Advanced Polymer Modifier Could Help Adoption of PLA for Packaging Applications

An advanced polymer modifier that could speed the growth of polylactic acid (PLA) polymers in packaging forms the basis of a presentation at the Sustainability in Packaging Conference in Orlando, Fla., Feb. 24 by Carol Casarino, global technology manager for Packaging and Consumer - DuPont Packaging & Industrial Polymers. Her presentation is entitled, "New Materials and Opportunities in Sustainable Packaging."

"Our latest trials show that DuPont Biomax Strong 120 overcomes limitations that have held back widespread use of bio-based PLA," said Casarino. "Not only does it deliver remarkable toughening effects in brittle PLA materials, it also reduces crinkly film noise and cuts power consumption while increasing thermal stability during extrusion."

Dr. Carol Casarino, global technology manager for Packaging and Consumer – DuPont Packaging & Industrial Polymers.

Until now, the crinkly sound of PLA-based films has limited their acceptance in flexible packaging applications such as snack bags. Preliminary testing of monolayer films shows that Biomax Strong 120 reduces such noise even at just a few percent loading. Furthermore, by combining PLA containing Biomax Strong 120 with layers of flexible materials, it's feasible to design PLA-based packaging structures that produce no more noise than conventional packages, according to Casarino.
"During extrusion, Biomax Strong 120 melts quickly and acts as a lubricant in the solids conveying sections of the extruder," Casarino reports. "That can result in an increase of up to 21 percent in extruder energy efficiency with just 2 weight percent of Biomax Strong 120."

Major improvements in thermal stability during processing are seen with the addition just 2 to 5 percent of Biomax Strong 120 to PLA, according to Casarino. That can pay off with greater use of regrind during extrusion. It also could help expand the use of PLA in extrusion coating, which uses relatively high processing temperatures.

Biomax Strong 120 was originally developed as a toughening modifier, and it is remarkably effective as such. It sharply reduces brittleness, as indicated by flexural fatigue tests showing a nine-fold improvement with just 1 percent of the modifier in amorphous sheet. In crystallized sheet, dramatic reductions in brittle behavior also are seen. In addition, the modifier produces major improvements in elongation with loading levels of just a few percent, according to Casarino.

DuPont Packaging & Industrial Polymers is a world-class manufacturer of high-performance resins and films for a variety of packaging and industrial applications. Its best known ethylene copolymer products include DuPont Surlyn resins for packaging and industrial applications, Appeel lidding sealant resins, Bynel coextrudable adhesives, Selar PA amorphous polyamide barrier resins, Nucrel acid copolymers, Elvax EVA copolymers, Elvaloy, Elvaloy AC, Entira and Fusabond modifiers, and Vamac ethylene acrylic elastomers.

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