The molecular structure of guar gum is shown in Fig. 1 . Guar gum is extracted from the endosperm of the leguminous plant guar bean as a free-flowing powder. The powder is generally white to light yellowish brown in colour and is nearly odourless. Guar gum is composed of approximately 75–85% polysaccharide, 5–6% protein, 2–3% fibre and 1% ash.
Guar gum is a non-ionic neutral polysaccharide, with D-mannose linked by a β-1,4 bond as the main chain and D-galactose linked at the α-1,6 position as the branch chain. In general, the molar ratio of galactose to mannose is 1:2. The spatial structure of the plant is a curled spherical structure, with mannose on the inside and galactose on the outside. The ratio of mannose to galactose varies slightly for different plant varieties.
Guar gum  is a type of water-soluble natural polymer, which can be quickly hydrated in cold or hot water to obtain a translucent viscous liquid. The viscosity of a guar-gum-containing aqueous solution reflects the molecular weight of guar gum, while the swelling rate reflects the degree of difficulty that is encountered in swelling in guar gum applications. Higher temperatures can accelerate the swelling of guar gum, weaken the hydrogen bonding between molecular chains, increase the elongation of molecular chains and reduce the viscosity.
Notably, guar gum can form a high-viscosity aqueous solution at low concentrations  due to entanglement between polymer chains and intramolecular and intermolecular hydrogen bonding. The viscosity of 1% guar gum in aqueous solution is approximately 4000–6000 MPa∙s. In addition, guar gum aqueous solutions exhibit typical winding polymer characteristics, corresponding to the pseudoplastic fluid characteristics of a non-Newtonian fluid, with no yield stress. Because guar gum is widely utilized and exhibits a high viscosity and rheological properties in natural rubber, the THz absorption of guar gum was studied in this work, with guar gum acting as a representative colloid for further experimental research.