Additive Manufacturing of Carbon Using Commodity Polypropylene

Abstract

focused on research and product development of carbon-based materials, exemplified by the discoveries of fullerene, [10] carbon nanotubes [11] and graphene, [12] as well as fabrication of porous carbon [13] and carbon black additives for many commercial applications. [14] However, most industries can only employ these functional carbon materials as fillers, necessitating additional components, often polymer matrices, for imparting processability. [15,16] The presence of matrix materials can greatly diminish many intrinsic advantages of carbons, leading to compromised material performance. Furthermore, necessary steps of mixing and processing in composite manufacturing may lead to high energy consumption and carbon footprint, resulting in an enormous negative impact on the environment. Enabling ondemand manufacturing of carbons with controlled macroscopic structures is necessary to unlock their full potential in various applications, while addressing urgent societal challenges including climate change and environmental sustainability.Generally, creating structured carbon materials rely on the use of polymer precursors, combined with pyrolysis-based approaches to allow their conversion to carbon materials. [17][18][19] A common example in this area is carbon fiber manufacturing, which uses polyacrylonitrile (PAN) as a carbon precursor and involves multiple processing steps, including fiber spinning, drawing, thermal stabilization/crosslinking and carbonization. [20] Alternatively, many other carbon precursors have been reported, including pitch-based chemicals, [21] lignin, [22,23] cellulose, [24,25] polyethylene (PE), [26][27][28] polypropylene (PP) [29,30] and polybenzoxazines. [31,32] While these chemical can be effectively converted to carbons, the scope of most work in the area of structured carbon production is associated with fibril materials; [33] the ability of manufacturing carbon with complex architectures at macroscopic scale is largely underexplored.In recent years, additive manufacturing (AM) has attracted significant attention in both academic research labs and largescale manufacturing facilities, leading to wide recognition as a key future manufacturing technology. [34] AM can create products through layer-by-layer addition without the need for tools and molds, which is also inherently less wasteful than traditional subtractive-based methods due to its significantly Carbon materials are essential to the development of modern society with indispensable use in various applications, such as energy storage and high-performance composites. Despite great progress, on-demand carbon manufacturing with control over 3D macroscopic configuration is still an intractable challenge, hindering their direct use in many areas requiring structured materials and products. This work introduces a simple and scalable method to generate complex, large-scale carbon structures using easily accessible materials and technologies. 3D-printed, commercial polypropylene (PP) parts can be thermally stabilized through cracking-faci...

Precursor design for efficient synthesis of large-pore, sulfur-doped ordered mesoporous carbon through direct pyrolysis

“…Notably, sulfonation induced crosslinking in polyolefin systems has been demonstrated as a diffusion-controlled reaction. [29][30][31] Herein, by including unsaturated bonds in the precursor design of the amorphous polyolefin-containing systems (Fig. S1 †), it is found that the required crosslinking time can be significantly reduced from 4 h (for SEBS) to 20 min (for SBS), corresponding to nearly 8-fold enhancement in reaction kinetics.…”

Sulfonation-Induced Cross-Linking and Nanostructural Evolution of a Thermoplastic Elastomer for Ordered Mesoporous Carbon Synthesis: A Mechanistic Study

“…The 145 °C reaction condition approaches a plateau after reaction for 4 h at a value of 48%, which increases slightly to 52% after reaction for 8 h; these mass gain values are similar to those of other studies using polypropylene as a carbon precursor. 43,44 It is worth noting that extension of the reaction at 145 °C to 12 h results in a slightly decreased value for both mass gain and gel fraction. It is observed that this sample breaks down into very fine powders after reaction (Figure S3), suggesting that the decreased mass gain and gel fraction are potentially due to significant degradation/scission of the polymer chains becoming prevalent at long reaction times suggesting oversulfonation.…”

Direct Upcycling of Woven Polypropylene Fabrics to Carbon‐Based Joule Heaters

“…Notably, the sulfonation reaction introduces sulfonic acid groups which impart hydrophilicity to the PP backbone, facilitating acid penetration to further promote crosslinking. As a comparison, a previous study investigated the use of PP‐based filaments to prepare 3D structured carbon, [ 51 ] through similar sulfonation‐based crosslinking and carbonization approach. Investigation of the 3D printed structure's morphology after crosslinking revealed the formation of micron‐sized cracks which promoted diffusion of sulfuric acid throughout the structure and subsequently accelerate reaction kinetics.…”