Cellulose nanocrystal in poly(lactic acid)/polyamide11 blends: Preparation, morphology and co-continuity

• Published in: European polymer journal 2018-01, Vol.98, p.11-20
• Main Authors: Heshmati, Vahid, Kamal, Musa R., Favis, Basil D.
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; Cellulose; Cellulose nanocrystal; Coalescing; Interfacial energy; Localization; Low level; Morphology; Nanocrystals; Poly(lactic acid); Polyamide11; Polylactic acid; Polymer blends; Rheological properties; Rheology; Surface tension
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2017.10.027

[Display omitted] •Localization of cellulose nanocrystal in PLA/PA11 is studied for the first time.•CNC locates in the PA11 even when the blend is prepared from a PLA/CNC mixture.•PLA/PA11 morphology with a matrix/dispersed form does not change with adding CNC.•The pore size of cocontinuous PLA/PA11 drops from 13 to 3 μm with adding 1% CNC. In this work, for the first time, cellulose nanocrystal (CNC) is incorporated into poly(lactic acid)/bio-polyamide11 (PA11) blends at different loadings through a combination of solvent dissolution, casting and melt mixing. Atomic force microscopy (AFM) and rheology analysis demonstrate an exceptional level of CNC dispersion using this technique. CNC is fed into the blends through prepared PLA/CNC or PA11/CNC mixtures via melt mixing in an internal mixer. In the PLA/PA11/CNC system, the CNC particles perfectly segregate into the PA11 phase at all compositions after mixing, irrespective of whether the PLA/CNC or the PA11/CNC mixture is used. These findings are supported by thermodynamic predictions based on interfacial energy. There is virtually no influence of CNC content on the PLA/PA11 morphology when it is in a matrix/dispersed phase form. This is attributed to the already low level of coalescence resulting from the low interfacial tension between PLA and PA11. However, when coalescence phenomena are fully maximized through the preparation of a co-continuous system (PLA/PA11 50/50), then CNC addition dramatically diminishes coalescence even at values as low as 1 wt% CNC. It is suggested that the retarded relaxation of the CNC filled PA11 domains is the main mechanism governing this coalescence reduction.