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Solvent bonding thermoplastics with cyclohexanone mixture

JRickert (Bioengineer) (OP)
10 Oct 11 17:25
We routinely bond PVC tubing to thermoplastic components using solvent.  We use primarily cyclohexanone and dichloromethane.  We have been experiencing some issues with cracking when bonding PVC tubing to polycarbonate components.  We have identified that the cyclohexanone is the chemical which is causing the issues as it relieves molded in stress from the plastic part.  Cyclohexanone is used in the mixture as a lubricant to allow the plastic tubing to be easily inserted into the plastic part.  This assembly is done manually.

I am wondering if anyone can provide some help identifying another solvent that could take the place of the cyclohexanone in our mixture.
btrueblood (Mechanical)
10 Oct 11 17:42
I don't think there is any such thing as a solvent that is "good" to use on polycarbonate.  The material is known for stress cracking (crazing) due to exposure to various chemicals.  The dicholoromethane is the likely one here.

patprimmer (Publican)
10 Oct 11 18:55
Sabic and Bayer will both publish Technical Data Sheets fe gluing PC.

From memory both recommend dichloromethane. I think acetone is also suitable.Acetone certainly works with PVC.

PC is exceptionally bad to aromatic hydrocarbons and most chlorinated hydrocarbons.

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Demon3 (Materials)
10 Oct 11 18:56
Pat's right that solvents and PC don't get along well.

If I read right, you add the cyclohexanone as a lubricant. Could you use a water-based lubricant? That would have the best chance to work and not ruin the PC. Try for example polyethyleneglycol in water or other water-based lubricant.

Chris DeArmitt PhD FRSC CChem

JorgeEspinosa (Materials)
17 Nov 11 22:27
Hello JRickert,
Could you please expand a bit? What grade of PC are you using? And are you flexible PVC tubing?  DEHP? DEHP-Free? if so which plasticizer does your tubing has?

JRickert (Bioengineer) (OP)
21 Nov 11 11:05

We are using Bayer's RX1805 Medical grade PC with flexible DEHP PVC tubing. I am checking on the plasticizer. It is a material sourced from Poly One and extruded at Colorite.
gao7857 (Mechanical)
22 Nov 11 12:19
This is an interesting topic. Will/could the bonding strength be equivalent to the two bonded materials? say, for PVC and PC
Demon3 (Materials)
22 Nov 11 15:17
When bonding a material to another piece of the same material you should be able to get very good strength because the polymer chains will mix and entangle. The strength of plastics come from entanglements.

When bonding two dissimilar materials you will probably get much poorer adhesion strength. The reason is that dissimilar polymers do not mix on a molecular level 99 times out of 100. So the chains will not mix and entangle with each other across the bond.

Chris DeArmitt
Plastic Training Webinars since 2003

dwightdixon (Materials)
7 Dec 11 20:41
The DOP in the flexible vinyl will eventually crack polycarbonate that has any molded stress in it. You need to use a barrier glue to bond the two together. Baxter does it with an glue they make internally, that I developed when I was there, 20 years ago.  I think they still use it.  

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