Heat resistance of PLA

Hi all

Just idle musings really - I don't have a 3D printer, but I have a friend who has a friend who does - and was wondering how standard PLA prints cope with hot water, up to boiling temps to be on the safe side? From what I've read, it seems PLA is slightly absorbent(?) but to what extent? For example, If I had a PLA printed cup permanently full of room temperature water, how long would it last? And how long with boiling water? Minutes, days, years?

Would other printable materials be better in relation to water?

No specific project in mind, just trying to learn more about the capabiities.

Thanks for any advice/thoughts on the matter,

Rob

The 'glass transition' temperature of PLA is between 60 and 80 degC. This is not the melting temperature but that where it begins to soften. The printer heated bed is often set to around the transition temperature to maintain a better degree of adhesion 'stickyness'. So basically your cup will remain solid below 50degC but start to distort at 70degC.

Nothing to do with temperature but it is unlikely that a printed cup would actually retain water for long due to slight voids in the material between layers and at joins where the layer steps up.

I can also state that PETG is not microwave proof. I put some silica gel crystals in a 3D printed box to rejuvenate them using the microwave. The box distorted presumably due to the heat of the steam liberated from the silica gel. Again the glass transition temperature is way below the 220degC melting point.

For more info see *** Article on All3DP ***

John

Edited By Journeyman on 16/11/2021 16:18:28

I printed some cookie cutters for the grandkids. They did not survive the dishwasher. (cookie cutters, not the Grandkids!)

I printed some kitchen knife handles in PLA, they last about two months of dishwasher abuse. Some bend slightly and some split - but strangely it's not delamination; the cracks are perpendicular to the laminations.

I tested pieces in a dishwasher.

They survived an economy wash but at 65 degrees they showed distortion.

On the other hand outdoor aerial parts have lasted years. Black is supposed to be best for outdoors because it has more UV resistance..

Neil

Edited By Neil Wyatt on 16/11/2021 16:56:30

I printed a replacement coffee percolator lid in PLA and annealed it overnight in an oven at 110C, which allowed it to then easily withstand the boiling water/coffee in use. It failed a couple of years later, but from a drop rather than from delamination.

Andrew.

Thanks everyone, very informative

Rob

As stated, heat treating PLA (referred to colloquially as 'annealing' will both:

1. significantly strengthen the PLA part
2. make it temperature stable up to about 120c (ie as good as ABS)

But it needs to be done relatively carefully to avoid warping or distorting the part. I use one of the small consumer bench top ovens that I removed the top element from. I also recalibrated the temp control using a temperature probe on the middle shelf (ie where the item to be heat treated is placed) to have a more accurate indication of actual part temperature.

The best results I found are obtained by bringing the part up to to 60c, 80c, then 100c in one hour for each stage, and then back down in one hour stages. There can be very slight shrinkage on X and Y axis that may affect larger parts.

I would like to be able to rig up some sort of programmed PID control to do avoid having to do the settings manually but haven't been able to figure it out!

If you go down the same route, try to get a circulating oven if they make them - the internal temperature will be much more even.

Thanks for the info about annealing, I'll try it with my knife handles.