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Bioplastic Advances Closing the Performance Gap!

Donald Rosato – Jun 5, 2020

TAGS:  Biobased Solutions       

Bioplastics will only become a true alternative to traditional polymers made from non-renewable sources when their performance reaches the same level. Important progress is being made, not only with bioplastic polymers themselves but also in the additives and compounding technologies that help improve and expand their property profiles.

Bioplastics Performance Advances
Bioplastics Performance Advances
Source: Plastics Institute of America

Let's explore more about the various bioplastics, bio-based additives and compounding technologies in detail...

Achieving Sustainability with Bio-based Additives

Delving further, sustainability is advancing on the biopolymer additive front. Achieving 100% sustainability with fully renewable-sourced polymers like PolyLactic Acid (PLA) and PolyHydroxyButyrate (PHB) has been limited due to the availability of key, fully bio-based additives such as processing aids.

Clariant's Licocare® Rice Bran Ester Waxes

Major global specialty additive supplier Clariant has developed its Licocare® rice bran ester waxes to meet this challenge. These materials come from bran husk that is thrown out during rice processing. The bran husk provides the ingredients to make a sustainable wax with a chemical structure similar to traditional Clariant montan waxes.

Clariant developed a process to separate the underivatized bran wax into its aliphatic acids and polyols, and then to re-esterify these into high-temperature processing aids, mold releases and dispersion agents analogous to its existing montan ester waxes. These improved rice bran wax products exhibit:

  • Improved mold release capability
  • Color pigment dispersion
  • High heat stability in PLA as well as in traditional engineering plastics

The following bar chart defines the injection molding demolding force of NatureWorks’s Ingeo™ Biopolymer 3001D PLA resin containing 0.3% of various waxes, tested to Clariant’s internally developed cylinder pull test method. The minimized drag on a molded part with the Licocare® RBW 102 wax reduces scrap potential as a result of part surface blemishes or part deformation during ejection, potentially leading to an overall cycle time reduction.

Clariant Pull Test Method Measuring Demolding Force in Injection Molding
Clariant Pull Test Method Measuring Demolding Force in Injection Molding

UPM's Formi EcoAce Biocomposite Granulate

Finally, a fresh route to very high sustainability, near 100% renewably sourced, granulates has become market available. Finland’s UPM has developed a Formi EcoAce biocomposite granulate made from certified wood cellulose fibers together with a certified renewable TRUCIRCLE™ polypropylene resin by SABIC, that in turn originates from wood-based feedstock from UPM’s biofuel production.

Each ton of UPM’s naphtha saves three tons of greenhouse gas emissions compared to fossil fuel-based naphtha. Molded and extruded end-use applications include:

  • Food contact utensils
  • Personal care products, and
  • Consumer goods

Formi EcoAce is touch wise warm and silky smooth, and available in multiple light and dark shaded colors.

Next in the UPM product pipeline is a Formi FibCo concentrate that will contain roughly 90% fiber content targeted at plastic compounders who want to develop their own natural fiber product lines, potentially extending into interior automotive applications. On the consumer goods front, single-use cutlery will soon to be banned in Europe, and UPM’s Formi EcoAce biocomposites are primed to enter this market.

UPM’s Formi EcoAce Fork and Knife Cutlery
UPM’s Formi EcoAce Fork and Knife Cutlery

New Patented PLA/OLA Plasticizer Blends by Condensia Quimica

Condensia Quimica is working to develop solutions to overcome PolyLactic Acid (PLA) limitations, such as:

  • Poor heat resistance
  • Degradation sensitivity
  • Property loss during repeated processing

Bioplastics like PLA exhibit rigid and brittle behavior with low plastic deformation below their glass transition temperature of approximately 60°C. It is required to plasticize PLA in order to extrude flexible films.

Existing plastic resin plasticizers have limited PLA compatibility. Also, their non-degradability is a major disadvantage in biodegradable PLA applications. Thus, thin, flexible PLA films have not been commercialized in the food products industry.

Condensia Quimica has patented a new approach for plasticizing PLA using blends of Lactic Acid Oligomers referred to as OLAs.

  • The following torque curves reflect the plasticizing power for various PLAs plasticized with different commercial OLA types trade named Glyplast.
  • These OLA plasticizers exhibit similar extrusion processing profiles to those PLAs plasticized with a standard plastic resin polyadipate or diethylhexyl adipate.

Condensia Quimica’s PLA/OLA Plasticizer Blends Stress-Strain Curves/Mechanical Properties
Condensia Quimica’s PLA/OLA Plasticizer Blends Stress-Strain Curves/Mechanical Properties

Films containing 20% Glyplast OLA have a glass transition temperature (Tg) that is suitable for extrusion manufacturing use. These thin, flexible PLA films show mechanical characteristics similar to those of flexible thin films made of polyvinyl chloride or polyethylene while being easily degradable.

Currently, Condensia Quimica offers a series of additives obtained from bio-renewable raw materials.

  • These additives are fully biodegradable and compostable via ISO (International Standards Organization) test method 20200.
  • When used in mixtures with PLA, they make it possible to obtain stretch films with good mechanical properties as shown in the above figure without loss of transparency.

Next, let’s take a look at a new low shear compounding approach for mineral-filled, bio-based PolyLactic Acid (PLA) compounds.

Analyzing Talc-filled PLA by NatureWorks & Farrel Pomini

Many compostable bioplastics are polyesters. They are shear sensitive by nature, so low shear processing is required to help maintain polymer integrity and achieve increased physical properties.

PLA supplier NatureWorks is collaborating with compounding equipment company Farrel Pomini. In their processing study, molecular weight loss results in talc-filled PLA were compared using a Farrel Continuous Mixer (FCM) versus a traditional Twin-Screw Extruder (TSE).

Farrel Pomini Co-Rotating Intermeshing Twin Screw (L) Compact Processor CP Series II (R)
Farrel Pomini Co-Rotating Intermeshing Twin Screw (L) Compact Processor CP Series II (R)

The FCM uses a non-intermeshing, counter-rotating twin-rotor design which imparts controlled levels of shear on the polymer blend, making it a good technology for handing shear, and temperature-sensitive materials such as PLA. Variables studied include:

  • Molecular weight (Mw) retention
  • Melt temperature
  • Dispersion of the talc (measured by the Filter Pressure Value or FPV)
  • Specific energy (SE)
NatureWorks/Farrel Pomini’s Talc Filler Level vs Different Variables
NatureWorks/Farrel Pomini’s Talc Filler Level vs Mw Retention (Top), Talc Filler Level vs Melt Temperature (Middle), Specific Energy vs Talc Filler Level (Bottom)

The top figure shows molecular weight retention vs talc filler levels. This indicates that with the CP mixing technology, the Mw retention was at least 95% up to the 50% fill rate with a drop to 88% at 60% fill.

Comparing the data in the top and middle figures, there appears to be a correlation between lower processing temperatures and improved Mw retention in the CP. Similar results are anticipated as these studies are expanded to larger machines.

The bottom figure shows the specific energy (SEI) required per kilogram expressed in kW-h/kg (kiloWatt-hours per kilogram).

  • When evaluating the CP curve, a gradual increase in SEI is seen as filler level is increased.
  • In the TSE curve, a decrease in SEI is observed, which can be explained by noting the change in Mw in the TSE samples. This is attributed to the lower loss in Mw, reducing energy requirements when filler levels are increased.

PolyPropylene (PP)-based Biocomposites by Trifilon

Continuous work is advancing on plastic resin-based biocomposite development. Swedish biocomposite maker Trifilon is producing PolyPropylene (PP)-based compounds using natural fiber hemp sourced from European farms as a reinforcement. It describes the compounds as second-generation materials. This means that the plant ingredients are used to improve performance rather than simply to bulk out the plastic.

Trifilon’s Natural Fiber Reinforced BioLite® PPC (green) Compound Versus Traditional Plastics
Trifilon’s Natural Fiber Reinforced BioLite® PPC (green) Compound Versus Traditional Plastics

First-generation biocomposites were great for their era, considering cost, the upcycling of a waste stream, and the impact on CO2 footprint. Trifilon studied the interactions between hemp fibers and the polymer molecules and developed smart ways to optimize those bonds.

A recent application is an electric-powered cooler by end-user Dometic. It is made using Trifilon’s BioLite® PPC, where the biocomposite derived from hemp gives it an attractive flecked surface finish.

Trifilon’s BioLite® Electric-Powered Cooler
Trifilon’s BioLite® Electric-Powered Cooler

Bioplastics Professionals: Stay Alert!

Identify new opportunities with bioplastics to focus your R&D on right projects with a structured review of game-changing innovations (bio-based materials & future trends...). Join the course "Bioplastic Tour: Innovations & Trends by Donald Rosato" today.

Bioplastic Innovations & Trends

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