Table 1: Physical properties of samples.

Material (CHFs)Thickness ()
(mm)
Density (Kg⋅m−3)Porosity ()Airflow resistivity () (Pa⋅s⋅m−2)Tortuosity ()

Raw20344
Treated (1% NaOH)20438
Treated (2% NaOH)20566
Treated (5% NaOH)20584
Treated (8% NaOH)20615