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Effect of processing techniques and residual solvent on the thermal/mechanical properties of epoxy‐cellulose nanocrystal nanocomposites
Author(s) -
Qiu Ke,
Tannenbaum Rina,
Jacob Karl I.
Publication year - 2021
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.25685
Subject(s) - materials science , epoxy , composite material , solvent , nanocomposite , ultimate tensile strength , mixing (physics) , composite number , curing (chemistry) , cellulose , dispersion (optics) , dynamic mechanical analysis , polymer , chemical engineering , organic chemistry , chemistry , optics , quantum mechanics , engineering , physics
Epoxy nanocomposites reinforced with 0–5 wt% cellulose nanocrystal (CNC) were fabricated by solution casting method. The CNCs were first dispersed in the hardener together with a co‐solvent and subsequently mixed with epoxy monomer using two different protocols: bulk mixing and dropwise mixing. The dropwise mixing resulted in more homogeneously‐dispersed CNCs and provided better mechanical properties, particularly higher tensile strength, tensile modulus, and work of fracture with increasing CNC content. Investigation of various CNC/hardener mixtures with different solvent content showed that the residual solvent in the composite mixture had an impact on the curing behavior of the nanocomposite epoxy and may have lowered its crosslinking density, leading to T g depression. However, the presence of the solvent was shown to be essential for the preparation of a well‐dispersed CNC phase in the hardener solution, and to form homogenous composite mixtures. Our results show that the reinforcement effect due to higher CNC concentration is more significant than the solvent effect in the hardener system and shows greater improvement in mechanical properties. The CNC component reversed the solvent plasticizing effect through its superior mechanical reinforcing effects, and the dropwise mixing process led to better dispersion compared with the bulk mixing process.