The 3D printing industry has a dirty little secret. Most resins and inks used today come from petrochemical sources, and many contain toxic acrylic compounds that aren’t great for the environment or the people handling them. For an industry built on creating things layer by layer, the raw materials tell a different story.
But that might be changing.
A team of researchers has been working on something that sounds almost too neat: a fully biodegradable polyester synthesized from renewable plant-derived building blocks, designed for 3D printing applications. No toxic solvents. No catalysts. Just chemistry that tries to play nice with the planet.
The Problem with Current 3D Printing Materials
Most UV-curable resins in 3D printing rely on acrylic compounds. They work well, but they come from petroleum and have toxicity concerns. In medical applications, where 3D printing is making real strides, that’s a problem.
The core challenge is finding something that works as well without the environmental baggage. Enter itaconic acid.
Why Itaconic Acid Is a Big Deal
Itaconic acid is an unsaturated dicarboxylic acid produced through fermentation. Think fungi like Aspergillus terreus munching on carbohydrates to produce something genuinely useful. The US Department of Energy lists it as one of the twelve most valuable platform chemicals from biomass.
What makes it special is the C=C double bond hanging off its side chain. That bond means the material can be UV-cured after printing, exactly what you need for many additive manufacturing techniques. Itaconic compounds are non-toxic, biodegradable, and have even shown antibacterial and anticancer properties.
But working with itaconic acid alone isn’t straightforward. The polymerization reaction tends to hit a wall, and unwanted side reactions isomerization into less reactive forms and premature radical polymerization mess things up.
The Smart Fix: Adding Succinic Anhydride
The researchers brought in succinic anhydride as a co-monomer. It is also renewable produced through microbial fermentation and serves a dual purpose: it helps the reaction proceed more efficiently and reduces the crosslinking problems that plague itaconic-only systems.
Combine that with 1,8-octanediol the longest water-soluble aliphatic diol, already used in medical applications and you get poly(octamethylene itaconate-co-succinate), or POItcSc. A mouthful, but the chemistry works.
Getting the Conditions Right: The Box-Behnken Approach
Rather than running endless trial-and-error experiments, the team used a statistical design method called Box-Behnken to find the optimal synthesis conditions with just 15 experiments.
They looked at three variables:
- The molar ratio of itaconic acid to succinic anhydride
- Reaction time
- Reaction temperature
And they measured three outputs: how many carboxyl groups converted to ester bonds (the measure of reaction completeness), how many C=C double bonds survived the process (critical for later UV curing), and a combined score for viscosity, visual quality, and utility.
The optimal recipe turned out to be a 50:50 split between itaconic acid and succinic anhydride, reacted for 7 hours at 150 C. At that temperature, unwanted isomerization stays minimal, and the carboxyl group conversion hits about 83%.
What the Numbers Actually Mean
The optimal product achieved an 83.3% conversion of carboxyl groups and retained 88.7% of its C=C double bonds (measured by NMR). The molecular weight hit about 1001 g/mol (number average), with a weight-average of 3129 g/mol and a dispersity index of 3.1. These are reasonable numbers for a polycondensation product.
The viscosity at room temperature was 14.4 Pas, dropping to 3.6 Pas at just 36.6 C. That temperature sensitivity matters because the material can be printed with a slightly heated nozzle, flowing easily through the print head and holding its shape once deposited.
Thermal Stability That Holds Up
DSC analysis showed the polymer is semi-crystalline, with a glass transition temperature lower than similar materials made with shorter diols. The longer eight-carbon chain gives the polymer more mobility. The material melts in a range that is practical for processing, and it degrades at temperatures well above what it would see in normal use.
The real standout is thermal stability. The polymer starts significant degradation around 270 C, with peak mass loss at 405.5 C. That is higher than comparable itaconate polymers, thanks to the longer diol backbone.
Rheology: Why This Works for 3D Printing
The POItcSc resin is shear-thinning. Its viscosity drops as shear rate increases, which is basically the ideal behavior for extrusion-based 3D printing. Push it through a nozzle under pressure, and it flows. Once it lands on the print bed, the shear stops, and the viscosity recovers, so the material stays put.
Oscillation tests confirmed that viscous properties dominate over elastic ones (G G), meaning the material is not significantly crosslinked. It is a true resin that can be printed and then cured afterward. The crossover point where elastic behavior takes over happens at about 86 C, which sets an upper limit for the print head temperature.
Where This Could Go
Right now, POItcSc looks like a strong candidate for Direct Ink Writing (DIW) 3D printing applications, particularly in medicine where material biocompatibility is non-negotiable. The team also noted potential for thermoplastic polyester films, given the low melting range, fast crystallization, and solid thermal stability.
There is still work to do. The UV-crosslinking behavior needs to be studied in detail, and the mechanical properties of cured parts need characterization. But as a starting point for a fully renewable, biodegradable, and functional 3D printing resin, this is promising.
The Bottom Line
The polymer industry does not pivot overnight, and replacing petroleum-based acrylic resins will not happen fast. But work like this shows there is a viable path forward. Renewable monomers, solvent-free synthesis, no catalysts, and a final product that is biodegradable and functional for real applications? That is a blueprint for what greener manufacturing could look like.
The question is not whether bio-based polymers can compete with petrochemical ones anymore. The question is how fast we can scale them up.