Why is DPOA called an active film-forming aid?

2021-09-25   Pageview:636

Dicyclopentenyloxyethyl acrylate (DPOA) is an unsaturated polymerizable organic substance, homopolymer Tg=33℃, odorless.

In latex paint formulations with higher Tg values, no film-forming additives are needed, but DPOA is added and a small amount of drier, such as cobalt salt, is added. DPOA can lower the film-forming temperature and make latex paint film-forming at room temperature. However, DPOA is non-volatile and not only environmentally friendly, but also undergoes oxidative free radical polymerization under the action of a drier, which increases the hardness, anti-sticking property and brightness of the coating film. Therefore, DPOA is called an active film-forming aid.












Waxes are fatty derivatives with hydroxyl or hydrogen groups, one of the most effective rheology modifiers in non-aqueous coatings, the most important of which is hydrogenated castor oil (HCO), which is prepared by hydrogenation of liquid castor oil. Converted to waxy solid [1, for easy dispersion, a micronized wax is used, which makes it easier to disperse the crystals. The product can be added in the grinding stage before the pigment dispersion has started. After the dispersion, with the slight increase in temperature, the crystals are swelled by the solvent, and the product is fully activated under shear conditions. The entangled triglycerides are subjected to the additional action of hydrogen bonds to form a colloidal structure in the organic continuous phase. When using paint such as brushing, the viscosity is greatly reduced, which helps the coating film to spread, wetting and leveling.

At the end of brushing, leveling begins, and then thixotropy is formed to prevent the paint from sagging on the vertical surface. Modified castor oil is classified as a pseudoplastic thixotropic agent. It has a fast re-tack time and can be thickly coated on vertical surfaces. It can be used as a pre-gel in clear coatings. The product shamrock ptfe wax should form a dispersed phase in the system and cannot be uniformly dissolved in the component sub-levels. Care must be taken to avoid that these waxes are completely dissolved at high temperatures. At this time, the rheological properties will be completely lost, and the wax will form crystals after cooling.

The paint begins to precipitate and forms film defects. This phenomenon is commonly known as “crystallization” and must be avoided by strictly controlling the temperature. Sometimes, the temperature in the grinding stage has exceeded the specified limit, which will result in the end product being unqualified. The closer to the critical temperature of activation, the better the thickening effect. The critical temperature depends on the solubility of the solvent used. Aromatic solvents are lower and aliphatic solvents are higher.


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