Table of Contents
Polylactide (PLA) - Sustainable specialty plastic with future potential
Polylactide (PLA) is becoming increasingly important in the plastics industry and is regarded as a pioneering alternative to fossil-based plastics. As a bio-based polyester, PLA is produced from lactic acid, which is mainly obtained from renewable raw materials such as corn starch or sugar cane (1). Its particular importance lies not only in its sustainable production, but also in its wide range of possible applications, from packaging to special technical applications.
Compared to petroleum-based plastics, PLA has a significantly lower carbon footprint, as the plants already bind CO₂ during their growth, which is released again during subsequent disposal (1). This CO₂ neutrality makes PLA an important building block for a sustainable plastics industry. Forecasts show a significant increase in the production capacities of bioplastics such as PLA by 2028, with growth rates of up to 13% per year (2).
Material science basics and types of PLA
Basic thermal properties
PLA has characteristic thermal properties that define its possible applications. The glass transition temperature is around 55-65 °C, which ensures dimensional stability at moderate temperatures. The melting point varies between 150-180 °C depending on crystallinity, with typical processing temperatures of 180-220 °C.
The crystallinity of PLA is a decisive factor for the mechanical properties and can vary between 0-45 % crystalline content. Amorphous PLA is transparent and more flexible, while semi-crystalline PLA has higher strength and improved thermal stability. As PLA is slow to crystallize, nucleating agents (e.g. talc or zinc oxide) are often used during processing to achieve the desired crystal structure.
Types and variants of PLA
The diversity of PLA is reflected in various commercially available types:
Basic types according to stereochemistry:
- PLLA/PDLA (poly-L- and poly-D-lactide): Both forms differ in their molecular handedness (chirality). D- and L-lactic acid are mirror-image variants of the same molecule. Their combination can form so-called stereo complexes, which have a higher thermal stability.
- PDLLA (poly-D,L-lactide): Amorphous, more flexible, often used for medical applications.
Functional variants:
- High-temperature PLA: Improved heat resistance up to approx. 100 °C.
- Transparent PLA: Optimized for high clarity.
- Filled PLA: Reinforced with wood fibers, minerals or carbon fibers.
Copolymers and blends:
- PLA/PBAT blends: Improved flexibility and degradability.
- PLA/PHA copolymers: Optimized marine degradability.
- Block copolymers: Properties can be specifically adjusted without additives.
Technical properties and resistance
Mechanical and thermal properties
PLA impresses with its outstanding rigidity and dimensionally stable properties up to a glass transition temperature of around 55-65 °C. The technical characteristics make PLA interesting for many special applications, but also show clear limitations. The tensile strength is 50-70 MPa, the modulus of elasticity 3-4 GPa, which makes PLA a good choice for applications that require a stable geometry.
Positive technical features:
- High tensile strength (50-70 MPa) and modulus of elasticity (3-4 GPa)
- Dimensional stability up to the glass transition temperature (55-65 °C)
- Good surface hardness and scratch resistance
- Flame retardant (LOI > 26 %): A key positive property that makes PLA clearly preferable to other biopolymers such as polyhydroxybutyrate (PHB) or polyacetate.
- Excellent surface quality and transparency
Stabilities and limitations
The chemical resistance of PLA to many media is good, but shows specific weaknesses. PLA is resistant to alcohols, oils and weak acids, but is sensitive to strong bases and concentrated acids, which can cause hydrolysis of the ester bonds.
UV resistance:
PLA has moderate UV stability, which can be significantly improved with suitable additives. UV absorbers such as benzotriazoles or benzophenones as well as stabilizers based on hindered amine light stabilizers (HALS) are often used to prevent yellowing and loss of properties during prolonged exposure to sunlight. Without such additives, PLA tends to yellow and become brittle when exposed to UV light.
Mechanical resistance:
The continuous service temperature is around 50 °C. Above the glass transition temperature, there is a significant loss of strength.
Technical limitations:
- Low impact strength (2-5 kJ/m²) and brittleness at room temperature
- Moderate heat resistance (above 60 °C problematic without modification)
- Sensitivity to hydrolysis at high humidity and elevated temperatures
- Limited UV and chemical resistance under continuous load
- Creep tendency under long-term stress
However, its low impact strength and moderate thermal stability set limits: Standard PLA is not suitable for highly stressed or thermally intensive applications above 60 °C. Even above the glass transition temperature, the material begins to deform or loses its dimensional stability.
Sustainability comparison: PLA versus fossil plastics
The sustainability of PLA in direct comparison to conventional plastics shows clear advantages, but also specific challenges. The production of PLA requires
Key sustainability benefits of PLA:
- Renewable raw material base from maize or sugar cane
- Reduced energy requirement in production by 25-68% (due to lower processing temperatures and bio-based raw material extraction)
- Smaller CO₂ footprint due to CO₂ absorption by plants during growth
- Biodegradability under industrial composting conditions
Challenges and limitations:
- Land and water consumption for raw material production
- Potential competition with food production
- Mining only under optimal industrial conditions
- Significantly slower decomposition process in home compost or in nature
A key feature of sustainability is its biodegradability in accordance with DIN EN 13432. Under optimal industrial conditions, PLA decomposes into water, carbon dioxide and biomass within a few months. However, the actual decomposition depends heavily on temperature, humidity and microbial activity – it is much slower in home compost or in the wild.
Innovation potential and further development
The further development of PLA offers far-reaching opportunities for the specialty plastics industry. Modern processes such as reactive extrusion and innovative block copolymers are opening up new fields of application – such as flexible films for packaging, additive manufacturing or textiles (3). Specific blends and copolymers with other biopolymers make it possible to control the properties of PLA in a targeted manner.
Innovative synthesis technologies can further improve the properties of bio-based plastics. For example, block copolymers are used to create a more flexible and recyclable PLA film material without the addition of plasticizers (4). New PLA types enable processing on standard industrial machines, which makes it easier for SMEs to enter production.
Development approaches for improved PLA properties:
- Block copolymers for increased flexibility and impact strength
- Blends with other biopolymers (PBAT, PHA, PBS)
- Additives to improve heat resistance and UV stability
- Wood-polymer composites for special applications
- Optimized recyclability and circular economy
- Nucleating agent for controlled crystallization
The combination with natural fibers and the use of alternative bio-based polymers enable solutions for special applications that were previously difficult to substitute. Advances in chemical and mechanical recycling make recyclable use realistic, especially in the case of PLA, which can be recycled with less energy input (5).
Typical applications and market opportunities
PLA has established itself in numerous branches of industry and is considered one of the most versatile bio-based plastics. The largest market segment is the packaging industry, where PLA is widely used due to its transparency, dimensional stability and compostability. Typical applications include food packaging such as films, cups and trays, as well as disposable tableware, flexible packaging, labels and pressure-sensitive adhesive solutions.
Another rapidly growing field is 3D printing . Here, PLA impresses with its ease of processing, good dimensional stability and low shrinkage. It is used in prototype construction, for design objects, architectural models and in the education sector and by hobby users. Functional components with moderate mechanical and thermal requirements can also be reliably produced from PLA.
PLA is also widely used in medical technology and pharmaceuticals due to its biocompatibility and degradability. Examples include resorbable implants and screws, surgical sutures, wound closures, disposable devices and drug capsules as part of drug delivery systems.
In addition to these established markets, new areas of application are increasingly emerging. In the automotive industry, PLA-based materials for interior trim, decorative parts, upholstery and temporary components are being tested in the manufacturing process. PLA is also gaining importance in the electronics and consumer goods sector – for example for appliance housings, toys, household items or sports and leisure products, as long as they are not exposed to high temperatures.
In the textile sector, PLA is processed into nonwovens, technical textiles, filter materials and blended fibers for clothing. Its bio-based origin and compostability make it particularly attractive for applications with a limited useful life.
The social acceptance of sustainable materials and increasingly strict regulatory requirements are promoting the use of PLA in many industries. Accordingly, the market share of bio-based polymers is growing continuously – not only in the packaging sector, but increasingly also in technical and durable applications.
Conclusion
PLA is positioning itself as a sustainable and technically versatile alternative to traditional plastics in the specialty plastics industry. The advantages lie in its bio-based production, reduced carbon footprint and biodegradability under industrial conditions. With 25-68% lower fossil energy requirements and significantly lower greenhouse gas emissions, PLA offers clear sustainability benefits.
The technical properties with a glass transition temperature of 55-65°C and a melting point of 150-180°C make PLA suitable for many applications, but also show defined limits. The limited thermal stability and restricted impact strength limit its use in highly stressed or thermally intensive applications. Nevertheless, innovative developments such as block copolymers, functional blends and the large diversity of available PLA types open up new possibilities for targeted property improvements.
The different PLA variants, from highly crystalline PLLA to flexible copolymers, enable a wide range of typical applications from packaging to medical technology and technical components. The continuous improvement of chemical, UV and mechanical resistance through additives and modifications is constantly expanding the range of applications.
Market forecasts with annual growth rates of up to 13% until 2028 underline the potential of PLA. For the future, it is crucial that the circular economy is optimized and raw material production is sustainable. PLA is therefore on the threshold of a sustainable plastics industry – efficient and versatile, but still with relevant system limits in terms of degradability and long-term stability.
List of sources
(1) Pack-Verde: Materials science – PLA
(2) Bayern Innovativ: Future vision of bioplastics as the key to sustainability –
(3) University of Stuttgart: Polylactide development
https://elib.uni-stuttgart.de/bitstreams/db9dbe4a-21bf-47bb-b9af-83947b161a24/download
(4) Haute innovation: PLA film material
https://www.haute-innovation.com/magazin/nachhaltigkeit/pla-folienmaterial/
(5) Innovation Report: Bio-based plastics
