Melt rheology and mechanical crystal transformation in an immiscible blend with poly(vinylidene fluoride) matrix

Abstract

Effect of immiscible polyamide 6 (PA6) on the melt rheology and stretch-induced crystal transformation of poly (vinylidene fluoride) (PVDF) matrix is reported. PA6 is dispersed as submicron droplets in the PVDF matrix, responsible for significant enhancement in the melt elasticity. Nevertheless, crystallization habits of PVDF matrix from melt are little affected by submicron PA6 droplets, and the a-form of PVDF prevails in the blends. Upon mechanical stretching, the a-form is converted to the b-form, which is remarkably reduced with the increasing of PA6 content in the blends. It could be correlated with the decreased tensile stress in the presence of submicron PA6 droplets that act as stress concentrators.

Simultaneously improving thermal conductivity and dielectric properties of poly(vinylidene fluoride)/expanded graphite via melt blending with polyamide 6

“…For the PVDF/PA6 blend, the PA6 droplets in the PVDF matrix significantly increase the G' and η* especially at low frequency, even the PA6 has lower melt elasticity and complex viscosity than the PVDF at the test condition. Similar result that PA6 droplets with small domain size in the PVDF matrix significantly enhance melt elasticity and complex viscosity at low frequencies was also reported for PVDF/PA6 blend with PA6 content of 15 and 30 wt% (by weight) 42 . Moreover, the tan δ of the PVDF/PA6 sample is obviously reduced.…”

“…While, the T c of the PVDF decreases from 139.9 to 134.9°C, indicating that the crystallization of the PVDF phase is suppressed by the micron‐sized PA6 droplets. On the other hand, no obvious exothermic peak for the PA6 phase is found at the DSC cooling curve, meaning that the crystallization in the PA6 droplets is retarded seriously due to the confined crystallization in the PA6 droplets with small domain size 42,44,45 . Similar result that crystallization in the submicron PA6 droplets is retarded to a large extent was also reported by Na et al 42 Most crystallization in the PA6 droplets can only occur upon heating as evidenced by the appearance of a weak exothermic peak at around 191°C.…”

“…It implies that the PA6 droplets suppress the PVDF molecular relaxation. The increased elasticity and complex viscosity and suppressed relaxation of the PVDF/PA6 sample could be attributed to the fact that the molecular chain motion of the PVDF is significantly restrained by the large phase interfaces provided by the micron PA6 droplets 42,43 …”

“…Similar result that PA6 droplets with small domain size in the PVDF matrix significantly enhance melt elasticity and complex viscosity at low frequencies was also reported for PVDF/PA6 blend with PA6 content of 15 and 30 wt% (by weight). 42 Moreover, the tan δ of the PVDF/PA6 sample is obviously reduced. It implies that the PA6 droplets suppress the PVDF molecular relaxation.…”

Improving the dielectric performance of poly(vinylidene fluoride)/polyaniline nanorod composites by stretch‐induced crystal transition

“…There exists a more facile and effective strategy to increase the dielectric constant of polymers by transforming the polymer crystal from non‐polar crystal into polar crystal . The typical polymer is PVDF with two dominating crystals, α‐crystal and β‐crystal .…”