ASA: The UV-Resistant Alternative to ABS

The realm of 3D printing has welcomed a relatively recent entrant—Acrylonitrile Styrene Acrylate (ASA) filament. This material brings forth several advantages when compared to the more ubiquitous Acrylonitrile Butadiene Styrene (ABS) filament. In this discourse, we will thoroughly examine the properties and performance of these two thermoplastics to discern their respective merits.

Introduction to ASA Filament

ASA filament emerged a few years ago as a viable alternative to ABS for fused deposition modeling (FDM) 3D printing. The distinguishing factor between ABS and ASA lies in the incorporation of acrylate in ASA, imparting superior weathering and UV resistance compared to ABS. ASA outperforms ABS in enduring sunlight, humidity, and other environmental factors that can deteriorate plastics over time.

Like ABS, ASA is derived from the petrochemical styrene and boasts an amorphous structure, ensuring good dimensional stability as the material solidifies post-printing. ASA also delivers a glossy surface finish and high impact strength, comparable to ABS in most cases.

ASA’s advantages over ABS primarily stem from its enhanced weatherability and reduced propensity to warp during the printing of large objects. These attributes position ASA as an excellent choice for outdoor applications such as patio furniture, automotive components, and other scenarios where UV and moisture resistance are pivotal.

Key Properties and Characteristics

Let’s delve into a closer examination of the physical and mechanical properties of ASA and ABS filaments:

• Impact Strength: Both ABS and ASA exhibit commendable impact resistance due to their amorphous structures. Parts crafted from either material can endure bumps, drops, and short falls without succumbing to cracks or shattering. While ASA may hold a slight advantage in resilience, both materials perform admirably in this regard.
• Tensile Strength: The maximum tensile stress that ABS and ASA can withstand before undergoing permanent deformation is comparable. ABS typically has a tensile strength averaging around 40 MPa, with ASA slightly lower at 36–38 MPa on average. For non-structural components, both offer sufficient tensile strength.
• Heat Resistance: ABS and ASA showcase nearly equivalent heat resistance, maintaining structural integrity up to approximately 85–95°C. This makes both materials suitable for applications like automotive parts that must endure hot environments. However, neither material is capable of withstanding very high temperatures.
• Chemical Resistance: ABS and ASA exhibit resistance to oils, greases, and various solvents. ASA may have a marginal edge in resisting alkalis, acids, and other chemicals at higher concentrations, but both plastics perform well compared to other FDM materials. Caution should be exercised with strong polar solvents like acetone for both.
• Weatherability: This is where ASA surpasses ABS. The acrylate in ASA imparts significantly enhanced UV light and moisture resistance. Printed ASA parts can endure months or years of sun exposure with minimal material degradation compared to ABS.
• Printing Performance: In terms of printing characteristics, ASA and ABS demonstrate similar behavior. Both melt at temperatures around 220–260°C and can be printed on most desktop FDM printers with a heated bed. No specialized hardware is required for printing with either material.
• Part Cooling: Both ABS and ASA prints necessitate gradual cooling after extrusion, requiring cooling fans to be turned off or set to low speeds during printing. Insufficient cooling can lead to layer separation or cracks in finished parts.
• Bed Adhesion: Print bed adhesion can pose a challenge with both ASA and ABS due to plastic contraction upon cooling. The use of a heated print bed (80–110°C) along with adhesion aids like glue, tape, or an adhesion promoter spray yields optimal bed adhesion.
• Warping: ASA holds an advantage in this aspect, being less prone to warping and detachment from the print bed compared to ABS. Large ABS prints are highly susceptible to warping, while ASA’s characteristics make it more conducive to printing sizable objects without warpage and edge curling.
• Post-Processing: Minimal post-processing is required for both ASA and ABS prints. Supports can be easily removed, and the smooth surface finish generally eliminates the need for sanding or polishing (though these processes can enhance aesthetics). It’s worth noting that an acetone vapor bath, effective for smoothing ABS parts, does not work as effectively on ASA due to its chemical resistance.

ASA vs. ABS: Which to Choose?

Determining whether to choose ASA over ABS, or vice versa, depends on specific requirements. Here are some general guidelines:

• Choose ASA When:
  • Good heat resistance and impact strength are needed.
  • Dimensional stability across large prints is crucial.
  • Weather resistance is paramount (e.g., outdoor use).
  • A glossy, smooth finish is desired.
• Choose ABS When:
  • The smoothest possible surface finish is desired (suitable for acetone vapor treatment).
  • A diverse range of color options is important.
  • Heat resistance beyond 80–90°C is required.
  • The printing area is prone to static (ASA builds up more static charge).

ASA holds a significant advantage over ABS in terms of UV/moisture resistance, making it well-suited for automotive and outdoor applications. Both filaments, characterized by amorphous structures, offer good impact strength. For extensive prints, ASA’s reduced warping proves beneficial.

While ASA generally incurs a slightly higher cost than ABS due to its more advanced formulation and lower market availability, many find the additional cost justified for the enhanced weather resistance in intended use cases.

Both filaments can yield quality printed parts with appropriate slicing settings and printing techniques. Experimenting with both materials will help determine which properties align with specific needs and desired characteristics. Careful consideration of the advantages and disadvantages outlined here is crucial when selecting a material.

Printing With ASA Filament

If ASA is the chosen material for a 3D printing project, consider the following tips for optimal results:

• Utilize an enclosure to maintain a stable, warpage-free print environment.
• Print on tape, glue, or other adhesion promoters to prevent detachment from the bed.
• Employ a heated bed (100–110°C) for maximum layer bonding.
• Reduce part cooling by keeping fans off or set to low speeds.
• Optimal nozzle temperature is roughly 240–260°C.
• Print the first layer hot and slow for maximum bed adhesion.
• Store the filament in an airtight container with desiccant when not in use.

ASA excels for larger prints where ABS might succumb to cracking, curling, or detachment from the print bed. The improved interlayer bonding prevents the entire print from detaching or deforming.

By adhering to these tips, ASA prints can exhibit exceptional visual appeal and possess the physical properties needed for demanding applications.

Conclusion

Both ASA and ABS stand out as excellent materials for fused deposition modeling 3D printing. ASA notably offers superior weatherability and UV/moisture resistance compared to ABS while maintaining similar mechanical properties. This positions ASA as an ideal choice for automotive parts, outdoor applications, or any scenario where resistance to the elements is critical.

ABS remains a viable option when high-temperature performance, ease of post-processing, or a wide color selection is required. Additionally, ABS is slightly more cost-effective than ASA at present. However, for extensive prints, ASA’s diminished warping provides a clear advantage.

When selecting a material, carefully evaluate the environment in which the 3D printed part will be used. Consider factors such as the expected temperature range, exposure to sunlight and moisture, required accuracy and detail, and other application-specific requirements. Armed with an understanding of the relative merits and drawbacks of each material, one can make an informed decision based on their unique 3D printing needs.