19 research outputs found
Thermally Conductive-Silicone Composites with Thermally Reversible Cross-links
Thermally conductive-silicone
composites that contain thermally
reversible cross-links were prepared by blending diene- and dienophile-functionalized
polydimethylsiloxane (PDMS) with an aluminum oxide conductive filler.
This class of thermally conductive-silicones are useful as thermal
interface materials (TIMs) within Information Technology (IT) hardware
applications to allow rework of valuable components. The composites
were rendered reworkable via retro Diels–Alder cross-links
when temperatures were elevated above 130 °C and required little
mechanical force to remove, making them advantageous over other TIM
materials. Results show high thermal conductivity (0.4 W/m·K)
at low filler loadings (45 wt %) compared to other TIM solutions (>45
wt %). Additionally, the adhesion of the material was found to be
∼7 times greater at lower temperatures (25 °C) and ∼2
times greater at higher temperatures (120 °C) than commercially
available TIMs
Recyclable, strong thermosets and organogels via paraformaldehyde condensation with diamines
Nitrogen-based thermoset polymers have many industrial applications (for example, in composites), but are difficult to recycle or rework. We report a simple one-pot, low-temperature polycondensation between paraformaldehyde and 4,4′-oxydianiline (ODA) that forms hemiaminal dynamic covalent networks (HDCNs), which can further cyclize at high temperatures, producing poly(hexahydrotriazine)s (PHTs). Both materials are strong thermosetting polymers, and the PHTs exhibited very high Young's moduli (up to ∼14.0 gigapascals and up to 20 gigapascals when reinforced with surface-treated carbon nanotubes), excellent solvent resistance, and resistance to environmental stress cracking. However, both HDCNs and PHTs could be digested at low pH (<2) to recover the bisaniline monomers. By simply using different diamine monomers, the HDCN- and PHT-forming reactions afford extremely versatile materials platforms. For example, when poly(ethylene glycol) (PEG) diamine monomers were used to form HDCNs, elastic organogels formed that exhibited self-healing properties
Recyclable, strong thermosets and organogels via paraformaldehyde condensation with diamines
\u3cp\u3eNitrogen-based thermoset polymers have many industrial applications (for example, in composites), but are difficult to recycle or rework. We report a simple one-pot, low-temperature polycondensation between paraformaldehyde and 4,4′-oxydianiline (ODA) that forms hemiaminal dynamic covalent networks (HDCNs), which can further cyclize at high temperatures, producing poly(hexahydrotriazine)s (PHTs). Both materials are strong thermosetting polymers, and the PHTs exhibited very high Young's moduli (up to ∼14.0 gigapascals and up to 20 gigapascals when reinforced with surface-treated carbon nanotubes), excellent solvent resistance, and resistance to environmental stress cracking. However, both HDCNs and PHTs could be digested at low pH (<2) to recover the bisaniline monomers. By simply using different diamine monomers, the HDCN- and PHT-forming reactions afford extremely versatile materials platforms. For example, when poly(ethylene glycol) (PEG) diamine monomers were used to form HDCNs, elastic organogels formed that exhibited self-healing properties.\u3c/p\u3