How latex film formation and adhesion at the nanoscale correlate to performance of pressure sensitive adhesives with cellulose nanocrystals

Elina Niinivaara, Alexandra Ouzas, Carole Fraschini, Richard M. Berry, Marc A. Dubé, Emily D. Cranston*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Emulsion polymerized latex-based pressure-sensitive adhesives (PSAs) are more environmentally benign because they are synthesized in water but often underperform compared to their solution polymerized counterparts. Studies have shown a simultaneous improvement in the tack, and peel and shear strength of various acrylic PSAs upon the addition of cellulose nanocrystals (CNCs). This work uses atomic force microscopy (AFM) to examine the role of CNCs in (i) the coalescence of hydrophobic 2-ethyl hexyl acrylate/n-butyl acrylate/methyl methacrylate (EHA/BA/MMA) latex films and (ii) as adhesion modifiers over multiple length scales. Thin films with varying solids content and CNC loading were prepared by spin coating. AFM revealed that CNCs lowered the solids content threshold for latex particle coalescence during film formation. This improved the cohesive strength of the films, which was directly reflected in the increased shear strength of the EHA/BA/MMA PSAs with increasing CNC loading. Colloidal probe AFM indicated that the nano-adhesion of thicker continuous latex films increased with CNC loading when measured over small contact areas where the effect of surface roughness was negligible. Conversely, the beneficial effects of the CNCs on macroscopic PSA tack and peel strength were outweighed by the effects of increased surface roughness with increasing CNC loading over larger surface areas. This highlights that CNCs can improve both cohesive and adhesive PSA properties; however, the effects are most pronounced when the CNCs interact favourably with the latex polymer and are uniformly dispersed throughout the adhesive film. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)'.

Original languageEnglish
Article number20200330
Number of pages18
JournalPHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A: MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
Volume379
Issue number2206
Early online date2 Aug 2021
DOIs
Publication statusPublished - 20 Sep 2021
MoE publication typeA1 Journal article-refereed

Keywords

  • pressure sensitive adhesives
  • coalescence
  • cellulose nanocrystals
  • film formation
  • adhesion
  • emulsion polymerization
  • ATOMIC-FORCE MICROSCOPY
  • MECHANICAL-PROPERTIES
  • POLYMER DIFFUSION
  • SURFACE
  • NANOCOMPOSITES
  • BEHAVIOR
  • MODEL
  • REINFORCEMENT
  • MODULATION
  • MORPHOLOGY

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