Ethan Clarke
Plastic deformation is an irreversible process in which an object changes its size or shape due to an applied force. It is important to note that even after the removal of the applied force, the deformation remains. This is in contrast to elastic deformation, where the object recovers its original dimensions after the load is removed. Plastic deformation involves the breaking of atomic bonds and the movement of dislocations within the material. The malleability and ductility of a material are factors that contribute to its propensity for plastic deformation. In the context of PLA (polylactic acid), a common material used in 3D printing, there are certain limitations when it comes to plastic deformation. PLA exhibits brittleness and limited elongation at break, which restricts its use in applications that require significant plastic deformation under high-stress conditions. However, efforts are being made to enhance the mechanical properties of PLA, including treatments such as annealing and the addition of nucleating agents, to improve its performance and increase its applicability in various fields.
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What You'll Learn
PLA softens at 70°C
Plastic deformation is an irreversible process where an object changes size or shape due to an applied force. It can be observed in objects made from materials such as steel or plastic. Plastic deformation can occur through various mechanisms, including slip, twinning, and thermoelastic deformation (creep). Thermoelastic deformation involves a change in material dimensions with temperature changes, with the material behaving elastically at low temperatures and more plastically at higher temperatures.
Polylactic acid (PLA) is a common 3D printing material that is not very heat-resistant. Untreated PLA typically begins to soften around 60°C to 65°C, with a glass transition temperature range of 140°F to 150°F. At temperatures above 60°C, PLA will start to warp, shrink, and bend under stress.
To improve the heat resistance and strength of PLA, a process called annealing can be used. Annealing involves gradually exposing the PLA to controlled levels of heat, allowing the molecular structure to rearrange and become stronger. While annealing can improve the characteristics of PLA, it can also cause shape and dimensional changes. For example, when annealed at 70°C, PLA undergoes significant dimensional changes, including shrinkage along the X and Y axes and extension along the Z axis. At higher temperatures, PLA will experience warping, and at 170°C, it will completely melt.
Therefore, while PLA softens at temperatures above 60°C, annealing can be employed to enhance its heat resistance and overall strength. However, the trade-off is that annealing can lead to shape and size alterations, requiring careful consideration when working with PLA.
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PLA is used in 3D printing
PLA, or polylactic acid, is a popular material used in 3D printing. It is a thermoplastic polymer with high strength and modulus, and it is known for its excellent biodegradability. Being made from common crops like cassava and corn, it is environmentally friendly and helps reduce CO2 emissions during production, digestion, or composting. This makes PLA an attractive material for those seeking to minimize their environmental footprint.
One of the advantages of using PLA in 3D printing is its ease of use. It is user-friendly, with minimal warp issues, and offers a wide range of styles and color options to choose from. This versatility makes it a popular choice for beginners in 3D printing, as it prints with minimal issues and is cost-effective. The low viscosity of PLA ensures an appropriate flow rate, making it ideal for extrusion-based printing methods.
Another benefit of PLA is its ability to create highly detailed prints. This level of detail is particularly useful in fields such as architecture, where companies like Killa Design use PLA to create to-scale models of their architectural designs. These models can then be used to explain complex concepts to clients or for educational projects. Additionally, in the medical field, 3D-printed PLA models can be used to explain procedures to patients or to train doctors.
Despite its advantages, PLA has some limitations when used in 3D printing. One of its main disadvantages is its lack of durability and impact resistance. While PLA projects can last a long time when not exposed to wear and tear, they are prone to breaking under stress or pressure, which is known as plastic deformation. This makes PLA less suitable for applications that require strength and impact resistance. Additionally, PLA has poor dimensional stability, and its low melting point can be a concern in certain environments.
Overall, PLA is a widely used material in 3D printing due to its ease of use, versatility, and biodegradability. While it may not be suitable for applications requiring high durability or impact resistance, it is perfect for creating detailed prototypes, models, and visual aids across various industries, including architecture and medicine.
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PLA is very brittle
PLA, or polylactic acid, is a popular material used in 3D printing for its ease of use, aesthetic detail, and affordability. However, one common issue with PLA is its tendency to become brittle. Brittle PLA can be extremely frustrating to deal with, often resulting in failed prints and wasted material.
Brittleness in PLA is primarily caused by exposure to humidity and moisture. When exposed to air, PLA can absorb moisture, leading to a degradation in its mechanical properties. This results in a reduced ability to withstand stress and an increased tendency to crack or break. The presence of moisture can also cause printing issues, such as underextrusion and oozing, further contributing to the brittleness of the material.
To prevent PLA from becoming brittle, proper storage is essential. PLA should be stored in a dry environment, away from moisture, and kept in an airtight container. Desiccants can also be used to absorb any residual moisture in the air or within the filament itself. Additionally, it is recommended to use the filament promptly after opening, as prolonged exposure to air can increase the risk of moisture absorption.
Another factor contributing to PLA brittleness is age. Over time, PLA can become more brittle, even if properly stored. This ageing process may be accelerated by exposure to light, particularly UV light, which can cause degradation and increase the material's fragility. Therefore, it is advisable to use PLA filament within a reasonable timeframe and to protect it from prolonged light exposure.
While good-quality filaments from reputable manufacturers may be more resistant to brittleness, even the best filaments are susceptible to moisture-related issues over time. As such, it is crucial to prioritize proper storage and handling to minimize the chances of PLA becoming brittle and affecting the quality of 3D printing projects.
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PLA is used in medical implants
Polylactic acid (PLA) is a biopolymer that is widely used in medical implants. It is a versatile material that can be easily synthesized from abundant renewable resources and is biodegradable. PLA has been used in various healthcare applications, including tissue engineering, regenerative medicine, cardiovascular implants, dental niches, drug carriers, orthopedic interventions, cancer therapy, skin and tendon healing, and medical tools/equipment.
One of the key advantages of using PLA in medical implants is its biocompatibility. PLA has favourable biocompatibility properties, which means it can safely coexist with biological systems. When PLA comes into contact with biological media, it begins to break down into lactic acid (LA) or carbon dioxide and water through hydrolysis. These degradation products are safe and well-tolerated by the body, as they can be metabolized intracellularly or excreted in urine and breath. This makes PLA an ideal material for implantable devices, as it can be tailored to different therapeutic needs and safely degraded by the body over time.
The biodegradation of PLA can be tuned to specific requirements by adjusting the molecular composition and physical architecture of the device. For example, using L- or D- chirality of LA can slow down or lengthen the degradation rates, respectively. This tunability allows for greater control over the performance and longevity of medical implants made from PLA.
Another advantage of PLA in medical implants is its 3D printability. As a 3D-printable biopolymer, PLA has been instrumental during the COVID-19 pandemic in creating much-needed personal protective equipment (PPE) and ventilator modifications. The ability to 3D print PLA expands its potential in the healthcare industry, allowing for the rapid prototyping and customization of medical implants and equipment.
However, there are some considerations to keep in mind when using PLA in medical implants. One potential issue is the low-temperature performance of PLA. Raising the temperature of a PLA object to 160°F (70°C) can soften it significantly, which could lead to failure under constant stress or pressure. Therefore, the temperature sensitivity of PLA should be carefully considered when designing and using PLA-based implants.
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PLA degrades slowly in landfills
Plastic deformation is an irreversible process in which an object changes its size or shape due to an applied force. This occurs when the force required to break the atomic bonds in a crystal plane is exceeded. The property of a material to undergo deformation under pressure is known as plasticity, and it is a characteristic of plastic materials, particularly their molding and altering capacity.
Polylactic acid (PLA), a popular bioplastic, is known for its ability to undergo plastic deformation. Raising the temperature of a PLA object can soften it, and it has been observed that PLA will degrade slowly in the sea, lasting only a few years. While PLA can break down, this process requires very specific conditions. It is often claimed that PLA is biodegradable, but this is not entirely accurate. PLA is only biodegradable under industrial composting conditions and anaerobic digestion. In reality, most 3D printing waste ends up in landfills, where there is no evidence of PLA being biodegradable.
The slow degradation of PLA in landfills is a significant concern. While PLA does eventually degrade, the process can take a long time, and during this period, the plastic can negatively impact the environment. Additionally, the degradation of PLA in landfills can lead to the production of methane, a potent greenhouse gas. This issue has been addressed through the development of recycled PLA filaments, which aim to divert materials from landfills and promote sustainability.
PLA's limited biodegradability presents a challenge, and recycling offers a viable alternative. Some companies recycle PLA waste into new products or 100% recycled filament, contributing to a circular economy. However, access to recycling facilities may be limited, and regular recycling programs typically do not accept PLA.
To summarize, while PLA is technically biodegradable, it does not readily degrade in landfills. The slow degradation process and the environmental impact of PLA waste highlight the importance of proper recycling and the development of more sustainable practices in the 3D printing industry.
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Frequently asked questions
Plastic deformation is when an object changes size or shape due to an applied force, and this change is irreversible.
Plastic deformation is caused by the breaking of a limited number of atomic bonds by the movement of dislocations.
Elastic deformation occurs when a material recovers its original dimensions after being deformed, whereas plastic deformation is irreversible.
As temperature increases, materials tend to behave more plastically and can undergo thermoelastic deformation, which involves a change in material dimensions.
PLA is a type of plastic that can undergo plastic deformation, but its ability to deform at high stress levels is limited due to its brittleness. Efforts are being made to improve its mechanical properties.
