echemi logo
Product
  • Product
  • Supplier
  • Inquiry
    Home > Coatings News > Paints and Coatings Market > Essential characteristics of water-based industrial coatings

    Essential characteristics of water-based industrial coatings

    • Last Update: 2021-04-14
    • Source: Internet
    • Author: User
    Search more information of high quality chemicals, good prices and reliable suppliers, visit www.echemi.com

    Essential characteristics of water-based industrial coatings

    Basic characteristics of water

    Non-combustible, non-toxic, non-polluting

    Economical, sustainable resources

    Freezing at 0℃, boiling at 100℃

    Strong polarity, dissolves and disperses ionic substances

    Dissolve a small amount of oxygen and other gases

    Versatility in neutral, acidic or alkaline environments

    High chemical reactivity, hydrolysis and corrosion

    Biological necessity

    The essence of water

    Two elements, three atoms;

    The four hybrid orbitals come from the oxygen 2s, 2px, 2py and 2pz atomic orbitals, pointing outwards from the oxygen nucleus to the corners of the tetrahedron;

    The asymmetric charge distribution becomes a polar molecule (α=114°29′, β=104°27′);

    Intermolecular hydrogen bonds, the hydrogen nucleus interacts with the lone pair of negative charges of neighboring water molecules to produce a hydrogen bond with an energy of about one-tenth of the molecular O-H bond.

    Aqueous solution structure

    Liquid water is a highly organized substance.



    The detailed arrangement of molecules in liquid water is indeterminate at com" href="">coatingol.


    com .
    Based on the hexagonal ice structure, each water molecule is connected to four adjacent water molecules.


    Derived from the structure of ice, some extra molecules occupy the interstitial space and exchange with molecules in the hydrogen bond network.


    The average number of adjacent molecules of water molecules increases from 4 in ice to 4.
    4 in the freezing point of liquid.
    Water is denser than ice.


    Water has one of the highest known dielectric constants, 78 at 25°C.
    The higher the dielectric constant of the medium, the lower the energy required to separate opposite charges, which makes water one of the factors that make water an effective solvent for ionic substances.

    The principle of water-based organic resin

    The principle of water-based technology: polymer molecules are coated with hydrophilic substances/chemically grafted with hydrophilic groups, (or after neutralization) they can be diluted with water.

    External emulsification: Emulsifier (ionic or nonionic) is added to the water phase to form micelles, which are formed by emulsion polymerization to form latex; or hydrophilic substances are added, which are obtained by reverse emulsification.
    Usually called emulsion.

    Self-emulsification: grafting hydrophilic groups (-COOH, -CH2-CH2-O-, -NH2, etc.
    ) on polymer molecules, (or after neutralization) can be diluted with water.
    Usually called a dispersion.

    Macro morphology of water-based resin

    Macro form (emulsion, slightly transparent dispersion, transparent solution)

    Most water-soluble resins are not really soluble in water (except polyvinyl alcohol, cellulose, polyacrylic acid), but form a relatively stable polymer colloidal dispersion solution after the amine salt solution of an organic solvent is diluted with water.

    Microscopic morphology of water-based resin

    Heterogeneous system: latex particles, polymer aggregate particles

    Free hydrophilic substances, neutralizers, co-solvents, etc.

    Water-based resin dilution viscosity change-water-based dispersion, water-based resin

    Viscosity peaks exist during the dilution of water-based resin

    There is no viscosity peak in the aqueous dispersion, and the viscosity changes greatly compared with the resin solution

    Water-based resin dilution viscosity change -water-based resin

    Water-based resin viscosity is also related to molecular weight, polarity and amount of co-solvent.

    Distribution of solvents in water-based resins

    The solvent is unevenly distributed in the water phase and the polymer phase; it affects the viscosity of the system, the aggregation of particles into a film, and the evaporation and stability of water

    Drying process of water-based industrial coatings

    Volatilization of water and organic solvents

    Strong interaction deviates from Raoult's law

    Relative humidity affects water volatilization, and has little effect on solvents

    Azeotropic effect

    The heat capacity and heat of vaporization of water are abnormally large

    (Boiling point, butyl acetate (126℃) volatilizes faster than n-butanol (118℃))

    Wet stage

    The volatilization rate of the mixed solvent is controlled by factors such as vapor pressure, surface temperature, relative humidity, air velocity, and surface area to volume ratio.


    It has a linear relationship with the thickness of the paint film.


    Dry stage

    The volatilization rate of the mixed solvent is determined by the diffusion rate of the solvent molecules.


    The relationship with the thickness of the paint film is quadratic.


    Denseness of water-based paint film

    The film formation process involves diffusion between particles and molecules

    Heterogeneous film (relative to solvent-based coatings)

    Structure and composition of water-based paint film

    Heterogeneous dense coating film; there are enriched areas of different substances; hydrophilic substances/groups still partially remain in the coating film.



    Corrosion of water-based industrial coatings


    Flash rust concept and evaluation


    ISO12944-4 defines flash rusting as'slight rust formation on a preparedsteel surface soon afterpreparation'


    ASTMD 610-85 (1989) Standard Test Method for Evaluating the Degree of Rust on Painted Steel Surface


    Influencing factors of paint "flash rust"

    Water-based polymer type (important factor)

    Relative humidity during film formation (very important factor)

    System pH (factor of low importance)

    Metal type (important factor) at the metal weld (submerged arc welding)>cast iron>carbon steel

    A classic example of water-based industrial coating application -electrophoretic coating

    It is suitable for comprehensive coating of complex shapes, uniform film formation, thin film, high performance, and automation.

    This article is an English version of an article which is originally in the Chinese language on echemi.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to service@echemi.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

    Contact Us

    The source of this page with content of products and services is from Internet, which doesn't represent ECHEMI's opinion. If you have any queries, please write to service@echemi.com. It will be replied within 5 days.

    Moreover, if you find any instances of plagiarism from the page, please send email to service@echemi.com with relevant evidence.