Common additives can reduce fluorescence problems that recyclers have discovered with polyethylene naphthalate resins.
The ability to remove the fluorescence ``removes one more obstacle that new marketers may have using PEN resins,'' according to a Shell Chemical Co. official.
The Food and Drug Administration has been holding back U.S. commercialization of PEN resin because of concerns about its compatibility with the more-established PET recycling stream. Wellman Inc., a major PET recycler, had indicated that PEN's fluorescence adversely affects the ability to dye fibers used in carpet and textiles, a primary outlet for recycled PET.
Petitions before FDA seeking clearance for PET/PEN blends, and asking whether the blends can use the same resin identification code as PET, are still pending, according to industry lawyer Jerome Heckman.
According to Shell, additives that absorb ultraviolet light, including Cyasorb UV3638 and Tinuvin 234, do not add to the cost of the PEN raw material, and do not affect recyclers' automatic sortation equipment.
``While no marketers of products packaged in PEN have discovered any negatives due to the fluorescence of PEN, the ability to eliminate it removes one more obstacle that new marketers may have using PEN resins,'' Ed Sisson, commercial development manager for the Polyester Business at Shell Chemical Co., said in a news release.
``The additional benefit is that the additives provide a way to address the fluorescence question raised about PEN in the recycle stream. Since some of the additives and their analogues are already used in PET bottles in the United States today, there should be little reason to expect that their use will negatively affect recycling applications.''
Sisson added that the problem concerning fluorescence has not been clearly communicated.
``[PEN] may fluoresce,'' he said. ``If it's a concern, now there's a way to get around it.''
The additives can be added by the polymer manufacturer, bottle manufacturer or recycler.
Shell also announced that its Hipertuf line of polyester resins based on PEN received positive assessment certificates from the National Industrial Chemicals Notification Assessment Scheme, a division of Worksafe Australia. The firm has approval to import Hipertuf resins into Australia.
The certificates mark ``a major milestone in the commercial globalization of our naphthalate-based polymers,'' said Rod Boyd, Shell Australia technical manager for chemicals and solvents.