Camphene as a Mild, Bio-Derived Porogen for Near-Ambient Processing and 3D Printing of Porous Thermoplastics

Abstract

Porous structures are ubiquitous in nature due to their advantageous mechanical and transport properties. These structures have inspired various synthetic porous polymer technologies, including lightweight structural materials and membranes. While many manufacturing processes have been developed to generate porous thermoplastics, these usually include hazardous processes, such as high pressures and temperatures, or chemical components. Furthermore, few are compatible with additive manufacturing methods, such as 3D printing. Herein, we introduce bio-derived terpene camphene as a solvent and porogen for the freeze-casting of thermoplastic parts under mild conditions. Enabled by a low melting point (50 °C), camphene is used as a solvent for melt processing camphene-polymer solutions at moderate temperatures that later undergo room-temperature crystallization to template polymer-rich domains. Due to its high vapor pressure, camphene can be sublimed directly from these biphasic structures, resulting in an interconnected microporous polymer structure. Various polymers are demonstrated to be soluble in camphene, including polystyrene, an olefinic elastomer, a polystyreneblock-poly(ethylene-ran-butylene)-block-polystyrene elastomer, a cyclic olefin copolymer, and poly(ethyl methacrylate). Porous samples of each polymer were generated from camphene mixtures via compression molding, cooling, and subsequent vacuum annealing at room temperature to remove camphene. The porosity and pore structures were dependent on solution composition, including both the polymer type and polymer loading. Across the compositions investigated, porosity decreased monotonically from 93 to 65% with increasing polymer content. In the case of polystyrene, samples with pore diameters varying from ∼20 to <5 μm were generated. Rheological measurements were conducted on a series of polystyrene−camphene solutions to understand and optimize the formulation and conditions for direct ink write 3D printing. Porous parts with complex structures were successfully printed under mild conditions. These results underscore the advantages of camphene as a sustainable, nontoxic porogen and will inform future development of porous polymer systems derived from these methods.

Performance of Fabrics with 3D-Printed Photosensitive Acrylic Resin on the Surface

“…Camphane [ 37 ] may have been used in the mixture as an odor neutralizer for other ingredients used in the mixtures of acrylic inks. However, it is also known to be used as a porogen, which is a substance added to a material to create pore structures.…”

UV-Assisted Direct Ink Writing of Dual-Cure Polyurethanes

“…Resins were printed on a customized, in-house DIW system, previously used to print degradable, biosourced networks 30 and porous polymeric structures. 31 The DIW setup 32 consists of a 3-axis gantry and positioning system (modified Stratasys Dimension FDM printer) with a linear actuator for dispensing the resin, which is detailed in Figure S1. G-code files for printing were generated by using the Slic3r software, and printer operation was conducted via Repetier software.…”