Pigments are finely milled organic or inorganic crystalline solids which are insoluble in the medium they are in. Pigments exist as crystalline solids with their structure determining the properties of the pigment. All crystal structures of high performance pigments from close packed solids, so the pigment has the properties of low solubility and high thermal stability. This is due to strong intermolecular forces of attraction within the structure. Chlorination of molecules can help the packing of a pigment, as they improve the interactions between molecules. However this is not always the case as sometimes chlorination can twist an orientation of a molecule, which leads to the molecule being less symmetric and make packing less close, therefore making the pigment more soluble.
THis would lead to the pigment to then not be high performing.Inorganic pigments are usually brighter and last longer than carbon containing organic pigments. They alter the appearance of a material by absorbing or scattering light. Pigments are mostly inorganic salts and oxides, for example chromium and iron oxides, which are usually in powder form. The colour properties of the pigment rely on the size of the particles that make up the pigment. The colours of the pigment are visible because of the absorption of electromagnetic radiation in the UV and visible light sections of the spectra.
The colours become visible as the molecule absorbs the light energy which causes electron excitation, meaning the electron becomes excited and moves from a lower energy level to a higher energy level. Then the electron de-excites and releases a photon equivalent to the energy it absorbed, which to us is seen as the colour of the pigment. In pigments were the molecule is unsaturated the group responsible for the colour/release of the photon is called the chromophore. If two or more chromophoric groups are conjugated in a molecule the energy needed to excite the electrons will be lower, therefore the wavelength of light will be longer, and the intensity of the pigment will increase. The intensity is larger compared to an unconjugated chromophoric group. High performance pigments are pigments which have certain properties which are more appealing for use than just regular pigments. High performance pigments (HPPs) are pigments which have better resistive properties than regular pigments. For example HPPs have high colour strength, meaning they transmit colour to other materials very well.
Also HPPs have high solubility and high thermal stability, which is defined by the pigments ability to retain its structure at high temperatures. In addition to these properties high performance pigments have good light and weather fastness, this is the ability to maintain the pigments colour in different light and weather environments. As a result of these properties are commonly used for automotive and house exterior paint because the pigments will keep their colour for longer and through harsher environments compared to regular pigments. High performance pigments are designed with the three necessary E’s in mind: effectiveness, economy and ecology. Theses three are defined by technical performance, benefits for the customer and environmental safety. Improved effectiveness could suggest better colour strength and higher pigment saturation. Improved economy could mean expanding the uses for high performance pigments so the customer gets more use for what they’ve bought. Lastly improved ecology could propose that the pigments are less damaging and toxic to the environment when the pigments are being made but also when they are in use.
HPPs are also designed so they have low migration meaning that the pigments won’t transfer or move from the material they are on. There is four different types of migration that HPPs are designed to withstand: penetration, contact, evaporation and condensation. Migration through penetration is when the pigment moves from the pigmented side of the material to the unpigmented side of the material. Contact migration is when the pigments migrate when they come in contact with another material. The optimisation of the three E’s and low migration is what makes the pigment high performing. Bismuth vanadate is a type of HPPs which shades range from greenish-yellow to red-ish-yellow.
The composition of this pigment is BiVO?, however the pigment can also be mixed with the structure of 4BiVO? X 3Bi?MoO?. For Bismuth vanadate to be a high performance pigment it has had to have organic stabilisers added to the structure. Bismuth vanadate is used to colour plastics, however colour change from the pigment may occur as the vanadium ions become reduced as the plastic melts. Although thermostable types of Bismuth vanadate can be formed by the pigment being protected in a multi-layer coating of boron, zinc and silicon oxides. Cerium is used in HPPs to enhance the pigment and adds light fastness making the pigment more photostable. Cerium sulfide pigment forms a red pigment which has high thermal stability, the pigment is also a very good UV light absorber with no noticeable photocatalytic effects. The pigment is non-toxic and a good alternative for cadmium sulfide pigment, which is toxic. To conclude high performance pigments are very important for the improvement in the ink and paint industry.
As they allow the industry to produce higher quality of inks and paints which are more versatile in their use. Also the improvement of high performance pigment is important in Chemistry as it demonstrates that the size and shape of molecules can be used to predict the colour and properties of pigments. Being able to predict the properties of these pigments allows us to alter the molecules to make the pigment more high performing. References:Despite higher costs, improved properties are driving growth for high performance pigments in a variety of printing markets, including packaging, outdoor signage and non-impact printing., Savastano.D, 2005Accessed on 1-12-17https://www.inkworldmagazine.com/issues/2003-08/view_features/high-performance-pigments-105024/ As printing ink manufacturers are challenged to offer newer color choices and higher performance options, they are turning to high performance and special effect pigments to meet this need., Pianoforte.K, 2009Accessed on 1-12-17https://www.inkworldmagazine.com/issues/2002-08/view_features/high-performance-pigments-104910/Dyes and Pigments, Gurses.A, Gunes.K, Gurses.M.S, 2016 High Performance Pigments, Edwin B Faulkner, Russell J Schwarts, 2009