Toward Sustainable Aesthetic Transparent Wood from a Fast-Growing Hardwood Species: Paulownia Wood Templates Infused with Epoxy Bioresin

TL;DR

Researchers developed transparent wood from Paulownia wood using a bioresin, creating a sustainable material with aesthetic and functional properties.

Contribution

This study introduces Paulownia tomentosa as a novel fast-growing species for transparent wood production using epoxy bioresin infusion.

Findings

Delignification of Paulownia wood achieved 10–15% dry mass loss with preserved dimensional stability.

Infusion with epoxy bioresin increased optical transmittance up to 60% while restoring tensile strength.

The transparent wood retained visible natural wood features and improved brightness.

Abstract

Lignocellulosic biomass is an attractive renewable resource
for
the development of engineered materials in the framework of a green
economy. Transparent wood (TW) products show great potential in green
architecture, energy saving building, optical devices, electronics,
energy storage, and conversion devices. The fabrication of TW products
proceeds through the delignification of bulk wood samples followed
by infiltration with a refractive index-matched polymer. This study
is focused on Paulownia tomentosa (Thunb.) Steud.,
a fast-growing species rarely investigated, is characterized by low-density
wood and a distinct early to late wood pattern in each growth ring.
Delignification was performed by a conventional bleaching route. Aesthetic
wood was obtained by infusing the delignified templates with an epoxy
bioresin. The characterization was performed by nondestructive techniques:
optical microscopy, scanning electron microscopy, X-ray diffraction,
FT-IR spectroscopy, Raman spectroscopy, and UV–vis spectroscopy.
Thermal degradation profiles were acquired by thermogravimetry, and
mechanical strength was evaluated by tensile tests. The chemical treatment
led to 10–15% dry mass loss, mainly due to the removal of lignin,
and the efficacy of delignification was comparable for transversal
and longitudinal bulk wood. The removal of a minor amount of hemicellulose,
especially for axial samples, also occurred. Delignified templates
preserved dimensional stability in wet and dry states and showed increased
Segal crystallinity index (CI), reduced thermal stability, improved
total optical transmittance, increased brightness, and loss of tensile
strength. The infusion with the bioresin led to aesthetic wood characterized
by increased optical transmittance (up to 60% at 800 nm) combined
with fully recovered tensile strength and preserved natural wood features
clearly visible to the naked eye.

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