RESEARCH ARTICLE Melt‐blending of unmodified and modified cellulose nanocrystals with reduced graphene oxide into PLA matrix for biomedical application Nidhi Pal 1 | Somesh Banerjee 2 | Partha Roy 2 | Kaushik Pal 1,3 1 Department of Mechanical and Industrial Engineering, IIT Roorkee, Uttarakhand 247667, India 2 Department of Biotechnology, IIT Roorkee, Uttarakhand 247667, India 3 Center of Nanotechnology, IIT Roorkee, Uttarakhand 247667, India Correspondence Kaushik Pal, Center of Nanotechnology, IIT Roorkee, Uttarakhand 247667, India. Email: pl_kshk@yahoo.co.in Funding information Science and Engineering Research Board, Grant/Award Number: SB/S3/ME‐024/2015 In this article, we successfully fabricated the bionanocomposites using cellulose nanocrystals (CNCs) and reduced graphene oxide (rGO) reinforced into biodegradable polylactic acid (PLA) matrix through melt‐mixing method. Due to the affinity differ- ence between hydrophilic CNC and hydrophobic PLA, the surface modification of CNC was employed using quaternary ammonium salts (CTAB) as a surfactant. The nanocomposites were developed using different blend ratios of CNC/modified CNC (1, 2, and 3) wt% and (0.5 wt%) rGO into the polymer matrix. The morphology of CNC, q‐CNC (modified CNC), and nanocomposites were inspected by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). It is demonstrated from tensile tests that, the nanocomposite with 1 wt% CNC and rGO showed maximum tensile strength compared with PLA and its nanocomposites. Moreover, the nanocomposite with 1 wt% CNC and rGO was also having maximum thermal stability. From cytotoxicity evaluation, it is observed that all the nanocompos- ites are nontoxic and cytocompatible to HEK293 cells. In addition to this, the nano- composite with q‐CNC showed enhanced barrier properties compared with PLA and PLA/CNC/rGO nanocomposite. The results obtained from different characteriza- tions showed that the incorporation of surfactant onto CNC improved the dispersion in PLA but at the same time deteriorated the PLA matrix. KEYWORDS cellulose nanocrystal, melt‐mixing, polylactic acid, quaternary ammonium salt 1 | INTRODUCTION Polylactic acid (PLA) is an aliphatic polyester, compostable, and bio‐ based polymer which is attained from renewable resources such as sugarcane and corn starch and is a justifiable substitute to petrochemical‐based products. It has established numerous applica- tions in different areas such as biological scaffolds, drug delivery, and food packaging industry as well as in automotive industry. PLA can be injection molded into different shapes, extruded into films, and spun to obtain fibers. PLA made products are bio‐degradable and observed to fully disappear within 30 days in ideal conditions. However, the mechanical and processing requirements in many applications cannot be alone satisfied by PLA. Thus, to meet those requirements, efforts have been reported through various different approaches, such as blending of PLA with other bio‐based polymers 1 or may be with non–bio‐based nanofillers for example carbon nano- tubes, clay, 2-4 and cellulose nanocrystals (CNCs). CNCs as a nanofiller would constitute an excellent alternative to reach the requirements without sacrificing the biocompatibility and biodegradability of PLA. 5 CNC are rod‐shaped nanoparticles which can be obtained by acid hydrolysis of cellulose fibers, 6,7 which is an abundant natural biopoly- mer present on Earth, and have 1 to 100‐nm diameters with length varying in tens to hundreds of nanoscale. 8 It has been recognized as a potential reinforcement agent for biodegradable polymers which Received: 27 April 2019 Revised: 13 July 2019 Accepted: 13 July 2019 DOI: 10.1002/pat.4736 Polym Adv Technol. 2019;1–12. © 2019 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/pat 1