Chemical Degradation of Polycarbonateby Dymax Adhesive

Analysis of White Stain inside Cured Part

Part 9: UV Adhesives and the Chemical Fragility of Polycarbonate

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.

What Happened to the Polycarbonate?

White Stain Seen Through the PC Wall Prior to DissectionWhite Stain is Connected to the PC

White Stain Remains on PC After Adhesive is Peeled Back

PolycarbonatePeeled-backDymax Adhesive

Polycarbonate

White Stain Remains on PC Higher Magnification

Polycarbonate Polycarbonate

White Stain Remains on PC

The White Stain is Partially Depolymerized Polycarbonate so FTIR shows thatit contains Absorptions for PC, Oligomers, and BPA Monomer

Polycarbonate

White Stain

Bisphenol A

The Surface of the Adhesive that was against the PC is encasedin a thin shattered PC Film that again contains Oligomers and BPA

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

Polycarbonate

BPA

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

Polyurethane Tube

What Chemical(s) Attackedthe Polycarbonate?

O

O

NO

OHO

OHO

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 CrackPolycarbonate and Amides can Depolymerize it to Bisphenol A.

Pre-UV Adhesive

Post-UV Adhesive

Adhesive Taken Off Device

Adhesive’s Spectrum Pre and Post Polymerization by UVDouble Bond at 1612 cm-1 Completely Consumed by Polymerization

Double Bond

Double Bond @ 1614 cm-1

N, N, Dimethylacrylamide’s Double Bond is Consumed during the PolymerizationThe Two Carbons Become Part of the Cured Adhesive’s “Backbone”

The Absorption Disappears as the Adhesive CuresThis Chemical Attacks the Polycarbonate

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

Double Bond