4 Four Fundamental Properties of Carbon Black FinenessParticle Size DistributionStructureAggregate Size/Shape DistributionPorosityPore Size DistributionSurface ActivitySurface Functionality Distribution
5 Properties of Carbon Black - Primary Particle Size Measured directly by Electron Microscope or indirectly by tint test, ISA, NSAA wide distribution of particle sizes within a product, but similar particle size within an aggregateBirla Carbon make blacks with mean particle sizes from 8 nm to 100 nmRaven 410100 nmConductex 7055 Ultra42 nmRaven 5000 Ultra II8nmRaven 125521 nm
6 Surface area and its influence Smaller particle diameter generally leads to high surface areaSurface area typically measured by nitrogen absorption (ASTM D6556) or iodine titration (ASTM D1510)Birla Carbon’s carbon blacks have surface areas ranging from m2/gHigh surface area is the single biggest predictor of color performance (masstone and tint)Higher surface area increase viscosity and conductivity and UV protectionHigh surface area lower dispersibility
8 Structure – Oil Absorption Number (ASTM D2414) Oil Absorption Number, primarily influenced by aggregate size/shape, may be influenced by porosityThe amount of oil to reach a peak torque, results given as cubic centimetres of oil per 100 g carbon black
9 Effect of Structure on Performance Higher structure (OAN) leads toSlightly lower blackness and tint strengthBetter dispersibilityHigher viscosity and vehicle demandHigher electrical and thermal conductivity
10 Porosity and its Influence Porosity is caused by oxidation in the reactor and is controlled by residence timeIndicated by a difference between Nitrogen Surface Area (NSA) & Statistical Thickness Surface Area (STSA)High porosity gives an increase inConductivityViscosityMoisture pick upHigh porosityEnables a low loading in conductive applicationsDecreases gloss
11 Surface Activity and its Influence Property describing the interaction of a carbon black surface with its surroundingsFurnace carbon blacks can be chemically surface treated after production to mimic channel blacksIncrease of surface activity by an increased number of acid groups leads to improved dispersionImproves wetting of the carbon black by most vehicle systemsReduces viscosity in liquid systemsReduces conductivityCarbon Blackas producedPost treatment adds oxygengroups to the surfaceOxidation950 OCNo Oxygen
12 Measurement of Surface Activity Volatile (Mass loss at 950 °C)Usually indicative of oxygen function groups, sometimes influenced by moisture, sulfur and toluene extractpH (ASTM D1512)Generally assumed to indicate surface acidity by oxygen functional groups, often strongly influenced by sulfur levelsOxygen ContentDirect measure of bulk oxygenXPS AnalysisMeasure of surface composition by atomic type, and some qualitative information on oxygen functionalities
13 Oxygen Functionality – Volatile All of these functionalities can be present on the surface in different amounts, currently we do not control which species are on the surface of the carbon blackIncreasing AcidityCarboxylPhenolAldehydeLactoneQuinoneAnhydrideEther
15 Stages of Dispersion Process PremixingGrindingDepends onPremixingGrindingLetdown
16 Correct Carbon Black Product For full color coatings, a high surface area product, which gives a jet color and blue shadeFor tint applications, there is a tradeoff between strength and blue shade. Higher tint products giver a browner shade, lower strength products give a blue shade.
19 Dispersant ChoiceSurfactants Low molecular weight dispersing agent which can modify the properties between the pigment and resin solution by lowering their interfacial tension.Polymeric Dispersants Higher molecular weight dispersing agents, composed of anchoring groups and polymeric chains that stabilize dispersions via a steric stabilization mechanism.
20 Surfactants Can be Classified by Head Group Type Anionic – negative chargeSodium dodecylsulfate (SDS) also called sodium lauryl sulfate(C12H25)OSO3NaGood for basic pigment surfacesCationic – positive chargeCetyltrimethylammonium bromide (CTAB)(C16H33)N(CH3)3BrGood for acidic pigment surfacesNonionic – No chargeOctaethylene glycol monododecyl ether(C12H25)(OCH2CH2)8OHGood for neutral pigment surfacesZwitterionic – both postive and negative charge (on different parts of the molecule)Phosphatidylcholine (as seen in lecithin)
21 Surfactants Can be Classified by Tail Type SaturatedUnsaturatedMonounsaturatedPolyunsaturated
22 Phosphatidylcholine Structure Red - choline and phosphate groupBlack – glycerolGreen - unsaturated fatty acidBlue - saturated fatty ac
23 Polymeric Dispersants Polymeric dispersants are at least a two-component structure which combines the following requirements:Specific Anchor Groups The dispersant must be capable of being strongly adsorbed into the carbon black surface via the anchoring groups.Polymer Chains The dispersant must contain polymeric chains that give steric stabilization in the required solvent or resin system.
28 SummaryThe first stage in getting the best from your carbon black, is choosing the right carbon black initiallyTailor dispersant and resin chemistry to optimize performanceLadder study to optimize loading
29 Further Information : Thank you MSDS, brochures and other information is available at birlacarbon.comThe International Carbon Black Association website carbon-black.org also contains useful health and safety information including a users guide