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Với mỗi bề mặt có chất liệu khác nhau thì sử dụng một loại sơn công nghiệp chuyên dụng phù hợp với loại vật liệu đó. Các loại sơn công nghiệp có đặc tính quan trọng nhất là chống ăn mòn, tăng tuổi thọ và bảo vệ tối ưu các kết cấu vật liệu, công trình công nghiệp. Với những yêu cầu khắt khe về tính bảo vệ và sự phát triển của nhiều loại vật liệu mới như hiện nay thì các loại sơn công nghiệp luôn được cải tiến không ngừng nghỉ theo thời gian. Mục đích là đem đến các sản phẩm có thể đáp ứng những yêu cầu đặc biệt của công trình công nghiệp và kiến trúc, đảm bảo khả năng bảo vệ cực cao khỏi môi trường khắc nghiệt.
Frosio course hand-out: Section 08 Paints and coatings Paint technology Frosio 08 Paints and coatings slide # Paint consists of: • Liquid: Vehicle / Varnish – Binders – Thinners (solvents) • Dry: Powders / Pigments – – – – Colour pigments Active / Reactive pigments Extenders Barrier pigments • Chemicals: Additives – – – – – Production enhancers Storage facilitators Application aids Appearance improvers Service life strengtheners FROSIO grouping: Binder, Pigments, Extenders, Solvents, Additives Frosio 08 Paints and coatings slide # Frosio course hand-out: Section 08 Paints and coatings Composition of paints Binder Natural Resin •Drying oil •Coal Tar •Nitrocellulose Synthetic Resin •Alkyd •CR •Epoxy •Polyester •Polyurethane •Silicate •Vinyl •Polysiloxane Paints Pigments Extenders Solvents Colouring Fillers Inhibitive pigm Stress reducing Additives Hydro carbons Wetting agent Ketones Anti-settling Cathodically protective Esters Drier Ethers Anti-skinner Biocides Alcohols Plasticiser Water Frosio 08 Paints and coatings slide # Binders Frosio 08 Paints and coatings slide # Frosio course hand-out: Section 08 Paints and coatings The properties of a paint will be decided by the binder • Describes the type of paint/coating • Bind pigments and extenders to a solid film • Provides the adhesion to the substrate and cohesion, flexibility in the film • Provides the water, chemical, solvent and UV resistance Frosio 08 Paints and coatings slide # Types of binders: Synthetic resin: • Alkyd • CR • Acrylic • Epoxy • Polyurethane • Vinyl • Silicate • Polyester Frosio 08 Paints and coatings Natural resin: • Drying oil • Wood rosin • Coal Tar • Bitumen • Nitro-cellulose slide # Frosio course hand-out: Section 08 Paints and coatings Modified binders • A modified paint may contain more than one binder, e.g.: – Coal Tar Epoxy – Vinyl Tar – Epoxy Mastic • A binder may be modified chemically by attaching new groups to their molecules, e.g.: – Styrenated Alkyd – Polyurethane-oil Alkyd – Epoxy Ester Frosio 08 Paints and coatings slide # DRYING / CURING MECHANISM • The properties of a paint film is closely related to how the binder dries or cures • The three most common drying / curing mechanisms are: Physically Drying (solvent evaporation) Oxidatively Curing (reaction with oxygen in the air) Chemically Curing (chemical reaction between base and hardener) Frosio 08 Paints and coatings slide # Frosio course hand-out: Section 08 Paints and coatings Physical drying • The solvents evaporate • Molecules pack and melt together to form a paint film • No chemical bonds Paint technology: Physical_drying1 Frosio 08 Paints and coatings slide # Physical drying Waterborne paints Water evaporating = Dispersed droplets Droplets are packing Droplets melt together, co-solvents evaporate Frosio 08 Paints and coatings slide # 10 Frosio course hand-out: Section 08 Paints and coatings Curing (drying) by oxidation • The solvents evaporate • Oxygen enter the paint and the reaction starts • The binder molecules link together through a chemical reaction with oxygen Paint technology: Oxidation_drying1 Frosio 08 Paints and coatings slide # 11 Chemical curing • The solvents evaporate • Component A and Component B molecules moves towards each other • They link together through a chemical reaction • A three dimensional network is formed which give the solid paint film Frosio 08 Paints and coatings Paint technology: Curing_good1 slide # 12 Frosio course hand-out: Section 08 Paints and coatings Insufficient mixing of two-pack paint • Proper mixing is a prerequisite to obtain proper curing • Insufficient mixing makes it impossible for the molecules to come in contact with each other • A three dimensional network will not be formed Frosio 08 Paints and coatings Paint technology: Curing_bad1 slide # 13 What factors may influence the drying process ? • • • • • • Relative humidity, % R.H Ventilation Temperature Film thickness Number of coats Evaporation rate of the solvents Frosio 08 Paints and coatings slide # 14 Frosio course hand-out: Section 08 Paints and coatings Curing Mechanism of some Binders Oxidising Physically drying • • • • • • • Chlorinated rubber Vinyl Acrylic Latex Bitumen Tar A/F-polymers • Alkyd Chemically curing • • • • • • Frosio 08 Paints and coatings Epoxy Polyurethane Polyester Vinylester Silicate Polysiloxane slide # 15 Mixing of two-pack paints Visual mixing control • It is difficult to verify proper mixing when the base is clear • A dark base makes it easier to see when the mixing is complete • Insufficient mixing results in reduced protective properties of the paint system Application: Mixingcontrol1 Frosio 08 Paints and coatings slide # 16 Frosio course hand-out: Section 08 Paints and coatings The dry binder consists of large molecules Large molecules gives: a) Good mechanical strength b) Good chemical resistance Physically drying binders: Molecules are large before drying starts Chemically curing binders: Large molecules are formed during curing Frosio 08 Paints and coatings slide # 17 The surface tolerance depends on the penetrating properties of the binder Vinyl Chlorinated rubber Epoxy Polyurethane Urethane alkyd Surface tolerant paint: Epoxy Mastic Alkyd Boiled linseed oil Raw linseed oil Frosio 08 Paints and coatings slide # 18 Frosio course hand-out: Section 08 Paints and coatings Surface tolerant paints are recommended for uneven substrates • Most paints can be applied to steel blast cleaned to Sa 2ẵ ã Not all paints possess the required wetting property for successful application on uneven substrates • Surface tolerant paints give a longer life time on such substrates Frosio 08 Paints and coatings Paint technology / Surface tolerant2 slide # 19 Epoxy Mastics are “Surface Tolerant” and “High build” Steel Traditional paints • Low coverage • Poor penetration Steel • Good penetration • High Build Epoxy Mastic Frosio 08 Paints and coatings slide # 20 10 Frosio course hand-out: Section 08 Paints and coatings Cross section of hydrolysing antifouling Epoxy seal Reduction in thickness after polishing CD 1118 nr 44 Antifouling Primer Frosio 08 Paints and coatings slide # 81 Why is hydrolysis so important ? Because: • Linear erosion rate assures long term antifouling property • No porous leach-layer means good adhesion after over-coating • Continuous smoothing of the surface ensures good fuel efficiency • Hard film maintains its good appearance Frosio 08 Paints and coatings slide # 82 41 Frosio course hand-out: Section 08 Paints and coatings Cross section of hybride antifouling Epoxy seal Polishing Antifouling Leach layer Primer Frosio 08 Paints and coatings slide # 83 Release rate for Antifoulings Release rate (µg/cm2 / day) Comparison of release rate of biocide for different A/F-types 40 Conventional A/F 30 Long life A/F Minimum release level for fouling protection Self polishing A/F 30 10 Frosio 08 Paints and coatings Time, years slide # 84 42 Frosio course hand-out: Section 08 Paints and coatings Anti-fouling for Aluminium hulls Special requirements: • Must be free from Copper • Metallic Copper in contact with aluminium will cause bi-metallic corrosion, perforating the hull plates in very short time • Must perform at speeds up to 50 knots (e.g for catamarans) • Preferably self-polishing type (best performance) Frosio 08 Paints and coatings slide # 85 A paint system may be compared to a house First: The basement - Primer coat Finally: The roof - Top coat Second: One or several stories - Midcoats They all have a special function • In the house • In the paint system Frosio 08 Paints and coatings slide # 86 43 Frosio course hand-out: Section 08 Paints and coatings Primers Primers are universal for most anticorrosive coating systems and are considered the most important component of the system The most important properties of primers are listed as follows: Adhesion (strong bonding to substrate) Cohesion (high internal strength in the film) Inertness (strong resistance to corrosion and chemicals) Intercoat bond (high bonding to intermediate coat) Appropriate flexibility Frosio 08 Paints and coatings slide # 87 Intermediate or Body coats The principal purposes of an intermediate coat is to provide: Thickness for total coating Strong chemical resistance Resistance to moisture vapour transfer Increase electrical resistance for the coating system Strong cohesion Strong bonding to primer and topcoat Frosio 08 Paints and coatings slide # 88 44 Frosio course hand-out: Section 08 Paints and coatings Topcoats Topcoats also perform several important functions as they: Provide a resistant seal for the coating system Form the initial barrier towards the environment Provide resistance towards chemicals, water, and weather Provide a tough and wear-resistant surface Provide a pleasing appearance Frosio 08 Paints and coatings slide # 89 What film-thickness should corrosion protecting paint systems have ? Deciding factor is the environment: In a dry inland atmosphere and indoor 120 microns will be sufficient In an aggressive industrial environment and along the coast and at sea, 250 - 300 microns will be necessary Number of coats is also of importance and not only the film thickness 100 microns in coats (50 + 50 microns) are giving better protection than 100 microns in coat Special coatings may be applied in thick coats Frosio 08 Paints and coatings slide # 90 45 Frosio course hand-out: Section 08 Paints and coatings Generic types of paint Frosio 08 Paints and coatings slide # 91 Alkyd Paints Advantages • • • • • • • • Good application properties 1-component Good weather durability Good wetting properties Good recoatability Good levelling properties Good gloss retention Dry heat resistant up to 120 ºC Limitations • • • • • • Frosio 08 Paints and coatings Poor chemical resistance (especially against alkaline) Limited water resistance (submerged) Limited solvent resistance Limited film thickness per coat Poor adhesion to CR Never to be used on Zinc slide # 92 46 Frosio course hand-out: Section 08 Paints and coatings Modified Alkyd paint • Styrene alkyds - Quicker drying, need stronger solvent • Silicone alkyds - better gloss retention • Urethane alkyds - Quicker drying, better water and chemical resistance Can be applied in thicker coats (60-100 microns DFT) Frosio 08 Paints and coatings slide # 93 Chlorinated Rubber Paints • • • • • • Advantages Physically drying Not temperature dependent Easy to recoat One component Very good water resistance Relatively good chemical resistance • • • • • Limitations Poor solvent resistance Low solid content Relatively poor wetting properties Thermoplastic Dry heat resistant up to approx 70 °C Frosio 08 Paints and coatings slide # 94 47 Frosio course hand-out: Section 08 Paints and coatings Vinyl paints Advantages • Physically drying • High chemical resistance • Good water resistance • Quick drying • Not temperature dependent • One-component Limitations • Low solid content • Poor resistance against strong solvents • Dry heat resistant up to • approximately 80 ºC Used for: Exterior objects above water Offshore on top of Zinc-ethylsilicate Frosio 08 Paints and coatings slide # 95 Pure Epoxy Paints Advantages • Chemical curing • Very good chemical resistance • High alkali resistance • Moderate resistance to acids • Good adhesion • Very low permeability • High mechanical strength • Dry heat resistant up to 120 ° Frosio 08 Paints and coatings Limitations • Chalking • Temp dependent • - component • Requires blast cleaning • Overcoating time slide # 96 48 Frosio course hand-out: Section 08 Paints and coatings Vinyl Tar - Modified type Advantages Disadvantages • Higher content of solids • Higher water resistance • Better wetting properties • Cost advantages • Bleeding • Dark colours • Tar on cancer list Used for: Under water areas Frosio 08 Paints and coatings slide # 97 Acrylic Paints Advantages • Physically drying • Not temperature dependent • Easy to recoat • One component • Good water resistance • Relatively good chemical resistance • Good weather resistance • Replaces CR & Vinyls Limitations • • • • High VOC Poor solvent resistance Low solid content Relatively poor wetting properties • Thermoplastic Frosio 08 Paints and coatings slide # 98 49 Frosio course hand-out: Section 08 Paints and coatings Curing agents for Epoxy Paints Polyamides: Normal epoxy paints Amine and amine adduct: Solvent free coatings Tankcoating Isocyanates: Low temperature curing Reaction with -OH Frosio 08 Paints and coatings slide # 99 Epoxy Paints- General Curing Diagram Temperature, ºC 40 30 20 10 14 28 Curing time, days Frosio 08 Paints and coatings slide # 100 50 Frosio course hand-out: Section 08 Paints and coatings Epoxy Coal Tar Advantages: Limitations: • Chemically curing • Dark colour • More flexible • Temp dependent • Excellent water resistance • 2-component • Better wetting properties • Recoating interval • Dry heat resistant up to • Bleeding when recoated 90 °C • Coal Tar is carcinogenic Frosio 08 Paints and coatings slide # 101 Epoxy Mastic Paints Advantages: Limitations: • • • • Surface tolerant • Chalking Not UV resistant High solids • Temperature High build dependent for curing Reduced application • Do not apply on thick time (less cost) layers of physically • Environmentally friendly drying paints • Minimum DFT 150 microns by airless spray Frosio 08 Paints and coatings slide # 102 51 Frosio course hand-out: Section 08 Paints and coatings Epoksy – Acrylic (Two-Pack Acrylic) Advantages • Very good weather resistance • Very good gloss retention • Very good chemical resistance • Very good solvent resistance • Cures down to °C • Potlife (24 timer) • Performance comparable to Polyurethane, but without using Isocyanate Limitations • 2-pack • Recoating: Early versions: before 12 hours or after days at 23 °C New versions: no particular restrictions Frosio 08 Paints and coatings slide # 103 Polyurethane Paints Advantages • Very good weather resistance • Excellent gloss durability • Very good chemical resistance • Very good solvent resistance • Cures down to °C Limitations • 2-pack • May cause skin irritation • Overcoating time Frosio 08 Paints and coatings slide # 104 52 Frosio course hand-out: Section 08 Paints and coatings Zinc Epoxy Advantages • • • • • • Chemically curing Good corrosion protection Good adhesion Require Sa ½ Good mechanical strength May be recoated with all types of paint, except Alkyd • Dry heat resistant up to 120 ºC Limitations • • • • Frosio 08 Paints and coatings Temperature dependent 2-component Film thickness: 25 - 50 Pm Not acid- and alkaline resistant (Resistant between pH 5-9) slide # 105 Zinc Ethyl-silicate Paints Advantages • Very good solvent resistance • Very high heath resistance (max 400 oC) • Very high mechanical strength • Very good adhesion to blast cleaned steel • Relatively good recoatability Frosio 08 Paints and coatings Limitations • Requires humidity for curing ã 2-pack ã Max DFT: 100 àm At higher DFT tendency of mud-cracking or checking slide # 106 53 Frosio course hand-out: Section 08 Paints and coatings Glass-flake Reinforced Polyester Advantages • Quick curing • Variable curing time • Application with airless • Excellent mechanical strength Limitations • Temperature dependent • Short potlife • Recoating interval - 12 hours • Glass-flakes reduce shrinkage, increases mechanical strength and water resistance • Bad curing may be experienced on Zinc primers and galvanised surfaces • Very good chemical resistance Frosio 08 Paints and coatings slide # 107 Vinyl ester coatings Limitation Advantage • Very fast curing • Very good adhesion • Very good abrasion resistance • Very good chemical resistance • Very good solvent resistance • Can be applied by normal airless spray • Glassflakes improve abrasion resistance • Short potlife (approximately 45 minutes) • Overcoating interval: - Min hours, max 24 hours • Limited shelf-life - Approximately months at 23 ºC • Dependent on temperature during application • Only to be applied on blastcleaned steel (Sa ½ ) Frosio 08 Paints and coatings slide # 108 54 Frosio course hand-out: Section 08 Paints and coatings Heat Resistant Paints: • Aluminium silicone: Resistant up to approximately 600°C • Zinc silicone: Resistant up to approximately 400°C Remember: – To be applied on Sa ½ – To be applied in thin coats only (20 µm) Heavier coats may give blistering – Zinc silicate must be fully cured before overcoating Frosio 08 Paints and coatings slide # 109 55