Hand grip moulding plastic

David,

My wife has had several joint replacements and in the stages between coming out of a rigid plaster or fibreglass cast and starting physio, they made her some supports moulded to her limbs with straps to remove for exercise and replace for support. They use a plastic sheet that when dipped in hot water would become really flexible and yet when cool was fully rigid. This was reversible so could be adjusted for fit just by warming it up.

I don't know what this stuff is called but if you know of any physio terrorists particularly working with wrists and hands, I'm sure they could help.

hth

Bob

I had the benefit of that stuff recently and they don't recycle it either, it gets binned. I tossed mine but it is as you say very workable when warmed in hot water and rigid at room temps. PLA maybe like used with a reprap. Maybe just pop into a local NHS hospital and ask to have a quick word with a physio or occupational therapist, I think both or one or the other use the stuff. I asked one of mine what they did with it after use and the main one said it got binned but she said that another had used it to make a sculpture, IIRC of a man sitting at a park bench. This was at Frenchay in Bristol.

Try polymorph, available from rapidonline.com

Alister,

Thanks, that's the stuff I was thinking of. Don't think I would ever have recalled the name to succeed in a search.

Thanks to the others for their help also.

David

(in a rather undignified fashion) on my backside. To reduce stress on my knuckles I made some wooden paddles, rather like old flatirons, but the sharp corners on these have now started to affect my thumbs (bad case of trigger thumb). ISTR that you can get a mouldable material that you can shape to fit your hand, and then harden off to form a permanent grip. Can anyone point me in the right direction? A Google search has

found the right words to search.

I recently enquired after products to repair the rubber brake hoods on my bike.

I was pointed at this stuff, which I'd never heard of:

It's a moldable, setting rubber.

It may be applicable to your needs.

BugBear

Thanks for that - it could be better than the polymorph - I was a bit concerned at having to mould it to my hand at 62 degrees.

David

Polycaprolactone AKA Polymorph.

was the cheapest supplier I found when I last bought any at about £30 per kg delivered.

A close, tightly wound layer of -cotton- sash cord or clothesline makes a nice hand grip. String works fine if you have the time and patience. Secure the ends the same way as a hangman's noose and trim them flush.

Not a problem as it has low thermal mass and is quite comfortable to handle at mouldable temperatures. Another option might be to use one of the thicker handlebar tapes used by cyclists such as :-

The heat isn't a big problem with polymorph, but it is a bit hard, perhaps too hard for long-term contact with flesh.

I don't know if sugro would be better, never having used it, but as it's flexible when set it might.

Of course they don't have to be made entirely of only one substance ..

-- Peter Fairbrother

[..]

I just looked at sugru prices, and ouch! £11 for 40 grams! It only has a six-month shelf life too.

I also looked at what sugru is - it's a silicone rubber - and I thought youcangetsilicone rubber much cheaper then that ..

You could use a two part RTV silicone, thickened with fumed silica (eg Cab-O-Sil) or a proprietary thixotropic additive. Ebay should have everything.

has a tale of Cab-O-Sil .. also, mix cab-o-sil with elastomer before adding hardener.

Or maybe just:

though you might still want more thickening

The cheapest method is probably to use silicone sealant mixed with corn flour, but beware, it gives off acetic acid for quite a while. It's also not going to be as tough as a RTV either.

Get a pack of corn flour, spread it on a tray and leave in a damp environment overnight, then add silicone sealant at about 1:1 to the corn flour (not the other way round). Nitrile gloves are useful here.

-- Peter

Interesting related 'Instructable' here:

--

Had another thought - a silicone rubber might get small bits of swarf stuck in it, whereas I don't think this would happen as easily with polymorph ...

-- Peter F

In article , David Littlewood writes

Having read the numerous very helpful replies here, I decided to have a go with Polymorph - it's a lot cheaper that Sugru, keeps indefinitely, and is re-usable. It also may have some uses in areas of modelling I indulge in. I'll let you know how I get on in due course.

Again, many thanks for the help.

David

That was my reaction too - some of the projects in the gallery have unjustifiable price tags on my estimate.

BugBear

writes

(in a rather undignified fashion) on my backside. To reduce stress on my knuckles I made some wooden paddles, rather like old flatirons, but the sharp corners on these have now started to affect my thumbs (bad case of trigger thumb). ISTR that you can get a mouldable material that you can shape to fit your hand, and then harden off to form a permanent grip. Can anyone point me in the right direction? A Google search

yet found the right words to search.

with Polymorph - it's a lot cheaper that Sugru, keeps indefinitely, and is re-usable. It also may have some uses in areas of modelling I indulge in. I'll let you know how I get on in due course.

Let us know how you get on.

BugBear

I moulded a handgrip for a camera flash bracket many moons ago by using the "lost wax" method - moulded a lump of wax around where I wanted the handle to be, sculpted it to shape with modelling knives etc, then a light flashing over the surface with a blowtorch to smooth out any surface imperfections. Then embeded the wax in plaster of Paris, leaving an opening/funnel for pouring, baked in the oven at gas mark 5 to get rid of the wax, and then filled the void with 2-part polyester resin (the stuff used to make GRP). Break off the PoP when the resin has cured. Worked very well,

Regards, Tony

In article , David Littlewood writes

I bought a tub of Polymorph, as suggested by Alistair. Followed the simple instructions and made handgrips, they worked fine. The Polymorph is very simple to use, simply pour the required amount into hot water at about 65 deg C, the white pellets turn clear fairly quickly, at which point you remove from the water and mould to shape. you have a few minutes before it starts to go firm again. It seemed to stick to the wood (oak) very well. The temperature of the plastic is not a problem (though the water is a bit hot while you are squeezing it out!). One thing I did find though - having done a test piece on a length of scrap wood, I decided to re-use it; although the plastic is fine being re-softened in this way, it takes *far* longer to soften in bulk form, and needed a few top-ups with hot water.

Again, thanks for all your helpful suggestions.

David

Greetings David, I had many appliances for my arms made from sheets of that plastic. After all the surgeries (14!) I saved all the braces and other instruments of torture made from the plastic. The other day I finally needed to use some to fixture a part. I just used the microwave to soften it. You need to be careful though because it can overheat quite fast. When the swelling would go down a week or so after one or the other arm was cut on I would reform the braces for a snug fit by holding the brace over the steam from a boiling kettle. Much more convenient than heating in a big pot of water. Cheers, Eric