Secret of Industrial 3D Printer Bed Temperature : Glass Transition Temperature

Glass transition can be defined as the transition of a material from a hard glassy state to a viscous, yet flexible state (or vice versa).


While passing the glass transition temperature, the molecule becomes a rubbery state that can only move little by little.

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If you look at the TDS (Technical Data Sheet) provided by the 3D printing material manufacturer, you can check the various physical properties of the material.

In the TDS, some of the physical properties included are the ultimate tensile strength, tensile modulus, and elongation at break. These properties were first investigated in our blog regarding the stress-strain curve.

In this blog, we will look at the glass transition temperature, which is one of the many other physical properties included in the TDS.

 

1. Glass Transition Temperature

Glass transition means the transition of a material from a hard glassy state to a viscous but flexible state (or vice versa).

In other words, think of when a hardened caramel candy turns into a chewy texture while one is chewing. 

In a similar manner, when a glass craftsman blows the hot softened glass with his mouth to create a shape, the glass transforms into a solid shape instantly,

Another scenario would be when you place a plastic object outdoors in the middle of winter, and it cracks or breaks.

All of these are examples to help comprehend glass transitions.

3D 프린터 소재 특징 유리 전이 온도

 

2. Glass Transition Temperature and Melting Point

When a solid crystalline substance is heated, the energy of the molecules increases, and when a certain temperature is reached, the heat breaks the bonds between the molecules and turns it into a liquid state.

We call this phase transition.

When the temperature reaches the melting point, the solid and liquid phases exist in equilibrium.

On the other hand, in the case of an non-crystalline material, there is no process of breaking the intermolecular crystal, and only the distance between the molecules gradually increases.

While passing the glass transition temperature, the molecule becomes a rubbery state that can move little by little.

3D 프린터 소재 특성 유리 전이 온도<Pure Crystalline Phase Transition and Pure Non-crystalline Glass Transition>

 

3. Non-crystalline and Crystalline Polymer

Each polymer with an non-crystalline structure has a unique glass transition temperature. 

The more complex the molecule of a polymer, the higher the molecular weight, the higher the glass transition temperature.

For example, if we compare PLA and ABS, the PLA molecular formula is [-C(CH3)HC(=O)O-]n, and ABS is  [(C8H8)x(C4H6)y(C3H3N)z]. So, ABS has a much more complex molecular structure.

The glass transition temperatures of both materials are 60 °C and 105 °C, respectively.

Pure crystalline polymers do not have a glass transition temperature.

Non-crystalline polymers and semi-crystalline polymers exhibit these properties.

Pure non-crystalline polymers don't have a melting temperature, they only have a glass transition temperature.

ABS, for example, does not indicate a melting temperature in its properties.

PLA has some crystallinity, and is classified as a semi-crystalline depending on the product.

In this case, the melting temperature is displayed.

 

4. The Meaning of Glass Transition Temperature in 3D Printing

So far, we have covered the glass transition temperature in detail.

So what does the glass transition temperature mean in terms of 3D printing?

For example, suppose that a part to be printed with a 3D printer is used in a 70℃ environment.

If the model is printed in PLA, the part will become rubbery in the environment of use and will not be able to maintain adequate strength.

Therefore, in this case, you need to print using the ABS material.

Readers who often used 3D printers may have noticed that the glass transition temperature of the print material and the bed temperature, at the time of printing, are similar.

Material ABS PLA
Glass Transition Temperature 105℃ 60℃

Bed Temperature (Weaver3 Studio)

80℃ 50℃
<Bed temperature is about 70~80% of Glass Transition Temperature.>

 

The reasons for keeping the bed temperature close to the glass transition temperature are as followed:

When the molten material is applied to the bedplate, it should not cool instantly, so that it  can properly adhere well to the next layer, ensuring that the printing success rate is high.

Also, it helps to prevents warping of the first layer.

 

In this blog, we have investigated the glass transition temperature, one of the major physical properties of 3D printing materials.

We hope that this information will help you choose the right material by analyzing the environment of use and the glass transition temperature of the material.

See you next time with more useful content.

Thanks.  


 

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