*2.2. Fourier Transform Infrared (FTIR) Analysis*

Analysis of the structure of the molecules and functional groups present in the samples were determined using an FTIR spectroscopy, to investigate the chemical bonding with the addition of soy flour and lignin as binders. The samples were ground into approximately 1.0 mg of powder, mixed with approximately <100 mg of potassium bromide (KBr), and was then compressed to form 1.0 mm thickness of pellet. In this analysis, FTIR spectrophotometer (IRPrestige21, Shimadzu, Japan) at the School of Industrial Technology, Universiti Sains Malaysia was utilized.

#### *2.3. X-ray Diffraction (XRD) Analysis*

XRD analysis was carried out using Bruker's D8 Advance X-Ray Diffractometer at the Center of Global Archeological Research, Universiti Sains Malaysia, to estimate the degree of crystallinity of the fabricated samples. On the sample holder, the powdered samples were hydraulically pressed into 25 mm diameter circular discs. The samples were radiated at energy of 40 kVp. The source used was Cu-Kα1, with wavelength λ of 1.54060 Å, scanning range of approximately 5◦ 2θ to 70◦ 2θ and scanning speed of 0.02◦ 2θ/s.
