PLA 3D Printing: Does Filament Colour Change Strength?

When choosing filament for 3D printing, it is easy to assume that different colours of the same PLA material will have identical mechanical properties. A study by Adi Pandžić, PhD tested that assumption by measuring the tensile properties of FDM-printed specimens. The results show differences among the colours tested, although the experiment does not identify what caused them.

Key findings

• The study tested 14 colours of PLA filament from the same manufacturer, with three specimens per colour and 42 specimens in total.
• Elastic modulus ranged from 2719 MPa to 3217 MPa. Red had the highest value and pink the lowest.
• Yield strength ranged from 30 MPa to 41 MPa, while ultimate tensile strength ranged from 35 MPa to 46 MPa. Red gave the highest and pink the lowest values for both measures.
• Toughness ranged from 10 J to 48 J: blue had the lowest result and pink the highest.
• Strain ranged from 7% to 108%. Pink reached 108%, while brown was reported at 35%.
• The paper reports that colour was associated with differences in the measured tensile properties, but the experiment covers only this filament and these printing conditions.

Why test the colour of PLA filament?

Fused deposition modelling, or FDM, is a widely used additive manufacturing process. A 3D printer heats thermoplastic filament and deposits it layer by layer. PLA, or polylactic acid, is a popular filament available in many colours. When a manufacturer lists the same properties for every colour, users may assume that changing colour affects only the appearance of a finished part.

That assumption matters in product development, education and prototyping, where a printed component may need to carry a load as well as meet a visual brief. Mechanical properties can matter alongside colour choice. However, an experiment on one particular filament can only describe how that material performed under the tested conditions. It does not establish that every PLA brand, batch or colour behaves in the same way.

What the study tested

The study used PLA filament from 3D Republika, with a stated diameter of 2.85 mm. The paper lists 14 selected colours: green, blue, white, orange, pink (magenta), red, gold, grey, silver, glow in the dark (GD), yellow, black, brown and purple. Three specimens were made for each colour. The study focused on tensile properties and prepared the specimens according to ISO 527-2.

The specimens were printed on an Ultimaker 2+ 3D printer. G-code was prepared using Cura 4.0.0. All specimens used 100% infill, meaning the model interior was fully filled according to the selected print setting. The print orientation was flat, with a 45° raster angle. Layer height was 0.15 mm, wall thickness 0.7 mm, print speed 60 mm/s, printing temperature 200 °C and build plate temperature 60 °C. The nozzle diameter was 0.4 mm.

Tensile testing was conducted on a Shimadzu AGS-X machine with a capacity of 100 kN, at a test speed of 1 mm/min. Tensile strength describes the stress a material withstands while being pulled, while elastic modulus describes its stiffness in the elastic region. The study recorded elastic modulus, yield strength, ultimate tensile strength, toughness and strain. Toughness was calculated as the area under each stress–strain curve.

What the results show

The red PLA specimens had the highest elastic modulus, 3217 MPa, while pink had the lowest, 2719 MPa. The paper reports that elastic modulus varied by up to 18%, depending on colour. Yield strength ranged from 30 MPa to 41 MPa, and ultimate tensile strength ranged from 35 MPa to 46 MPa. Red was at the top of both ranges and pink at the bottom. The paper reports differences of up to 36% for yield strength and up to 31% for ultimate tensile strength.

Toughness showed a different ranking. Blue had the lowest value, 10 J, and pink the highest, 48 J. The paper particularly notes the influence of yellow, purple, GD and pink on toughness. For strain, the paper describes pink and brown as having the most pronounced results: pink reached 108% and brown was reported at 35%. The overall range given in the conclusion is 7% to 108%.

These results do not point to one universally “best” colour. Red had the highest measured elastic modulus, yield strength and ultimate tensile strength. Pink had the highest toughness and strain, but the lowest modulus and strength values within the reported ranges. Which result matters most depends on the property relevant to the part being designed.

What the findings mean in practice

For engineers and product designers, the study is a reason not to assume that colour has no connection to the measured tensile properties of PLA. If mechanical performance matters, testing the specific filament colour intended for use may be worthwhile, using the same print settings and specimen geometry. The red and pink results also show why a single number is not enough to describe how a material performs: different properties can change in different directions.

For students, the experiment demonstrates how researchers can control conditions when comparing materials: one manufacturer and filament type, the same printer and settings, a defined print orientation and a standardised specimen shape. This makes it possible to focus on the question of colour rather than deliberately changing variables such as layer height, temperature or infill density. The paper does not test SLA printing or other materials, so its conclusions should not be transferred directly to those processes or materials.

Limitations and next steps

The study tested three specimens for each colour. The paper does not provide detailed statistics describing result variation or tests of statistical significance. The results should therefore be understood as findings from this experiment, not universal specifications for PLA colours. The study used filament from one manufacturer and examined tensile properties with one set of printing parameters. It did not analyse pigment composition, so the results do not explain why the measured values varied among colours.

The paper suggests future studies examine other mechanical properties, including bending, hardness and compression, and investigate colour effects in other materials, including ABS and PET.

Conclusion

Published in the Proceedings of the 30th DAAAM International Symposium on Intelligent Manufacturing and Automation in 2019, this study found differences in tensile properties among 14 colours of the PLA filament tested. The reported ranges included tensile strength from 35 MPa to 46 MPa, elastic modulus from 2719 MPa to 3217 MPa, toughness from 10 J to 48 J and strain from 7% to 108%. For practical filament selection, the findings make colour worth considering when mechanical behaviour matters, while keeping in mind that they apply to the material and printing conditions in this study.

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Author: Adi Pandžić, PhD in Mechanical Engineering

This article summarises a published research paper; please refer to and cite the original paper. About the author

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