Cellulose (2023) 30:5447–5471
5465
residue occurred, the ETW composite formed a visible layer of char on the residue, therefore, heat transfer between the flame and composite was pre- vented within 2 s. Cho et al. (2021) fabricated heat- shielding transparent wood by application of indium tin oxide on its surface. Balsa wood (50 × 50 × 1.4 mm 3 ) was delignified and infiltrated with epoxy to produce ETW with 80% light transmittance, die- lectric constant of 3.344 and the loss tangent was observed at 0.0552. The addition of indium tin oxide resulted in heat shielding ETW with approxi- mately 62% light transmittance. On the other hand, fabrication of heat shielding ETW by the addition of TiO 2 nanoparticles resulted in a higher transmit- tance and haze of 90% and 90%, respectively. The thermal conductivity was 0.3228 W m − K −1 (Wu et al. 2022). Fu et al. (2018) fabricated luminescent ETW by delignification of wood veneers followed by compression, impregnation of PMMA com- bined with quantum dots lamination and polymeri- sation. In another study, Wang et al. (2021) fabri- cated 1 mm, 2 mm, and 3 mm thick programmable shape-memory transparent wood (PSMTW) from balsa wood (density 126 kg m −3 ), using NaCIO 2 under acidic conditions, followed by infiltration of epoxy vitrimers. Light transmittances of 75.7%, 61.8%, and 52.8% were reported for 1 mm, 2 mm, and 3 mm thick PSMTW, respectively, whereas the haze for all the ETW samples was approx. 95%. Gan et al. (2017a) endowed transparent wood with magnetic properties by adding RI-matching MMA and magnetic Fe 3 O 4 nanoparticles into the deligni- fied wood template for application in light-trans- mitting magnetic buildings and magneto-optical devices. The magnetisation of ETW increased with an increase in the concentration of Fe 3 O 4 nanoparti- cles. However, the mechanical properties decreased with an increase in the concentration of the agglom- eration and concentration of the nanoparticles in the cracks in the aggregates. Rao et al. (2019) produced flexible ETW with potential application as a light shaping diffuser by infiltration of aqueous propyl- ene glycol (PG) and plasticised PVP into bleached wood veneers. A light transmittance as high as 80% and a haze of 90% were achieved at a ratio of 1:1 of PG and PVA. Images (Fig. 5) were used to dem- onstrate the flexibility of ETW (a) bent across the fibre direction; (b) bent across the perpendicular direction of fibre orientation; (c) twisted, and (d)
rolled. Wang et al. (2022) also fabricated flexible ETW by polymerisation of EDCP in a delignified wood template via an epoxy-thiole reaction. The resulting ETW possessed plasticity, shape manipu- lation capability, good thermal insulation and opti- cal properties. Bending tests were performed on the ETW of 2 mm thickness to measure the bend- ing deformation angles. Stress was applied by an external force on the ETW to form curved shapes at 60 °C and fixation temperature of 0 °C to obtain a temporary shape and recovery observed within 30 min when the temperature was increased back to 60 °C. T-ETW was initially deformed to a tem- porary curved shape with an angle of 0°. Measure- ments showed gradual recovery to original rectan- gular shapes of the deformed T- ETW marked by an increase in bending deformation angles from 0° to 3°, 8°, 18°, 40°, 100°, 144° and 156° from after 0 s, 10 s, 30 s, 1 min, 2 min, 5 min, 10 min and 30 min recovery time, respectively (Wang et al. 2022). In the case of L-ETW, an increase in bending deforma- tion angles from 0° to 3°, 14°, 39°, 91°, 161°, 166° and 170° from after 0 s, 10 s, 30 s, 1 min, 2 min, 5 min, 10 min and 30 min recovery time, respec- tively (Wang et al. 2022). Li et al. (2017b) produced luminescent transparent wood by the infiltration of quantum dots dispersed in a PMMA/oligomer liq- uid mixture. Yu et al. (2017) produced 5 mm thick heat shielding ETW from beech wood via NaOH, Fig. 5 Images showing the flexibility of ETW produced by infiltration of PG and PVA (a) (a) bent across the fibre direc- tion; (b) bent across the perpendicular direction of fibre orien- tation; (c) twisted and (d) rolled. Reproduced with permission Copyright 2019, Elsevier (Rao et al. 2019)
1 3 Vol.: (0123456789)
Made with FlippingBook Digital Publishing Software