Understanding vinyl ester resin as an effective lining and coating system.
What is Vinyl Ester Resin?
Vinyl ester resin is a thermosetting polymer. It has high corrosion resistance and excellent impact and stress-fatigue resistance. Highly cost-effective, it is widely used in pipelines, in the chemicals and petrochemicals industry as a form of secondary containment system, often for bund linings and in the marine industry in yacht hulls and aviation/aerospace sectors.
3 Categories of Vinyl Ester
There are three main categories of vinyl ester:
1) VE resins based on the reaction between methacrylic acid and diglycidylether of bisphenol A (DGEBPA). In terms of corrosion, these demonstrate broad resistance to aggressive chemicals making them particularly effective in environments exposed to high pH caustic solutions. For the most common vinyl ester resins used for composites, two mols of the diglycidyl ether of bisphenol A are chain extended with one mol of bisphenol A to form the epoxy backbone.
2) VE resins using a Novolac epoxy resin as a starting point. This leads to epoxy Novolac vinylester resins with a higher crosslink density versus the bisphenol A epoxy vinylester resins. As such, chemical penetration of the matrix is difficult and these resins are more resistant to organic solvents and mineral acids.
3) VE resins where tetrabromo bisphenol-A (TBBA) is used in the manufacture of the resin. Here, up to 20 percent of bromine is bound into its structure. This gives it good flame retardancy.
Vinyl esters ultimately use the best of polyester and epoxy resin, presenting both good mechanical properties and excellent chemical resistance, making them an ideal option for corrosive industrial environments.
Vinyl ester resins are a specific type of polyester resin demonstrating improved strength and chemical resistance is required in industrial applications. Initially a liquid, they undergo a curing process that transitions them from a viscous liquid to a solid, cross-linked structure.
As an isolated material, vinyl ester has limited durability. As such, it is combined with glass fibre reinforcements into the system to provide a mechanical backbone.
Vinyl ester resin properties can be modified through additive addition, the reinforcement materials can be adjusted to accommodate more demanding environments. The standard glass fibre matting (E-glass) can be upgraded to a C-glass type of matting, making it able to withstand more aggressive chemicals and making such a system able to better tolerate corrosive environments.
Vinyl Ester Resin Systems
A range of vinyl ester lining and coating systems exist. The composition is diverse, whereby different ingredients can be used to affect the overall properties of the system.
- Standard Bisphenol epoxy-based vinyl ester resin. This is versatile, offering excellent chemical resistance in a wide range of acidic and alkaline environments with high mechanical properties. Used to reinforce laminates to provide high impact and fatigue resistance. Ideal for hand lay-up in environments requiring resistance to corrosion and thermal cycling. Lowe water absorption and good aging properties.
- Bisphenol A-based epoxy vinyl ester resin. Highly cross-linked, low VOC and high-temperature resistance and mechanical properties. Ideal for hand lay-up. Provides excellent chemical resistance with particular suitability for corrosion applications.
- Brominated fire-resistant epoxy-based vinyl ester resin with excellent chemical resistance across acidic and alkaline environments. Good mechanical properties and capacity for greater fire resistance via the inclusion of antimony trioxide.
- Novalac epoxy-based vinyl ester resin. Highly cross-linked density vinyl ester resin with excellent mechanical properties at elevated temperatures – especially useful for solvent and chlorine containment. Offers both high heat distortion and tensile elongation. Ideal for hand lay-up.
- Rubber-modified epoxy vinyl ester resin with high tensile elongation and good impact resistance. Also presents low shrinkage, low peak isotherm and good adhesion to carbon, aramid and glass fibres as well as steel and concrete. Possesses excellent water resistance and good chemical resistance. Ideal for structures exposed to dynamic loads.
- Bisphenol epoxy vinyl ester resin offers cross-linking sites on both the polymer chain and the monomer system. This generates a high cross-link density and so leads to a resin that has a very high heat distortion temperature as well as excellent resistance to temperature to solvents and acidic environments. It also has very good retention of physical properties at elevated temperatures.
- Vinyl ester laminate reinforcements dictate the overall performance (mechanical, physical and chemical properties). Glass fibre-based reinforcements are presented with a range of sizings and binders. Key properties centre on wettability, chemical resistance and mechanical properties.
Surface Veils: well-constructed chemically resistant barriers utilising surface veils are required for polymer composites intended for chemical resistance. Surface veils based on C-glass and synthetic fibres exist. C-glass veils are popular since they have high wettability and excellent chemical resistance. Synthetic veils offer thicker and more resin-rich systems, but at the expense of lower wettability and maneuverability.
Additives can be added to increase mechanical properties and flame retardancy, but usually at the expense of chemical resistance.
Market size
The global vinyl ester market size was valued at $1.1 billion in 2020. It is projected to hit $2.1 billion by 2030, demonstrating a CAGR of 6.5% from 2021 to 2030.
Industrial Applications of Vinyl Ester
Demonstrating broad chemical resistance to a range of harsh substances – even at elevated temperatures – vinyl ester resins are deemed excellent forms of surface protection.
Used to contain select hydrocarbons, acids and alkalines, as well as bleaches, solvents and oxidising agents, the ability of vinyl ester to bond to concrete, steel and other substrates renders it an effective lining and coating system. Classic applications include the inside of storage tanks, resin floors and chemical containment bunds. Ingredient ratios within the vinyl ester blend, from resin composition to reinforcement type grade, have given rise to a range of different variants that are heavily tailored towards certain chemicals. Flame retardant ingredients can also be added, as can non-slip surfaces for environments expecting footfall.
Indeed, in a broader context chemically resistant fibreglass bund linings have been cited in COMAH reports on secondary containment as being viable lining options by the HSE. Indeed, they meet key criteria for effective secondary containment linings:
- Seamless and impervious
- Chemically resistant to select substances
- Impact resistant and abrasion resistant
- Optional flame retardant
- Low-to-medium cost for materials and installation
- UV-resistance
Vinyl Ester Bund Lining Installation
The installation of a vinyl ester lining or coating typically involves multiple steps. The underlying concrete (or other substrates) should be first dried out. Instances of refurbishment should see adequate repairs and surface preparation performed in advance. If dealing with fresh concrete or that which has been exposed to dampness or ingress, the moisture levels should be dry to 75% relative humidity (RH) as detailed in BS8204. It should also possess no rising damp or ground water pressure. Efforts should be made to render the surface mildly abrasive and amenable to adhesion – and sharp edges should be scaled back.
Thereafter, a primer should be applied as a means to (1) improve adhesion between the vinyl ester system and (2) act as a moisture-curing agent to block residual or future damp rising into the lining. Thereafter, a glass fibre matting (powder-bound, not emulsion bound), is applied to the primer-coated surface with a chemically resistant vinyl ester resin, thus creating a fibreglass laminate system. A protective tissue is then applied to the laminate, acting as a chemically protective veil prior to a final coat of pigmented vinyl ester resin.
Properties of Vinyl Ester Resins
The properties of vinyl ester resins are outlined below and have been adapted from the Handbook of Polymers.
| Property | Value |
|---|---|
| Common name | vinyl ester resin |
| CAS name | vinyl ester resin; benzene, ethenyl-, polymer |
| Acronym | VE |
| CAS number | 36425-15-7; 68002-44-8; 926021-66-1; 877997-30-3; 855482-93-8; 848485-23-4; 208520-04-1 |
Commercial Supply
Manufacturers AOC, Ashland, Dow, Reichhold
Trade names Vipel, Hetron, Derakane, Dion
Physical Properties
| Property | Value | Unit |
|---|---|---|
| Density (at 20oC) | 1.03 - 1.15 | g/cm3 |
| Thermal expansion coefficient (23-80°C) | 0.11 | 10−4 °C−1 |
| Glass transition temperature | 55 - 145 | °C |
| Heat deflection temperature at 1.8 MPa | 108-115 | °C |
| Property | Value | Unit |
|---|---|---|
| Tensile strength | 16 - 95 | MPa |
| Tensile modulus | 3,000 - 3,800 | MPa |
| Tensile stress at yield | 77 - 88 | MPa |
| Elongation | 2.5 - 9 | % |
| Flexural strength | 60 - 163 | MPa |
| Flexural modulus | 3,200 - 3,400 | MPa |
| Compressive strength | 82 | MPa |
| Abrasion resistance (ASTM D1044) | 100 | mg/1000 cycles |
| Shrinkage | 1.65 | % |
| Melt viscosity, shear rate = 1000 s-1 | 400 - 800 | mPa.s |
| Water absorption, equilibrium in water at 23°C | 0.1 | % |
| Chemical Type | Resistance |
|---|---|
| Acid dilute/concentrated | good/low |
| Alcohols | good/low |
| Alkalis | good |
| Aliphatic hydrocarbons | good |
| Aromatic hydrocarbons | low |
| Esters | good |
| Greases & oils | good |
| Halogenated hydrocarbons | low |
| Ketones | low |
Future Applications of Vinyl Ester Resin
Vinyl ester resin continues to be the subject of much research into curing, thermal, chemical, oxidative properties. It is particularly popular in industrial sectors requiring good structural attributes, corrosion and chemical resistance as well as low cost relative to other compounds.
Self-healing polymers: self-healing composites have a broad range of applications. Incorporating microcapsules (10 – 650 microns filled with benzoyl peroxide and vinyl ester resin) into epoxy resin showed anti-corrosion and self-healing properties. Salt-spray testing showed no signs of corrosion after 50 days of exposure.
Frequently Asked Questions (FAQs)
Q. What substrates can vinyl ester be applied to?
A. Concrete, timber, plywood and other structurally sound surfaces with a low moisture content and level of abrasiveness are suitable for application. Damp, contaminated (grease, chemicals, dust, moisture, etc.) and excessively hot (>30 oC) or cold (<5 oC) surfaces are not suitable.
Q. What is the difference between vinyl ester and polyester resin
A. Vinyl ester is between polyester and epoxy in terms of cost and performance. It exhibits higher failure strain, up to 6-9%, compared to 2-3% for common polyesters according to marine composite studies. GRP composites with vinyl ester matrices have significantly better delamination strength (>25%) compared to laminates with an isophthalic polyester resin matrix.
Vinyl esters are a form of polyester resin that has been strengthened by epoxy resin addition. They are more chemically resistant and less absorbent of water.
The cross-bonding of vinyl esters is better than that of polyesters and so there is less delamination. Moreover, vinyl esters bond to core materials much more effectively than polyesters. Vinyl esters are less sensitive to ambient conditions (temperature and humidity) than polyesters.
Q. What are vinyl ester resin curing times?
Generally, several hours for a partial cure and 24-48+ hours for a ‘full cure’. Curing times vary depending on the temperature and level of catalyst used.
Q. Who installs vinyl ester linings?
Vinyl ester linings are installed by professional contractors like Strandek. Operating since 1976, we have decades of experience and have completed thousands of project across the country.
Q. What is the difference between E-glass, C-glass and S-glass fibre matting?
The following has been adapted from the Introduction to Plastics Engineering:
– ‘E’ stands for ‘electrical’; E-glass is a good electrical insulator that is cost-effective yet still possesses good mechanical properties centering on strength and Young’s modulus. Density = 2.54 g/cm3; tensile strength = 1.7 – 3.5 GPa; Young’s Modulus = 69 – 72 GPa.
– ‘C’ stands for ‘corrosion’ or ‘CR’ for ‘corrosion resistant‘ as this matting has superior resistance to chemical corrosion. This makes it ideal for the containment of more aggressive chemicals when used in conjunction with resistant resins. Made with borosilicates. Commonly referred to as C- or CR-glass. Density = 2.48 g/cm3; tensile strength = 2.0 – 4.5 GPa; Young’s Modulus = 85 GPa.
– ‘S’ stands for high silica content. S-glass is able to withstand higher temperatures than other types. Density = 2.48 g/cm3; tensile strength = 1.7 – 2.8 GPa; Young’s Modulus = 70 GPa.
Note: Cemfil: this is an alkali-resistant glass fibre. Density = 2.70 g/cm3; Young’s Modulus = 80 GPa.
Q. Is vinyl ester flammable?
In a standard form, vinyl ester is flammable, but flame-retardent ingredients are added to eliminate this risk.
Q. Vinyl ester fibreglass concrete lining
A. Vinyl ester-based fibreglass linings can be applied to concrete. They provide an excellent waterproofing barrier that is both durable and abrasion resistant. It is also resistant to a range of chemicals.
Health and Safety
Vinyl ester resin has a strong, pungent odor that can cause eye, nose, and throat irritation if inhaled. It can also irritate the skin and cause dermatitis. Hazardous fumes can also be generated when vinyl ester resin is heated or exposed to certain chemicals. Contact can cause chemical burns if it comes in contact with skin.