3D Printed Polymers: Solvent Compatibility Charts Must Be…

Quick Answer Box: Solvent Compatibility for 3D Printed Parts

Introduction: Why Solvent Compatibility Matters for 3D Printing

The world of 3D printing has revolutionized prototyping and manufacturing, but it has brought new challenges—especially when it comes to chemical resistance. Researchers Kirill S. Erokhin, Evgeniy G. Gordeev, and Valentine P. Ananikov from the Zelinsky Institute of Organic Chemistry at the Russian Academy of Sciences have conducted groundbreaking research revealing why traditional solvent compatibility charts fail for 3D printed parts.

When you create functional 3D printed parts for medical devices, automotive components, or laboratory equipment, understanding how these parts react to chemicals is critical. A part that works perfectly in air might dissolve or delaminate when exposed to solvents, leading to catastrophic failure in critical applications.

This research, published in the journal Scientific Reports under the title “Revealing interactions of layered polymeric materials at solid-liquid interface for building solvent compatibility charts for 3D printing applications,” demonstrates that 3D printed parts require dedicated, not simple, solvent compatibility charts.

The Fundamental Problem: Layered Structure vs. Solid Manufacturing

Traditional plastics manufacturing methods like injection molding create solid, homogeneous parts. In contrast, FDM (Fused Deposition Modeling) 3D printing builds parts layer by layer, creating a fundamentally different internal structure with:

• Porosity: Tiny gaps between extruded filaments that allow solvents to penetrate
• Layer boundaries: Weak points where materials from different print layers meet
• Anisotropic properties: Different strength and chemical resistance in different directions

These structural differences mean that even if a material like PLA is chemically resistant in its solid form, a 3D printed PLA part may dissolve or delaminate when exposed to solvents.

Research Methodology: Comprehensive Testing

The researchers conducted rigorous testing to understand how 3D printed parts interact with various solvents:

Materials Tested

The study evaluated 12 different thermoplastic materials commonly used in 3D printing:

• Standard Materials: ABS, SBS, PLA, Nylon, PP, PE, PETG, HIPS, POM
• Specialty Materials: Primalloy (elastomer)
• Composite Materials: PLA-Cu (copper-filled), Nylon-C (carbon-filled), Ceramo (ceramic-filled)

Solvents Used

Twelve different solvents were tested, ranging from gentle to aggressive:

1. Dichloromethane (DCM) – highly aggressive organic solvent
2. Tetrahydrofuran (THF) – strong organic solvent
3. Acetone – common solvent for ABS smoothing
4. Dimethylformamide (DMF) – industrial solvent
5. Toluene – aromatic hydrocarbon solvent
6. Ethyl acetate – ester solvent
7. Triethylamine (TEA) – amine solvent
8. Acetic acid – weak acid
9. Ethanol – common alcohol
10. Sulfuric acid – strong acid
11. Sodium hydroxide – strong base
12. Water – neutral solvent (control)

Experimental Setup

The researchers used a Picaso 3D Designer Pro 250 printer to create test specimens. For standard materials, they used a 0.3 mm nozzle with 0.2 mm layer height. For filled materials, they used a 0.5 mm nozzle with 0.35 mm layer height to prevent nozzle clogging.

Each specimen was immersed in a solvent and monitored for one hour. The researchers measured changes in the part’s surface area to quantify degradation. A change of more than 20% indicated complete instability, 2-20% indicated moderate stability, and less than 2% indicated good stability.

Key Findings: Material Performance Rankings

Table 1: Chemical Resistance Ranking of 3D Printed Materials

Resistance Level	Materials	Best For
Highly Resistant	PP, PE, POM, Nylon, Nylon-C	Chemical storage, lab equipment, containers
Moderately Resistant	PETG, Primalloy	Limited chemical exposure, moderate applications
Low Resistance	PLA, ABS, SBS, HIPS, PLA-Cu, Ceramo	Non-chemical applications, decorative parts, prototypes

Detailed Material Performance

Polypropylene (PP) and Polyethylene (PE)

PP and PE demonstrated exceptional chemical resistance across all tested solvents. These materials maintained their structural integrity even in aggressive organic solvents like DCM and THF. Their excellent chemical resistance makes them ideal choices for chemical storage containers, lab equipment, and any application requiring solvent exposure.

Polyoxymethylene (POM)

POM showed outstanding chemical resistance, comparable to PP and PE. Its mechanical properties combined with chemical stability make it an excellent choice for precision parts that may encounter chemical exposure.

Nylon and Nylon-C

Both standard Nylon and carbon-filled Nylon-C exhibited high chemical resistance. The carbon filler in Nylon-C did not compromise chemical performance, offering the added benefit of improved mechanical strength and thermal stability.

PETG

PETG showed moderate resistance, performing well against acetone and toluene, as well as ethyl acetate and DCM. This makes PETG a good middle-ground material for applications requiring some chemical resistance without the specialized handling requirements of PP or PE.

Primalloy

As an elastomer, Primalloy demonstrated moderate resistance to solvents. However, it was notably unstable in THF, dissolving within seconds. Its flexible nature makes it suitable for applications requiring both elasticity and moderate chemical resistance.

PLA, ABS, SBS, HIPS, PLA-Cu, and Ceramo

These materials showed poor chemical resistance to organic solvents. They are incompatible with acetone, ethyl acetate, toluene, DMF, THF, and DCM. Interestingly, the fillers in PLA-Cu and Ceramo did not improve chemical resistance—the underlying PLA polymer still dominated the behavior.

Solvent Compatibility Matrix

Table 2: Solvent Compatibility for Common 3D Printing Materials

Material	Water	Ethanol	Acetone	Toluene	DCM	THF	DMF
PP	✓	✓	✓	✓	✓	✓	✓
PE	✓	✓	✓	✓	✓	✓	✓
POM	✓	✓	✓	✓	✓	✓	✓
Nylon	✓	✓	✓	✓	✓	✓	✓
PETG	✓	✓	✓	✓	✗	✗	✗
PLA	✓	✓	✗	✗	✗	✗	✗
ABS	✓	✓	✗	✗	✗	✗	✗
✓ = Compatible (stable), ✗ = Incompatible (dissolves/delaminates)

Types of Chemical Degradation

The researchers identified four primary mechanisms by which solvents degrade 3D printed parts:

1. Disintegration

The part completely breaks apart into fragments. This occurs when the solvent penetrates deeply between layers, dissolving the material’s binding properties. PLA in DCM is a classic example of disintegration.

2. Delamination

Layers separate from each other while maintaining their individual integrity. This is particularly common in acetone exposure, where PLA layers peel apart but don’t dissolve completely. The weak interlayer adhesion in 3D printed parts makes them susceptible to this type of failure.

3. Molecular Dissolution

The polymer chains themselves break down and dissolve into the solvent. This is the most severe form of degradation, resulting in complete loss of material. DCM is notorious for causing molecular dissolution in many thermoplastics.

4. Swelling

The part absorbs solvent molecules, causing it to expand and become soft. Swelling may not cause immediate failure but can compromise dimensional accuracy and mechanical properties. This is often observed with less aggressive solvents or during the early stages of exposure.

Why Traditional Compatibility Charts Fail

Traditional solvent compatibility charts are based on solid, injection-molded plastics. These charts don’t account for the unique structure of 3D printed parts:

Porosity as a Factor

3D printed parts contain microscopic gaps between extruded filaments. These gaps act as pathways for solvents to penetrate deep into the part’s interior. Even if a material is chemically resistant on its surface, solvents can work their way between layers and cause internal degradation.

Layer Boundary Weakness

The interfaces between print layers are weaker than the bulk material. Solvents exploit these weak points, causing layers to separate. This delamination occurs even when the material itself would be chemically resistant in solid form.

Anisotropic Structure

3D printed parts have different properties in different directions. Chemical resistance may vary depending on whether the solvent attacks parallel to layers or perpendicular to them. Traditional charts, which assume isotropic behavior, can’t predict these directional differences.

Print Parameter Influence

The quality of a 3D printed part—and therefore its chemical resistance—depends heavily on print parameters like:

• Extrusion multiplier: Higher settings reduce porosity and improve resistance
• Layer height: Thinner layers generally improve chemical resistance
• Print temperature: Proper temperature ensures good layer bonding
• Print speed: Slower speeds often produce better interlayer adhesion
• Infill density: Higher infill reduces solvent penetration pathways

Improving Chemical Resistance: Three Strategies

The researchers identified three approaches to improving solvent resistance in 3D printed parts:

1. Polymer Modification with Additives

Chemical additives can be incorporated into filaments to protect against solvent action. These additives work by:

• Creating a barrier layer that prevents solvent penetration
• Reacting with solvents to neutralize their effects
• Modifying the polymer structure to reduce solvent affinity

Chemical-resistant filaments are already available on the market, often incorporating proprietary additives. These specialized materials come at a premium price but can enable applications that would otherwise be impossible with standard filaments.

2. Optimizing Print Parameters

Proper print settings can significantly improve chemical resistance by reducing porosity and improving layer bonding:

• Increase extrusion multiplier: Use 1.0-1.1 to ensure proper filament flow and reduce gaps
• Lower layer height: Print at 0.1-0.15mm for better layer adhesion
• Optimize temperature: Use the upper end of the recommended range for better layer fusion
• Reduce print speed: Slower printing allows better layer bonding
• Increase wall thickness: More perimeter lines reduce solvent pathways
• Use higher infill: 100% infill for chemical-critical applications

3. Adjusting Part Geometry

Design choices can mitigate solvent effects:

• Minimize exposed surfaces: Reduce the area that contacts solvents
• Design for drainage: Avoid pockets where solvent can pool
• Use smooth surfaces: Post-processing can seal surface pores
• Consider orientation: Print so that layer lines don’t align with stress points
• Add protective coatings: Apply chemical-resistant coatings after printing

Practical Applications and Considerations

Medical and Laboratory Equipment

Medical devices and lab equipment often require exposure to disinfectants, sterilization agents, and other chemicals. PP, PE, and POM are excellent choices for these applications due to their broad chemical resistance. However, designers must ensure print settings optimize for chemical resistance rather than just speed.

Automotive Applications

Automotive parts may encounter fuels, oils, and cleaning agents. Nylon and PP offer good resistance to many automotive chemicals. For parts exposed to aggressive solvents, designers should consider post-processing treatments or coatings.

Chemical Storage and Handling

For containers and vessels that will hold chemicals, PP and PE are the materials of choice. Their excellent resistance to a wide range of solvents makes them suitable for short-term storage applications. However, designers must consider that even resistant materials may degrade over long-term exposure.

Aerospace Applications

Aerospace applications require materials that can withstand extreme conditions, including exposure to aviation fuels, hydraulic fluids, and deicing agents. High-performance materials like PEEK and Ultem offer superior chemical resistance but require specialized printers capable of reaching 350-400°C.

Limitations and Future Research

While this study provides comprehensive data on short-term solvent exposure (one hour), several areas require further investigation:

• Long-term exposure: Parts exposed to solvents for days, weeks, or months may show different degradation patterns
• Temperature effects: Elevated temperatures may accelerate solvent penetration and degradation
• Mixed solvents: Real-world applications often involve solvent mixtures with complex interactions
• Mechanical stress: Parts under load while exposed to solvents may fail faster than unstressed parts
• UV radiation: Combined UV and solvent exposure may produce synergistic degradation effects

Recommendations for 3D Printing Practitioners

Based on the research findings, here are practical recommendations:

Material Selection

Choose materials based on your chemical exposure requirements:

• For chemical storage: Use PP or PE
• For lab equipment: POM or Nylon for chemical resistance plus mechanical strength
• For general prototyping: Use PLA, ABS, or PETG for non-critical applications
• For aggressive solvents: Consider high-temperature materials like PEEK (requires specialized printer)

Print Settings Optimization

Adjust your print settings for maximum chemical resistance:

• Use the highest extrusion multiplier that doesn’t cause over-extrusion defects
• Print at lower layer heights (0.1-0.15mm) for better layer bonding
• Use maximum wall thickness and infill for critical parts
• Print at the upper end of the temperature range
• Consider using a larger nozzle (0.4mm+) for better layer adhesion

Testing Before Deployment

Always test parts with the specific chemicals they’ll encounter:

• Create small test samples using your exact print settings
• Expose samples to actual chemicals for the intended duration
• Inspect for swelling, discoloration, delamination, or weakening
• Perform mechanical testing before and after exposure if applicable

Post-Processing for Chemical Resistance

Consider post-processing treatments to improve resistance:

• Smoothing: Acetone vapor smoothing for ABS (ironically improves resistance to other solvents)
• Epoxy coating: Apply clear epoxy to seal surface pores
• Chemical-resistant spray: Use specialized coatings for harsh environments
• Heat treatment: Annealing can improve interlayer bonding

Conclusion

This research represents a significant step forward in understanding the chemical behavior of 3D printed parts. The key takeaway is that traditional solvent compatibility charts don’t apply to 3D printing—the layered structure, porosity, and print parameters all play critical roles in determining how a part will react to chemical exposure.

For practitioners, the message is clear: choose your materials carefully, optimize your print settings for chemical resistance, and always test before deploying parts in chemically demanding environments. The materials with the best chemical resistance—PP, PE, POM, Nylon, and Nylon-C—should be your go-to choices for any application involving solvent exposure.

As 3D printing continues to expand into functional applications, understanding and controlling chemical resistance will become increasingly important. This research provides a solid foundation for making informed decisions about material selection, print parameter optimization, and part design for chemical-critical applications.

Sources:

1. Erokhin, K. S., Gordeev, E. G., & Ananikov, V. P. (2020). Revealing interactions of layered polymeric materials at solid-liquid interface for building solvent compatibility charts for 3D printing applications. Scientific Reports, 10(1), 3991. DOI: 10.1038/s41598-019-56350-w
2. Picaso 3D. (n.d.). Designer Pro 250 3D Printer. Retrieved from picaso-3d.com
3. Scientific Reports. (2020). Solvent Compatibility Charts for 3D Printing Applications. Nature Portfolio.
4. MatWeb. Material Property Data. (n.d.). Thermoplastic Materials Database. Retrieved from matweb.com

Frequently Asked Questions

1. Why do 3D printed parts fail in solvents when the same material is resistant in solid form?

3D printed parts have a fundamentally different structure than solid, injection-molded parts. The layered construction creates porosity and weak interlayer boundaries that allow solvents to penetrate and cause delamination, even when the base material is chemically resistant. Traditional compatibility charts based on solid materials don’t account for these structural differences.

2. Which 3D printing materials are best for chemical resistance?

Based on comprehensive testing, the most chemically resistant materials are: Polypropylene (PP), Polyethylene (PE), Polyoxymethylene (POM), Nylon, and carbon-filled Nylon (Nylon-C). These materials showed excellent resistance across all tested solvents, including aggressive organic solvents like dichloromethane and tetrahydrofuran.

3. Can I improve the chemical resistance of my 3D printed parts?

Yes, there are three main approaches: (1) Optimize print parameters—use higher extrusion multipliers, lower layer heights, increased wall thickness, and higher infill density to reduce porosity; (2) Use chemical-resistant filaments with protective additives; (3) Apply post-processing treatments like epoxy coatings or chemical-resistant sprays to seal surface pores.

4. Is PLA suitable for applications involving chemical exposure?

PLA is generally not recommended for chemical exposure applications. While PLA is resistant to water, ethanol, and aqueous solutions, it rapidly degrades in organic solvents like acetone, toluene, DMF, THF, and dichloromethane. PLA is better suited for decorative parts, prototypes, and applications that won’t encounter chemical exposure.

5. How long should I test my 3D printed parts before using them with chemicals?

For safety-critical applications, test for at least the maximum expected exposure time, plus a safety margin. The research tested for one hour, but many real-world applications involve longer exposure. Consider testing for 24 hours, one week, or longer depending on your application. Always test with the actual chemicals and concentrations the part will encounter.

6. Can post-processing like acetone vapor smoothing improve chemical resistance?

Interestingly, yes. While acetone dissolves ABS and some other materials, acetone vapor smoothing creates a sealed surface layer that can improve resistance to other solvents. However, the smoothed part will still be vulnerable to acetone itself. For applications requiring resistance to multiple solvents, consider chemical-resistant coatings instead.

7. Are filled materials like PLA-Cu more chemically resistant than standard PLA?

According to the research, filled materials like PLA-Cu and carbon-filled Nylon generally behave similarly to their unfilled counterparts. The filler material doesn’t significantly improve chemical resistance—the base polymer’s properties still dominate. However, carbon-filled Nylon (Nylon-C) did show excellent chemical resistance, maintaining the good performance of standard Nylon.

8. What are the signs that my 3D printed part is degrading from chemical exposure?

Watch for these warning signs: (1) Swelling or expansion of the part, (2) Discoloration or cloudiness, (3) Surface becoming sticky or soft, (4) Layers beginning to peel apart (delamination), (5) Cracks or fissures appearing, (6) Complete disintegration in severe cases. If you notice any of these signs, remove the part from chemical exposure immediately.