In recent years, as stricter regulations on plastic usage have been implemented, the ban on non-biodegradable plastic bags in supermarkets, retail stores, and the food industry has created a growing demand for sustainable alternatives.
Among these, PLA (Polylactic Acid) has emerged as one of the most popular and widely used substitutes.
Known for its biodegradability and eco-friendly properties, PLA is setting a new standard for green materials in industries worldwide.
In this article, we will delve into what PLA is, explore its characteristics and applications, and uncover why it is regarded as the future of the plastics industry.
What Is PLA?
Polylactic acid (PLA), also known as polylactide, is a new type of bio-based and renewable biodegradable material.
It is derived from renewable plant resources (such as corn and cassava) through processes including saccharification, fermentation, and chemical synthesis, ultimately yielding high-molecular-weight polylactic acid.
PLA plastic is environmentally friendly and non-toxic, and it can degrade into water and carbon dioxide under specific conditions, making it widely regarded as an eco-friendly material.
How Are PLA Material Made?
Polylactic acid (PLA) can be synthesized through two main methods: direct polycondensation of lactic acid (DPC) and ring-opening polymerization (ROP) of lactide.
The direct polycondensation method uses lactic acid as the monomer to directly undergo a condensation reaction.
This approach doesn’t require the addition of catalysts; it only involves lactic acid and a solvent, making the process relatively simple and easy to operate.
As a result, it reduces production costs and improves efficiency.
The ring-opening polymerization method uses lactide as the monomer.
This process involves two steps: ring-opening and polymerization, resulting in linear high-molecular-weight polymers.
This method is highly efficient at converting cyclic monomers into high-molecular-weight polymers through a well-controlled reaction.
The resulting PLA meets the requirements for its widespread application as a biodegradable material in various fields.
Types of Polylactic Acid
Polylactic Acid is a bio-based, biodegradable polyester polymer composed of multiple lactic acid monomers.
Based on the optical activity of lactic acid molecules, PLA can be classified into the following three types:
- Poly-D-lactic acid (PDLA): PDLA is synthesized from D-lactic acid monomers.
- Poly-L-lactic acid (PLLA): PLLA is synthesized from L-lactic acid monomers. It is typically isotactic, with high tensile strength, but has lower elongation at break and impact toughness.
- Poly-D,L-lactic acid (PDLLA): PDLLA is synthesized from an equal mixture of D-lactic acid and L-lactic acid monomers. It is generally amorphous and degrades more quickly.
What Are The Properties Of PLA？
As a bio-based and biodegradable polymer, PLA stands out for its exceptional properties, including high tensile strength, excellent transparency, and the ability to degrade into natural substances under specific conditions.
Physical & Chemical Property
Property | Value |
Density（g/cm³） | 1.25-1.28 |
Melting Point（℃） | 176 |
Glass Transition Temperature（℃） | 60-65 |
Characteristic Viscosity（dL/g） | 0.2-8 |
Heat Transfer Coefficient(w/m·k) | 0.025 λ |
PLA is relatively stable at room temperature but easily degrades into carbon dioxide and water under high temperatures, acidic or alkaline conditions, and microbial activity.
Mechanical Property
PLA has a tensile strength of 40-60 MPa, an elongation at break of 4-10%, and a modulus of elasticity ranging from 3000 to 4000 MPa.
While PLA exhibits good strength, it lacks toughness and is prone to bending and deformation.
To enhance its mechanical properties, it is often blended with materials such as PBAT, PBS, PCL, or natural rubber.
Thermal Performance
Polylactic acid has good thermal stability, with a typical processing temperature range of 170–230°C.
It can be processed using various methods, including extrusion, spinning, biaxial stretching, and injection molding.
Optical Properties
PLA exhibits high transparency and gloss, making it particularly suitable for visual packaging.
Its transparency and gloss require minimal modification, ensuring excellent visibility and decorative effects for packaging applications.
Advantages of PLA
Here’s a summary of the advantages of PLA:
1.Environmental Friendliness: PLA plastic is biodegradable and can decompose into carbon dioxide and water under natural conditions, making it eco-friendly and free of environmental pollution.
2.Renewable Resources: Made from abundant and renewable plant-based resources like corn, PLA reduces dependence on non-renewable resources such as petroleum and wood.
3.Versatile Processing: PLA has excellent physical properties and is compatible with a wide range of processing methods, including blow molding and thermoplastic processing, enabling its application in diverse industries.
4.Biocompatibility: PLA’s degradation product, L-lactic acid, is metabolized by the human body, making it suitable for medical applications such as surgical sutures, injectable capsules, and implants, with FDA approval.
5.Barrier Properties: PLA films have excellent breathability, oxygen permeability, and odor barrier characteristics, along with strong antibacterial and antifungal properties.
Disadvantages of PLA
While PLA offers numerous benefits, it also comes with certain limitations:
- Brittleness: PLA is inherently brittle and lacks toughness, making it unsuitable for applications that require significant plastic deformation or high stretchability.
- Heat Sensitivity: PLA plastic is highly sensitive to temperature, softening and losing dimensional stability in high-temperature environments, which restricts its use in heat-resistant or precision-demanding fields.
- Degradation Challenges: Although biodegradable, PLA’s degradation process can be slow and difficult to control,
particularly in conditions with unsuitable temperature and humidity.
These limitations highlight the challenges of using PLA in applications that demand durability, heat resistance, or precise performance.
Processing Methods For PLA Materials
Through various processing methods, PLA can be transformed into diverse forms such as plastic products, filaments, and fibers.
Injection Molding
In PLA injection molding, modified PLA resin is typically used. The resin is melted in an injection molding machine and then injected into a mold where it cools and solidifies.
This method is highly suitable for producing items like containers, caps, and industrial components.
Extrusion
Extrusion is a common technique for manufacturing PLA products such as pla filament,film,and tube.
By heating PLA resin and forcing it through a die, continuous profiles or thin layers are formed efficiently.
Stretch Forming
PLA is first extruded into cast sheets and then stretched using biaxial stretching equipment to produce biaxially oriented PLA films.
These films offer excellent water vapor permeability and are highly effective for preserving the freshness of fruits and vegetables.
Spinning
PLA is dissolved in a solvent and processed through a spinning machine to create fibers.
This method is ideal for producing PLA-based fibers, non-woven fabrics, and other textile products.
These methods maximize the versatility of PLA, enabling its application across industries ranging from packaging to textiles.
Common Applications Of PLA
PLA products are widely used across various fields, including medicine, agriculture, food packaging, and 3D printing.
Textiles: PLA fibers are ideal for producing sportswear, casual clothing, school uniforms, and undergarments.
Packaging Materials: PLA is used for food packaging, biodegradable plastic bags, and food containers, offering eco-friendly alternatives to traditional materials.
Medical Industry: PLA’s biocompatibility makes it suitable for surgical sutures, tissue engineering scaffolds, and drug delivery systems.
Agricultural Sector: PLA-based biodegradable mulch films help maintain soil moisture and temperature while naturally degrading after use, eliminating the need for retrieval.
3D Printing: PLA 3D printing filament is widely used for creating models, prototypes, and functional components, making them a popular choice in desktop 3D printing manufacturing.
Is PLA Food Safe？
With the widespread application of PLA products, concerns about their safety have grown, leading to questions like “Is PLA food safe?” and “Is PLA toxic?”
In reality, PLA (Polylactic Acid) is safe when used under normal conditions and produced in compliance with regulations. PLA is a non-toxic polymer plastic with excellent biocompatibility and food-grade safety.
Its monomer, lactic acid, is a commonly used food additive that breaks down into glucose through glycolysis in the body, posing no harm to human health.
The U.S. Food and Drug Administration (FDA) has approved PLA for medical applications such as surgical sutures, injectable capsules, microspheres, and implants.
Additionally, PLA is fully biodegradable, breaking down into carbon dioxide and water through microbial activity in nature, leaving no environmental pollution.
This makes PLA an eco-friendly material with relatively low production energy consumption and a reduced carbon footprint.
Furthermore, PLA is the only biodegradable plastic with excellent antibacterial and antifungal properties, adding another layer of safety and versatility to its applications. These characteristics affirm that PLA is not only food safe but also an environmentally sustainable and non-toxic material.
Can PLA Plastic Be Recycled?
Yes, PLA plastic can be recycled, but the process differs from traditional plastic recycling due to its unique composition as a biodegradable material.
Here’s how PLA recycling works and its current advancements:
1.Hydrolytic Depolymerization
A white paper published by Total Corbion highlights that PLA can be depolymerized through hydrolysis to regenerate identical PLA resin.
The recycled PLA maintains the same quality and food-contact approval as the original material.
For example, Luminy rPLA grades contain 20% or 30% recycled content, derived from a mix of post-consumer and post-industrial PLA waste, with third-party certification provided by SCS Global Services.
2.Enzymatic Recycling
Researchers have developed innovative enzymatic methods to recycle PLA efficiently.
For example, scientists at King’s College London recently created a solution using an enzyme found in laundry detergents to chemically recycle PLA within 40 hours.
This technique is particularly useful for single-use items like coffee cups and food containers.
PLA plastic, as an eco-friendly material, plays a crucial role in environmental protection and resource conservation due to its recyclability.
By adopting appropriate recycling methods, we can achieve efficient utilization of PLA plastics, contributing to the sustainable development of our planet.
PLA vs PLA+
When comparing PLA vs PLA+, the two materials show significant differences in characteristics, application scenarios, and printing requirements.
PLA is one of the most widely used materials for 3D printing, known for its low melting temperature, excellent layer adhesion, and minimal odor.
However, it has some limitations, including brittleness and poor heat resistance, making it less suitable for high-temperature or high-load environments.
To address these drawbacks, manufacturers developed PLA+, a modified version of PLA that incorporates additives and modifiers to enhance its mechanical properties.
PLA+ offers superior strength and toughness compared to standard PLA, with higher tensile strength and reduced brittleness, making it more resistant to cracking under pressure.
Additionally, PLA+ requires a slightly higher printing temperature than PLA and exhibits better overhang performance, reducing stringing during printing.
These improvements make it a better choice for applications that demand greater flexibility and durability.
In terms of printing settings, PLA+ often necessitates a higher extrusion temperature, and specific settings may vary depending on the brand and formulation.
When deciding which material to use, consider your application needs. For example:
- PLA+ is ideal for models and decorative items requiring higher toughness and faster printing speeds.
- If you need better impact resistance, heat resistance, and chemical durability, PETG might be a more suitable option.
For a detailed comparison of PLA vs PETG and advice on choosing the right material for your application, check out our article, “PLA vs PETG” for more insights.
Conclusion
In conclusion, polylactic acid as an innovative biodegradable material, is rapidly becoming a popular choice in the injection molding companies.
Its excellent biodegradability, strong physical and mechanical properties, and wide range of applications make it a standout material for sustainable production.
If you’re looking to start a PLA injection molding project, contact FOWMOULD today!
We offer free quotes and provide professional injection molding solutions tailored to your needs.