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Polylactide (PLA): Complete Guide to Accelerate your 'Green' Approach

Polylactide (PLA): Complete Guide on Bio-based & Biodegradable PolymerRapidly growing concerns related to environmental and health safety, limiting dependence on petrochemical raw materials, reducing carbon footprint ... are among the few factors driving inclination towards use of biopolymers.

There exist several biopolymers today and thanks to the excellent degradation behavior and versatility of PLA:

   » It is now widely used in packaging sector right from a niche product in organic trade to premium packaging for branded goods
   » High-performance grades, that are an excellent replacement for PS, PP, and ABS, are gaining traction in more demanding applications


What makes PLA a very versatile polymer and material of choice in several applications today? Let’s check out in detail...

What is Polylactide (PLA)?


PLA or Polylactide (also known as Polylactic Acid, Lactic acid polymer) is a versatile commercial biodegradable thermoplastic based on lactic acid. Lactic acid monomers can be produced from 100% renewable resources, like corn and sugarbeets.

Molecular Structure of Polylactic Acid (PLA, polylactide) Bioplastic
Molecular Structure of Polylactic Acid (PLA, polylactide) Bioplastic

Polylactide has been able to replace the conventional petroleum-based thermoplastics, thanks to the excellent combination of properties it possesses.

It is one of the most promising biopolymers used today and has a large number of application such as Healthcare and medical industry, Packaging, Automotive applications etc.

As compared to other biopolymers, PLA exhibits several benefits such as:

  1. Eco-friendly – It is renewably-sourced, biodegradable, recyclable and compostable
  2. Biocompatible – It is non-toxic
  3. Processability – It has better thermal processability compared to poly(hydroxyl alkanoate) (PHA), poly(ethylene glycol) (PEG) and poly(γ-caprolactone) (PCL)

Polylactides break down into nontoxic products during degradation and being biodegradable and biocompatible, reduce the amount of plastic waste.

Polylactides (PLA) Lifecycle

Nowadays, there are many producers of PLA, some of them are:


» View All Commercially Available PLA Grades & Suppliers in Omnexus Plastics Database

This plastic database is available to all, free of charge. You can filter down your options by property (mechanical, electrical…), applications, conversion mode and many more dimensions.

Continue reading or click to go on specific section of the page:


What is Lactic acid and how PLA is manufactured?

Lactic Acid Monomer Structure      
Lactic Acid Monomer Structure Lactic acid (LA or 2-hydroxypropionic acid) is the most widely occurring hydroxycarboxylic optical active acid. This chiral molecule exists as two enantiomers – L- and D-Lactic Acid.

Polylactide is based on lactic acid monomers obtained from the fermentation of sugars, beet-sugar, cane-sugar etc. obtained from renewable sources such as sugar cane or corn starch.

PLA has stereoisomers, such as:
  • Poly(L-lactide) (PLLA)
  • poly(D-lactide) (PDLA), and
  • Poly(DL-lactide) (PDLLA)

Poly-lactic acid is an aliphatic polyester and can be obtained using different routes:

  • Direct polycondensational reaction
    It usually leads to low molecular weight polymers which then can be converted to higher molecular weight polymers by addition of chain coupling agents.

  • Ring opening polymerization
    PLA is produced by formation of lactide monomer first and Formed lactide is then put through ROP usually using metal alkoxides as catalysts resulting in high molecular weight polyester – PLA.

  • Azeotropic dehydrative condensation
    organic solvents are introduced into reaction mixture to ease up removal of water thus producing higher molecular weight product.

Methods for Polylactic Acid (PLA) Production

Methods for Polylactic Acid (PLA) Production
(Source: Royal Society of Chemistry)

Currently first two methods are the most used techniques for industrial production. ROP currently dominates as the process of choice for industrial PLA producton due to low time consumption and a high molecular weight final product, making it probably the most used and viable method to produce PLA, although high temperatures and low pressure must be still used to achieve the final product.

However, new methods such as polymerization using microwave irradiation and ultrasonic sonochemistry could lead to faster and cheaper production of PLA.

Typical Characteristics and Properties of Polylactic Acid


PLA is a bio-based, biodegradable and biocompatible polymer which has proved itself to be a promising alternative for petroleum-based polymers.


However, in the previous year, the commercial viability of PLA was limited by its high production costs compared to its petroleum-based counterparts.

Today, by optimizing the LA and PLA production processes, and with increasing PLA demand, a reduction in its price can be achieved.

Most of the commercial L-PLA products are semi crystalline polymers with a high melting point ca. 180°C and having their glass transition temperature in the range of 55 – 60°C, as it is desirable that PLA should have some crystalline content to benefit the quality of the finished product.

  • PLA is a high strength and high modulus thermoplastic with good appearance
  • It has high stiffness and strength, comparable to polystyrene (PS) at room temperature
  • Less energy is required in its production when compared to other plastics and has better thermal processing

Further development of composites, nanocomposites and bio composites is expanding the properties and potential applications of PLA.

However, there are still some disadvantages associated with the polymer:

  • Its glass transition temperature is low (Tg ~ 55°C)
  • Its poor ductility, low impact strength and brittleness limits its use as compared to other thermoplastics such as ABS
  • It has low crystallization rate and processing results mainly in amorphous products
  • As compared to PET (aromatic polyester), PLA is much more susceptible to chemical and biological hydrolysis
  • It is thermally unstable and has poor gas barrier performance
  • It has low flexibility and requires long mold cycles
  • It is relatively hydrophobic
  • It has slow degradation rate

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PLA Properties Improvement


PLA properties can be altered or improved by use of additives and developing polymer blends. Some of the examples are:

Plasticization: Lactide monomer is an excellent plasticizer for PLA however it tends to migrate to the PLA surface. Other plasticizers such as Citrate esters & low-Mw PEG have shown only modest improvements in toughness, but this is accompanied by a dramatic loss in tensile stress at break and tensile modulus.

Mineral Fillers such as ppt CaCO3 at 30% loading provides substantial improvement in the impact toughness of PLA.

Impact modifiers are also found to increase PLA properties however adding them will compromised the compostability of the PLA.

Polymer Blending: PLA/PCL blends Polycaprolactone (PCL) is also a degradable polyester and due to its low Tg it exhibits rubbery characteristics with an elongation at break of approximately 600%, which makes it an ideal candidate for toughening polylactide.

PLA blends with PHA have shown significant improvement in impact toughness with a modest decrease in modulus and strength as well as without compromising bio-based content and compostability of PLA.

The development of PLA nanocomposites using nanoscale fillets represents a better alternative to traditional composites. Due to their high surface area, improved matrix adhesion and aspect ratio these nanofillers (colloidal silica, clay platelet...) offer enormous advantages over traditional macro- or micro-particles (e.g., talc, glass, and carbon fibers). For example, PLA-clay nanocomposites show improved mechanical, barrier optical, and thermal properties.


Popular Applications of Polylactic Acid


Food Contact Approved Polymer for Packaging

Food Contact Approved Bio-Polymer for Packaging
PLA is a Food and Drug Administration (FDA) approved polymer for use a food contact material. It can be used as a food packaging polymer for short shelf life products such as fruit and vegetables.

The common packaging applications of polylactides include as containers, drinking cups, sundae and salad cups, overwrap and blister packages

Extremely Biocompatible Plastic in Healthcare and Medical Industry


Thanks to its biocompatibility and biodegradability, the healthcare and medical industry is making good use of polylactide to manufacture tissue engineering scaffolds, delivery system materials, or covering membranes and different bioabsorbable medical implants.

Due to its versatility, PLA has been investigated for membrane applications (e.g. wound covers), implants and medical devices (fixation rods, plates, pins, screws, sutures, etc.), and dermatological treatments (e.g. facial lipoatrophy and scar rejuvenation).

Applications of PLA in Healthcare and Medical Industry

   » Find Suitable PLA Grade for your Next Medical Development

Growing Use of Polyactide in Structural Applications


Biobased PLA and PLA-based composites are comparatively new for high-end automotive as well as electrical and electronics applications. These composites show better tensile strength and impact characteristics and hence could be used for interior parts of automobile or safety helmets.

Improved material properties enable PLA suitable for use in floor mats, pillar cover, door trim, front panel and ceiling material. PLA Biocomposites are proposed for use in cover spare wheel or translucent roof in hybrid concept vehicles.

Polylactide Biocomposites Could Find Applications in Translucent Roof in Hybrid Vehicles
Polylactide Biocomposites Could Find Applications
in Translucent Roof in Hybrid Vehicles

However, there still are certain features which limit the commercialization of PLA in other structural applications.

Fibers and Fabrics Made from PLA


Fibers and Fabrics Made from PLA PLA is also suitable for textile fiber applications such as shirts, carpets, bedding, mattress, sportswear etc. due to to its low moisture absorption, low smoke generation capability as well as good resistance to UV light.

The polymer also has potential in mulch films and compostable garden waste bags, structural protective foams, insulation materials etc.


Processing Methods and Conditions for PLA Grades


PLA can be easily processed like other thermoplastics through conventional processing techniques like injection molding, film extrusion, blow molding, thermoforming, fiber spinning etc. to yield molded parts, films, or fibers.

Requirements for PLA Processing Via Injection Molding


PLA resins can be successfully dried using most standard drying systems. Advised conditions for standard desiccant based column dryers are:
  • A predrying of 2 to 4 hours at 45°C up to 90°C is recommended.
  • A moisture level lower than 250 ppm will help keep the melt viscosity stable over time at elevated temperatures.
  • Typical desiccant dryer regeneration temperatures exceed the melt point of PLA resins.
  • To prevent issues with pellet bridging, sticking or melting, the drying system should be verified to ensure temperature control is adequate during operation as well as during regeneration cycles since valve leakage is common in many systems.

Colorants and slip agents can be added as a masterbatch at 15-30-wt% in PLA by dry blending with the neat resin in the required amount and adding the blend to the injection molder. The additions of colorants have been successfully done using liquid injection technology as well.

Since PLA is not compatible with most incumbent materials, it is important that all additive masterbatches use PLA as carrier

Polylactide Injection molding grades are compatible with the use of hot runner systems. Typical conditions for injection molding are:

  • Adapter Temperature: 185 - 200°C
  • Dew Point: (-)40 - (-)35°C
  • Die Temperature: 185 - 200°C
  • Drying Temperature: 45 - 100°C
  • Feed Temperature: 165 - 185°C
  • Melt Temperature: 154.4 - 243.3°C
  • Mold Temperature: 10 - 105°C
  • Nozzle Temperature: 171.1 - 220°C
  • Back Pressure: 0.345 - 1.724 MPa
  • Injection Pressure: 55.16 - 137.9 MPa
  • Moisture Content: 0.01 - 0.025%
  • Screw Speed: 20 - 200 rpm
  • Drying Air Flow Rate: 14.16 l/pm

Plate-out of lactide can occur over time if injection speeds are too low, and/or mold temperature is too cold.

Another concern is that PLA shear-thins slower and to a lesser extent than resins like PS, PE, and PP. Because of this, filling of the mold is a concern especially for thin-walled products like drinking cups. It might be possible to overcome this issue my experimentation and finding the right melt temperature and injection speed necessary to fill the part.

Usually, one will have to raise the melt temperature, which can have an adverse effect on the cooling time of the part while in the mold.


Injection Molding / Extrusion: How to Avoid Plastic Quality Crashes

Polylactide Fiber Melt Spinning Grade Processing


Polylactide fiber melt spinning grades are designed for extrusion into mechanically drawn staple fibers using conventional fiber spinning and drawing equipment. They can be used as a low melt binder polymer in a sheath-core configuration.

  • General-purpose screws with L/D ratios of 24:1 to 30:1 and 3:1 compression ratios are recommended. 
  • Typical melt spinning temperatures are 220 - 240°C. 
  • The recommended moisture content to prevent viscosity degradation and potential loss of properties is < 0.005% (50 ppm). 
  • Typical drying conditions are 8 to 12 hours at 40°C - 50°C.

Like PET the Polylactide fiber melt spinning grades require either high filament velocity or drawing and controlled heat setting to control shrinkage.

In-line drying capabilities are essential to process PLA Injection Stretch Blow Molding grades.

Polylactide Heat Seal Layer Processing


Can be coextruded with other PLA resin to form a sealant layer for biaxially oriented PLA film.

  • Drying prior to processing is essential. In-line drying is required. 
    • A moisture content of less than 0.025% (250 ppm) is advised to prevent viscosity degradation. 
    • Typical drying conditions are 4 hours at 11°F (45°C).
  • PLA polymers will process on conventional extruders. Configure general purpose screws with
    • L/D ratios from 24:1 to 30:1 
    • compression ratio of 2:1 to 3:1.
  • Melt temperature : 210°C
  • Feed section: 180°C
  • Compression section: 190°C
  • Metering section: 200°C
  • Die: 190°C

Screw cooling capabilities through the feed section are necessary to prevent the resin from sticking to the screw root. Smooth barrels are recommended. This grade is suitable only as a heat seal layer in a coextrusion process. Processing polylactide as a monolayer film is not recommended.

Processing Requirements for Polylactide High Heat Films


Polylactide extrusion grade can be converted into a biaxially oriented film at up to 150°C (300°F).

  • PLA resins can be successfully dried using most standard drying systems. In-line drying is required: 
    • a predrying of 4 hours at 80°C (175°F) is recommended. 
    • A moisture level lower than 250 ppm (0.025%) will help keep the melt viscosity stable over time at elevated temperatures.
  • PLA polymers will process on conventional extruders. Configure general purpose screws with:
    • L/D ratios from 24:1 to 30:1 
    • compression ratio of 2.5:1 to 3:1.
  • Melt temperature: 200°C - 220°C
  • Feed section: 180°C
  • Compression section: 190°C
  • Metering section: 200°C
  • Die: 200°C

PLA resins will also process on conventional cast tenter equipment.

Polylactide Spunbond Processing


Polylactide spunbond grades process on conventional spunbond equipment.

  • General-purpose screws with: L/D ratios of 24:1 to 30:1 and 3:1 compression ratios are recommended.
  • Typical melt spinning temperatures are 220- 240°C. Like PET the PLA spunbond grades require either high filament velocity or drawing and controlled heat setting to control shrinkage.
  • In-line drying capabilities are essential to process PLA Injection Stretch Blow Molding grades. 
  • The recommended moisture content to prevent viscosity degradation and potential loss of properties is < 0.005% (50 ppm). 
  • Typical drying conditions are 4 hours at 80°C. 

PLA Filaments for 3D Printing


3D Printing using PLA filaments is a promising way to produce complex biomedical devices according to computer design. This process opens new development using patient-speciļ¬c anatomical data as well as in wide range of industrial and architectural applications.

PLA printing was found feasible for the such applications mainly by using direct or indirect 3D printing and fused deposition modeling technologies.

   » Find Suitable PLA Grade for 3D Printing

Commercially Available Polylactide Bioplastic Grades





This plastic database is available to all, free of charge. You can filter down your options by property (mechanical, electrical…), applications, conversion mode and many more dimensions.



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