“We currently employ a solvent process using Cyclohexanone to bond a PVC tubing with an ABS molded hub. We are going to be switching from ABS to a Pebax (thermoplastic elastomer). We believe there are issues with the Cyclohexanone creating the bond with the Pebax that we desire, and I’m looking for some info regarding our process - is it appropriate to continue to solvent bond (maybe with a different solvent) or to switch to a new process (UV adhesive for example)?”

Solvent bonding typically works with amorphous thermoplastics such as PVC, ABS, PC, PMMA, and PS. Pebax belongs to the family of thermoplastic elastomers and has a good resistance to solvents in general. Depending on the grade and softness, it may swell in certain solvents but will not behave like amorphous thermoplastics do. If you replace the ABS with Pebax, you need to switch to a new bonding process. UV light-curable adhesives are a good option. I would recommend trying Dymax medical grade adhesives 204-CTH-F and 209-CTH. They both adhere well to PVC and Pebax and several other commonly used plastics.

Adhesives 204-CTH-F, 209-CTH, Adhesives, bond Pebax, Cyclohexanone, light-curable adhesives, Pebax, Pebax to PVC, Plastic Bonding, solvent bonding

“What is the difference between newtonian viscosities and thixotropic viscosities? How would that impact my application?”

Newtonian products are materials which have the same viscosity even under different shear rates. Water, milk, and mineral oil are examples of common newtonian materials. Thixotropic materials on the other hand will flow when a shear force is put onto the material (like squeezing a tube of toothpaste), but when the force is removed, the material will not flow. A newtonian material might be used to pot an application or fill a cavity, while a thixotropic adhesive might be used to dispense a bead along a molded ridge.

Adhesives adhesive viscosity, newtonian, thixotropic, Viscosity