Enhanced Resins & Additives At Biopolymers Conference
Close Up: Biopolymers
An industry gathering sponsored by NatureWorks is a forum for materials, additives, and processing advances.
Innovation Takes Root 2014, the fourth biennial international biopolymers conference and exhibit, took place in Orlando, Fla., in February. It was hosted by NatureWorks LLC, Minnetonka, Minn., the maker of Ingeo polylactic acid (PLA) and the world’s largest producer of bioplastics. Participating in this year’s two-day event were 41 speakers and around 370 attendees—a record—from 27 countries and 209 companies. There was ample news in upgrading the properties and processability of biopolymers through additives, reactive processing, and tailored isomer composition. Other developments included non-halogen flame-retardant engineering bio-blends and novel applications like PLA expandable bead foams.
A new entrant in this growing field is Floreon-Transforming Packaging Ltd. of Hull, U.K. The company has offered products for sale only in the last few months. As explained by technical director Andrew Gill, Floreon offers fully formulated compounds of Ingeo PLA and additives, including combinations of two other biodegradable polyesters. It can also provide masterbatches of PLA with additives. These additives are said to make PLA up to four times tougher than the neat polymer and to enhance processability while retaining high stiffness, transparency, gloss, and over 90% biobased content. Films gain a softer feel and make less noise when crinkled. Process temperatures can be lowered with some formulations. The compounds are biodegradable and can be converted back to lactic acid feedstock and repolymerized into virgin PLA.
Current Floreon compounds include general-purpose Floreon 100 injection grade, Floreon 200 opaque white-pigmented grade for sheet extrusion, Floreon 300 for extrusion blow molding, Floreon 400 for films, Floreon 500 for injection stretch-blow molded bottles, and Floreon 600 for thermoforming. Trials comparing Floreon 100 with neat PLA reportedly showed more than 50% reduction in extruder amps to produce sheet and 20% lower injection pressure to mold bottle preforms.
Also announced at ITR 2014, Metabolix Inc., Cambridge, Mass., has just begun to commercialize new grades of its Mirel PHA (polyhydroxyalkanoate) biopolymer designed specifically to modify PLA. This is an extension of its recent introduction of PHA grades for modifying flexible and semi-rigid PVC (see July ’13 feature article). In both cases, Metabolix has come up with new amorphous, rubbery grades of its normally rigid and semicrystalline Mirel PHA. According to Bob Engle, v.p. of biopolymers, PHA acts as a flexibilizer and impact modifier for PLA, much as it does for PVC. It adds ductility and toughness without lowering the Tg or HDT of PLA. Mirel is inherently compatible with PLA and forms two-phase blends that remain clear at up to 20-25% PHA. The rubbery additive has a Tg of -30 to -50 C, and Engle says it is similar in efficiency and cost-effectiveness to standard impact modifiers of ABS, MBS, or acrylic in the same Tg range. A key difference is that PHA retains full compostability of the compound.
Metabolix is starting with a ready-to-use PLA compound (designated P4004) containing its PHA modifier. The compound is designed for rigid sheet extrusion and thermoforming. The modifier reportedly makes the formed sheet cut cleanly and prevents deformation of the package during heat-sealing. Later this year, Metabolix aims to offer the modifier separately as a masterbatch in a PLA carrier. Metabolix will also expand capacity for modifier grades of PHA by 4-10 million lb in the near future.
Another firm offering both enhanced PLA compounds and property-boosting masterbatches is Hangzhou Seemore New Material Tech Co., Ltd. in Hanzhou, China. Its Biopolysun modified PLA compounds include grades for transparent film, high-tensile-strength film, heat-resistant tableware, foam sheet extrusion, and clear, heat-resistant baby bottles. Its Bioseemore line of PLA additives includes compatibilizers for fillers and bio-alloys, hydrolytic stabilizers, nucleants, chain extenders, melt-strength enhancers, and plasticizers.
‘HIGH-PRODUCTIVITY’ PLA & NOVEL BEAD FOAMS
NatureWorks presented brand-new “high-productivity” Ingeo HP grades for injection molded and thermoformed food-serviceware. Polymerized from lactides with very low D-isomer content, they go beyond the capabilities of high-heat grades such as Ingeo 4032D and 3001D, which were introduced for these applications only a year ago. Three new Ingeo HP grades reportedly offer 15° C higher HDT at 66 psi, plus three times faster crystallization for shorter cycles. With addition of nucleation additives, Ingeo 3100HP can achieve around 40% higher stiffness than nucleated Ingeo 3001D at 100 C.
Takemoto Oil & Fat Co. of Japan, represented here by Goulston Technologies, Inc., Monroe, N.C., says it can improve performance of Ingeo HP with its LAK-301 PLA nucleant. Takemoto announced its new LAK-900 ready-to-use compound, described as an optimized dispersion of 1% LAK-301 in Ingeo HP2500 or 3100.
Technology development firm Interfacial Solutions, River Falls, Wis., showed how its reactive twin-screw extrusion process for “hyperbranching” PLA can dramatically improve properties and processability while reducing costs through use of recycled material. Hyperbranched PLA boosts impact strength while increasing flowability. The company is offering new deTerra grades of hyperbranched PLA based on recycled resin.
Ongoing development of PLA expandable bead foams was presented by Biopolymer Network Ltd. of New Zealand, a collaboration of three NZ research organizations. Its Zealafoam process is designed to produce a “drop-in” substitute for EPS bead foam that can be processed on the same equipment, though under different conditions. It uses commercial PLA pellets, which are first impregnated with CO2 blowing agent under low pressure at ambient temperature. Impregnation time is said to be short, after which the beads can be molded in rapid cycles. Current Zealafoam densities are greater than 24 g/L (1.5 lb/ft3). The company molded 43L fish boxes of Zealafoam in place of EPS and obtained good results in mechanical and thermal insulation tests.
FR ENGINEERING BIO-BLENDS
Progress in “greening” engineering bio-blends was reported by Dr. Joe Kuczynski of IBM’s senior technical staff at its Materials and Processes Engineering Laboratory in Rochester, Minn. He presented an update on a multi-year project to replace PC/ABS with a partially biobased blend for covers of computer servers. The greatest technical challenge was achieving UL 94V-0 flame resistance—non-halogenated—at 1.6 mm. While this essentially decorative application does not require all the impact strength of PC/ABS, it must be cost-neutral for IBM.
Kuczynski reported that IBM has approved a custom blend of 30% PLA in PC from PolyOne Corp., Avon Lake, Ohio, which achieves 94V-0 at 1.58 mm and meets all other IBM requirements. IBM has also qualified a grade of this reSound bio-alloy with 40% PLA, but it costs more. Kuczynski also reported that a blend of 20% PLA in PC in the Eco Solutions line from RTP Co., Winona, Minn., achieved 94V-0 but had not yet received the UL yellow card required by IBM. And IBM is testing a PC/PLA blend from Bayer MaterialScience, Pittsburgh
IBM is also testing a proprietary Terraloy engineering blend with 40% PLA from Teknor Apex Co., Pawtucket, R.I. Edwin Tam, Teknor manager of new strategic initiatives, reported that his firm can produce bioblends with 30-40% PLA that achieve 94V-0 at 1.5 mm and HDT up to 85 C, only 5° C less than standard FR-PC/ABS. He said impact strength of the blends remains a challenge—only 1.7 ft-lb/in. notched Izod vs. 6.0 for PC/ABS. However, cone calorimeter ignition tests showed lower smoke generation and lower peak heat-release rate for the PLA blend than for PC/ABS.
While IBM’s goal was to add some renewable content to its computer housings without sacrificing cost or properties, Arkema Inc., Bristol, Pa., achieved something quite different: It found that blending PLA with acrylic produces a beneficial synergistic effect. PLA increases the flow of acrylic so dramatically that a higher-molecular-weight acrylic resin can be used without the sacrifice in processability that normally would result. The upshot is superior properties for the blend compared with standard acrylic while retaining good moldability. Arkema’s Plexiglas Rnew blends, introduced in 2011, show improved flow, significant increase in chemical resistance, and a step change in impact strength, equaling that of PETG and close to that of PC.
Arkema currently has three grades of Plexiglas Rnew with 20% to 35% PLA. Recent improvements in clarity have yielded a general-purpose grade, C520, that boasts the same haze and light transmission as standard acrylic.
MORE ADDITIVES NEWS
Wacker Chemie of Germany (U.S. office in Adrian, Mich.) recently launched the Vinnex family of additives for PLA and other biopolymers, such as PHA/PHB and thermoplastic starch. Vinnex powders and resins are based on polyvinyl acetate (some are copolymers), which is itself biodegradable, thereby maintaining compostability of Vinnex/biopolymer blends. Vinnex is described as a “co-binder” that compatibilizes biopolymers with each other, with other resins like PBS (polybutylsuccinate) and cellulose acetate, and with polar fillers—thereby increasing flexibility to tailor bio-blends with specific properties. Vinnex is miscible with both PLA and PHA/PHB. Most grades of Vinnex are approved for food contact.
Wacker also reports that blends of Vinnex alone with biopolymers yield improved flexibility, soft touch, toughness, and processability (melt strength). In PLA, Vinnex also is said to maintain transparency while improving self-sealability and paper adhesion and reducing film noise to a level comparable to PET. In PHA/PHB, Vinnex is said to increase melt strength for blown film extrusion and to optimize crystallinity for faster molding cycles. PLA/PBS blends with Vinnex compatibilizer are said to thermoform easily.
Nucleating agents are recognized as essential additives for PLA, enhancing crystallinity to speed cycles and improve HDT. Among the latest developments are Ecopromote-UP from Nissan Chemical Industries of Japan. It’s designed for high-speed injection molding with cycle times as short as 10 sec. Ecopromote-TF is for PLA crystallized sheet, improving transparency and HDT. Also new from Nissan Chemical are Ecopromote-C nucliant to speed crystallization of PHA, Ecopromote-GA nucleant for PGA (polyglycolic acid), and Ecopromote-TW nucleant for nylon 12.
Toyota Tsusho America, Inc., Southfield, Mich., is offering newly commercialized Tribio nucleant masterbatches for PLA from Dai-Ichi Kogyo Seiyaku Co., Ltd. in Japan. Containing 10% active ingredient, two grades are offered for PLA sheet and thermoforming. Both grades increase heat resistance and impact strength, but Tribio X-003 is tailored for highest impact, while Tribio T-310 delivers maximum transparency enhancement.
New plasticizers for PLA were presented by Proviron of Belgium (U.S. plant in Friendly, W.Va.). The company is in the prelaunch or developmental phase for six non-phthalate plasticizer families in the Proviplast C series. Two are partially biobased and foodapproved grades and two are 100%-biobased grades for which food approval is pending. (Two more are non-biobased.) All of these are available as easy-dosing dry pellets suitable for injection molding or extrusion. Proviplast C plasticizers are said to be very efficient and compatible with PLA, with low exudation or migration. They provide soft and tough elastomeric or polyolefin-like behavior to PLA.
Polyvel, Hammonton, N.J., plans to commercialize by July an improved PLA nucleator masterbatch that can be used to reduce cycle time and improve trimming/cutting of thermoformed sheet. Still in development is a PLA blowing-agent masterbatch for foam sheet.
The rate of loading for a plastic material is a key component of how we perceive its performance.
The polymers we work with follow the same principles as the body: the hotter the environment becomes, the less performance we can expect.
Molders should realize how significantly process conditions can influence the final properties of the part.