Introduction

Modern dyes provide more than just being pretty. They have become indispensable tools for a variety of industries. Today various dyes are created to meet the necessities of various industries. Dyes are available in various forms. Instances are dry powders, granules, pastes, liquids, pellets, and chips. Today the role and application of pigments have enhanced. There would scarcely be any industry left where dyes and pigments don't play any substantial role. The challenge is now to determine pigments that are capable of not only long-lasting applications but as well are environmentally secure.

Application of Dyes and Pigments

From acting as colourants for plastics, textile dyeing industries and the extremely sophisticated biotechnology industry, dyes are touching lives everywhere. Dyes and pigments are as well utilized via industries for inks and tinting. Other industries, where dyes are utilized in a variety of products comprise paper and pulp, adhesives, art supplies, beverages, ceramics, construction, cosmetics,  food,  glass,  paints,   polymers,  soap,  wax, biomedicine and so on.

Overview of the Important Applications of Pigments

Paints- A diversified application in the whole gamut of paints that comprise decorative and shielding coatings, in paints that are oil and resin based, automotive ends, emulsion paints, distempers and so on.

Printing inks- Pigments are utilized in all types of printing inks, which comprises inks for printing metal foils, lacquers and so on. Pigment finishes for leather and textiles: Colouration application for popular textiles these as polyesters, nylon and so on Colouration of  Plastics-  Pigments  are  utilized  in  host  of  plastic applications that includes poly vinyl chloride (PVC), rubber and synthetic polymers, urea-formaldehyde (U-F) and melamine- formaldehyde moulding  powders polystyrene, nylons, polyfins, phenol-formaldehyde (P-F), acrylonitrile-butadiene-styrene resins (ABS).

Industrial Application of Dyes and Pigments

Colourants for Plastic Industry

Colour selection is one of the essential things to be considered in the plastics industry. Colour is an integral part of the plastic material and it should not be considered as an afterthought. The whole system of colouring has to deal through using what is termed to as a total systems approach. No doubt the colour enhances the part's functionality, but it has as well the potential to degrade assured material properties as impact strength, if not properly applied. The colourants which are employed in the plastic industries are the dyes and pigments. Both dyes and pigments exhibit colour through the procedure of observable light absorption and scattering. Typically colour formulations usually have 4 colourants. Black and white is employed basically to control the value and Chroma, while 2 coloured pigments or dyes are applied to found the Hue. The consequential colour that is achieved is governed through the laws of subtractive mixing, the similar law that is employed in printing and painting.

Cement industry

Over the years, people have produced interesting consequences through mixing cement and pigments in dissimilar ways and in different proportions. Concrete is derived from cement. For about last one century, pigments have been utilized by concrete to give them different colours. Whenever pigments are mixed by concrete, then actually, such pigments tint the colour of the paste portion of the concrete.

To ensure a long lasting cement colour shade, the pigment which is being utilized in the cement, must have a good quality. Such pigments (colour) are made from both usual and synthetic iron oxide, cobalt, titanium dioxide and chromium oxide. From iron oxide pigments, red, black and yellow colour can be attained. From cobalt pigments, blue colour can be acquired. White colour and green colour can be attained from titanium dioxide and chromium oxide respectively.  Other colours like buffs, brown, tans, coppers, oranges, chocolates and many other colours can be obtained from the blends of the red, black and yellow coloured iron oxide pigments. Such coloured pigments are: water-wetable, lightfast, alkali resistant and won't unenthusiastically influence the firmness and strength of the cement. But, one thing we should remember about the concentration of such pigments in the cement. This concentration should be within the range of 10% of the weight of the cementation ingredients.

Ceramic industry

The applications of dissimilar pigments on ceramics are brought in different forms. Such applications are as follows:

In Coating  Ceramic  Materials; Ceramic Glaze; Frits-  By formulating these coating applications of pigments on ceramics, the end utilizes get attractive looking products by more durability and utility.

In Glaze development- One of the applications of pigments on ceramics is to expand leading glazes for various whiteware ceramics. Such comprise sanitary ware, tile, dinner ware etc. In preventing Ceramics Corrosion and colour fading- In this procedure, via applying pigment coating and protective layer through other kind of chemicals, the corrosion of the metals can be prevented. The lasting consequence of colours as well enhances. For enforcing the different applications on ceramics, numerous types of special pigments are available. How much of which pigment will be utilized depends upon the needed colour intensity. But, the quantity of pigments that is utilized for such applications can vary from 1% to 10%. This variation doesn't make any noticeable impacts on the substances. Enamel (colourful) can be produced by colouring the melt during manufacturing. Enamel can as well be generated via combining colouring stains during the milling procedure.

Colourants for Security Printing

In view of the ever rising threats of the cases involving forgery and fraud being committed in the financial institutions involving currency, both dyes and pigments play a vital role in giving cutting edge solutions to detect and prevent such fraud. Here we will talk about about the fluorescent dyes as well as about the luminescent pigments as applied in security applications.

Considerable research over the last decade or more  on the study of fluorescence  has  borne  fruits  in  the  form  of  development  of  new fluorescent dyes. These security dyes are now applied increasingly in the very sensitive area of security printing. The fluorescent dyes are providing ways to generate and pertain effectively controlled 'signatures'. The United States Pharmacopeia (USP) of such dyes is that they are customized and are printed as patches on dissimilar types of surfaces.

Each of them has a signature element that is able to identify the patch as authentic. As the different dye formulas are able to fluctuate their fluorescence characteristics in different repeatable ways, as a consequence unique signatures can be attained. A extremely popular Example of a dye, which is utilized in security printing is that of Coumarin.

Coming  now  to  Luminescent  pigments,  such days  a  new  range  of luminescence has  been expanded that are either excited through ultraviolet (UV) or infrared (IR) or applied in security printing applications. Here a few exact utilizes of the luminescent pigments in the security printing are conversed.

Security Printing and prevention of counterfeiting- Security marks and elements that aren't visible under usual light are made through Luminescent pigments. They can't be duplicated even through the ultra sophisticated photocopiers. They can be simply verified using an extremely easy Ultra violet light or a luminescence sensor. That is the reason why security  printing  of  stamps, checks,  credit  cards, licenses and so on are done  through Luminescent pigments Brand Protection and Security of Products- In applications that engage product security, luminescent  pigments are utilized  in making tamper evident seals for pharmaceuticals and other products. When it comes to brand protection, luminescent pigments and fluorescent dyes are utilized for proprietary invisible security marks and characteristics that get printed on products, packaging and labels.

Property classification and Prevention of loss- As the invisible security marks generated via luminescent dyes aren't visible under normal conditions, don't deface the  property and can't  be eliminated they are an ideal forensic tool.

Colourants for Cosmetics Industry

Dyes have found a wide variety of utilizes in the cosmetics industry. Be it the hair dyes or lipsticks or nail polish shampoo everywhere there is wide utilized of dyes. Most of the commercial hair dye formulas available now are complex that use bountiful of ingredients and the formulas also differ considerably through manufacturers. The dye chemicals that are utilized in making hair dyes usually consist of amino compounds, like 4-amino- 2-hydroxytoluene and m-Aminophenol. Pigments of metal oxides, as titanium dioxide and iron oxide, are as well employed.

Fig: Colourants for Cosmetics Industry

In the category of decorative cosmetics, the majority of colours utilized are pigments. It is the inorganic pigments that are popular through cosmetics but are subject to purity levels of important metals. The range of inorganic pigments utilized in cosmetics is usually made up of various chemical kinds. A few of the popular ones are presented in the table.

Table: Applications of Pigments

In addition to this several kinds of organic pigments are as well utilized along through water soluble and oil soluble dyes in the cosmetics application. Several instances of water soluble dyes are following here.

Dyes in Medicine

Dyes are now a significant ingredient in medical tests. Many of the tests, which are carried out on patients utilize dye to get precise consequences. One these instances are that of Fluorescein angiography. Fluorescein angiography derives its name from fluorescein, the dye that is utilized extremely successfully for carrying out tests. Angiogram is a extremely expensive test that provides information about the circulatory system.

Colourants for Agriculture Industry

Primarily there are 3 major kinds of agricultural industries that employ the dye. They are the crop shield industry, fertilizer industry and the seed dressing industry. The function of the dye utilized here is for colouring of agricultural chemicals or in the identification procedure of agricultural chemicals. The basic selection criteria based upon the subsequent:

Colour strength of the particular dye

Dye colour

Colour stability

Compatibility of the dye with the particular agent

(i) Fertilizer Industry: Fertilizers are often added by colouring to differentiate between qualities and to avoid any kind of errors in application. Fertilizers are as well coloured for purely marketing purposes. Generally water depend pigment is often utilized in the diluted form and is sprayed onto the fertilizer or sometimes incorporated into a melt.

(ii) Crop Protection Industry: Utilize of colourants in crop protection agents of the kind insecticide and fungicides assists to clearly demarcate treated areas from the untreated ones. In addition, the dye stuffs as well assist in promoting safety in the handling methods. Colouring of pesticides or herbicides is usually done through mixing chromatic pigments through dry powder formulations of the agents. Milori blue is a extremely popular pigment that goes well through viticulture fungicides. Other categories of pigments include lithol rubine, heliogen blue and so on. Dyes utilized in the crop protection industry are Solvent dyes, Acid dyes or Basic dyes.

(iii) Seed Dressing Industry: The major objective of colouring the seed dressings is utilized for marking and a warning reference. To avoid any sort of confusion and making sure that it doesn't end up being employed as fodder. The most significant colourant employed here is red by typical concentrations of 600 ppm.

Paper industry

Over the years Paper makers have utilized dyes. Seeing the growth in the paper industry it can be safely assumed that Dyes for paper industry has an extremely promising future. Given underneath is a comprehensive list of the different grades of paper that are open to dyeing.

Writing and printing paper

Tissue - Facial, toilet, towel, napkin

Copier papers

Boards/Cover papers

Decorative laminated paper

Packaging grades - corrugated case stuff

Envelope grades

Specialty papers like, label, laundry tag, posters

The dyes that are utilized comprise sulphur dyes and cationic direct dyes. Other than such 2 popular options, acid dyes and basic dyes are as well utilized. Sulphur dyes are diminished alkaline solutions.

Coming to the Cationic Direct Dye, several features that make them suitable towards employ in paper are:

An extended conjugation

A planar molecular structure

An excess of positive charge over the negatively charged surface groups

A typical structure of a cationic direct dye is given here.

Pigments in Paints Industry

Pigments are the colouring elements present in the paints. They have a very special place in the paints industry. The paints industry uses them from a broad array, which includes specialty pigments to manufacture paints for a variety of applications. Ranging from automobiles to buildings to hardware the list is virtually endless.

The paints that employ the wide variety of pigments can be broadly classified according to application into 2 kinds. They are colourants for the industrial applications and architectural/decorative applications respectively. The pigment kinds are:

(i)  Earth colour Pigment- Earth colours are derived from natural sources and are inorganic in nature (for example metal oxides). Instances that can be specified of earth colours are: ocher, umber, terra di siena, bolus, Swedish red and so on.

(ii)  Mineral Pigments- Mineral pigments comprise synthetic inorganic pigments. They contain among others chrome oxide green, titanium dioxide, iron oxide yellow, red, brown and black, ultramarine blue, nickel-titanium yellow and so on. One of the disadvantages of mineral pigments is the toxicity and ecological imbalance.

(iii)  Plant Colour Pigments- Plant colours are sourced from natural organic pigment found in plants. Examples of plant colours can be given of indigo, alizarin red, woad, reseda, alkanna violet and saffron.

(iv) Synthetic Pigments- Synthetic Pigments are the most widely utilized artificial organic pigments and dyes. They provide the benefit of synthesisation of approximately any shade, particularly of pure colour tones and gives dazzling visual consequences. Instances are: azo, dioxazine and phthalocyanin.

Wire and Cable Industry

In the Wire and cable industry, various kinds of pigments are utilized to colour polyolefins.  Mainly they are employed for Wire Identification Methods. As in cables, it can be seen that the colouring done on the outer layer is governed through a different set of requirements as from the inner layers. Pigments that are employed in the wire and cable industries are of 2 kinds inorganic and organic. Newer alternatives that are coming in to the market are identified as the 'mixed-phase metal oxide' pigments.

Instances can be known of, yellow nickel titanates and blue and green cobalt aluminates. A comparatively new entrant is the brilliant yellow bismuth vanadate. Organic pigments are as well employed but aren't as popular because they are more hard to disperse than inorganic ones leading to possible loss in mechanical strength.

Table: Common Pigments and Applications

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