materials feature | Titanium dioxide
DuPont has developed
software that
calculates the opacity of films to optimize TiO2 usage
company said. Tronox also talked about the differences in applica-
tions for chloride and sulphate grades: “Over the last few years, we have seen a strong divergence between high-quality and low-quality applications in the market,” investors were told. “High-quality plastics applications – durable profiles and films, high-end films, and high-performance engineering plastics – continue to demand better performance characteristics from the chloride grades as well as sulphate grades produced in the West. Lower quality plastics applica- tions have largely converted to lower quality sulphate titanium dioxide, which is primarily produced in China.” At the moment, despite the location of several major producers in China, and the fact that the country is
TiO2
the world’s largest producer, much of what is made there, stays there. But things are changing. In fact, China became a net exporter of TiO2
aspects of the film construction such as weight percent- age of additives like TiO2
, the thickness desired and the
number of layers in the film to best fit their cost constraints for opacity.
Diverging markets In a recent discussion about TiO2
applications with
investors, Tronox said trends have changed little over the last 10 years. “Customers always want more from their TiO2
dispersion, rheology, exterior durability, brightness, colour, and opacity with our chloride TiO2
,” the , and we are constantly trying to deliver better producers of TiO2 in 2011, according
to reporting agency The Petrosil Group. Henan Billions Chemicals is one of the top three in China. Dong Yong-ai, manager of
the import and export department at the company, says that the current expansion of its sulphate production facility will take it to second position. In terms of capacity, Sichuan Lomon Titanium Industry is the largest producer in China, with Shandong Dongjia in second place. Yong-ai says that Henan Billions’ actual output already puts it ahead of Dongjia, and it is in top position for exports. While Henan Billions does not currently have any products tailored for the plastic industry outside
TiO2 Making the most of particle size
Speaking at AMI’s Masterbatch Conference 2013 in Frankfurt last year, DuPont Titanium Technologies’ Bernd Zimmer- mann told delegates how to get the best out of TiO2 in plastics. Products containing TiO2
look white because the TiO2 scatters the light. Light
scattering is a function of the refractive index of the material, the thickness of the product, and the concentration of the scattering material. The high refractive index of TiO2
for further optimising the scattering effect. He explained that rutile TiO2
, which has
an even higher refractive index (2.7) than anatase (2.5), can come in various sizes. Two different TiO2
grades with identical means
that it is virtually always going to provide a better opacifying effect than potential rival products such as calcium carbonate and zinc oxide, which have RIs little more than half that of TiO2
. However, Zimmermann emphasised the importance of particle size 30 PIPE & PROFILE EXTRUSION | March/April 2014
crystal structure can have different opacity performance. Smaller particles provide higher scatter in the blue region of the visible light spectrum, giving a so-called high undertone. The natural yellow tint in many thermoplastics, sometimes empha- sised during processing, is thus cancelled out, giving a “cleaner” colour (see graph).
The opacifying effect of TiO2
is a function of refractive index and particle size
www.pipeandprofile.com
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