Crystalline forms of PVDF fiber filled with clay components along processing steps

Abstract

There is a growing interest in the supply of autonomous electronic devices, particularly in the field of smart textiles. Energy harvesting is considered as a clean and renewable alternative technology to reach this objective. One of the methods explored is scavenging the energy from ambient mechanical vibrations by using piezoelectric materials. Due to textile requirements, the development of PVDF based fibers appears to be an interesting solution. However, the amount of its b crystalline form should be as high as possible. PVDF/clay components (modified or unmodified clay as well as organic modifier) containing up to 5 wt % additive are prepared by melt spinning. FTIR and XRD experiments show that the most important factor for obtaining high levels of b crystalline form is to increase the drawing ratio. The results indicate also that an organic modifier (quaternary ammonium salt) influences the crystalline forms and leads to a high ratio of b phases.

Hybrid lead-free polymer-based nanocomposites with improved piezoelectric response for biomedical energy-harvesting applications: A review

“…An organic modifier (quaternary ammonium salt) influenced the crystalline form of meltelectrospun PVDF and led to a high β phase content [36]. Filling dioctadecyl dimethyl ammonium chloride (which is found in C15A -Cloisite ® ) into PVDF provided a 150% increase in the β-phase content.…”

“…PVDF scaffolds were also prepared by melt spinning [35], and from PVDF/clay components (modified or unmodified clay with an organic modifier) containing up to 5 wt% of an additive [36]. Stretchable PVDF piezoelectric generators that exhibited excellent responses under extremely large applied strains (more than 100%), were prepared by electrohydrodynamic directwriting using a mechano-electrospinning process [37].…”

Formation of Oriented Polar Crystals in Bulk Poly(vinylidene fluoride)/High-Aspect-Ratio Organoclay Nanocomposites

“…This is the way exfoliated clay–polymer nanocomposites are formed. , Organoclays, resulting from modification of surface clay minerals with amphiphilic molecules, are known for their potential in enhancing mechanical, thermal, or barrier properties as well as reducing the flammability of plastics. Smectite clays are also known to have an influence on the crystallization behavior of semicrystalline polymers, including the ability to affect their anisotropy, nucleation rate, degree of crystallinity, or even altering their crystal structures. − In the context of this work, it is particularly important that organoclays are already known to generate β- or γ-crystals of PVDF. , In order to supplement the knowledge in this field, we demonstrate that high-aspect-ratio organoclays may additionally promote formation of oriented, lamellar crystals of PVDF. The orientation effects observed here are similar to those reported by Beaucage for high-density polyethylene (HDPE)–organoclay films .…”

“…35−37 In the context of this work, it is particularly important that organoclays are already known to generate βor γ-crystals of PVDF. 18,38 In order to supplement the knowledge in this field, we demonstrate that high-aspect-ratio organoclays may additionally promote formation of oriented, lamellar crystals of PVDF. The orientation effects observed here are similar to those reported by Beaucage for high-density polyethylene (HDPE)−organoclay films.…”

“…Heterogeneous nucleation or postcrystallization treatment, such as stretching and/or poling at a temperature below the melting point, triggers the formation of one of the polar crystalline phases. In the polar crystals, the PVDF chains are either in all-trans conformation (TTTT′, β-polymorph) or are trans-dominated with mostly periodically distributed gauche - conformers (TTTGTTTG′, γ-polymorph). − Addition of nanoparticles such as clays or organoclays is also known to enhance formation of polar crystals in the bulk VDF-based polymers. ,− Apart from the aforementioned ways, formation of the polar crystals may also occur during crystallization from solution by controlling the solvent evaporation rate or the specific polymer–solvent interactions. , …”