Evaluation of wetting and dispersing additives for the use in waterborne anticorrosive paints Düsseldorf, 12.09.2013, Martin Muth
Content 1. Introduction 2. Functionality and chemistry of wetting and dispersing additives 3. Test methods 4. Results 5. Summary
Introduction Evaluation of wetting and dispersing additives for the use in waterborne anticorrosive paints Why is this topic of relevance?
Waterbased anticorrosive paints Market share 2012 6% conventional paints waterborne paints 94% Market study, Strategic Analysis of the Protective and Marine Coatings Market and the Resins Market, NC38-39, Frost & Sullivan, June 2013 Advantages Low organic solvent content (VOC) Less odor than conventional systems Not flammable Fewer toxic compounds Disadvantages Complex film forming process Limitations for application (low temperatures, high humidity ) Flash rust More expensive Manufacturing of paint more difficult
Wetting and dispersing process 1 Wetting 2 Dispersion 3 Stabilization
Pigment Dispersion Agglomerate Primary Particles Dispersion Flocculation Flocculated Deflocculated
Typical Surface Tension Values Solvents Resins Pigments/ Fillers 80 70 Water mn/m 60 50 Aqueous 40 30 20 Xylene White spirits Conventional Fillers/ inorganic pigments Organic pigments
Domains of a wetting & dispersing additive Binder-affinic domain Pigment-affinic domain
Impact of wetting and dispersing additives Tailored domains (binder and pigment affinic) are needed for the best performance of the additive Solubility/ compatibility of the additive is achieved by polar binder affinic domains based on e.g. polyethers, acidic groups, salt structure These polar domains stay in paint film and make it easier for ions and water to penetrate
Structures of wetting and dispering additives (1) 1. Fatty acid esters 2. Phosphoric acid esters 3. Polyurethanes 4. Polyacrylates 1.Fatty acid esters
Structures of wetting and dispering additives (2) Phosphoric acid ester Polyurethane
Acrylate chemistry Statistic Copolymer Gradient polymer by CPT Block Copolymer by CPT
Testing methods Water uptake/ Diffusion 1. Gravimetrical 2. Infrared spectroscopy 3. DSC 4. Permeability? Weathering tests 1. Salt spray test 2. Early water resistance
Used system and additives Styrene-Acrylate formulation based on: Type: anionic Styrene-Acrylate Emulsion Neutralization: Ammonia ph value: 7,0-7,5 Solid content: 51% Additive Chemical structure Neutralizing agent FS-1 Fatty acid Amine 1 FS-2 Fatty acid PS-1 Phosphoric acid ester Amine 2 PU-1 Polyurethane Amine 1 AC-1 Polyacrylate Amine 3 AC-2 Polyacrylate Base 1 AC-3 Polyacrylate Base 2 AC-4 Polyacrylate Amine 3 AC-5 Polyacrylate (CPT) Base 2 [8]
Water uptake Gravimetric vs. Differential Scanning Calorimetry Melting peak of water vs. HHHHH(water)=333,3 J/g
Water uptake after 6 hours 16,0 14,0 12,0 Water uptake/ % 10,0 8,0 6,0 4,0 2,0 0,0 Ref. FS-1 PS-1 PU-1 AC-1 AC-2 AC-3 AC-4 AC-5 Scale 7,2 9,6 8,8 9,4 11,6 11,1 12,6 5,7 9,4 DSC 7,3 10,6 13,2 6,3 10,2
Water Diffusion: IR spectroscopy 0,100 A 0,075 d water B Absorption 0,050 0,025 0 hours 4 hours 24 hours 48 hours C 0,000 3.800 3.600 3.400 3.200 3.000 Wave number / cm -1 A: cup containing water B: free coating film C: ATR crystal d: film thickness
Diffusion coefficient after 24 hours water storage 4,0E-10 Diffusion coefficient cm 2 /s 3,0E-10 2,0E-10 1,0E-10 0,0E+00 Reference PS-1 FS-1 PU-1 AC-1 AC-2 AC-3 AC-4 AC-5
Permeability 45% humidity Name R 2 V [g/(m 2 *d] Control 0,9994 26 93% humidity FS-1 0,9991 26 PU-1 0,9984 24 AC-1 0,9949 46 AC-2 0,9995 38 AC-3 0,9979 29 AC-4 0,9983 24 AC-5 0,9987 26 V = Density of water diffusion DIN EN ISO 7783
Early water resistance Water application after 4h drying Water application after 24h drying DIN EN ISO 2409
Early water resistance - adhesion Additive 4h drying [GT] 24h drying [GT] Control 1 1 FS-1 5 5 PS-1 2 2 Control after 24h PU-1 0 0 AC-2 5 5 AC-1 5 5 AC-1 after 24h AC-3 2 3 AC-4 0-1 0-1 AC-5 0 0 AC-5 after 24h
Salt spray test DIN EN ISO 9227 Temperature: 35 C NaCl concentration: 50±5 g/l
Results salt spray test AC-1 AC-2 FS-1 AC-4 PS-1 Control PU-1 AC-3 AC-5 140 384 500 600 700 hours in salt spray test
Result overview
Influences of chemical variations Delamination (W d ) 25 20 W d / mm 15 10 5 0 Modif. 1 Modif. 3 Evaluation after 400 h salt spray test, n=3 panels
Influences of chemical variations Blistering 5 4 3 2 1 0 Modification 3 Determination: 0 = no blisters, 5 = many blisters Evaluation after 400 h salt spray test, n=3 panels
Summary The influence of wetting & dispersing additives on the properties of a waterbased paint film was evaluated by various methods: Water uptake (gravimetrical, DSC) Water diffusion (IR spectroscopy) Permeability Early water resistance Salt spray test All applied methods allow a clear differentiation, but do not necessarily correlate with each other Conclusion: chemistry of the wetting & dispersing additive has a significant influence on the paint film properties Careful selection by using the appropriate test method