Densification of timber: a review on the process, material properties, and application

Cabral, John Paul; Kafle, Bidur; Subhani, Mahbube; Reiner, Johannes; Ashraf, Mahmud

doi:10.1186/s10086-022-02028-3

Journal of Wood Science

Official Journal of the Japan Wood Research Society

Table 2 Summary of densification methods

From: Densification of timber: a review on the process, material properties, and application

	Conditioning stage	Pre-heating/pre-treatment stage	Compression stage	Cooling stage	Post-Treatment Stage
TM	MC = 12–13%	Usage of platens or steam	Usage of heated platens	Temperature < 100 °C before release	Post-heating (ThermoWood Process)
			Temp = 130 °C–180 °C
			Pressure < = 14 MPa
	No thickness limitation	Open process	Holding time = minutes–hours		Post-steaming
	No thickness limitation	Open process	Open process		Post-steaming
THM	MC = 12%	Usage of saturated steam	Usage of heated platens and steam	Temperature = 60 °C	Not required
			Temp = 110 °C–200 °C
			Pressure < = 13 MPa
	No thickness limitation	Enclosed process	Increased steam pressure and temperature as treatment	Purging of the steam pressure before release
	No thickness limitation	Enclosed process	Holding time = minutes–hours	Purging of the steam pressure before release
VTC	MC = 12%	Conditioning the timber through heat or steam compression such that the glass transition temperature of the timber constituents is reached	Usage of heated platens	Temperature < 100 °C before release	Not required
			Temperature = 80 °C–200 °C (varies depending on T_g)
			Pressure = 2–4 MPa
	Virgin Timber Thickness = 3–12 mm	Usage of rapid vapour decompression to induce mechanosorption and to lower the compression modulus of the timber	Annealing Temperature < T_g
	Virgin Timber Thickness = 3–12 mm		Holding time = minutes
CHEMICAL	Follows densification method used	Impregnation using chemicals, such as acetyl anhydride, PF, MF, or other substances	Lower compressing pressures due to softening of timber constituents by impregnation	Follows densification method used	Not required
CHEMICAL	Follows densification method used		Holding = minutes to hours	Follows densification method used	Not required

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