Bio-Degradable (Compostable)

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BIO-DEGRADABLE (COMPOSTABLE)

Biodegradable Twin screw extruder line

Many new players have emerged in the Biopolymer space with new materials and many new formulations. Co-Rotating Twin Screw Extruders provide excellent material mixing capabilities for all Polymers, including Biopolymers. You should consider your machinery supplier as a development partner to achieve your goals in the areas of melt and mix quality, production rates, and other parameters, regardless of formulation. Make sure your machinery supplier has the facilities and the know how to help you test material formulations and improve your processes.

As with any compounding project, a certain amount of trial and error is inevitable in process development for new Biopolymer formulations. Some are successful from the start; others needs more work to become commercially viable.

Biopolymer compounds characterize into three categories:

  • Starch-based Polymer compounds;
  • Bio resin compounds containing Bio Resins such as PHA, PLA or PHB;
  • Biopolymer compounded blends, defined as a compound containing two or more bio resins, starch-based Polymers and / or petroleum-based Polymers)

End Applications:

  • Disposable tableware
  • Agricultural Products such as Mulch Films.
  • Straws
  • Carry Bags, Medical waste Bags, Nursery Bags
  • Electrical Home appliances cover Bags
  • Moulded Cutlery
  • Cookie trays thermoformed

Processing Biopolymers

Here are some key processing considerations for Bio Resin compounds and Biopolymer compounded blends on a Co-Rotating Twin Screw Extruder:

Modular Twin Screw design: Design the equipment for maximum flexibility; purchase long extruders having 48:1 L/D, with multiple vent and feed location options. It’s much easier to open or close up an available vent location, or to add or remove a Side Feeder from an available location, than to purchase new barrels or extend the Extruder after the initial capital purchase.

Biopolymers are typically high hygroscopic:

Biopolymers are typically hygroscopic and require cautious handling prior to processing. It is effective to place an atmospheric vent early in the extrusion process to minimize hydrolysis of the Biopolymer and to avoid pre-drying of the materials. A vacuum vent is a requirement. Don’t think of a vacuum system as a non-essential add-on; it is an integral part of the extrusion process that is often the difference between making a quality product or not.

Biopolymers are shear and pressure-sensitive:

Biopolymers rapidly degrade when exposed to excessive heat and / or shear. The shear exposure of the material is directly proportional to the Extruder screw speed and inversely proportional to the gap between the extruder Screws and the Barrels.

Biopolymers degrade rapidly, making purging important: Degradation of Biopolymers is more rapid than most petroleum based Polymers. It is highly recommended to lower the Barrel heat or turn the heats ‘OFF’ if the Extruder is going to be standing for more than 1 to 2 hr. If the heats are left on for long periods while the Extruder is not running, purge the Extruder with a low cost heat-stable polymer that has a slightly higher melt viscosity than the bio resin. If the viscosity of the purge material is too high, it can show up as contamination for many hours after starting up production again.

PLA / PBAT / PVA

High Torque Twin Screw Extruders Selection chart:
ALPHA ZV20 ZV30 ZV40 ZV50 ZV62 ZV72 ZV90

Output kg/hr

 0.5-15 10-50 50-150 75-250 100-350 150-550 250-750

Screw Diameter (mm)

 20 30 42 50 62 72 90

Effective L/D ratio

 18-48 18-48 18-48 18-48 18-48 18-48 18-48

Motor Power (kw)

 5.5 22/30 45/55 55/75 90/110 160/180 225/250

Advance Key Features:

  • Higher L/D for better dispersion
  • High Dispersion & Homogenous mixing of different particle size
  • High Torque design to carry heavy thrust load generated during processing
  • High degassing Vacuum unit to control moisture
  • Moisture controlled below 30 ppm
  • Electric heating & liquid cooled Barrels for precise heat controls
  • Modular Screw & Barrel design to compound different compostable
  • Easy maintenance due to modular segmented technology
  • Dosing Feeder with vertical agitator to avoid bridging
  • Water cooling die edge cutting technology for uniform pelletizing
  • Touch screen & PLC Controls easy to operate Control Panel
  • Interlocking’s for safety and Data recording batch to batch