colorant summary ,Titanium dioxide

1. Titanium
dioxide
Colorant Summary
Amina Tariq

2. We mightnotevenrealise it, buttitaniumdioxide (Tio2,CIP White 6) isan essential partof our
everydaylife.Itisan integral componentof large numberof consumergoodsandproductsof
dailyuse suchas cosmetics,paints,dyes,varnishes,textiles,paper,plastics,food, printinginks,
rubber,adhesives,coatings,ceramics,roofingmaterials,watertreatmentagents,automotive
products,self-cleaningglass,pavingstones, Gratzel Cells, tattoosandcatalystsystems[1]
.The
usesof thiswonderful pigmentmentioned above bynomeansare exhaustive;rathertheyjust
give an ideaof type of industryandproductswhere itis usedon a dailybasis. Fig1; Ground TiO2
[5]
Titaniumdioxide,the oxideof metal titanium,isaninorganicwhite solid substance (showninfig1),andisgenerally
consideredtobe chemicallyinert.WhatmakesTiO2 anexcellentchoice asa pigmentis propertieslike:thermal
stability;poorsolubility; non-flammabilityandnon-toxicity. Titaniumdioxide isapolymorphiccompoundasitoccurs
inthree crystal modifications:rutile; anatase;andbrooklite (forcrystal structuressee fig2& 3 below).From
commercial pointof viewonlyrutileandanatase crystal formsare of industrial value asbrooklite isdifficultto
produce,andhas no knownindustrial applications.In1897, Dr. J. Overtonwasthe firstpersonto introduce titanium
compoundsaspigmentsusingamixture of rutile withthe mediumasthe resistantpaintonships’bottoms [10]
.
Fig2; Crystal structure of rutile [5]
Fig3; Crystal structure of anatase [5]
The two mostimportanttitanium- ore mineralsare ilmenite (FeTiO3) andnatural rutile (TiO2),andbothare usedin
the manufacture of differentendproducts [9]
.Eventhoughtitaniumdioxideisnaturallyoccurringpigment,high
demandhasledto syntheticproductiontomeetthe supplyof evergrowinguse of this pigment. In2003, the biggest
producersof TiO2 were Australia,SouthAfricaandCanada [11]
. The world’slargestrutile mine,the SierraRutileMine,
isin SierraLeone.In1995, this mine wasreportedtoproduce 25% of world’srutile production [11]
.Oncommercial
scale it isproducedusing sulphate andchloride processes[6] [7]
.
The great versatilityof titaniumdioxideisdue toitsvariouspigmentgrades,shapesandsize.TiO2 canbe usedeither
inmicroscale or nanoscale (ultrafine) particleform[3]
.Asananoparticle itisusedin cosmeticsparticularly sun
creamsbecause of its unparalleledabilitytoreflect,scatterandabsorbharmful UV light- hence protectingthe skin
beneathit[2]
.TiO2 isa physical filterforUVA light(wavelengthof 315-400nm) andUVB (wavelengthof 280-315nm)
radiation.Asitis chemicallyinertitwill notdecolouriseunderUV light.TiO2 nanoparticleshave tobe laminatedwith
inorganicsurface modifierssuchasaluminaandsilica,because particlesthatcome intocontact withwaterproduce
free radicles suchashydroxyl radicals,which are potentiallyharmful tohumans.Coatingblocksthe particles’ contact
withthe skinand waterbyimprovingdispersionandproviding photostability- hence renderingtitaniumdioxidevery
safe to use [2] [4]
.TiO2 as nanomaterial istransparent,andisnotusedas a colorant because fundamentallyits
propertiesare differentfrompigmentsize particles,anddoesnotimpartcolouror opacityto a product such as sun
cream [1]
.At present,sun protectionfactorhasbeenmade possibleusingjustnanoscaleTiO2
[3]
.
As a brightwhite pigment,TiO2 isextensively usedinpaintsand surface coatings.Forthese applications, Ithassome
excellentproperties,suchashighopacity,gooddispersability,highrefractive index,stronglightscattering,incident-
lightreflection, highUV resistance,excellent tintingstrengthandhighhidingpower [3] [4] [8]
. Whitetitaniumdioxide
pigmentscurrentlyinuse are mostly rutile,inthe micrometressizerange,asanatase formisprone to yellowingand
has poorweatherfastness.Particlesize isof paramountimportance tooptimisethe lightscatteringinthe visible
range,thisis achieved byusingthe primaryparticle size of roughlyhalf the wavelengthof the lighttobe scattered,
that ishalf of 400-700nm forvisible light [1]
.Thisscatteringof light whichresultsinhighopacity iscausedbyhigh
refractive index of TiO2 (rutile,2.70),the incidentlightenters throughthe crystal slowlyanditspath isconsiderably
changedas opposed tothe air, if the alignmentof the small particlesisinthe randomdirections,thiswillresultin
highrefractive index leadingtoscatteringof lightandhighopacity, asnot much lightpassesthrough [8]
.
TiO2 ina true sense isa white pigmentof 21st
century.Itplaysa vital part ina range of industriesinthe formof raw
material,intermediate orasan endproduct.In any case the propertiesof the pigment,suchasparticle size,surface
area,shape,dispersibilityandrheologyneedtobe tailored tofulfil the requirementsof aspecificapplication.

3. Bibliography
1) TitaniumDioxide ManufacturerAssociation. AboutTitanium Dioxide.[Online].2012. [Accessed22
November2015]. Availablefrom:
http://www.cinkarna.si/filelib/tio2/tdma_about_tio2__20120914.pdf
2) The Royal Societyof Chemistry.Titaniumdioxide.[Online][Accessed3December2015]. Available from:
http://www.rsc.org/chemistryworld/podcast/CIIEcompounds/transcripts/titanium_dioxide.asp
3) Steinbach,C.Nanoparticles&Nanomaterial- KnowledgeBase Nanomaterial.[Online].2009.[Accessed20
November2015]. Availablefrom:
http://nanopartikel.info/en/nanoinfo/materials/titanium-dioxide/material-information#literatur
4) DuPontTi-Pure titaniumdioxide.[Online].[Accessed20 November2015]. Available from:
https://www.chemours.com/Titanium_Technologies/en_US/tech_info/literature/Coatings/CO_B_H_65969_
Coatings_Brochure.pdf
5) Douma, M. Curator. In Pigmentsthroughthe ages- detailedpigmenthistories.[Online].2008. [Accessed18
November2015]. Availablefrom:
http://www.webexhibits.org/pigments/indiv/technical/titaniumwhite.html
6) Christie,M.R. ColourChemistry.[Online].Cambridge:Royal Societyof Chemistry,2001 [Accessed4
December,2015]
7) Buxbaum,G.ed. Industrial inorganicpigment.2nd
,completelyrev.ed.Chichester:Wiley-VCH, 1998.
8) Royal Societyof Chemistry.TiO2 Photocatalysis:Usesof TitaniumDioxide.[Online]. [Accessedon22
November2015]. Availablefrom:
file:///E:/Masterclass-TiO2_6_Uses%20of%20titanium%20dioxide.pdf
9) Miller,A.J.Titanium;a materialssurvey.[Online].1957. [Accessed6December,2015].
Available from:http://hdl.handle.net/2027/mdp.39015078459594
10) Tyler,M.P.Trendsin white-pigmentconsumption.[Online].1889. [Accessed6 December,2015].
Available from:http://hdl.handle.net/2027/mdp.39015077569278?urlappend=%3Bseq=9
11) Royal Societyof Chemistry.TiO2:Manufacture of TitaniumDioxide.[Online].[Accessedon1December
2015]. Available from:
http://www.rsc.org/learn-chemistry/resource/res00001267/tio2-photocatalysis-manufacture-of-titanium-
dioxide