Micro-Chemical Analysis / adhesives and polycarbonate / FTIR Microscopy and Expert Analysis / Medical Device Problem-Solving, Failure Analysis, and Reverse Engineering

1. Chemical Degradation of Polycarbonate
by Dymax Adhesive
Analysis of White Stain inside Cured Part
Part 9: UV Adhesives and the Chemical Fragility of Polycarbonate

2. ABSTRACT
>Polycarbonate (PC) has poor resistance to attack by a large number of chemicals.
>Chemicals that “plasticize” PC cause problems that include clouding, warping,
crazing, cracking, breaking, falling apart, etc. For example, Formula 409 contains
about 10% “grease cutter” and will quickly destroy PC; especially when the PC has
a relatively low Molecular Weight and/or lots of molded-in-stress pulling it apart.
>Chemicals that are “Bases” (electron donators) catalyze the polymerization of PC
and therefore can also catalyze the reverse reaction, depolymerizing PC into
oligomers of Bisphenol A (BPA) monomer or the BPA monomer itself. For
example, Amines famously do this to PC.
>A major ingredient of the Dymax adhesive is N,N-Dimethylacrylamide (a base). It
is well-known that many adhesives will attack PC if they are in contact with it too
long prior to being cured. This chemical is one of the reasons for this. When the
adhesive is completely cured, this chemical is completely consumed (this fact is
demonstrated using the spectra herein).
>The white stain on the PC in contact with the “cone” of adhesive is partially
depolymerized PC. Its FTIR spectra show the presence of both PC and the
endgroups (that appear as BPA and its oligomers) are formed from the scissioning
of PC. The adhesive must be quickly and fully cured to prevent this.
>The side of the adhesive cone that was peeled free from the PC is coated with
a thin shattered film of PC. The side that was in contact with the Polyurethane
(PUR) is coated with the PUR. Thus, the adhesive is tougher and more tenacious
than either polymer.

3. What Happened to the Polycarbonate?

4. White Stain Seen Through the PC Wall Prior to Dissection
White Stain is Connected to the PC

5. White Stain Remains on PC After Adhesive is Peeled Back
Polycarbonate
Peeled-back
Dymax Adhesive
Polycarbonate

6. White Stain Remains on PC Higher Magnification
Polycarbonate Polycarbonate

7. White Stain Remains on PC

8. The White Stain is Partially Depolymerized Polycarbonate so FTIR shows that
it contains Absorptions for PC, Oligomers, and BPA Monomer
Polycarbonate
White Stain
Bisphenol A

9. The Surface of the Adhesive that was against the PC is encased
in a thin shattered PC Film that again contains Oligomers and BPA

10. Thin Shattered Film on Adhesive that was against the
PC contains Polycarbonate, BPA, and Oligomers
Polycarbonate
BPA

11. The other side of the adhesive was against the
Polyurethane and it is encased in that Polyurethane
Polyurethane Tube

12. What Chemical(s) Attacked
the Polycarbonate?

13. O
O
N
O
OH
O
OH
O
DYMAX Disclosed 5 Components of this Adhesive
N,N-DimethylacrylamideIsobornyl Acrylate
Irgacure 184 Darocur 1173
Reactive Diluents
Photoinitiators
Ketone
Amide
These 4 are All Ketones and one is also an Amide. Ketones can Craze and Crack
Polycarbonate and Amides can Depolymerize it to Bisphenol A.

14. Pre-UV Adhesive
Post-UV Adhesive
Adhesive Taken Off Device
Adhesive’s Spectrum Pre and Post Polymerization by UV
Double Bond at 1612 cm-1 Completely Consumed by Polymerization
Double Bond

15. Double Bond @ 1614 cm-1
N, N, Dimethylacrylamide’s Double Bond is Consumed during the Polymerization
The Two Carbons Become Part of the Cured Adhesive’s “Backbone”
The Absorption Disappears as the Adhesive Cures
This Chemical Attacks the Polycarbonate

16. The Isobornyl Acrylate’s Double Bond is also Consumed by the Polymerization
Double Bond