Modeling of light scattering and haze in semicrystalline polymers

Abstract

This article reports a new model approach for the description of light scattering in semicrystalline polymers, to describe more precisely the influence of supermolecular structure on the optical properties. This is the first study in which light scattering of polymer films has been modeled using exact Mie scattering theory of radially anisotropic spheres. As a model material a well‐known polymer, isotactic polypropylene (iPP) was used. Samples were prepared with different sample thicknesses and crystalline structures in order to identify the key parameters of light scattering in polycrystalline polymeric systems. Validation haze measurements were carried out with a spectrophotometer equipped with a 150 mm snap‐in integrating sphere. It was found that the optical properties of the polycrystalline sample can be described using multiple light scattering on these scattering centers. Good agreement was found between the simulated and experimentally measured haze values which proves the reliability and applicability of our new approach.

Inline Quality Control through Optical Deep Learning-Based Porosity Determination for Powder Bed Fusion of Polymers

“…In contrast, merely insignificant influences of the monitored spectrum can be observed for the application of an insufficient energy density level, shown in Figure 10 b. With regard to the wavelength-dependent analytic modeling of light scattering in semi-crystalline polymers by Molnár et al (2020) [ 57 ], the observed wavelength dependencies can be correlated with the occurrence of Mie scattering inside the melt pool. Therefore, wavelength-dependent deviations are associated with varying concentrations and geometries of spherulites, defects and pores inside the melt pool.…”

Optical properties of PVDF-TrFE and PVDF-TrFE-CTFE films in terahertz band

“…As the crystallinity in the structure increase, the density increase resulting in a slower speed of light traveling through the structure. The amount of light transmitted through the material also depends on the thickness, therefore many thin polymers depict high transparency [17]. PVDF is a semicrystalline polymer with crystallinity ranging from 35%-70% depending on the polymerization method.…”

“…Normalized transmission plotted in figure 3 is a ratio of light transmitted through and total light incident on the material. The amount of light attenuated due to scattering in the material is measured by the scattering attenuation parameter (α s ) [17]. This parameter (α s ) is mathematically calculated by the product of nucleus density (n o ), and extinction cross-section (C ext ).…”

Thermochromic Fenestration Elements Based on the Dispersion of Functionalized VO2 Nanocrystals within a Polyvinyl Butyral Laminate

“…By encapsulating the VO 2 nanocrystals in a SiO 2 shell with an intermediate refractive index of ca. 1.8, light scattering at the discontinuous filler/laminate-matrix interface is greatly alleviated. ,,− In the absence of a dispersing agent, hydrophilic VO 2 @SiO 2 nanoparticles remain somewhat agglomerated even upon shear mixing, which gives rise to Mie scattering that degrades the optical clarity of the films. ,, The importance of the coupling agent is readily apparent in Figure A, where the use of surface functionalization suppresses haze and increases the visible light transmittance from ∼26.9% to 47.6%. Contrasting VO 2 @SiO 2 nanocomposite fenestration elements with different extents of functionalization for the same overall active filler loading (0.8 mg/mL), functionalization with 6.1 wt % is found to be optimal, yielding NIR modulation of 22.3% and T 555nm of 47.6%.…”