Metabolix strategy focuses on demonstrating the performance and value that Mirel™ PHA polymers can bring to target applications. This performance is often characterized by the physical properties of the polymer such as crystallinity and rheology, and by the property enhancements that the PHA can bring to other materials.
These recent PHA polymer innovations bring distinct performance advantages into the Metabolix product portfolio by including fully amorphous materials with the more widely known semi-crystalline grades and they open up interesting new growth opportunities for Metabolix in enhancing other bioplastic materials.
Metabolix has demonstrated significant value in using PHA polymers to enhance the performance of polylactic acid, commonly known as PLA, and the most widely used bioplastic in the world today. Projections suggest PLA demand growth as high as 20% per year into a broad range of applications from food to packaging, and more recently into 3D printing and automotive uses.
PLA is a brittle polymer and often modified to improve its ductility. Plasticizers are one mode of improving PLA ductility, but can have the drawbacks of reducing toughness, lowering the glass transition temperature (Tg) resulting in lower heat resistance and narrowing the processing window. Metabolix has demonstrated the effectiveness of using amorphous PHA copolymers to “rubber toughen” PLA bringing both ductility and toughness. Not being a miscible plasticizer, PHA modifiers will not significantly lower the Tg of the PLA nor compromise the processing window.
Used at normal usage levels like other effective rubber modifiers for PLA, Metabolix PHA modifiers are claimed to be distinct in that they will not compromise the high biocontent or compostability of PLA. Inherent compatibility with PLA also means blending is relatively straightforward and clarity can be maintained without the need to tune refractive indices.
In PLA fibers, PHA modifiers added at levels at or below 5% have demonstrated a remarkable ability to improve the “hand,” a complex measure of softness, pliability and feel, by as much as 60%. This effect is a combination of ductility enhancement and elongation leading to thinner filaments and reduced shrinkage. By dramatically improving the softness characteristics of PLA nonwovens, expanded potential is possible in personal hygiene, home care and medical applications where skin contact requires a gentle touch and feel. In these single use applications, the renewability of PLA measured in high biocontent (and potential for industrial compostability) is important and uncompromised by PHA modifiers.
In PLA sheet, PHA modifiers have demonstrated the ability to eliminate the brittle edge trimming issues improving safety and reducing scrap. The combination of ductility enhancement and elongation leads to the potential for a significant improvement in impact strength. Similar benefits are now realized in injection molded single-use items. In blown film, improved flexibility and toughness approaching HDPE has become a reality with PLA-based films.
By extending the range of its PHA technology to develop new differentiated products, and focusing on the natural advantages of these PHA materials — compatibility, renewability, and biodegradability — Metabolix claim they have built a foundation for new growth in PHA bioplastics and brought value to PLA through improved performance and expanded opportunities.