Apr 012013
 

Polycaprolactone (Polymorph, Morphplast)

A low temperature theromplastic polymer of considerable interest to Remap members.

It has a fusing temperature of about 60° C and can be hand moulded to produce brackets, handles etc.  Polymorph can be turned to a mouldable condition by immersion in hot water.  When put in hot water it turns from opaque to clear and in this condition can be moulded in a variety of ways including by hand.  It has the consistency of slightly stiff Plasticene and  remains workable until a much lower temperature however once it has set it remains rigid until heated up to 60°C again.

When fully cooled it is white and very similar in appearance and physical properties to a broad range of polythenes but somewhat stiffer, stronger and tougher.  It is a true thermoplastic and can be re-heated and thermoformed any number of times.  It is also bio-degradable.

Chemical name:
Caprolactone polymer or Oxepanone polymer

Commercial designation:
CAPA 680 (specification 118310)

Fusing point:
60-62° centigrade

Tensile strength:
580 kg/cm2

General Hazards:
Non-hazardous

Available from a number of outlets on the suppliers page

Using Polymorph

The following sequence show making a simple prototype of a hand mould.  From beginning to end this took about 10 minutes.  The odd angle of some of the photos came about because the subject was also the photographer!  Some better images are to come.

Using Polymorph is quite easy.  It is supplied as granules.

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Simply place the granules in a pan of boiling water

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Don’t leave the heat on under the pan unless it is a very thick based one as otherwise bits of the Polymorph may stick, don’t worry if it does – let it cool and they easily come loose.

The granules turn transparent as they become soft

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When fully transparent the Polymorph has reached 60° C and can be removed (a fork does this wel) land moulded.

Any old bits left over from previous work can be remelted if required.  Polymorph is a true thermosplastic and can be melted and reused any number of times.

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Below is the blob of Polymorph taken out of the pan.  Though 60°C sounds too hot to handle, and 60°C water can cause burns, Polycaprolactones specific heat and conductivity are low enough that it isn’t hard to handle at this temperature.

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Within a very short time of removal it is cool enough to handle.  I’m pressing my hand into this blob to make a hand support.  It isn’t sticky, simply wetting your hand with plain water prevents any sticking at all. As you can see it moulds easily.  You can’t see the other hand moulding the plastic as it’s holding the camera!

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The waste from the ends was stretched and pulled over to form the top.  The Polymorph is cooling now and returning to its opaque state.  It’s still mouldable though.

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This is the final prototype from the front.  The fingers protrude but are held fairly rigidly.

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View from the back where the hand fits in.

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Once set Polymorph is tough and rigid.  It can be machined, drilled, tapped and cut as Nylon although cutting temperatures must be kept low to stop it melting and becoming adhesive (which it does above about 110°C).  The photo above and below show it supporting 15kg of steel bar.

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Example uses

Because it moulds so easily and has high set stregth Polymorph is idea for jobs such as making larger knobs for cookers etc for people with poor grip.  All that is needed is the knob, a suitable mould surround and some Polymorph.

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The aluminium ring cut from a scrap piece of tubing.

Before moulding the knob give it and the tube a lght coating of polish to act as a mould release agent.

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Heat up the Polymorph as above and then press it firmly onto the knob in the mould.

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The bottom  (top at the moment) can be levelled by using a kife kept in boiling water and pressing down on the surface with the kife blade.

After a short time the Polymorph starts to turn white as it cools. polymorph06

It can now be removed from the tube and the knob removed.polymorph07

You now have the base and knob fitting onto which a handle can be fitted. Because it is similar to nylon in its set state the handle can be attached with self tapping screws.

 

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If you need to use a longer handle, to reach a gas fire control for example, simply mould the fitting with the knob :-

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 April 1, 2013  Posted by at 17:22 New Materials