Water-assisted extrusion and injection moulding of composites with surface-grafted cellulose nanocrystals – An upscaling study. (1st March 2021)

• Record Type: Journal Article
• Authors: Forsgren, Lilian; Venkatesh, Abhijit; Rigoulet, Florian; Sahlin-Sjövold, Karin; Westman, Gunnar; Rigdahl, Mikael; Boldizar, Antal
• Is Part Of: Composites. Number 208(2021)
• Publication Date: 2021-03-01
• Subjects: B. Mechanical properties -- C. Extrusion -- C. Injection moulding -- Cellulose nanocrystals; Composite materials -- Periodicals; Materials science -- Periodicals; Composite materials; Periodicals; Electronic journals; 620.118
• DOI: 10.1016/j.compositesb.2020.108590
• Languages: English
• ISSNs: 1359-8368

Abstract

Abstract: The large-scale surface modification of cellulose nanocrystals (CNC) was carried out to produce CNC-containing composites, in a scale of 3 kg, using industrial-scale melt processing techniques such as twin-screw extrusion and injection moulding. Two different polymer matrices, ethylene-acrylic acid copolymer (EAA) and low-density polyethylene (LDPE), were reinforced with 10 wt% unmodified cellulose nanocrystals (CNC) or surface-treated CNC, where a 2-hydroxyproyl-N-diallyl group had been grafted onto the sulphate half-ester groups on the CNC surfaces. This was achieved by mixing an aqueous CNC dispersion and the polymer pellets directly in the twin-screw extruder followed by a second dry compounding step prior to shaping by injection moulding. The injection-moulded materials were characterized with respect to their mechanical properties and thermal stability. The addition of 10 wt % CNC resulted in all cases in an increase in the yield strength and stiffness by 50–100%, most significantly for the EAA based composites. There were indications of the presence of a stable interphase and a percolating network in the EAA-based materials, according to dynamic-mechanical measurements. A reduction in thermal stability was observed for the melt-processed samples containing diallyl-modified CNC and discoloration in the EAA based samples. Highlights: Water-assisted extrusion mixing was successfully upscaled. Improved interaction with EAA7 when surface modified CNC was used. Increased stiffness and a rather large elongation at break maintained. Industrially plausible manufacturing from surface modification to final composite.