Pathway Control of PVDF Polymorphs: Melt‐Extrusion‐ Induced β Phase and Solution‐Casting‐Induced γ Phase

ABSTRACT Polyvinylidene fluoride (PVDF), a semicrystalline polymeric material, exhibits five crystalline phases (α, β, γ, δ, and ε), with its crystalline structure altered under different fabrication conditions. This work systematically investigates the effects of extrusion temperature (190°C–210°C) and screw rotation speed (30–110 rpm) on the crystalline phases, crystallinity, and thermal stability of PVDF, while also exploring the recrystallization behavior of PVDF during solution casting. The results demonstrate that melt extrusion can convert PVDF crystal forms from the α‐phase to the β‐phase, increasing the β‐phase fraction to 75.69%–81.94%. The screw rotation speed is the primary cause of this variation. Under different processing conditions, the crystallinity of PVDF is increased by 0.93%–6.10%, and the decomposition temperature is improved by approximately 20°C through melt extrusion. For the solution casting process, it causes a β‐phase to γ‐phase transition in PVDF, achieving γ‐phase fractions of 66.23%–74.74%, with the crystallinity values of 51.05%–56.58%.