Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions

Authors: ZHOU, LING - South China University Of Technology; HE, HUI - South China University Of Technology; MEI-CHUN, LI - Louisiana State University; SONG, KUNLIN - Louisiana State University; Cheng, Huai; WU, QINGLIN - Louisiana State University

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2016
Publication Date: 8/1/2016
Citation: Zhou, L., He, H., Li, M.-C., Song, K., Cheng, H.N., Wu, Q. 2016. Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions. Carbohydrate Polymers. 153:445-454.

Interpretive Summary: Cottonseed hull is a byproduct of cotton processing and is currently used as roughage in animal feed, as a garden or field mulch, or as a component of the growth media for mushroom production. Because cottonseed hull is available and inexpensive, it is useful to develop new uses with higher value. In this work, cottonseed hull was extracted for the first time to produce cellulose nanocrystals and nanofibers. The treatment processes included sulfuric acid hydrolysis, mixed acid hydrolysis and mechanical disintegration. The nanomaterials were characterized by scanning and transmission electron microscopy, FT-IR, steady-state and dynamic rheology. Through these means, the chemical composition and morphology of cellulose from cottonseed hull and cellulose nanomaterials were compared. Furthermore, the structure-rheology relationships of nanocellulose and their blended suspensions with poly(vinyl alcohol) were studied. Nanocellulose is being used as a strength additive for paper, functional filler for composites, thickener for food, absorbent in hygienic products, and many other applications. The nanocellulose extracted from cottonseed hull can be expected to have similar applications.

Technical Abstract: This work aims to extract and characterize fibrous, rod-like and spherical cellulose nanoparticles (CNs) from cottonseed hull and to investigate the structure-morphology-rheology relationships. The rheological behavior of poly(vinyl alcohol) (PVA)/CNs suspensions was also examined to guide the solvent casting process of isolated CNs/polymer composites. A multistep procedure, involving acidic sodium chlorite bleaching and alkali treatment, efficiently removed lignin and hemicelluloses as verified by FTIR spectra and SEM. Cellulose nanofibers (CNFs) were isolated by mechanical disintegration using wet disk milling and high-pressure homogenization. TEM and SEM results show that a rigid entangled network of nanofibers was formed in suspension and well-kept after freeze-drying. Spherical cellulose nanocrystals (SCNCs), which were prepared by mixed acid hydrolysis under ultrasonic treatment, had an average diameter of 30 nm from TEM measurement. After being freeze-dried, most SCNCs maintained similar spherical shape with irregular aggregations. Cellulose nanocrystals (CNCs) resulting from sulfuric acid hydrolysis had dimensions of 50 to 150 nm in length and 5 to 10 nm in width and self-assembled into a film-like structure after freeze-drying. Rheology results indicated that the rheological behavior of both CNs and CNs/PVA water suspensions strongly depended upon the morphology, dimensions (width, length and aspect ratio), and concentration of CNs.