Creating a Biopolymer Compound
With new materials and innovation methods for compounding, sometimes the compounder has a rather wide range of possibilities on what kinds of materials could be created. So how much biopolymer in a compound is enough? This interesting challenge was addressed by Roger Avakian, Vice President for Scientific Development, PolyOne™ Corporation, at an Emerging Technology Forum (ETF), sponsored by PolymerOhio and held in Columbus.
PolyOne in Avon Lake, OH, is the world’s largest independent compounder. One of their products, reSound™ is a biopolymer compound that can be used in combination with thermoplastic resins to produce numerous desirable strength and resilience properties well-suited for building and construction applications.
PolyOne is well positioned today in disposable goods and for future opportunities with the emerging durables sector, said Avakian. “Disposable goods have a much shorter expected life than durable products, which are designed to live 10 to 30 years.” Disposable goods have much lower technical requirements than products from engineering polymers, vinyl, products, and other longer lasting goods.
A key product of PolyOne is reSound™, a biopolymer compound (as are polylactic acid [PLA], polyhydroxybutyrate [PHB], poly-3-hydroxy butyrate-co-valerate [PHBV], others). Biopolymers are made via a biological fermentation process from renewable raw materials. But, as Avakian pointed out, combining engineering thermoplastic resins with bio-derived polymers is a balancing process of creating a compound that meets performance requirements and using enough bio-derived content to substantially reduce the products’ carbon footprint. How much biopolymer can be in a compound and be enough? Avakian answered, “From sustainable resources that can be renewed, such as in 10 years, we decided that 30 percent would be necessary (the minimum) to really make an impact.”
“But we also had to look at our customers and find out what properties they needed, or, in the case of packaging, find out what materials are needed, especially for contact with food.” “We determine what temperature would work, what amount of impact the material would have to be able to withstand, what engineering properties were needed, how feasible the use of such a material would be in today’s injection molding equipment, whether the material would need the same cycle times, how the biopolymer compound would function with other materials that are available today, and, additionally, whether the materials could be used for food packaging.”
The heat distortion temperature (HDT) of biopolymers presented a big challenge. PLA is made from corn. PolyOne was getting PLA from a supplier in Nebraska, and the material did not have good heat and impact strength. “Our challenge was to move PLA to higher performance properties,” Avakian said. His team began by looking at prior art. To customize the materials, they got inputs from customers, and focused their efforts on materials that needed to be developed to meet market demands.
Actually adjusting the engineering qualities of the PLA polymer meant working with various percentages of PLA across a range of HDT vs. room temperature (RT) notched izod impact testing – this comprised their design space used to modify and maximize the PLA content of reSound compounds and test for sufficient durability before using the biopolymer compound for enhanced applications, Avakian said. For example, PLA/reSound materials showed dramatically less fungal growth at 16 weeks’ exposure testing than both starch compounds or starch/petro-based polymer compounds at 2 weeks’ testing.
PolyOne is continuing to explore processes that are well-suited for such materials as reSound. “We are exploring a breadth of processes, including injection molding, profile extrusion, sheet calendering, and thermoforming,” Avakian said. Plasticized PLA is also being explored for its applicability to end uses requiring flexibility and resilience. Plasticized formulations are being explored to make materials “softer,” such as for a shower curtain.
For now, the PolyOne biopolymers “are in C stage of stage gate for introduction,” said Avakian. “We are now looking at markets, price and value, and customizing formulations for specific markets, including electronics enclosures, communications, transportation, food handling, and others.”
“PolyOne has identified a viable approach to improved heat distortion of PLA under normal injection molding conditions with compositions that include approximately 50 percent PLA. Our reSound™RS1100 has food approval grade; RS1200 can be formulated for food approval,” said Avakian. “We have demonstrated robust processability/performance and composition in reSound compounds with regard to grade of PLA utilized, and our approach does not require high purity PLA.” Avakian concluded by saying that as PolyOne moves forward with biopolymer compounds, various grades of PLA are being applied to give the properties required. One goal is that the compounds must be reusable for molders, which have typically 40 percent of materials that need to be recycled internally to the process. There are plenty of challenges and plenty of progress to report.
PolyOne Corporation is the world’s premier provider of specialized polymer materials, services, and solutions. In 2010, its annual revenues totaled $2.6 billion. PolyOne has corporate headquarters in Avon Lake Ohio, U.S.A., and operations in North America, South America, Europe, and Asia. The operations include 51 manufacturing facilities and 13 warehouses in 20 countries, serving more than 10,000 customers in 35 countries with more than 35,000 products.
PolymerOhio, Inc. is a polymer industry-specific Ohio Edison Technology Center, which is funded by the Ohio Department of Development. PolymerOhio focuses on enhancing the global competitiveness of the polymer industry, including companies from the plastics, rubber, bioproducts, and advanced materials segments.