Construction Products Comparison of Binder Types Exterior Products - - PowerPoint PPT Presentation

Construction Products – Comparison of Binder Types

Exterior Products

Plastisols Fluoro carbons Polyur- ethanes Polyesters High Build (up to 200µm), tough, corrosion resistant PVC – environmental issues? Excellent UV resistance to wide colour range Corrosion resistance inferior to Plastisols / Polyurethane Good UV & Corrosion resistance Not as tough as Plastisol Low Cost

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• Only moderate durability overall (however, improving)

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Comparative Product Performance

UV Resistance (Aesthetics) Resistance to Corrosion (Durability)

Polyurethane Plastisols Polyvinyldene Fluoride Silicone Modified Polyester Polyester

Key areas of future focus

• Reduce cost:

– ‘De-engineer’ paint systems – Improve efficiency of process

• Reduce cure temperatures, increase line speeds,

improve control of coating thickness applied, reduce scrap & other waste. – Decrease required thickness of Zn layer (e.g. MagiZinc)

• Increase value of product:

– High quality premium products developments – ‘Negative-energy foot-print’ of buildings:

• Photovoltaic coatings
• Transpired solar collector

Vehicle Additives Industrial/Marine Pigments Resin Solvent Strengthe ner Colorants Inhibitors Alkyd Epoxy Urethane Polyesters Vinyls Acrylic Siloxanes Benzene Toluene Xylene Thinners Zn Dust Zn Chromate Zn Phosphate Polyaniline C black TiO2 ZnO Glassflake Fibers Mica Thickness UV absorbers Surfactants Wetting Agents Drying Agent High Performance Coatings Solventless PVDF Underwater coatings Fire Retardant Coatings Waterborne Coatings Sol-gel Route Dispersion Method

Factors on which Coating Selection Depends

Environment in which the coating to be applied

• Steel
• Non-ferrous (Al, Cu etc. )
• Non Metal – Plastic, Glass etc.

The substrate type Surface Condition of the substrate Temperature of the substrate Application method Weathering conditions Life of the coating Cost

Conventional Coatings

Oil Based – Alkyd Coatings Epoxy Based Urethane Coatings Polyester Vinyl Coatings Chlorinated Rubber Polyvinyledene Coatings ( PVDF)

High Performance Coatings

One those which are functional specific Can be applied in highly aggressive environment. Have high Corrosion resistance High Erosion & abrasion resistance Can dry very fast Can give large thickness in one coat

Coatings for Offshore Structures

How Offshore Structures differ from Onshore and Land Based Structures

• Marine Structures are in

the most corrosive

• environment. Further,

corrosion of various parts/component depends upon whether it is at : – Atmospheric Zone – Splash Zones – Tidal Zone – Immersed Zone – Buried Zone

Protective coating System for Submerged Zone

Submerged structures is usually protected with a coating and Cathodic Protection. Coating must be compatible with the CP system Initially for such a system coal tar epoxy was applied on a Sa21/2 prepared surface up to DFT of 400m Recently this has been changed to glass flake epoxy – 2 component each 225 um ( total thickness 450 um) The CP system used in combination is usually a sacrificial anode system. Zn electrodes are generally used.

Tidal Zone

Just 1-2 meter below the splash Zone Always wet. Maximum corrosion Maximum Bio corrosion

• Be applied underwater
• Should have curing under water
• Must have antifouling properties

The Coating should

Chemistry of Underwater Coatings

• Once we have made diepoxy prepolymers, we

tie them all together by adding a diamine.

Properties of a Typical Underwater coating developed by us and its comparison to a commercial product

Properties Benchmark Fast Cure Epoxy

1

Touch Dry 2 hours 1.5 - 2 hours

2

Hard Dry 10 hours 7-8 hours

3

Ease of Application Good Good

5

Impact resistance(ASTM 2794) 13 joules passed 13 joules passed

6

Cross hatch adhesion 4A 5A

7

Pull off adhesion(D4541) 2.2Mpa 3.2Mpa

8

Cylinderical Mandrel Flexibility(D522)

170 175

9

Abrasion resistance(D4060) 7 mg 5mg

10

Tensile strength 3.98Mpa 18.3Mpa

Application

• Underwater:

– Brushes - Using vigorous circular motion. – Underwater pump with round brush - using vigorous circular motion

Splash Zone

Is the most corrosive area of the offshore structure. This part of the structure is subjected to continuously dry and wet spell, each time sending depositing more salt to the structures during dry spell. Erosion by waves also damages this part of the structure. Any coating used must therefore by quite rugged and also quite resistant to aggressive environment. Due dry and wet cycle, partially coated surface can be exposed to sea water imparting high level of chlorides and wetness to the intermediate coat. The preferably coating system must be applied in a single coat for higher thickness and should have low curing time so that it cures fully before the wet spell attacks the member.

Offshore Structures

Glass Flake Reinforced Polyester Coating to achieve 750um in one coat

Coating systems for Splash zone

Originally the legs were coated with coal tar epoxy. Three coats of 125-150um were applied on blast cleaned surface after Zn-rich primer ( organic /Zn silicate). Silica filled ( flint-reinforced) compounds are mainly solvent free epoxy claddings, which were applied by spraying or trawling directly to blast cleaned steel in a dry film thickness of 3-5 mm. Monel 400 ( Ni-Cu alloy with 67% Ni, 32% Cu) sheathing, thickness 1-5 mm, was attached to the tubular steel either by bonding or by welding. . Glassflake reinforced coatings – high build or high solid coating by spraying one or two layers with a total thickness of 500 um. Thick rubber or neroprene coatings are applied to a thickness of 6-13 mm.

Coating systems for Splash zone

Bituminous wrappings from which the wrapping material usually is glass fiber. Before wrapping the steel is coated with a coaltar of bituminous primer. A Zero maintenance system can be a Aluminum thermal spray coating. This also allows reduced corrosion allowance on all the splash zone members. Solventless Glassflake coating with a fast curing characteristics is the best system It can be applied with modern Airless Spray system to a thickness of 800 um in

• ne coat. Expected to give life 6-10 years. 15 years life is

expected if thickness be made 1500 um.

Glass Flake Polyester Coating

Isopthalic Based Polyester Coating 100% Solventless System Can be applied at 90% RH Applied on Sa2½ Blasted Surface Applied by Airless Spray for 800 um in one single coat. High Curing time. Both Surface preparation and application

• f coating can be finished in Low tide to

High tide duration.

Substrate Substrate Coating Glass Flakes Moisture Penetration

Advantage of this system

Good tough & highly corrosion resistant. Can be applied in single coat to a thickness more than 800-1000m. Cures in less than 20 minutes in normal temperature of 30oC. Can be coated in 90% RH Has impact and abrasion resistance Has UV and weathering resistance

High Durability Coatings

Polysiloxanes Coating

• Based upon -Si-O- bond which is
• Stronger than –C-C-bond ( 108Kcal compared to 83Kcal for –

C-C- bond)

• That is not affected by sunlight and has strong Gloss and

Colour retention properties R R RO – Si – O – Si - R + H2O= - Si-OH + RHO R R R R R R

• Si-OH + HO- Si -

= - Si –O - Si - R R R R Used where long term Gloss and Colour retention is required

Polyvinylene Di-Fluoride ( PVDF )

Highly resistant to Strong Acids / Alkalies Resistant to UV Light Basically, it consists of 70% fluoride resin ( Kynar 500) having 42% of Flurine Content with 30% of acrylic resin. Can be applied by spray, on line coating

The C-F bond is one of the strongest known (PVDF shown below)

Fluoropolymer Bonds are Less Likely to Break

• C –F – Bond Strength 149 Kcal/m

Hybrid Coatings

One Coat of Metallized Coating Second Coat of Sealer Coat

• Pure Zn
• Zn-Al alloy ( Zn-15%Al)
• Al
• Al-Mg Alloy

Based upon the principle of providing large concentration of anodic material which can provide cathodic protection: Life Achieved can be 25 years to 50 years

Intumescent Coatings

INTUMESCENCE

Intumescence is defined as the swelling of certain substances when they are heated Intumescent coatings - on heating form an expanded multicellular layer, which acts as a thermal barrier that effectively protects the substrate against rapid increase of temperature, thereby maintaining the structural integrity of the building

Mechanism

MECHANISM

Fire Rating

Components of Intumescent Coatings

Acid Source Carburising Agent Blowing Agent Binder

Disadvantages of available Intumescent Coatings

Use formaldehyde and other toxic substances Fire resistant chemicals suspended in water Fragile char barrier Additive must be thermally stable at polymer processing temperature, which is often in excess of 200°C The thermal degradation process of the polymer, must not adversely interfere with the intumescence process

Formulation example

Heat Resistant Layer Sodium silicate 40 %

• Potassium silicate 40 %
• Aluminium Tri hydrate 4%
• Borax 4%
• Water 12%

An inorganic intumescent layer

• Sodium silicate 40 %
• Potassium silicate 40 %
• Silicon Carbide powder 4%
• Borax 4%
• Water 12%

OBSERVATION Poor surface application Poor water resistance Poor CO2 resistance Char formation not uniform

Summary & Conclusions

• Key areas to future,
• To develop solvent-free process /products
• Faster manufacturing process
• Eco friendly - To remove heavy metals…
• To develop functional coating (Texture, Anti-

soiling / Self cleaning, Anti-bacteria, longer gloss/Colour retention,…)

• High performance coating – fuctional

specific

Thank you