Light-Curable Adhesives and Recycling PET
“I am looking for an adhesive that can be used to bond an injection-molded PET part to a stretch blow-molded PET container. Ideally, this adhesive should be compatible with the PET recycling stream. Any recommendations?”
There are a few options available to bond PET to PET, whether injection molded or stretch-blow molded. One available option is light-curable adhesives. These adhesives are available from Partner Pak, and a few other players in the market that work closely with the container/packaging industry. While DYMAX has not tested each material for the recycle-ability of our adhesives, David Cornell, the Technical Director from APR (Association of Postconsumer Plastic Recyclers, www.plasticsrecycling.org) offered these comments regarding PET clamshells
Does the presence of the adhesive:
- Cause the PET to yellow when re-melted?
- Cause the IV of the PET to fall excessively when melted?
- Cause haze in melted PET?
- Cause films to crystallize too quickly?
- Cause black specks in melted PET?
Generally, one should find out by testing a control of un-bonded components and a test sample of bonded components. Make new components by grinding up bonded and un-bonded structures separately and processing as regrind after the hot water wash. If you find no difference in appearance and performance at 25% and 50% regrind levels, the adhesive is probably not going to be an issue if the clamshells are recycled.
Clamshells generally are not pursued as sources of recycled PET, but PET clamshells do occasionally end up in bales, asked for or not. As such, the real world experience would have the adhesive present at much less than 25% of the recyclate. But if you can show no problems at 25%, concerns will be allayed. The cured adhesive should not affect solid stating performance, but should be tested fully.
My thought is that there is no problem with recycling PET sealed with a DYMAX light-curable adhesive since our adhesive is a clear thermoset (when cured) that constitutes a small % of the total assembled package.