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200096

Project description:

Project no:
200096
Title:
Transparent Oriented Strandboard
1st project leader:
Laborie, Marie-Pierre - Forest Biomaterials, Institute of Earth and Environmental Sciences, University of Freiburg, Freiburg im Br
2nd project leader
Description:
Oriented strand board stands (OSB) is one of the most widespread wood-based composites deemed for structural application. With a modulus of elasticity of 4.4 Gpa and a bending strength of 20 to 30 MPas, it is commonly used as a primary sheathing component in buildings.

Recently, transparent wood (Fink 1992) has emerged as a new class of material, which could have semi-structural applications (Zhu et al 2016). Transparent wood transmits 90% of light, display haze properties and depending on the wood species used achieves tensile moduli of 2-4 GPa and tensile strength in the range of 10 to 150 MPa in the longitudinal direction of wood (Li et al. 2018). Additionally, transparent exhibits higher ductility and work to fracture than glass, which is highly desirable for building applications (Li et al 2018b). As it builds on the hierarchical organization of wood, it displays a similar anisotropy as wood while retaining a rather low density of ca 1.2 g/cm3 compared to other construction materials (Li et al. 2018a). It is therefore particularly interesting for building applications. Transparent wood is currently prepared by wood delignification followed by an infiltration and polymerization of a synthetic resin, most often an epoxy or acrylic resin, presenting a similar refractive index as the delignified cellulosic template. Unfortunately, to date only small pieces of transparent wood (190 mm x 210 mm x 40 mm, Li and Zheng 2019) could be produced due to the fragility of the delignified template. This doctoral work will investigate the possibility to prepare OSB using transparent wood flakes in order to deliver a structural, transparent and large sized- OSB. The research involves the optimization and upscaling of the production of transparent wood flakes together with the process optimization of transparent OSB manufacture towards maximum transparency and mechanical performance. In this process, multiple infiltrating resins should be investigated for their suitability and performance towards the manufacture of transparent OSB composites.
References:
Fink S., 1992, Holzforschung 46, 403-408

Li Y, Fu Q., X. Yang and L. Berglund, 2018a, Philosophical transactions Soc. A, 376:20170182

Li y., Vasileva H., Sychugov I., S. Popov and L. Berglund, 2018b, Advanced optical Materials, 2018, 6, 1800059

H. Li , X. Guo, Y. He , R. Zheng, 2019, European Journal of Wood and Wood Products (2019) 77:843–851. https://doi.org/10.1007/s00107-019-01431-w

Zhu, M., J. Song, T. Li, A. Gong, Y. Wang, J. Dai Y. Lao, W. Luo, D. Henderson and L. Hu, Adv. Mater. 2016, 28, 5181-5187.
Methods that will be used:
Optimization of the preparation of transparent wood flakes: various delignification procedures should be tested in order to prepare the most robust delignified templates. Additionally, a series of synthetic resins, including epoxies, acrylates and polyurethanes shall be tested. The infiltration of the resin and its compatibility with the wood polymers will be investigated with spectroscopic and microscopic approaches. The optical and mechanical properties of the transparent flakes will be tested with UV/Vis spectroscopy, colorimetry and microtensile testing.

Characterization and modelling of resin hardening: the chemistry and kinetics of hardening of the selected resin will be studied by vibrational spectroscopy and thermal analysis, in particular with differential scanning calorimetry and dynamic mechanical analysis. Cure kinetics models should be developed based on this characterization.

Optimization of OSB manufacture with transparent wood flakes: OSB panels will be prepared by hotpressing transparent wood flakes, utilizing the impregnating polymer matrix as bonding agent. A Design of experiment will be conducted to optimize the processing conditions and the final density profile of the OSB.

Performance assessment of transparent OSB: the transparency and optical properties of the resulting transparent OSB will be tested with UV/ Vis spectroscopy and colorimetry. Mechanical performance of the OSB will be evaluated in accordance to ASTM D1037. Possible structure-properties relationships should be established between veneer attributes and OSB properties.
Collaboration partners:
Prof. Siegfried Fink, Chair of Forest Botany, University of Freiburg
Expected candidate‘s qualification:
The candidate should have a wood science and technology background and /or a chemical engineering /chemistry background. He/she should have experience working in a wet chemistry laboratory as well as in the manufacture of wood-based composites. Experience with common analytical tools for polymer characterization (vibrational spectroscopy, thermal analysis, microscopy) are desirable. The candidate should demonstrate excellent commands of english both in writing and in speaking.
Keywords:
Oriented strand board, transparent wood, polymer science, mechanical properties, wood/polymer interface