Hello O&P colleagues,
Thank you all so much for your responses to my question! Below is my
original O&P-L post, followed by the responses.
Bill Lifford, CP
Progressive O&P, Inc.
/_*ORIGINAL POST:*_/
/I am in the process of fabricating a foam lined AFO for a patient and
have always had trouble when molding plastic directly over foam, in that
the heat of the plastic squashes the foam down to almost nothing in some
areas of the cast. We’ve been trying different methods to remedy this
and I’d like to see what ideas you may have that might be better,
easier, or both. For this latest AFO, I modified the cast and molded
3/16″ foam over it (actually, heated the foam and stapled the foam on
the anterior aspect of the cast)./
/I then wrapped the whole thing with Saran wrap to protect it and casted
the foam-covered positive model, then poured it — so now i have a
plaster representation of the original model plus the thickness of the
foam. /
/My plan was to mold polypro over this new positive model, trim it the
way i’d like, then apply glue to the foamed cast and the plastic brace
and put ’em together while the glue is wet. I’d then tape the whole
thing together so nothing could move and let the glue dry. My thought
was that the foam inside the finished brace would then be full-thickness
and perfectly installed without wrinkles or other mess-ups (all of which
I have done in the past!)/
/ Is there a glue that would be appropriate for fabricating the AFO in
this way? Most of the stuff we have here is contact cement-type stuff
and results have been only okay so far. Are there better glues than can
be used “wet” for this type of application? /
/Thanks in advance for your insights and suggestions! I will of course
share them with the list so that all may benefit./
/ Bill Lifford, CP/
_*THE RESPONSES:*_
I’d try to find a new technician/<----(this one was sent by my boss!:-) ) /------------------------------------------ The problem with "wet" glue is that you would need to perferate the foam to allow the solvents in the glue to evaporate--thus turning the 'liquid' into 'glue'. There are vinyl and plastic adhesives available, (more clear and less yellow than contact cement) but all rely on solvent evaporation to 'make things stick'. Hopefully the ventilation will work ------------------------------------------ We will put contact cement on both surfaces really quick with two persons, then put it together while wet so they slide into place nicely, then put back on the cast and put a bag over it and apply vaccum for 30 minutes or so...works well. ------------------------------------------ How about Poly Adhesive or spray glue? ------------------------------------------ A lot of work duplicating the model. One thing to watch out for is when you heat the foam and pull it, you want to be careful that you don't stretch it too thin getting the wrinkles out of the instep area. I sometimes will do foam from the ankles and up (if I can) to help the brace fit into shoes, and then there is no stretching needed and your foam will be full thickness. Also, when you pull over foam, as soon as you get full suction, bleed the vacuum down to 8 to 10 and set up a box on a stand and cover the AFO as soon as you pull it to help hold the heat in the plastic so it does not cool too fast on the outside because the foam will hold some heat on the inside. This will keep the brace from changing shape after you cut it off which sometimes happens with lower vacuum. You can also pull the plastic at its lowest working temperature and pull it as soon as it turns clear to help keep from overheating the foam and crushing it under too high vacuum. ------------------------------------------- What I do in this situation is to use a material that is the same thickness as the foam but firm. Pull the polypro over this but using nylon stockinet to separate it. When the afo is trimmed, pull away the firm material and add the foam to the mold. Add glue to both sides and apply the afo to the foam while on the mold. This works well for me. Good luck! Hope this answered your glue question. ------------------------------------------- Wow! That's a lot of work! Try this, pull a layer of 3/16 poly pro over your original mold, cut the seams down wile it's still soft. Once it cools, apply one panty hose, and pull a second layer of poly pro. Cut off to your trim lines and remove both sections, discard inner layer. Now you have room for your liner. Put the liner on the mold, paint the outside of the liner, and inside of the AFO with poly adhesive, and let dry. Once they dry, pull a blue leg bag over the calf, and another small piece over the foot leaving the heel exposed. Pop the AFO onto this, adhering the heel, then slide the blue bags out. If the glue is dry enough they should come out easily. Or, you could just add small extra pads over the bony prominences of your liner, and just pull directly over that. Hope this makes sense! ------------------------------------------- Hi I don't know about glue in particular but as far as not crushing we've had good luck with aliplast 3/16 foam. My problems with glue are that even if you use clear you can still see the brush strokes through the AFO and it looks terrible. I have used 3M Super 77 spray adhesive before but not over an entire AFO. I've used it in certain sections like the foot plate and the calf area. It appears to adhere well and the results look good. It's best if you spray both sides-that is AFO and the foam- and let it dry for a minute or two before applying. But again I don't know how well it would work over an entire AFO. Hope this helps. ------------------------------------------- I would suggest 2 coats of glue - let one dry and the second one add thinner to make it runny and extra "wet" to glue together. I just use renia glue for this. You can bag it and vacuum it quickly to help the glue adhere. Another suggestion might be to lower the vacuum pressure to about 12-15 mmhg once you have acheived the initial vacuum. I usually mold at abou 22-25 mmhg and once the seal is acheived I lower the pressure if there are any pads in the mold. If there are no pads I leave it on full. Good Luck! ------------------------------------------ The biggest reason for this is your vacuum is too high. Turn it to 6 to 8 in-lbs. That is all you need to form plastic. Poke holes in the foam using a spike roller or pins. ------------------------------------------ The type of glue that I like is called Ortec, it is clear and dries clear so it will not yellow on the polypro like poly adhesive. And it is a wet glue. But the easiest way to get it done is to find a box and send it to Puget Sound Innovations. If you have any other questions don't hesitate to call. ----------------------------------------- Hi William, good idea, but it sounds like a lot of work...we usually mold in a dense foam like nickleplast as a spacer, and then we replace it with the more compressable foam we'd like to use as the liner, it usually works quite well.As for glue, spray glue works well... ----------------------------------------------- your method sounds good i would ues poly adheisive and only glue the bottom of the foot and the sides of the foot put them together wet and once dry then fold down the calf section and repeat the gluing process. hope this helps ----------------------------------------------- the problem is the amount of vaccum , Hot plastic will mold at 1 inch of Hg You realy don't need to have full vaccum. the other issue is do you really need a full liner ? Why not just pad the boney prominences? In the attached pictures you can see AN smo with pads but note the entire thing is not padded. padding in the picture is pelite. Most of our afos are padded similarly but we use 3/16 padding when we pull the plaltic and then remove the dummy pad and add a 1/8 aliplast pad exactly the same size after cut off. good luck ----------------------------------------------- Poly adhesive Fillauer! -----------------------------------------------
