Relationship between UV Transmittance and Compatibility of PVDF/PMMA Blends

Abstract

It has been well known that PVDF/PMMA blends are compatible in the melt state. UV transmittance of PVDF/PMMA blends was varied by blend ratio as well as cooling speed from the melt state. UV transmittance of quenched samples was higher than that of slowly cooled samples in all blend ratios. Higher crystallinity has been observed in the slowly cooled samples compared with the quenched samples by density method.
In the quenched samples, as PVDF amount increases, UV transmittance of PVDF/PMMA blends increases. When PVDF amount is 70wt%, UV transmittance of them is the highest value, 62%. As PVDF amount exceeds 70wt%, UV transmittance of them decreases. When PVDF is amorphous, UV transmittance of PVDF is very high. On the other hand, when PVDF is crystal, UV transmittance of PVDF is very low. PVDF and PMMA is compatibled by PVDF 70wt% and accordingly PMMA depress crystallization of PVDF. Therefore PVDF/PMMA blends has high UV transmittance. In the slow cooled samples, UV transmittance of PVDF/PMMA blends increases less than PVDF 30wt%. As PVDF amount exceeds 30wt%, UV transmittance of them decreases. The slow cooled samples is inclined to crystallize compared with the quenched samples.
PVDF has three crystal structures. When PVDF/PMMA is crystal, X-ray diffraction shows that the crystal structure is PVDF(II).