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Perished soles and heels


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Part 1 of the answer.

First of all you have to identify the product.

Is it 1. Thermoplastic Rubber

2. PolyUrethane

3. Thermoplastic PolyUrethane.

 

No1 melts when scoured and sticks to the band and Hands.

No2 scoures to a dust in the core area, but the edges which are more dense due to the moulding pressure, scour like plastic and have an almost shiny surface.

No3 has not hit the repair circuit in great volumes yet but when it does you may experience difficulty in attatching components to it.

 

Thermoplastic and Polyurethane deteriorate with age as soon as they leave the factory and have a given shelf life. More modern variations last much longer than the units produced in th 80s & 90s.

Just storing footwear in wardrobes can render the unit as perished without the footwear being worn.

 

Perished units can be detected by either bending the unit and noticing if there are any signs orf cracking over any part.

Or by scouring whereby the scoured area just crumbles away.

One the unit has perished in any area there is no way to stabilise the remaindind area enough to enable the adhesive to get a permanent grip.

Eventually the bond will fail.

 

The only sure fire remedy is to completely remove the old unit making sure that none remains in the lasting margin of the upper.

 

Then you can replace with a suitable material that should be more flexible than the original.

Now go to part 2.

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Part 2 of Perished units dealing with Adhesives.

(could be a long one this and I may need to split it as this information has never been printed before to my knowledge, so you have a first on the forum).

 

First of all identify the material as in part 1 (you can also do a test using a hot pice of metal touching the material, the ensuing flame colour denotes the material. this could also be published by request).

 

Ater identifying the material you need to choose the correct primer.

Primers are a wipe in the manufacturing trade not brushed on as too much soaks into the unit and may not dry. The primer is there to prime and this involves removing plasticizers that migrate to the surface when the unit is scoured (heat alters the molecular structure so no heat folks).

Primers should be wiped not brushed. A brush will contaminate the remaining primer. Primers must be kept in a closed container, do not leave it open, it should also be kept out of the light, that's why it's in a dark coloured glass.

 

Yellow label Rehagol for Thermoplastic only.

Green label PUR for Polyurethane only.

Part 3 is needed on the use of Adhesives and will have to follow.

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Perished units part 3 Adhesives.

It essential that there is a good keyway for the adhesive to get a grip onto before it dries, smooth shiny surfaces using a worn band are no use.

 

Each manufacturer of footwear will have a PU mix that will suit the particular style of shoe/boot and the method of manufacture.

it is therefore feasable to say there are many differing grades. No one adhesive will stick all varieties of PU, apart from the differing mixes there are different densities from soft spongy type to the rigid PU tops.

 

You will all have your own favoutite adhesives and I am not going to tell you that 1 works better than another, my choice at the mont are Bostic 50/50 just because I have been using it for years and got to know how to use adhesives properly, and KoroPlast, but I have only been using this for 2 years.

 

PU units are made in moulds and they have to be removed quickly from the mould when moulding is complete, ready for the next run. To get them out quick the mould is coated with a mould release agent, sort of a none stick coating. As the unit is formed under some considerable pressure this mould release agent is absorbed into the outer shell of the unit. The outer shell is much harder than the central core.

 

Now it goes without saying that if the unit wont stick to the mould you will not be able to stick a sole to the darn thing unless you remove the release agent first. OK, so you scour the sole area to put on a "Stick-on-Sole", nice clean new scoured area, or so you believe!.

 

What you have done is scour the release agent that was in the waist area over the centre of the sole, now nothing is going to permanently stick to the unit. It is important to scour toward the edges only, also the primer/wipe will remove some of the offending agent that you have spread accross the unit.

 

Right, so we have now got a clean surface onto which we can stick what the customer requests. Rule number 1, you must put on a material that will flex as much as if not more than the original unit otherwise springing of the waist will occur. Now got to go to part 4.

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Perished Units part 4.

You have primed/wiped using the correct primer and now are ready for the adhesive, use an adhesive with a viscosity that is very thin/runny, you want the adhesive to flow into the keyways formed by rough scouring. apply a thin coat, leave for 15 mins and give another coat.

You must now leave the adhesive to dry completely for a minimum of 2 hours and preferably overnight.(1st part of the curing process).

 

When you come to stick the two components together by means of a Press you must set the pressure to level whereby the press bed would not damage your hand if left underneath the bed!! I will eplain later.

 

The components need now to be re-activated as they are too dry for sticking by contact. It is imperitive that you do not allow the unit or the new component to warm through, you are only going to activate the adhesive, any heat to the unit or comonent and you will get a bond failure that will happen an hour or so later. Remember we use heat to remove soles!.

 

Now you are set to press the 2 together on a very low setting. The reason for this is two fold 1, too much pressure distorts the unit and will burst the bond. Second reason is in part 5 which you now need to go to.

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Perished Units part 5.

 

The second reason is more complex but I will try to explain.

Low density Polyurethane is Hygroscopic when the outer skin is worn away, in laymans terms it means that it will absorb water from the air.

It will also absorb moisture from the ground. you may not see of feel this moisture but it is there, the PU unit acting like a sponge.

 

NowWhen you empty your press reserviour at night you see the water in there that has been compressed out of the atmosphere around you, same happens when you compress the unit, the moisture gets forced to the surface and water under pressure will destroy the bond. (simple innit?).

 

Now once you have done everything to plan you must be aware of the next stage that most get wrong.

 

DO NOT SCOUR THE EDGES OF THE UNIT.

You must only scour the edges of the new material not the Unit as this wiollremove the dense moulded edge and allow water to penetrate during wear and as they are worn in the wet weather the compression of the wearer unto the unit will act like a press and the water will destroy the bond.

2nd part of the curing proccess is complete 24 hours after the 2 components are joined, this is when maximum bonding is effected.

 

Now this information is going to cause a few problems with the "While -U-Wait" brigade.

 

Tips. Sheets of absorbant material like blotting paper placed on top of the unit and placed under the press overnight (extreme low pressure) will remove most of the moisture.

Rigid PU units (Football boot soles) can be secured using the same technique, but use a new course band to scour the sole(or hand scour with a small piece of the new band)

 

END OF STORY.

 

Would not mind betting that this thread will get hijacked by some large organisation for distribution.

 

BY THE WAY,

The above information parts 1 to 5 Perished Units is not published anywhere and is copyright Hugh-Candoit 2006 this full post or part thereof must not be copied or published without the permission of the author.

 

What the trade now needs is Low Density Polyurethane in sheet form 8mm thick but who will manufacture it? pester your reps and suppliers for I can do no more!!

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Many thanks for the comments folks.

 

In reference to Mr J.Rowley hibs, John is a very good salesman and would share his thoughts with you. I remember him when he started with Frank Ball then got shifted to Caswell. I helped him with several projects including Adhesives both Solvent and Water Based. (now there's a thought!! an article on Water Based adhesives is needed, must remember later). Problem with John was that he was a product of 1 company and good as the company was, it did not solve the problems of repairers. The company he worked for was more into the Building Industry and we were small fry. (brings back memories of when I used to visit the factory in Leek.)

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  • 13 years later...
On 4/8/2006 at 1:13 AM, hibsjo(SCO) said:

So how do you repair this stuff?

We get a lot of stuff in that has perished (dry,brittle,crumbly,flakey) have tried to lower beyond perish mark and prime and build back.

Never had any success with this as it always seems to carry on perishing.

Thoughts.....?

 

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Wondering where there is a repairer that utilises this informative  series of posts in Sydney Australia ? The soles perishing seems to be 'product built-in obsolescence' and a pair of Camper shoes were not cheap... the top leather is in excellent condition - one sole perished ,the other is fine.

Best regards Anne

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