Poly(vinylidene fluoride)/bacterial cellulose nanocomposite films for touch sensor applications

Abstract

Flexible piezoelectric films of poly(vinylidene fluoride) (PVDF)/bacterial cellulose (BC) were successfully fabricated via solvent-casted and compression methods. The various weight percentage of BC (2.5-40 wt%) loading into PVDF matrix using dimethylformamide (DMF) as a solvent were studied on the basis of piezoelectric touch sensor. The crystalline phase of all PVDF/BC blend films were formed in both of a and β phase which mainly formed in piezoelectric β polymorph. The PVDF₉₀BC₁₀ was selected as a based nanocomposite to develop further due to this component demonstrated highest dielectric constant over other compositions at the frequency range of 10 MHz- 1 GHz and temperature of -50ºC - 100ºC. This research was firstly report the in-plane piezoelectric coefficient (d₃₃) of PVDF/BC blend films which as high as -11 pC/N. In order to achieve high piezoelectricity for piezoelectric touch sensor, the carboxyl multi-walled carbon nanotube (MWCNT) was introduced to enhance the d₃₃ of PVDF₉₀BC₁₀. MWCNT has high ability to polarize along an applied electric field which yield to high dielectric constant about 72 at temperature about 80ºC and frequency of 10 MHz. The addition of MWCNT 3 phr to PVDF₉₀BC₁₀ showed enhancing in d₃₃ from -11 pC/N to -15 pC/N and exhibited highest remanent polarization (Pᵣ) compared to other compositions. The combination of nano-network fiber implied a significant improving in thermal stability and dynamic mechanical properties due to intermolecular interaction among O- and F-atoms.