Amphiphilic Cellulose Nanocrystals for Aqueous Processing of Thermoplastics

Abstract

Conventional composite formulation of cellulose nanocrystals (CNCs) with thermoplastics involves melt compounding or in situ polymerisation. In this rather unconventional approach, polypropylene (PP) microparticles were finely suspended and stabilized, at varying weight loadings, in aqueous suspensions of amphiphilic CNCs to enable adsorption of the nanoparticles onto the thermoplastic. In order to achieve these suspensions, CNCs were modified with either octyl or hexadecyl groups. These modifications imparted hydrophobic properties to the CNCs, hence increasing interfacial adhesion to the PP microparticles. The modification, however, also retained the sulfate half ester groups that ensured dispersibility in aqueous media. The CNCs were evidently coated on the PP microparticles as revealed by confocal microscope imaging and had no detrimental effect on the melt properties of the PP-based composites. The approach is demonstrated to increase the Young’s moduli of CNC-thermoplastic composites prepared in optimum suspension loadings of 0.5 wt. % octyl-modified and 0.1 wt % hexadecyl-modified CNCs. This procedure can be extended to other thermoplastics as the ability to aqueously process these composites is a major step forward in the drive for more sustainable manufacturing.

Evaluation of Surface Free Energy Inducing Interfacial Adhesion of Amphiphilic Cellulose Nanofibrils

“…1,57,58 Onyianta et al also reported that the chemically modified amphiphilic CNCs can be compounded with polypropylene microparticles in an aqueous system. 59 Figure 5 shows the differences in W ad values between the ACC-BCNFs and various resins in water (the surface free energy parameters of the resins used for the calculations are listed in Table S6). These differences indicate that the acid− base interaction is the predominant component in adhesion interactions in water.…”

“…To date, CNFs, which have high mechanical strength, have mainly been used as fillers for nanocomposites. Kondo et al recently proposed an ecofriendly compounding process (i.e., gentle shaking) that involved the underwater adsorption of CNFs onto hydrophobic resin microparticles. ,, Onyianta et al also reported that the chemically modified amphiphilic CNCs can be compounded with polypropylene microparticles in an aqueous system …”