Since each type of filament is essentially a unique thermoplastic with a unique chemical composition that grants it a separate set of qualities, how well your 3D printed models perform in specific scenarios depends entirely on the filament you picked for the task.
As a result, whenever these qualities, such as the strength of the component you’re printing, are essential points of consideration for the print to serve its purpose correctly, appropriate filament selection becomes the first step to a successful 3D printing process.
In today’s article, our topic will be the ultraviolet and temperature resistance capabilities of PLA filament, in particular, which are especially vital factors to consider for prints that you are planning on using outdoors, where the plastic will both be exposed to heat and ultraviolet rays at once in a frequent and consistent basis.
So, how temperature resistant and UV resistant is PLA filament?
With a glass transition temperature of 60 degrees Celsius at most (it can be lower depending on the brand of the filament), we can consider PLA one of the worst options for projects where heat resistance is crucial.
While the structural degradation caused by UV rays won’t be as quick as the damage caused by heat, PLA is not exactly fantastic in terms of UV resistance either, with most 3D printed models getting discolored in a short amount of time.
Next up, we will discuss the temperature resistance and UV resistance capabilities of PLA in more detail, find out how to make PLA more temperature resistant when the situation calls for it, and finally, go through some PLA alternatives that are better in the heat resistance and UV resistance departments.
How Temperature (Heat) Resistant is PLA Filament?
Heat resistance is, without a doubt, one of the essential factors to consider when choosing the filament you will be printing with, as exposure to heat can definitely cause some damage to the structural integrity of your 3D printed models in some scenarios.
When you look at the specifications of a spool of PLA filament that you’ve bought, you will notice that there are two different temperatures mentioned, which are the printing temperature and the bed temperature.
Between the two, the printing temperature of the filament is primarily based on the melting point of PLA, which is the point where PLA will completely liquefy and be able to flow out of the nozzle freely.
On the other hand, the suggested bed temperature value is based on the glass transition temperature of PLA, which we can describe as the point where PLA will start losing its structural integrity, presenting itself in the form of softening and deforming of the plastic.
From this, we can conclude that the heat resistance capabilities of a filament are practically based on its glass transition temperature, which, in the case of PLA, is usually 60 degrees Celsius at most, with the figure showing slight differences depending on the material composition chosen by the brand.
Even though 60°C is a fairly high temperature when we think about it, this figure actually ranks PLA as the least-heat resistant filament option, meaning that PLA is not exactly a suitable option for projects where the component will specifically be utilized in high-heat environments.
How UV (Ultraviolet) Resistant is PLA?
The ultraviolet resistance of the filament primarily becomes essential in scenarios where your 3D printed model will be exposed to the sun, as ultraviolet rays, like heat, can cause damage to your 3D printed model and cause it to deform.
UV resistance is a factor where PLA falls quite short, as it’s susceptible to both short-term and long-term degradation as a result of consistent exposure to ultraviolet rays coming from the sun.
The short-term degradation due to UV exposure will present itself in the form of discoloration, where you will notice that the color of your PLA 3D printed model has faded or even thoroughly washed out in a relatively short period (<1 month).
Please note that the period can show some variance depending on the weather conditions and the brand of PLA used.
On the other hand, long-term degradation, which will most likely take up to multiple years, will cause the PLA to become weak and brittle, causing it to crack or even entirely break off when a slight amount of force is applied.
With these two points in consideration, even though PLA is one of the worst choices regarding UV resistance, we can conclude that it should be possible to use PLA for short-term projects where discoloration is not a problem or is remedied through post-processing, as the structural damage that UV exposure causes will at least take a couple of years.
What Are Some More Temperature (Heat) & UV (Ultraviolet) Resistant Alternatives to PLA?
As it’s no secret that PLA isn’t the best option when it comes to factors such as temperature resistance and ultraviolet resistance, opting for an alternative whenever these two qualities are vital is our primary recommendation.
ASA is, without a doubt, the first filament type that comes to mind regarding both temperature and ultraviolet resistance, with glass transition temperatures that go all the way up to 110 degrees Celsius and the capability not to suffer any structural damage from long-term UV exposure.
If you don’t have access to ASA or the necessary hardware to print with it, ABS is a fantastic choice that can offer the same heat resistance as ASA (but without the UV resistance, as ABS will eventually face UV degradation), while PETG can offer UV resistance that is comparable to ASA but with less resistance to heat (~90 degrees Celsius glass transition temperature).
How to Make PLA More Temperature (Heat) Resistant?
While switching to a more temperature-resistant filament would usually be the most straightforward way, in cases where your only option is PLA, and you need the heat resistance to be higher than it is, there are some methods you can follow to improve the heat resistance capabilities of PLA.
It’s possible to make PLA more temperature resistant (and also physically stronger) by applying a process known as annealing, where the 3D printed model is exposed to temperatures above the glass transition temperature of PLA for a particular amount of time, which causes the molecular structure of PLA to take a more crystalline form.
On the other hand, the annealing process is not without downsides, as exposing the plastic to temperatures that are higher than its glass transition temperature will cause it to lose its structural integrity and start deforming, which can end up with a significant loss of visual quality depending on the temperature and the amount of time used.
If you would like to anneal PLA and increase its heat resistance without the downsides that come with it, you will need to purchase high-temperature PLA instead, which is a particular type of PLA that is specifically designed and manufactured for the purposes of undergoing heat treatment.
While it may not matter too much for 3D printed models with decorative purposes, especially if you are planning to use them indoors exclusively, there are many scenarios where the temperature and the ultraviolet resistance capabilities of the filament come into play and become a point of consideration.
To quickly recap, we can consider PLA largely unsuitable for usage in cases where resistance to high temperatures is required, as its low glass transition temperature (~60°C) makes it highly susceptible to deformation due to heat exposure.
Unfortunately, PLA isn’t a type of filament that does well regarding UV resistance either, as long-term exposure to ultraviolet rays will slowly cause PLA to degrade and lose its structural integrity, and short-term exposure will most likely end up with the model becoming discolored.
While annealing PLA can indeed increase its temperature resistance by a considerable margin, especially when high-temperature PLA is used, opting for a type of filament that is more resistant to both temperature and UV is definitely a better idea for projects that will consistently be exposed to high heat and ultraviolet rays.
Mike started his 3D printing journey with the Anet A8 when it first came out back in 2017, and has been obsessed with 3D printers ever since. Nowadays, he primarily uses his Ender 3 to print functional parts that make his life more convenient whenever possible.