Own Kite Fittings
Back with some testing results.
After a full 24 hours in the window, the ferrule type fitting had about a 15 deg bend in it. It relaxed back to about 10 deg after 24 hours out. Note that it was not drilled all the way to the center - I do not know if this helped or hindered. As I said at the end of the first post, I would not choose this as my first material for a fitting. And based on the test, it is not the best material for a fitting under a lot of stress. But then again, how many fittings are under tension and stress for 24 hours.
Somewhere it was reported that this material might be in lesser volume after being melted. While it certainly does compact in size when the airspace between the pellets is eliminated and it is kneaded together, the volume by weight is exactly the same as the original package - even after heating, forming, drilling (see scraps collected), and sanding.
I finally received my other samples - Missing Link Brand. Sold by the manufacturer on Amazon - $2.99 for 1oz size (free shipping with Amazon Prime). This did not arrive until about 10 days after I ordered it - but they threw in an extra 1oz so I'm happy. This is the only brand that had a "flowable" formulation.
Unfortunately there were no instructions beyond the 140 - 144 deg F melting point listed on the label. The website did not have much information either but warned not to go above 145 deg F because it might burn your hands when handling. As usual, the material did not melt at the listed temperature. It started melting at 160 deg F and melted quickly at 180 deg F - the same as all the others.
Although I was really hoping for something different with the "flowable" formula, that title did not yield a plastic that would pour. Instead, it was simply very easy to mix and mold - it was not stiff. When compared to the other brands - the ease of mixing and molding was directly comparable to the Friendly Plastic (for which I made a new Maoi just to handle it at the same time and confirm my recollection). The "Standard" formula was stiffer to work - very comparable to the InstaMorph. The stiffness makes it harder to get mold details - but with some work and remelting they can be done just fine.
Out of curiosity and exploration of the differences in the plastics I remelted the original Moai. I kept the water between 180 and 200 deg F and they melted pretty quickly - a little longer for the centers.
When they are fully melted and clear - you can see the air bubbles and imperfections that were trapped in the plastic from the original casting.
I mixed all 3 Moai together to see how the plastics (InstaMorph, Friendly Plastic, Shapelock) reacted together. No visible reaction - the material blended together - and ultimately produced two new Moai that seem exactly the same as the original single product Moai. Having worked and reworked the plastic, I did not quite get all the folds out before molding and that showed up - but that was my haste and error, not a product fault.
As part of the abuse testing, I boiled the Friendly Plastic at 212 deg F for 15 minutes before casting the Moai above. The plastic was too hot to handle straight out of the water - but was fine after 30 seconds. No discernable effect on the plastic or the finished Moai was observed.
Continuing the heat abuse testing, I remelted the InstaMorph star in the toaster oven at 300 deg F.
After 30 minutes it was fully melted and sloping some. The original bubble imperfections in the plastic had joined and risen up toward the top of the melt but they could not break the surface tension of the plastic and escape.
After a full 60 minutes at 300 deg F the melt slope was more pronounced - it lost its star shape - but the material was still not pourable.
So I took the temperature up to 400 deg F. Within 5 minutes the plastic was bubbling from within and there was some noxious off gassing. So I pulled it out before it burned or changed too much.
Even at 400 deg F - the InstaMorph material is not flowable.
When the material cooled enough to handle I tried to get it to release from the foil - it would not. I did manage to push it into a mound on the foil and then pushed the mound into the mold. Even with the abuse it took the shape - albeit still attached to the foil and with some foil folded in.
When it cooled some (under cold running water) I was able to get the foil to release from the thin flat section. But the foil that was bunched or crinkled would not release.
So - now that the InstaMorph had been melted in water, formed in a cookie cutter, subjected to a belt sander, re-melted in a toaster oven at 300 deg F and then run up to 400 deg F --- I decided to throw it back in the water bath and see if I could remelt it and remove the foil.
No luck on getting the foil out - but it certainly lived up to the polymorphic qualities and remelted and remolded just fine. This stuff can really take some abuse.
Note the stirrer straw melted when I tried to use it to push around the InstaMorph when it was 400 deg F.
So next up was the impact test. A single blow with a hammer on the nose of the Moai - with the Moai on an anvil so that the full force of the hammer blow was right on the nose - resulted in no visible damage. The hammer bounced back when I struck it. These pieces are not going to break from impact - any spars in them will be the weak part of the equation.
Since a single hammer blow did not do anything, I tried multiple blows, still without effect. I then switched to the chisel hammer - and after 20 hard blows - all on the super abused InstaMorph with the foil folded in - I managed to mangle the surface some. No fractures or splits, just a torn up surface.
Paint test - now here finally was something this material doesn't do. It doesn't take spray paint. A fingernail scratch applied with moderate force removed the paint. I don't think this is much of an issue given that the material itself can be colored in a couple of ways (testing on that to come).
And finally (for now) a glue test. First I cut the cylinder in half. The material does not cut well - I was using a fine toothed hack saw and it generated a pretty ragged edge. I had to use a sharp knife to clean up the edges.
And so it is glued up waiting 24 hours. I do not expect much holding force from this glued joint.
There is also now a piece in the freezer for a brittle impact test in a day or so.
I remain totally impressed with this material. It can definitely be worked and reworked without issue. It is not going to melt apart in a hot car. Any spar in a fitting made from this material is going to break long before the fitting. I need to figure out the best way to work the material and keep air bubbles and imperfections out - but that should just be developing a technique.
Re: Polycaprolactone - Make Your Own Kite Fittings
I use Polymorph here in the UK which is identical.
I find it a very useful material for quickly making jigs and strips for holding things in place. One of the potential problems with it might be that it has a self lubricating quality to its surface and joints might be prone to working free.
Just a thought from my experience.
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