Surface modified microfibrillated cellulose‐poly(vinylidene fluoride) composites: β‐phase formation, viscoelastic and dielectric performance

Abstract

The effect of silylation of microfibrillated cellulose (MFC) surfaces on β‐phase formation in poly(vinylidene difluoride) (PVDF) and the resulting viscoelastic and dielectric performance of MFC‐PVDF composites is investigated. Two different organosilanes, namely aminated (A) and fluorinated (F), were used. Composites of PVDF and MFC at concentrations up to 10 wt%, both untreated and silylated, were prepared by solvent casting. The two different surface modifications did not markedly change the melting and crystallization enthalpy of the polymer. However, only A‐MFC was found to promote β‐phase compared to the untreated MFC and the F‐MFC, which was attributed to the formation of hydrogen bonds at the interface between the amine groups of A‐MFC and the fluorine groups of PVDF. The elastic modulus and the permittivity of all composites increased with the amount of MFC up to a maximum value, depending on the MFC modification, and then decreased. This effect was due to the formation of MFC aggregates and porosity, as further confirmed by a comparison of experimental moduli with a classical composite mechanical model. The highest elastic modulus and highest permittivity were obtained for the untreated MFC and A‐MFC composites with 5 and 1 wt%. © 2021 Society of Chemical Industry

Enhanced dielectric properties of freestanding, flexible, hydrophobic cellulose/poly(vinylidene fluoride) composite films

“…In a similar study, Poothanari et al reported a dielectric constant $10 with the addition of 1 wt% microfibrillated cellulose in PVDF matrix. 31 An enhanced dielectric constant of PVDF filled with 15 wt% cellulose nanocrystals of $47 was also reported by Lizundia et al 32 This article reports the synthesis of freestanding, flexible films of cellulose/PVDF. It also investigates the modulation in the morphological, microstructural, vibrational, and dielectric properties of the resulting films.…”

“…Thus, by suitably adjusting the ratio of the fillers to the host polymer, the composition can be tuned and a semi‐biodegradable freestanding, flexible film can be achieved which can be used for flexible device applications. In a similar study, Poothanari et al reported a dielectric constant ~10 with the addition of 1 wt% microfibrillated cellulose in PVDF matrix 31 . An enhanced dielectric constant of PVDF filled with 15 wt% cellulose nanocrystals of ~47 was also reported by Lizundia et al 32 …”

Fluorine Free Surface Modification of Microfibrillated Cellulose-Clay Composite Films: Effect of Hydrophobicity on Gas Barrier Performance

“…Figure 1a shows the FTIR spectra of reference and heat-treated films. In all cases, the characteristic peaks of cellulose structures are systematically visible (O-H stretching between 3600 and 3300 cm −1 , C-H stretching at 2900 cm −1 , C-C stretching around 1640 cm −1 , CH 2 stretching at 1432 cm −1 and 900 cm −1 , C-H bending at 1373 cm −1 , asymmetric vibrations of C-O-C and stretching of C-O at 1100, 1053, and 1028 cm −1 ) [34,35]. The peak intensity at 3325 cm −1 was reduced after heat treatment due to the decrease in the number of free hydroxyl groups, a consequence of the increase of crystalline cellulose [36].…”

“…Figure 2 shows the XRD spectra of the clay and the reference and heat-treated films. The silylated films were not investigated as it was shown that this treatment does not change the crystal structure of cellulose in MFC [34]. The clay displays characteristics peaks at 7.5 • ,19.6 • , 28.6 • , and 35.4 • corresponding to the (001), (100), (004), and (110) lattice planes of clay, respectively [41,42].…”