Engineered transparent wood composites: a review

Wood is a versatile resource due to its inherent properties such as low density, good weight to strength ratio, unique hierarchical structure, microscale pores, and ease of processing, including its biodegradability and renewability. In the building and construction industry, engineered transparent wood (ETW) may serve as a sustainable replacement for glass which is environmentally unfriendly in its manufacture and application. Natural wood is non transparent due to its low optical transmittance, therefore, lignin and chromophores are modified or eliminated, and a polymer is infiltrated in order to achieve transparency. Engineered transparent wood (ETW) exhibits excellent optical properties (transmittance > 80%), high haze (haze > 70%), thermal insulation (thermal conductivity less than 0.23Wm(-1) K-1), unique hierarchical structure, good loadbearing performance with tough failure behaviour (no shattering) and ductility. These properties extend wood applications to optical components such as solar cells, screens, windows, magnetic materials, and luminescent and decorative materials. This review details the production of ETW and how the wood density, wood thickness, wood type, wood direction, cellulose volume fraction, extent and type of delignification, polymer type, functionalisation of ETW affect the morphological, functional, optical, thermal, photodegradation and mechanical properties of ETW.