Role of poly(lactic acid) in the phase transition of poly(vinylidene fluoride) under uniaxial stretching

Abstract

The effect of poly (lactic acid) (PLA) on the crystalline phase transition of poly (vinylidene fluoride) (PVDF) from a-to b-phase under uniaxial stretching for immiscible PVDF/ PLA blends was investigated. The typical sea-island structure in the blends was found to facilitate the necking of PVDF and the transition from a-to b-phase due to the local stress distribution during stretching. The crystalline phase transition of PVDF in the blends is temperature-dependent and is affected by the content of PLA. The highest content of b-phase, F(b), was achieved in the samples stretched at 60 C, while the effect of PLA content on the crystalline phase transition of PVDF is more complex. F(b) increases slightly when the sample with a PLA content no more than 15 wt % is stretched at 60, 80, and 100 C, and decreases sharply for the sample containing 20 wt % PLA; in addition, the sample containing 10 wt % PLA exhibits the highest F(b) no matter what the stretching temperature is. The mechanism of the crystalline phase transition of PVDF during the stretching is interpreted from energy barrier of the transition from a-to b-phase and the morphological structures in the blends.

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

“…The change in viscoelastic properties in the PVDF/PA6 blends is much outstanding, as compared to other immiscible PVDF blends with coarse phase morphology. For instance, in a study regarding PVDF blends with polylactide (PLA), micron PLA droplets only have a slight effect on the viscoelastic properties of the blends …”

Stretch‐induced stable‐metastable crystal transformation of PVDF/graphene composites

“…The β/α ratio at 160°C stays around a quite low level in a large strain range as discussed in Figure A, suggesting that the β‐crystal is not directly formed from the recrystallization. According to literatures which pointed that the amount of β‐structure must be increased at the expense of the α‐phase, the formation of β‐phase at 160°C could be confirmed as a “recrystallization (α‐crystal) ‐β‐phase transformation.” Deformation of semicrystalline polymers under stretching leads to the orientation of chains and even the breakage of crystals . The α‐crystal lamellae induced by recrystallization from the melting of lamellar fragments is chain extended fibrillar crystals which are imperfect.…”

“…β‐crystal can be obtained by different techniques, among which the mechanical stretching of α‐crystal is the most important one . Numerous publications reported characterization and understanding of the mechanically induced structure‐transformation . Necking, defect, and heterogeneous stress are considered to play important roles in the structure transformation.…”

Stabilizing Polymeric Interface by Janus Nanosheet

“…It is reported that blend displays a bi‐continuous structure. [ 37 ] The amphiphilic JNS is preferentially located at the interface. Thanks to the irregular feature, the JNS becomes jamming at a low threshold ( Scheme ).…”

“…In the present case, the PVDF/PLLA blend at 60/40 (wt/wt) with a bi‐continuous structure was selected as the model. [ 37 ] After selectively etching PLLA with chloroform, the sample experiences a dramatic shrinkage to ≈100 µm from the original thickness of ≈300 µm (Figure S3a, Supporting Information). At the skin layers, the porous structure is less connected and easily disintegrated (Figure S3b, Supporting Information).…”