Introduction to Polylactic Acid

PLA’s popularity stems from its cost-effective production using renewable resources. It is the second most produced bioplastic and shares characteristics with traditional plastics while being biodegradable. PLA finds applications in various fields, including biomedicine, where its biocompatibility and tailored properties make it suitable for suture threads, bone fixation screws, and drug delivery devices. The production of PLA involves fermenting sugars, with corn being the most commonly used source. However, other options like sugarcane, tapioca root, cassava, and sugar beet pulp can also be used. PLA offers a sustainable alternative to conventional plastics, with its ability to biodegrade and be derived from renewable resources.

In this chapter, we will take you through PLA, a popular manufacturing material, so you can comprehensively understand PLA. Pictured to the left are some examples of our PLA products. Send your 3D files and we can provide processing services for you.

What Is PLA (polylactic acid)?

PLA, or polylactic acid, is a bioplastic derived from plant starches through ring-opening polymerization. It is a thermoplastic polyester widely used in medical devices, food packaging, injection molding, and 3D printing industries. PLA is biodegradable under suitable conditions and breaks down into non-toxic lactic acid. It has three sub-families with similar chemical compositions but different molecular structures.

When Was Polylactic Acid Invented?

Polylactic acid (PLA) was first invented in 1932 by Wallace Carothers and Julian Hill at the DuPont Company. However, the commercial production of PLA on a large scale did not begin until the 1990s when the Cargill Corporation and the Dow Chemical Company developed a cost-effective method for its production. Since then, PLA has gained significant attention as a biodegradable and renewable alternative to traditional petroleum-based plastics.

What Is Polylactic Acid Made From?

Polylactic acid (PLA) is primarily made from renewable resources such as corn starch, tapioca roots, sugarcane, or other plant-based feedstocks. The process involves fermenting these feedstocks to produce lactic acid, which is then polymerized to form PLA. The polymerization process converts the lactic acid molecules into long chains, resulting in the formation of PLA. The use of renewable feedstocks and the biodegradable nature of PLA make it a more environmentally friendly alternative to conventional petroleum-based plastics.

What Color Is Polylactic Acid?

Polylactic acid (PLA) is typically a translucent or transparent material, so it does not have a specific color. However, PLA can be easily pigmented during the manufacturing process to achieve a wide range of colors. This means that PLA products can be found in various colors, including but not limited to white, black, red, blue, green, and many others. The specific color of PLA depends on the desired application or aesthetic preference of the manufacturer or end-user. The picture below is an example of polylactic acid plastic raw materials:

polylactic-acid-raw-materials-image-800x600

What Does Polylactic Acid Look Like?

Polylactic acid (PLA) is a thermoplastic polymer that can have different physical properties depending on its molecular structure and processing conditions. The specific appearance of PLA products can vary based on factors such as color, additives, and processing techniques. PLA can be molded into various shapes and forms, including films, fibers, and 3D-printed objects. Overall, PLA has a versatile appearance that can be modified to suit different applications and aesthetic preferences. The picture below is an example of polylactic acid parts:

polylactic-acid-parts-image-800x600

What Are the Characteristics of Polylactic Acid?

Polylactic acid (PLA) possesses several notable characteristics, including:

1. Biodegradability: PLA is biodegradable, meaning it can break down into simpler, non-toxic compounds when exposed to certain conditions, such as high temperatures and moisture. This property makes PLA a more environmentally friendly alternative to traditional plastics.

2. Renewable resource: PLA is derived from plant-based feedstocks, such as corn or sugarcane, making it a renewable and sustainable material.

3. Transparency: PLA is typically transparent or translucent, allowing for the creation of visually appealing products.

4. Strength and rigidity: PLA exhibits good mechanical properties, including moderate strength and rigidity, making it suitable for a wide range of applications.

5. Processability: PLA can be easily processed using conventional plastic processing techniques such as injection molding, extrusion, and 3D printing.

6. Heat sensitivity: PLA has a relatively low melting point, which can limit its use in high-temperature applications. However, heat-resistant variants of PLA have been developed to overcome this limitation.

7. Limited chemical resistance: PLA has lower chemical resistance compared to traditional petroleum-based plastics, and it can be sensitive to some solvents and acidic substances.

8. Food-safe: PLA is considered food-safe and has been approved for use in food packaging and containers.

9. Versatility: PLA can be processed into various forms, including films, fibers, foams, and 3D-printed objects. This versatility allows for a wide range of applications across industries such as packaging, textiles, biomedical, automotive, and consumer goods.

10. Environmental impact: PLA is considered an environmentally friendly alternative to traditional plastics due to its biodegradability and renewable sourcing. When properly disposed of in industrial composting facilities, PLA can break down into carbon dioxide and water within a few months to a few years, depending on the conditions. However, it is worth noting that PLA may not readily biodegrade in home composting systems or in landfill environments, where the required conditions for biodegradation may not be present.

11. Thermal properties: PLA has a relatively low glass transition temperature, typically around 60-65 degrees Celsius. This means that PLA may soften or deform under moderate heat, limiting its use in high-temperature applications. However, heat-resistant PLA variants have been developed to overcome this limitation, offering improved temperature stability and broader application possibilities.

12. UV sensitivity: Unmodified PLA can be susceptible to degradation when exposed to prolonged ultraviolet (UV) light exposure. This can result in yellowing and reduced mechanical properties over time. However, UV-stabilized PLA grades or the addition of UV-absorbing additives can mitigate this issue, making PLA suitable for outdoor applications.

13. Barrier properties: PLA has moderate barrier properties, particularly against oxygen and moisture. This makes it suitable for certain packaging applications, such as food containers and films. However, PLA may have lower barrier performance compared to some petroleum-based plastics, and it may require additional coatings or laminations to enhance its barrier properties.

14. Printability and post-processing: PLA is widely used in 3D printing due to its good printability and compatibility with commonly available 3D printers. It can produce detailed and accurate prints with a smooth surface finish. Additionally, PLA can be easily post-processed through techniques like sanding, painting, and polishing to achieve desired aesthetics.

What Are Different Types of Polylactic Acid?

Several different types of polylactic acid (PLA) have been developed to suit specific applications and requirements. Some of the common types of PLA include:

1. Standard PLA

This is the most commonly used type of PLA and is suitable for a wide range of applications. It has good transparency, and moderate strength, and is often used in packaging, consumer goods, and 3D printing.

2. High-Heat PLA

This type of PLA has enhanced heat resistance compared to standard PLA. It can withstand higher temperatures without significant softening or deformation, making it suitable for applications that require heat resistance, such as hot-fill packaging or heat-resistant 3D prints.

3. Impact-Modified PLA

Impact-modified PLA is formulated to have improved toughness and impact resistance compared to standard PLA. It is used in applications where higher mechanical strength and durability are required, such as automotive parts or durable consumer goods.

4. Flexible PLA

Flexible PLA, also known as PLA elastomer or PLA-flex, is a type of PLA that offers flexibility and elasticity. It has rubber-like properties and is used in applications such as flexible packaging, textiles, and 3D printing of flexible objects.

5. Blended PLA

PLA can be blended with other polymers or additives to enhance specific properties. For example, PLA can be blended with polybutylene adipate terephthalate (PBAT) to improve its biodegradability or with polycarbonate (PC) to enhance its thermal and impact resistance.

6. Colored PLA

PLA can be manufactured in a wide range of colors by incorporating colorants during the production process. This allows for aesthetically appealing and vibrant PLA products.

What Are the Properties of Polylactic Acid?

In the table below, we summarize some common general properties of polylactic acid material :

What Are the Physical Properties of Polylactic Acid?

The table below lists some physical properties of polylactic acid:

PLA Material Physical Properties Table
Physical PropertyDescription
AppearanceTranslucent or transparent
ColorCan be pigmented into various colors
DensityTypically around 1.25 g/cm³
Mechanical StrengthModerate strength and rigidity
FlexibilityRelatively stiff, but can be modified for flexibility
TransparencyExhibits good transparency
Surface FinishSmooth and glossy
Water AbsorptionPLA has a moderate water absorption capacity
Thermal ConductivityLow thermal conductivity
FlammabilityPLA is combustible and burns with a yellow flame
OdorPLA typically has a mild, sweet odor
Processing TemperatureMelts and processes around 160-180°C
PrintabilityPLA is widely used in 3D printing
Barrier PropertiesModerate barrier properties against oxygen and moisture
What Are the Chemical Properties of Polylactic Acid?

The table below lists some chemical properties of polylactic acid:

PLA Material Chemical Properties Table
Chemical PropertyDescription
Chemical Formula(C3H4O2)n
MonomerLactic acid (C3H6O3)
Molecular WeightVaries depending on the polymerization degree of the PLA chain
StereochemistryPLA can exist in both L-lactide and D-lactide forms
BiodegradabilityPLA is biodegradable under specific conditions
HydrophilicityPLA has some degree of hydrophilicity
Chemical StabilityStable under normal conditions
SolubilitySoluble in certain solvents like chlorinated hydrocarbons
Thermal DecompositionPLA undergoes thermal decomposition at high temperatures
Melting PointTypically around 150-160°C
Glass Transition TemperatureTypically around 55-65°C
UV SensitivityPLA can be susceptible to UV degradation
Chemical ResistanceModerate resistance to chemicals and solvents
How to Compare the Main Polylactic Acid Types?

The following is a comparison of several common polylactic acid materials:

PLA Material Comparison Table
PropertyStandard PLAHigh-Heat PLAImpact-Modified PLAFlexible PLABlended PLAColored PLA
Tensile StrengthModerateHighModerateLowVariesSimilar to standard PLA
Flexural StrengthModerateHighModerateLowVariesSimilar to standard PLA
Impact StrengthModerateModerateHighLowVariesSimilar to standard PLA
Elastic ModulusModerateHighModerateLowVariesSimilar to standard PLA
Glass Transition Temp.55-60°C80-100°C55-60°C-10 to -20°CVaries55-60°C
Melting Temperature150-160°C170-180°C150-160°C130-140°CVaries150-160°C
The glass transition temperature (Tg) indicates the temperature at which PLA transitions from a glassy state to a rubbery state, and the melting temperature refers to the temperature at which PLA starts to melt.
What Is an Advantage of Polylactic Acid?

An advantage of polylactic acid (PLA) is its biodegradability. PLA is derived from renewable resources such as corn starch or sugarcane, making it a more sustainable alternative to conventional plastics derived from fossil fuels. It can be broken down by microorganisms in industrial composting facilities, resulting in less environmental impact compared to traditional plastics. Additionally, PLA has a lower carbon footprint during production, making it a more environmentally friendly option.

Here are some additional advantages of polylactic acid (PLA):

1. Versatility: PLA can be processed into various forms, including films, fibers, and 3D printing filaments, making it suitable for a wide range of applications. It can be used in packaging materials, disposable cutlery, medical implants, textiles, and more.

2. Renewable and Biodegradable: PLA is derived from renewable resources such as corn, sugarcane, or other plant-based feedstocks. Unlike traditional plastics derived from fossil fuels, PLA offers a more sustainable option. It is also biodegradable under specific conditions, such as in industrial composting facilities, reducing its impact on the environment.

3. Reduced Carbon Footprint: PLA has a lower carbon footprint compared to petroleum-based plastics during its production process. The use of renewable feedstocks and the energy-efficient manufacturing process contribute to its reduced environmental impact.

4. Safe for Food Contact: PLA is considered safe for food contact applications and is approved by regulatory agencies such as the U.S. Food and Drug Administration (FDA) for use in food packaging and containers.

5. Processability: PLA exhibits good processability, allowing it to be easily molded, extruded, and formed into various shapes. It can be processed using conventional plastic processing techniques, making it compatible with existing manufacturing infrastructure.

6. Transparency and Gloss: PLA has excellent clarity, making it suitable for applications where transparency is desired. It can be used to produce clear packaging materials or products where visual appeal is important.

What Are the Limitations of Polylactic Acid?

While polylactic acid (PLA) offers several advantages, it also has some limitations to consider:

1. Heat Resistance: PLA has lower heat resistance compared to traditional petroleum-based plastics. It begins to soften and deform at relatively low temperatures, typically around 60-70°C. This limits its suitability for high-temperature applications where materials with higher heat resistance are required.

2. Brittleness: PLA can be relatively brittle, especially in its pure form. It has lower impact strength and toughness compared to certain other plastics. This can make it prone to cracking or breaking under certain stress conditions.

3. Moisture Sensitivity: PLA is sensitive to moisture absorption, which can affect its mechanical properties and dimensional stability. High humidity or exposure to moisture over time can lead to degradation, reducing its overall performance.

4. Slow Biodegradation in Natural Environments: While PLA is biodegradable under specific conditions, such as in industrial composting facilities, its biodegradation is relatively slow in natural environments like soil or water. This means that PLA products discarded in conventional waste systems may not break down as quickly as expected.

5. Limited Chemical Resistance: PLA has limited resistance to certain chemicals, including some solvents and acids. It may undergo degradation or be susceptible to chemical attack in the presence of these substances.

6. Cost: PLA tends to be more expensive compared to traditional petroleum-based plastics. The production process and sourcing of renewable feedstocks contribute to its higher production costs, which can impact its competitiveness in certain applications.

What Is Polylactic Acid Used For?

Polylactic acid (PLA) is used in various applications across different industries. Here are some common uses of PLA:

1. Packaging Materials

PLA is widely used in the production of packaging materials such as films, trays, cups, and bottles. It can be formed into transparent, rigid, or flexible structures, making it suitable for food packaging, consumer goods, and other packaging applications.

2. Disposable Cutlery and Tableware

PLA is often used to manufacture disposable cutlery, plates, bowls, and cups. These products offer a more sustainable alternative to traditional plastic utensils and tableware, as they are derived from renewable resources and can be composted after use.

3. Textiles and Fibers

PLA can be processed into fibers and used in textiles and apparel. It is blended with other fibers like cotton or polyester to enhance its properties and create sustainable fabrics for clothing, household textiles, and non-woven materials.

4. Medical Implants and Devices

PLA is used in medical applications due to its biocompatibility and biodegradability. It is used in the production of surgical sutures, drug delivery systems, tissue engineering scaffolds, and other implantable medical devices.

5. 3D Printing

PLA is a popular material for 3D printing due to its ease of use, low toxicity, and biodegradability. It can be extruded into filaments compatible with 3D printers, allowing for the creation of various prototypes, consumer products, and custom parts.

6. Agricultural Films

PLA is used in the production of biodegradable agricultural films such as mulch films and greenhouse films. These films help to improve crop yield, conserve moisture, and suppress weed growth while reducing the environmental impact associated with traditional plastic films.

7. Stationery and Disposable Products

PLA is used to manufacture stationery items like pens, rulers, and folders. It is also used in the production of disposable products like straws, stirrers, and food containers.

What Processing Methods Are Suitable for PLA?

Polylactic acid (PLA) can be processed using various methods, including:

1. Injection Molding: Injection molding is a widely used method for processing PLA. It involves melting the PLA resin and injecting it into a mold, where it cools and solidifies to form the desired shape. Injection molding is suitable for producing complex shapes and high-volume production.

2. Extrusion: Extrusion is another common method for processing PLA. It involves melting the PLA resin and forcing it through a die to create a continuous profile, such as filaments for 3D printing or sheets for thermoforming. Extrusion is a versatile process and can be used for both mass production and prototyping.

3. Blow Molding: Blow molding is used to produce hollow objects, such as bottles or containers, from melted PLA. The process involves inflating a heated plastic parison inside a mold to take the shape of the desired product. Blow molding is suitable for producing large quantities of hollow PLA objects.

4. Thermoforming: Thermoforming is a process that involves heating a sheet of PLA material and then shaping it using molds or vacuum forming. It is commonly used for producing PLA packaging trays, cups, and other similar products.

5. Film and Sheet Extrusion: PLA can be extruded into thin films or sheets that are used for various applications, including packaging materials, agricultural films, and food wraps. Film and sheet extrusion processes involve melting the PLA resin and forming it into a continuous flat profile.

6. Fiber Spinning: PLA can be processed into fibers using methods such as melt spinning or solution spinning. These fibers can be used in textiles, non-woven materials, and composite reinforcements.

7. 3D Printing: PLA is a popular material for 3D printing due to its ease of use and availability in filament form. It can be used in various types of 3D printers, such as fused deposition modeling (FDM) printers, to create prototypes, functional parts, and artistic objects.

What Is The Cost of Polylactic Acid?

The cost of polylactic acid (PLA) can vary depending on several factors, including the supplier, market conditions, and the specific grade or formulation of PLA. Generally, PLA tends to be more expensive compared to traditional petroleum-based plastics.

The production of PLA involves the conversion of renewable feedstocks, such as corn starch or sugarcane, into lactic acid, which is then polymerized to form PLA resin. The production process and sourcing of renewable feedstocks contribute to the higher production costs of PLA. Additionally, factors such as economies of scale, supply chain dynamics, and market demand can influence the cost of PLA.

Generalize

This article offers a comprehensive overview of polylactic acid (PLA), a type of plastic material. It aims to provide a clear understanding of PLA by explaining its properties, and applications, and addressing frequently asked questions. For further inquiries, our team is readily available to assist you.

Ruitai specializes in the precise manufacturing of prototype parts and delivers comprehensive services tailored to various prototyping and production needs. We are dedicated to providing customized solutions and are pleased to offer a complimentary quotation. Please don’t hesitate to reach out to us at your convenience.

Disclaimer

Kindly note that the information presented in this article is solely for informative purposes. Ruitai Mould assumes no liability for the completeness, accuracy, or validity of the information provided, whether explicitly or implicitly stated.

Addressing Common Polylactic Acid Questions:

Q1: Does polylactic acid bond to glass?
A1: Polylactic acid (PLA) does not easily bond to glass. While PLA can adhere to some surfaces, including certain plastics, it typically does not form strong bonds with glass.

Q2: Is polylactic acid biodegradable?
A2: Yes, polylactic acid (PLA) is biodegradable. Under specific conditions, such as in industrial composting facilities with the presence of microbes and controlled temperature and humidity, PLA can undergo biodegradation.

Q3: Is polylactic acid safe?
A3: Polylactic acid (PLA) is generally considered safe for various applications. It is approved by regulatory agencies like the U.S. Food and Drug Administration (FDA) for use in food contact applications.

Q4: Is polylactic acid a plastic?
A4: Yes, polylactic acid (PLA) is a type of plastic. It is derived from renewable resources and falls under the category of biodegradable and bio-based plastics.

Q5: Is polylactic acid a polymer?
A5: Yes, polylactic acid (PLA) is a polymer. It is made up of repeating units of lactic acid monomers.

Q6: Is polylactic acid a powder?
A6: Polylactic acid (PLA) can be found in various forms, including pellets, granules, or powder. The specific form depends on the intended application and the manufacturing process.

Q7: Is polylactic acid soluble in water?
A7: Polylactic acid (PLA) is not highly soluble in water. While it can absorb some moisture, it does not readily dissolve in water.

Q8: Is polylactic acid strong?
A8: Polylactic acid (PLA) has moderate strength compared to other engineering plastics. Its tensile strength and overall performance can be influenced by factors such as molecular weight, processing conditions, and additives.

Q9: Is polylactic acid toxic?
A9: Polylactic acid (PLA) is generally considered non-toxic. It is widely used in various applications, including food packaging and medical devices, where safety is a concern. However, like any material, PLA should be used and handled according to recommended guidelines to ensure proper safety.

Q10: What material is PLA?
A10: PLA stands for polylactic acid, which is a biodegradable and bio-based polymer. It is derived from renewable resources such as corn starch, sugarcane, or other plant-based feedstocks. PLA belongs to the polyester family and is commonly used as a sustainable alternative to traditional petroleum-based plastics.