Table 3.

Selected studies on surface modifications of CNMs for PLA composites.

Type	Extraction Process and Source	Functionalization Method	Refs.
CNCs	Microcrystalline cellulose by acid hydrolysis	PLLA grafting using surface-initiated ring opening polymerization	[57]
	Microcrystalline cellulose by sulfuric acid hydrolysis	Glycidyl methacrylate (GMA) grafting	[58]
	Linter by sulfuric acid hydrolysis	PCL grafted via ring-opening polymerization under microwave irradiation	[56]
	Scoured cotton by HCℓ hydrolysis	One-pot Fischer esterification approach was adopted to esterify CNCs with lactic acid	[52]
	Bamboo particles by sulfuric acid hydrolysis	Salinization of CNCs by using triethoxysilane (A-151)	[55]
	Cotton pulp by mild H2SO4	Carboxylation using potassium permanganate and oxalic acid as oxidizing and reducing agent, respectively	[63]
CNFs	Microcrystalline cellulose was subjected to high-speed homogenizer	Acetylation using rice bran oil (RBO)	[54]
	Bamboo pulp pre-treated by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation by using a TEMPO/NaBr/NaClO system to facilitate disintegration by using a high-pressure homogenizer	Carboxylation of CNF via TEMPO oxidation	[61]
	Titanate coupling agent was dissolved in tetrahydrofuran (THF, 10 g) and introduced into 15 wt % of MCC in (THF)	The hydroxyl groups react with the monoalkoxy and neoalkoxy to form monomolecular layer	[64]
	Bleached pulp was homogenized with 30 passes at ~1000 bar and treated with 3-amino triethoxysilane (ATS)	Salinization using 3-amino triethoxysilane (ATS)	[65]