ERI: Experimental Investigation of Heat/Mass Transfer Associated with Ignition and Combustion of Biopolymer Nanocomposites in 3D Printing to Improve Their Fire Safety

Three-dimensional printing of polymers, which can be processed easily at reasonable cost, has enabled customized fabrication of objects with complex geometries and functionalities. However, many of the polymers used exhibit low thermal stability and high flammability, especially biopolymers such as polylactic acid (PLA), which is one of the most common feedstocks for fused filament fabrication (FFF). One potential solution to this problem is to print polymer nanocomposites. However, the layered structure and bonding in FFF can lead to anisotropic properties and internal voids or gaps between printed layers that are not found in their counterparts manufactured using thermocompression. These properties may affect the ignition and combustion behaviors of 3D-printed polymer nanocomposites. The principal aims of this project are to systematically study heat and mass transfer dynamics of 3D-printed PLA nanocomposites with FFF and to better understand their effects on ignition and combustion behaviors. The insight from this project may guide the design of new flame-retardant systems and improved fire safety for 3D-printed biopolymer products, which could reduce the frequency and severity of fires. This proposed research is a multidisciplinary project that integrates research and educational activities to enhance the pool of multidisciplinary engineers and professionals in local communities. The goal of this project is understand the heat transfer and mass transfer associated with the ignition and combustion of 3D-printed biopolymer nanocomposites. Literature is scarce on the use of polymer nanocomposites for 3D-printing applications to reduce their flammability hazards, although this technique is effective in bulk polymers manufactured using thermocompression. Samples manufactured using thermocompression show a uniform dispersion of nanoparticles, leading to a homogeneous and isotropic material structure. By comparison, samples manufactured using 3D printing show different structural characteristics. Besides the anisotropic properties and the presence of voids, 3D-printed parts often are not uniformly filled; instead, they have internal infill patterns that provide structural support while minimizing material usage. The choice of infill density can affect the heat transfer and mass transfer in the anisotropic condensed phase of burning polymers. However, few studies have been performed to investigate these effects and gain a fundamental understanding. The project will fill this knowledge gap with three main objectives: (i) synthesize biopolymer nanocomposites-based filaments for 3D printing, (ii) manufacture samples using FFF and determine structural characterization, and (iii) study ignition and combustion behaviors of 3D-printed PLA nanocomposite samples under well-controlled fire conditions. This project is expected to promote the development of performance-efficient and cost effective flame retardant biopolymer nanocomposites for sustainable 3D printing applications. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.