Cured plastisol not bonding with fresh hot plastisol layer

[Marc Arena]

Hi,

I'm looking for an effective way to get a strong bond between a cured layer of plastisol and freshly heated plastisol.

Any thoughts on priming or degrading the cured plastisol so the fresh bonds to it?  Is there an adhesive that can be sprayed onto the cured plastisol prior to layering with fresh plastisol?

Thanks
Marc

[toadfrogbaits]

I just wipe it down the bond area with acetone and shoot as hot as I can . Some times additives rise to the surface causing problems .

[mrex]

What are you trying to do? Sounds to me like your second color is not hot enough.

[ghostbaits]

This is an issue if you shoot plenty of half of a bait. If you don't dip over, you may have an issue with the bait staying together or de-laminating.

I have seen plenty that have been sold or sent out that just peel apart with a simple pull. Not sure guys know that the halves are not sticking together...

Personally, I don't think that there is any way you can make them all stick 100% of the time if they aren't shot within 24 hours or less. Nothing scientific there but seems that after 24 hours, the bait "cures".

Now that is why I have such great affinity to the twinjector. Never an issue of the sides sticking together.

Just my take on it though and my experiences. Others that shoot this way may have a different take or something they do to guarantee this sides are sticking.

Jim

 

[Marc Arena]

Thanks fellas.

I'd agree with the quicker turnaround time for getting a nice bond.  I did not have this problem when I'd make heads followed soon after by the final color coating.  Unfortunately, can't do this anymore.  Have a new production process in place and need to come up with a solution.

These are for very large tube jigs up to 14 inches long with a diameter of about 2 inches.  The cured plastisol parts (premade tube heads) are stored for days/weeks at a time before being put back on the mandrels.  The entire mandrel is then dipped to coat with color/flake.  After curing (doesn't make a difference if it is an hour or 24 hours) the heads and outer coating can be separated quite easily.

I have not tried wiping down with acetone, but the outer coating being applied is as hot as can be without scorching the material (stabilizer added to allow for extreme heating).

I'll try the acetone today.  Are there any other chemical agents, additives, adhesives.....other ideas?

Thanks
Marc

[ghostbaits]

I have also seen where some will use a mini torch and slightly heat the cured side. This takes some practice though. Or the heating element with a blade to fuse the sides.

Jim

[Marc Arena]

Did try the mini torch, definitely takes patience and delicacy to not scorch/burn the cured plastisol.  Unfortunately, not conducive to mass production.

Was thinking about bringing the temp up on the cured heads by microwaving for a short while or bathing in boiling water

[ghostbaits]

Never tried that but I doubt it will be effective. Temp not high enough.

What about touching to blade on soldering iron the way they put skirts on to grub bodies? Short of that, some soft plastics glue might be the only thing but not very attractive.

Jim

[ctom]

These are for very large tube jigs up to 14 inches long with a diameter of about 2 inches. 

This in and of itself may be the problem. Even hollow, the head's wall thickness where the two plastics make contact may be acting as a heat sink, sucking that all important heat away from the weld before it is made complete enough especially if a mandrel is used. That  mandrel would suck up the second plastic's heat too.

[ghostbaits]

http://www.youtube.com/watch?v=R_OHozRyI5w


http://www.caneycreekmolds.net/index.php?topic=660.msg3324#msg3324

Jim

[Jason]

Marc,

Are you making up a bunch of tubes with dipping rods and then coming back and dipping the heads based on orders, days / weeks later?

What brand of plastic are you using?

Jason

[Marc Arena]

Thanks for contributing everyone.

The heat sink analysis makes sense to me.  I do use thinner premade heads for certain color schemes (head and tails different colors, adding extra head coats at the end of the process) and I've noticed the inner thin premade head bonds better than the thick premade heads used for single color schemes.  Still not totally fused though.

Using a soldering iron would work, but the tube heads being as large as they are will be an issue.  Would only get a good bond on the area(s) I touch with the hot iron.  Would be tricky and time consuming to effectively get the majority of each head prepped for dipping in the fresh hot plastisol.  Spoke with several chemists today and they also thought the preheating of the premade heads prior to re-dipping would be the least likely solution.  I'm not sure why though...seems heat is the best solution.

The two other possibilities I brought to their attention were applying a cyanoacrylate glue (also known as CA or super glue) just prior to dipping, or using a chemical solvent to degrade the outer surface of the premade head making it soft and more apt to fuse with the fresh plastisol.  Both chemists thought the CA glue was the best option, but thought the solvent process also had potential.

I've tried the CA glue (prosoftbaitglue) and it works very well for what I'm trying to accomplish, problem being there is only a bond at the points where I apply the glue and finding an application method to get a very low viscosity glue to coat the the majority of the head is next to impossible.  The stuff is extremely runny and dries within seconds.  Today I ordered CA glues that have a higher viscosity (honey or syrup type consistency) and slower drying time (giving me 30-60 seconds prior to drying out).  Also, ordered specialty brushes for this type of glue.  Will play with that Thursday.

The chemists suggested MEK or Toluene as good options for using as a solvent dip prior to applying the fresh plastic.  Neither knew of anyone that has experience with this type of bonding process, but thought it was interesting and definitely worth trying.

After giving the heat sink more thought I think another option would be to scour/scuff the surface of the premade heads.  This might allow the heat from the fresh hot plastic to fuse into the miniscule tears and scratches.  I'd have to find the right wheel attachment for my angle grinder to quickly scuff up a bunch of heads while they are sitting on the mandrels.  I'm not real familiar with what is available that might do the job without tearing up the heads too badly....any thoughts??

Jason, yes I'm pre-making the heads and putting them back on the mandrels days/weeks later to coat the entire mandrel with final colors.  I've used plastisol from many different manufacturers and distributers.  Currently using Lurecraft.  Honestly, haven't tried Caney Creek but I'm always open any potential solution.  The problem of delamination has been consistent with three different kinds of plastisol since changing my production process to pre-making heads.

Marc