Dispersing a 10nm-sized metal oxide in a polymer matrix and examining the optical properties according to wt%.(10wt% ~ 60wt%)
It was expected that the higher the wt%, the lower the transmittance and the higher the haze, but unexpected results were shown.
In the 10 ~ 30wt% section, the TT gradually decreased, but after that, the TT increased as the wt% increased. But Haze increased with wt% in all sections.
I don't think there were any special mistakes in the experiment.
Is my prediction wrong that I expected the TT to decrease as the number of scattering nanoparticles increased? Or is there a principle behind that I don't know?
Please help me to understand this strange phenomenon.
Hochan Lee Transmission is a number concentration -projected area dependence. Bouguer's (Beer-Lambert) law is usually used to evaluate this.. You may have fewer particles at higher loadings due to aggregation and agglomeration. It's not possible to have a powder with free discrete independent particles of 10 nm. See:
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W081113DispersionNanotechnology.html
I do not know wether your polymer host is in liquid or solid phase. In the former case, by just increasing the nanoparticle percentage to levels as high as sveral tens% you may expect the onset and grwing aggregation of the metal oxide in larger particles or localized agglomerates, so loosing homogeneity of the system and causing a partial precipitation. A similar problem arises also in case of solid composites, if the mixing process is not properly realized (to maximize dispersion in the final product).
As a matter of facts, at large nanopowder concentration aggregation/precipitation may give raise to an average "LARGER" space of pure polymer (in the scale of your optical probe) so recovering a relatively high transmittance, while leading to an even higher haze value. By the way, this effect is well known in pigment industry, where flocculation of pigments in the resin host may be a somewhat tedious problem.
Hochan Lee Giuseppe Curro
Here's Figure 10 from an old paper of mine. The reference, [13], I used was:
J G Balfour, 'Opacity and Titanium Dioxide Pigments', Journal of the Oil and Colour Chemists Association (JOCCA), 6, 225 (June 1990)
I'm adding in my paper too.
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