materials feature | Titanium dioxide
solar refl ectance of polymers can help open up new markets for polymer products as they become less prone to warping,” the company says. “This means polymer products could be used in warmer regions of the world where they would have previously been unsuitable.” There are currently two products in the range: Altiris 550 pigment is intended for light to medium shades, while Altiris 800 is intended for use in medium and dark colours. “Altiris 550 refl ects more in the very near infrared part of the spectrum, as well as some visible light, so it has some whiteness,” said Rob Portsmouth, business development director at Huntsman Pigments. “It can be incorporated into colours that would normally have traditional TiO2
, for example a beige made from Huntsman’s
Altiris TiO2- based pigments reduce heat build-up in coloured vinyl siding
and profi les. However, Huntsman says that the additive is now receiving additional interest from the automotive and agricultural sectors for controlling temperature levels. For example, tests are being carried out on agricultural fi lms containing Altiris for better crop protection. Altiris grades work by refl ecting more infrared
radiation (which accounts for 53% of the radiation from
the sun hitting the earth’s surface) than regular TiO2 pigments, thanks to the structure and size of the crystals and the very durable thin silica coating around them; the coating assists in incorporating the pigment into polymers, and also minimises photo-catalytic activity in the application. Huntsman notes that high solar refl ectance can help
to reduce overall heat build-up, preventing distortion and premature failure of plastics parts. “Increasing the
brown and white – but the product will stay cooler.” Altiris 800, which refl ects even less visible light than Altiris 550, and more long infrared radiation, responds to increasing calls from producers of plastics as well as coatings for darker colours for applications such as vinyl siding and window frames. “Some of these products can get really warm in the summer, and they may twist and buckle,” Portsmouth said. Sean Reid, business development manager at Huntsman, says that the company believes that there is large scope for a new generation of polymers that are colourful and can better refl ect the heat. “Altiris has the potential to deliver energy effi ciencies and expand customer choice,” he said, adding that this is the fi rst time that the combination of tailored solar refl ectance from a single additive in almost any colour has been available.
Altiris pigments can be used with the same pigments that compounders already use with TiO2
. They are said
to be easy to disperse and incorporate into sophisti- cated systems. They contain no added heavy metals, and in some formulations less coloured pigment can be used. Huntsman provides customers with access to a newly developed software program to help them create the colours they want.
Huntsman’s Altiris pigments can reduce surface temperature by more than 50% in some colour ranges – tests carried out using Cary 5000 spectrophotometer on plaques approximately 100 microns thick. The standard coating contains Tioxide pigment and colour pigment.
28 PIPE & PROFILE EXTRUSION | March/April 2014
Software to help users make the best of TiO2 is also offered by DuPont, although it is aimed more at fi lm producers than compounders. “Many fi lm producers balance fi lm thickness, TiO2 content and cost to fi nd the most effective solution for fi lm opacity,” the company said, so it has created a model to highlight the effective- ness of TiO2 in producing a more opaque backdrop versus increasing fi lm thickness. The model incorpo- rates many fundamental aspects of scattering to calculate a theoretical opacity of multilayer fi lms. An added feature is the ability to calculate the opacity with other materials besides TiO2. With this calculation, fi lm producers can easily modulate certain
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