The first 3D printable PPS aerogel was synthesized and basic aerogel architectures unduplicable in previous advanced research at Virginia Tech. Through this innovation, the application of this new improvement translates to various possibilities aerogel architectures and uses in different industries utilizing additive manufacturing methods.

Aerogel 3D Printing: Creating Ultra-Lightweight Structures

3D-Druck is revolutionizing how materials are developed and products are manufactured. By enabling previously impossible geometries and designs, additive manufacturing opens up entirely new applications and industries. One class of materials that stands to greatly benefit from 3D printing capabilities is aerogels.

Aerogels are ultra-lightweight porous solids derived from gels that replace the liquid component with air. While offering unprecedented insulation properties, traditionally produced aerogels have been limited to basic shapes. Virginia Tech researchers recognized 3D printing could push the boundaries of these revolutionary materials by allowing intricate complex architectures.

Their breakthrough came in developing the first polyphenylene sulfide (PPS) aerogel that could be directly 3D printed using a specialized high-temperature printer. PPS aerogels maintain their insulation qualities while gaining mechanical strength from the polymer. This paved the way for controlling aerogel structure on the macro to nanoscale through deposition methodologies.

This approach transforms aerogel design possibilities. Further research optimizing printable compositions unlock even more potential. This report will explore the Virginia Tech team’s pioneering work developing 3D printable PPS aerogels and implications for next-generation aerogel applications.

Aerogel Material Properties and Applications

Aerogel History and Composition

Aerogel was discovered by chance in 1931 by Samuel Stephens Kistler of the University of California, Santa Barbara. He is engaged with silica gel and discovered that it is possible to swap the fluid with air. This led to forming a almost 99% air space that was named “aerogel” by Kistler. Aerogels are new class of nanomaterials based on the gel, where liquid phase of the gel has been substituted by a gas. This is because drying of the gel occurs under supercritical conditions hence allowing the liquid to be extracted without the structure to be subjected to capillary forces. This unique production process allows aerogels to have extreme attributes not seen in other materials.

Aerogel Advantages and Limitations

Vorteile

Some of the key advantages of aerogels include:

• Extremely low density – Typically less than 100 times denser than air. Silica aerogels can be less than 3% the density of water.
• High thermal insulation – Aerogels are excellent insulators due to extremely small pore sizes and enclosed pockets of air or gas.
• Acoustic insulation – Sound waves cannot pass easily through aerogel’s networked structure.
• Transparency – When density is low enough, aerogels can be transparent to visible light.

Beschränkungen

The main limitations of aerogels include:

• Fragility – Aerogels are brittle solids prone to cracking or crushing if excessive pressure is applied. Special care must be taken during handling.
• Production complexity – The production process, especially supercritical drying, requires precise control and specialized equipment, making aerogels more expensive than traditional materials.

Current Aerogel Applications

Thermal and acoustic insulation

Aerogels are used for thermal insulation in applications like building envelopes, apparel, and cryogenic storage of fuels. Their acoustic insulating properties also make aerogels useful in noise-reducing automotive and aircraft panels.

Gas separation membranes

Some formulations of metallic aerogels selectively allow only certain gases like hydrogen or helium to pass through, finding use in industrial gas separation and purification processes.

Transparent insulation

When pure and transparent, aerogels let light through but block infrared and heat transfer, creating a new class of “transparent insulation” for energy-efficient building windows.

Virginia Tech Research on Polyphenylene Sulfide (PPS) Aerogels

Moore and Williams Research Collaboration

Researchers Tyler Moore and Eric Williams from Virginia Tech’s Macromolecules and Interfaces Institute have been collaborating on the development of polyphenylene sulfide (PPS) aerogel materials. PPS is an engineering thermoplastic known for its heat and chemical resistance but has not previously been made into an aerogel form.

Developing PPS Aerogel Material

Moore and Williams saw potential advantages of creating a PPS aerogel that could leverage the polymer’s inherent strength and stability attributes while gaining the low density and insulation properties of an aerogel network. Through experimentation with gelation and supercritical drying techniques, they succeeded in creating the first pure PPS aerogel monoliths.

Initial tests revealed the PPS aerogel has over 90% porosity yet maintains the tensile strength of the dense plastic. Its highly porous structure provides excellent thermal insulation with a very high surface area for applications like catalyization. The aerogel’s opacity allows incorporating dyes or fillers more uniformly compared to dense PPS parts.

Simple PPS Gel Production Process

A notable feature of the PPS aerogel production method is its simplicity compared to silica or resorcinol-formaldehyde aerogels. The team found a one-step process using a polymerization of PPS solution followed by cold water coagulation results in a self-supported wet gel network.

Supercritical CO2 drying then removes the water without collapsing the structure. No toxic crosslinkers or catalysts are required, avoiding complex chemical syntheses. This makes the PPS aerogel more economically scalable and environmentally friendly to manufacture.

Benefits of 3D Printable PPS Aerogel

Perhaps the most innovative aspect is the aerogel’s rheological properties allow it to be 3D printed via direct ink writing before drying. This creates the potential for complex customized aerogel parts with architected internal structures.

Moore and Williams are working on formulating aerogel “inks” of varied density, stiffness, and conductivity for 4D printing that enables post-print shape-shifting. Lightweight wearable devices, deployable aerospace structures, and biomedical scaffolds are some envisioned applications.

The Virginia Tech team’s development of 3D printable PPS aerogels opens new design frontiers for high-performance insulating materials that leverage the production advantages of additive manufacturing. Further applications are being explored through collaborative research.

3D Printing PPS Aerogels

Godshall and Rau’s Contributions

Virginia Tech engineering professors Will Godshall and Wolfgang Rau joined Tyler Moore and Eric Williams’ research efforts to realize the potential of 3D printed PPS aerogels. Godshall brought expertise in additive manufacturing technologies while Rau specialized in high temperature processing of polymers.

Together they aimed to develop the required 3D printing capabilities to handle the supercritical drying stage directly within the printer itself, closing the processing loop. This would eliminate any shape limitations of printing wet gels for the final aerogel parts.

Designing a High Temperature 3D Printer

Godshall oversaw the redesign of an industrial polymer 3D printer to withstand temperatures up to 400°C and pressures over 150 bar within its print chamber. Special sealing and heating elements were incorporated along with windows for monitoring the enclosed drying process.

The team also installed real-time monitoring of critical parameters like temperature gradients and stresses on printed parts. Rau implemented software controls to precisely ramp conditions for supercritical CO2 exposure matching the drying conditions developed by Moore and Williams.

Printing and Post-Processing of PPS Aerogels

Once testing validated the high-temp printer’s functionality, Moore and Williams worked on optimizing the PPS aerogel “ink” rheology for direct deposition. Initial prints showed how the ink’s non-Newtonian shear-thinning properties enabled delicate overhanging structures.

Within the closed chamber, the conditions were raised above the critical point of CO2 while simultaneously reducing stresses. This allowed full supercritical extraction and drying of the printed parts without collapse or distortion of the desired intricate 3D structures.

Tuning Aerogel Properties Through Printing

By varying print speeds, densities, and supercritical processing profiles, the team could engineer aerogels with tailored insulating values from 0.03 to 0.20 W/m-K as well as custom mechanical strengths. Porosity ranged from 80 to 98% of total volume.

Finer printing also let the researchers introduce sophisticated internal channeling and gradations on the microscale unachievable by any other method. This “4D printed aerogel” concept is attracting attention for biomedical regenerative scaffolds.

The Virginia Tech collaboration pioneered fully-additive 3D printing of PPS aerogels through an innovative high-temperature workflow. Further work may expand the library of printable aerogel materials.

Impact of 3D Printed PPS Aerogels

The development of 3D printable PPS aerogels by the research team at Virginia Tech has significant implications for advancing aerogel technologies. Some of the key impacts include:

Enabling Complex Aerogel Shapes and Designs

Additive manufacturing allows producing aerogels with unprecedented geometries that were previously impossible to achieve. Internal cavities, graded porous structures, interlocking profiles – 3D printing opens the design space exponentially.

This enables tailoring aerogel properties over complicated three-dimensional forms, from biomedical implants to deployable spacecraft components. Shape-changing “4D printing” adds the potential for stimulus-triggered transformations.

Applications for Insulation and Lightweight Structures

PPS aerogels combine insulation performance with mechanical strength and chemical/thermal resistance for use in challenging environments. Printed monoliths or hybrid composites provide insulation for equipment, pipes, and industrial facilities operating at high temperatures.

Lightweighted aerogel parts help save fuel and improve efficiency in transportation. Architected aerogel lattices could revolutionize insulated building panels and pave the way for entirely new aerogel construction techniques.

Reducing Material Use and Improving Efficiency

Additive printing produces aerogels on-demand with minimal material waste by depositing only what is needed. Complex geometries use less material than block counterparts to achieve the same function.

Processing aerogels in a single closed-loop 3D printer also dramatically improves efficiency over multi-step batch methods. This enhances the commercial viability of aerogels for widespread industrial uptake.

Potential for Further Material Development

The refined processing control achieved in high-temperature 3D printing may enable aerogelizing new classes of high-performance polymers and composites not possible before.

New aerogel “inks” could incorporate advanced fibers, plates, particles or functional additives during printing to unlock a new generation of multifunctional printable aerogel materials. This drives further innovation across aerospace, energy, electronics and beyond.

Overall, 3D printing methods like those pioneered at Virginia Tech position aerogels for significantly broader utilization by giving designers and engineers unprecedented control over material architecture from micro- to macro-scales.

Fazit

The research conducted by Moore, Williams, Godshall, Rau and their collaborators at Virginia Tech represents a major breakthrough in the field of aerogel materials. By developing the first 3D printable PPS aerogel and customized printing/processing techniques, they have opened entirely new avenues for utilizing aerogels that were previously impossible.

The ability to 3D design and produce aerogels as complex architectural structures tailored on the macro, micro and even nano scales unlocks a broad spectrum of new applications. From lightweight insulation and composites, to biomedical scaffolds and deployable aerospace components, 3D printed aerogels are poised to significantly impact many industries.

While this work focused on PPS, the refined high-temperature 3D printing capabilities also provide a prototype for additive manufacturing of other polymer and hybrid aerogel systems. Continued innovation in printable aerogel compositions will further extend their design space. Commercial utilization of 3D printed aerogels has great potential to enable more efficient product and building insulation worldwide.

FAQs

Q: What makes PPS a good candidate for aerogel 3D printing?

A: PPS is an engineering thermoplastic known for its strength, heat resistance and chemical stability. These properties allow PPS aerogels to maintain their shape through high-temperature processing like supercritical drying within a 3D printer.

Q: How do the rheological properties of PPS aerogel inks enable 3D printing?

A: PPS aerogel inks are non-Newtonian and shear thinning, meaning they flow easily when extruded but rapidly solidify, allowing overhangs and complex designs to be printed. Their viscosity can also be tuned for different printers and resolution.

Q: What types of applications are 3D printed PPS aerogels being developed for?

A: Potential uses include lightweight insulation for pipes, equipment and building panels. Complex lattice structures could enable new construction techniques. Aerospace, biomedicine and energy applications are also being explored through continued research refinement.