PLA vs PETG vs ASA vs TPU: Solubility in Common Solvents

Why solvent compatibility matters

Choosing the right filament means more than matching mechanical specs. Solvent exposure is a real-world concern for:

• Post-processing: Vapor smoothing to improve surface finish and layer bonding
• Part cleaning: Removing flux residue, oils, or contaminants from printed parts
• Chemical environments: Parts used near fuels, cleaning agents, or industrial chemicals
• Adhesives and coatings: Many adhesives contain solvents that can damage prints
• Medical and food contexts: Sterilization agents, disinfectants, and cleaning solutions

The four most common desktop printing materials — PLA, PETG, ASA, and TPU — have dramatically different solvent resistance profiles. Understanding these differences prevents costly print failures and opens up post-processing options you may not have considered.

Chemical resistance overview

At the molecular level, solvent resistance depends on polymer polarity, crystallinity, and chain mobility. A solvent attacks a polymer when their solubility parameters are similar — this is the basis of Hansen solubility parameter theory. Highly crystalline or polar polymers tend to resist a broader range of solvents, while amorphous or non-polar polymers are more vulnerable.

PLA: dissolved by esters, slow acid/base hydrolysis

PLA (polylactic acid) is a biopolymer made from fermented plant starch. Its ester backbone makes it uniquely susceptible to solvents that interact with ester linkages — most notably ethyl acetate and other acetates. It also undergoes slow hydrolysis in acidic or alkaline water, which is why PLA degrades in composting conditions.

PLA is a semi-crystalline, relatively polar polymer with a glass transition temperature that the Filabase database puts at an average heat deflection temperature of 56°C across 379 measured filaments (range: 45–137°C, with most standard grades clustering 50–65°C).

What dissolves PLA

• Ethyl acetate — the go-to PLA solvent. Dissolves at room temperature; vapor can be used for surface smoothing. Works slowly enough to allow controlled application.
• DCM (dichloromethane) — extremely fast action, dissolves PLA in seconds. Highly toxic; rarely used by hobbyists.
• Chloroform — similar to DCM. Dissolves PLA rapidly.
• THF — strong solvent. Dissolves PLA and most common plastics.
• Ethyl lactate — a less toxic alternative ester solvent that dissolves PLA.

What affects (but doesn't dissolve) PLA

• MEK (methyl ethyl ketone) — attacks PLA surface, causes crazing and softening. Not as fast as ethyl acetate.
• Concentrated acids or bases — cause hydrolytic degradation over hours to days. Not a sudden dissolution but a gradual weakening.
• DMSO — limited effect; may cause slow swelling.

What PLA resists

• Water, IPA, ethanol at standard concentrations
• Gasoline, mineral spirits, most petroleum distillates
• Acetone (very slight effect; not enough for vapor smoothing)

PLA smoothing options

Ethyl acetate vapor smoothing is the standard approach for PLA. Place the part in a sealed container with a small amount of liquid ethyl acetate heated gently (40–50°C). Exposure time is typically 5–30 minutes depending on geometry and desired smoothness. The result is similar to ABS acetone smoothing — surfaces become glassy, but some dimensional loss occurs.

Note: ethyl acetate is flammable (flash point ~−4°C); use outside or in well-ventilated areas with no ignition sources. It is far less toxic than acetone vapor smoothing agents like MEK or DCM.

PETG: solvent-resistant but not solvent-proof

PETG (polyethylene terephthalate glycol) is a modified PET with glycol co-monomer that reduces crystallinity and improves printability. Its aromatic ring structure and ester backbone give it decent — but not exceptional — chemical resistance.

The Filabase database contains 185 PETG filaments with an average heat deflection temperature of 72°C (range: 58–100°C) and average tensile strength of 48.7 MPa. PETG's higher HDT compared to PLA (56°C average) means it handles warm environments better, but its solvent resistance remains a concern in industrial settings.

What attacks PETG

• Acetone — causes visible surface crazing and softening within minutes. PETG does not dissolve cleanly in acetone, but the surface is damaged enough to rule out acetone cleaning.
• MEK (butanone) — more aggressive than acetone on PETG; causes significant swelling and layer delamination.
• DCM — dissolves PETG. Useful as a bonding agent for PETG parts (similar to DCM welding for ABS/ASA).
• Chloroform, THF, DMF — all dissolve PETG. THF in particular is commonly used for PETG adhesive welding.
• Ethyl acetate — causes swelling; not as severe as MEK or acetone but still damages the surface.

What PETG resists

• Water (excellent — rated as moisture-resistant across most TDS data)
• IPA, ethanol at normal cleaning concentrations
• Dilute acids (e.g., citric acid, acetic acid at low concentrations)
• Gasoline, mineral oils, petroleum distillates
• Dilute sodium hydroxide (NaOH) at low concentrations, though prolonged exposure can cause hydrolysis

Can PETG be vapor smoothed?

There is no practical vapor smoothing agent for PETG. The solvents that affect PETG (acetone, MEK) cause crazing rather than clean dissolution and reflow. DCM and THF work but are too aggressive, toxic, and fast-acting for controlled smoothing. In practice, PETG parts are sanded, primed with filler, or left as-printed.

ASA: acetone-smoothable, strong chemical resistance otherwise

ASA (acrylonitrile styrene acrylate) is structurally similar to ABS but uses an acrylate rubber phase instead of butadiene, which gives it superior UV and weathering resistance. Its solvent behavior closely mirrors ABS: acetone is highly effective, and it resists fuels and mild acids well.

The Filabase database contains 67 ASA filaments with an average heat deflection temperature of 91°C (range: 76–105°C) — the highest of the four families in this comparison — and tensile strengths typically ranging 37–62 MPa. The high HDT makes ASA attractive for outdoor and under-hood applications, but you must verify solvent exposure in those environments.

What dissolves ASA

• Acetone — dissolves ASA readily. ASA can be acetone vapor smoothed using the same techniques as ABS: a sealed container with a small pool of acetone at room temperature produces strong smoothing in 5–20 minutes.
• MEK (butanone) — highly effective solvent for ASA. Used in MEK-based adhesives for bonding ASA parts.
• DCM, chloroform, THF, DMF — all dissolve ASA at room temperature.
• Cyclohexanone — effective solvent for ASA/ABS-type polymers.

What ASA resists

• Water (very good; low moisture absorption is one of ASA's advantages over ABS)
• IPA, ethanol, methanol at normal concentrations
• Dilute acids and bases
• Gasoline, mineral oils, petroleum distillates (better resistance than PLA and PETG)
• UV exposure — ASA is specifically designed to resist UV degradation, unlike ABS which yellows and embrittles

ASA smoothing in practice

Acetone vapor smoothing works on ASA the same way it does on ABS. Use a glass container or sealed enclosure, and warm the acetone gently (or leave at room temperature). ASA typically requires slightly longer exposure times than ABS — 10–30 minutes for good smoothing. The result is a glossy, layer-line-free surface. Acetone also works as an adhesive for bonding ASA parts without clamping.

A useful practical advantage: unlike ABS, ASA does not yellow with UV exposure after smoothing. Smoothed ASA parts can be used outdoors without a topcoat.

TPU: the solvent-resistant flexible

TPU (thermoplastic polyurethane) occupies a unique position in this comparison. It is a segmented block copolymer with hard polyurethane segments and soft polyether or polyester diol segments. This structure gives it outstanding resistance to most common organic solvents — including acetone, which readily dissolves ASA and ABS.

The Filabase database contains 109 TPU filaments with an average heat deflection temperature of 68°C (range: 44–100°C) and tensile strengths ranging 4–61 MPa (average 30.6 MPa). Shore hardness varies widely across the 85A–98A and into Shore D range.

What TPU resists (that other filaments don't)

• Acetone — TPU is largely unaffected by acetone. This is useful when bonding TPU parts to acetone-smoothed ASA or ABS — the acetone does not damage the TPU surface.
• Fuels (gasoline, diesel, petroleum) — TPU shows significantly better fuel resistance than PLA or PETG. This is why TPU is used for fuel line seals and gasket applications.
• Oils, greases — excellent resistance to mineral oils and synthetic lubricants.
• Dilute acids and bases — good resistance at low concentrations.
• IPA, ethanol — generally resistant.

What attacks TPU

• THF (tetrahydrofuran) — dissolves TPU. THF is the primary solvent used for TPU in industrial processing.
• DMF (dimethylformamide) — dissolves TPU. DMF is commonly used to dissolve polyurethanes for coating applications.
• DMSO (dimethyl sulfoxide) — attacks many polyurethanes, though rate depends on formulation.
• Concentrated acids — strong acids (e.g., concentrated H₂SO₄, HNO₃) hydrolyze the urethane linkages.
• Chlorinated solvents (DCM, chloroform) — cause swelling; some TPU grades partially dissolve.
• Polyester-based TPU grades — specifically vulnerable to hydrolysis in hot water and alkaline environments, more so than polyether-based grades.

Can TPU be vapor smoothed?

No practical vapor smoothing method exists for TPU. The solvents that dissolve it (THF, DMF) are extremely hazardous. Acetone — the safest common smoothing agent — does not affect TPU. TPU parts are typically printed with fine layer heights and left as-printed, or sanded lightly for minor smoothing.

Head-to-head solvent resistance summary

Practical scenarios: which filament to choose

Parts cleaned with IPA or ethanol

All four materials are safe to clean with IPA or ethanol at standard concentrations (70–90%). This is the safest routine cleaning solvent for printed parts across all four families.

Parts near automotive fluids

For parts that may contact gasoline, motor oil, or brake fluid, TPU offers the best resistance profile. ASA is also acceptable for fuel splash resistance. PETG is reasonable for petroleum products but should be tested. Avoid PLA for prolonged fuel contact as it will degrade over time in warm, wet environments.

Parts in outdoor chemical environments (pools, garden chemicals)

ASA is the best choice here: it combines good chemical resistance with UV stability and the highest average heat deflection temperature (91°C) in this comparison. PETG with UV stabilizers is a reasonable second option for lower-temperature applications.

Parts that need vapor smoothing

PLA: use ethyl acetate. ASA: use acetone. PETG and TPU cannot be practically vapor smoothed — choose PLA or ASA if smooth surfaces are a priority, or plan for sanding and filler primer instead.

Parts bonded with solvent adhesives

• PLA: ethyl acetate or MEK-based adhesives. Epoxy is also reliable.
• PETG: MEK or THF. Be aware that MEK crazes the surface slightly; apply quickly. Cyanoacrylate (super glue) also works well for PETG.
• ASA: acetone or MEK. Same approach as ABS. Apply, press together, hold for 30–60 seconds.
• TPU: solvent bonding is difficult. Use cyanoacrylate or specialized TPU adhesives. THF technically works but is extremely hazardous.

Chemical exposure in lab or workshop settings

For parts used near strong solvents (acetone, MEK, chlorinated solvents), none of the four common filaments are reliable. Consider PA (nylon), PP, or PEEK for demanding chemical environments. Among these four, TPU offers the broadest solvent resistance for organic solvents, while ASA handles the widest range of cleaning chemicals.

Hansen solubility parameters: the theory behind the chart

Hansen solubility parameter (HSP) theory predicts whether a solvent will dissolve a polymer based on three component parameters:

• δd — dispersion forces (non-polar interactions)
• δp — polar interactions
• δh — hydrogen bonding

A solvent dissolves a polymer when the solvent's HSP falls within the polymer's "solubility sphere." Key approximate HSP values for reference:

The key insight: IPA's δh of 16.4 MPa½ is far higher than any of the four polymer families (all below 8.5), which means IPA sits well outside their solubility spheres — hence the excellent resistance across all four materials. Ethyl acetate's balanced profile (δd 15.8, δp 5.3, δh 7.2) places it close to PLA's solubility sphere, explaining its effectiveness as a PLA solvent.

Safety considerations for solvent smoothing

Solvent smoothing with any of the above chemicals requires precautions:

• Ventilation: Work outdoors or in a well-ventilated area. Ethyl acetate and acetone vapors are flammable; MEK and THF are both flammable and more toxic.
• Containers: Use glass or metal — acetone and MEK attack many plastics, including some containers.
• Exposure time: Start with shorter times (5 minutes) and check progress. Over-smoothing melts detail and causes dimensional loss.
• Part wall thickness: Thin walls (< 1mm) can deform significantly. Start with small test prints.
• TPU and PLA together: If you are smoothing a PLA or ASA part that has TPU flex joints, the solvent will not attack the TPU — but mask or remove the TPU sections if precision is important.

Which filament to choose based on chemical environment

There is no single best choice — the right filament depends on what chemicals your part will encounter:

• Need acetone vapor smoothing? Choose ASA. Acetone smoothing works reliably, and ASA handles UV and heat better than ABS.
• Need ethyl acetate vapor smoothing? Choose PLA. It is the most accessible solvent for PLA smoothing.
• Cleaning parts with IPA? All four are safe. IPA is the universal safe cleaner for FDM prints.
• Fuel or oil resistance a priority? TPU for seals and flexible parts; ASA or PETG for rigid structural parts.
• Strong solvents in the environment? None of these four filaments are suitable — consider PEEK, PEI, or PP depending on the specific chemical.
• Outdoor use and occasional cleaning with household chemicals? ASA is the safest choice for combined UV and chemical resistance.

The Filabase database contains 533 PLA filaments, 185 PETG filaments, 67 ASA filaments, and 109 TPU filaments with mechanical and thermal data from manufacturer TDS documents to help you select the right material for your application.