Definition of thickener:
Thickeners can not only thicken coatings and prevent sagging during construction, but also provide coatings with excellent mechanical properties and storage stability. For water-based coatings, thickeners are particularly important!
Water and oily points. Especially the application of water-based thickeners is more common. After adding the thickener, it can adjust the rheology, thicken the adhesive and sealant, prevent filler precipitation, give good physical and mechanical stability, and control the rheology of construction (during construction) No sag, no dripping, no splashing), and it can also play a role in reducing costs.
Thickeners are very important for the manufacture, storage and use of coatings. They can improve and adjust the viscosity, and obtain the functions of stability, anti-settling, anti-seepage, anti-dripping, and thixotropy.
Viscosity: Viscosity is a measure of the viscosity of an object. It is an expression of fluid dynamics and its internal friction phenomenon. Newton believed that the force to maintain this velocity difference is proportional to the velocity difference perpendicular to the fluid (that is, the velocity gradient). , Which is expressed as viscosity.
Viscosity is a measure of the friction within a liquid molecule, and it is also a concrete reflection of the viscous flow properties of an object.
Viscosity = shear stress / shear rate
The unit of viscosity is usually “poise”, represented by P. The conversion of some viscosity units is as follows:
1 poise (P) = 0.1 Newton second/m2 (Ns/m2) = 3.6×102 kg/m2 (kg/m2h)
1 kilogram-force second/m2 (kgfs/m2)=9.807pa·s×98.07 poise 2 (P)
Classification of thickeners:
(1) Thickeners have the following categories:
Inorganic thickeners (gas phase white carbon black, sodium bentonite, organic bentonite, diatomaceous earth, attapulgite, molecular sieve, silica gel).
Cellulose ether (methyl cellulose, hydroxypropyl methyl cellulose, sodium carboxymethyl cellulose, hydroxyethyl cellulose)
Natural polymers and their derivatives (starch, gelatin, sodium alginate, casein, guar gum, shell gum, gum arabic, xanthan gum, soy protein gum, natural rubber, lanolin, agar).
Synthetic polymers (polyacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, modified paraffin resin, carbo resin, polyacrylic acid, polyacrylate copolymer emulsion, butadiene rubber, styrene butadiene rubber, polyurethane, modified Polyurea, low molecular polyethylene wax).
Complex organometallic compound (amino alcohol complex titanate)
Printing thickeners include (dispersion thickener, paint thickener, active thickener)
(2) Substances that can be used as thickeners:
|Newtonian fluid type||high-shear thickening polyurethane, cellulose||Viscosity hardly changes with shear force|
|Thixotropic||Modified polyurea, alkali swelling thickener||Shear increases and viscosity drops rapidly|
|Pseudo-plastic||Aluminum magnesium silicate, lithium magnesium silicate, polyamide, hydrogenated castor oil||Shear vanishing viscosity rises slowly, shearing increases vanishing viscosity rises rapidly|
|Anti-thixotropic||modified inorganic particles||Add shear viscosity to increase rapidly|
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