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Formulating and Applications of Fluorocarbon Resins Cure at Normal Temperature

Introduction

The outstanding strongpoints of fluorocarbon polymer coats are their superior exterior weatherability, durability, longevity and chemical resistance. Fluorocarbon polymers contain F-C bond in their inner chemical structures. The energy of F-C bond is very high (486kJ/mol). F atom radius is short (0.135nm). Therefore, fluorocarbon-polymer was endued excellent weathering resistance, stain-proof, easy to be washed, and acid resistance, alkali resistance. But traditional fluoropolymer coatings are thermoplastic and cannot be solved in solvents. They must be baked to form film only at high temperature. Thus, limited colors, a lower gloss and difficult to repaint makes their application be restricted.

Crosslinking versions FEVE fluororesin copolymers manufactured by Wuxi Wanbo coating Chemical Co. Ltd. have performances as the same excellent durability and chemical resistance as the traditional versions. The crosslinking versions have strict alternating structure. It is a true solution, colors and gloss can be adjusted in very wide range. And it can be formulated as two-pack fluorocarbon coatings that cured at normal temperature. The application areas are enlarged and can be applied in-situ. And it can be formulated as one-pack coatings that baked at middle temperature (140~150). The overall performances of the coatings have been reached or excelled the performances of HG/T 3792-2005 standard.

Formulation of Crosslink Fluorocarbon Coatings

(1)          Formulation Parameters

Type

Pigments

Resins

Flattening powder

Dispersing agent

Leveling agent

Note

White (gloss)

Rutile titanium oxide

WF-Q212

without

 

fluorocarbon modified silicone

1 Curing agent: HDI trimer

N3390 (NCO%=19.5% Bayer)

HDT90 (NCO%=19.5% Rodia)

TPA-90SB (NCO%=20.9%,

Asahi Kasei)

NCO/OH=1.1~1.3

2Dryer:

DBDTL 0~0.03% (total solid)

 

White (matt)

Rutile titanium oxide

WF-Q212

with

 

Color

Composite inorganic pigments

WF-Q212

/

EFKA 4060

Metallic (gloss)

Al pigment

Dosage :5%~10%

WF-Q211

without

/

Clear

-coat (matt)

/

WF-Q211

Flattening powder

without

(2)  The calculation of curing agent dosage in two-compound fluorocarbon coatings

 

                            OHV×42×fluorocarbon resin pure solid×EqNCO/OH

Curing agent dosage =                                            

(supply form: weight parts)                         561×NCO%

i.e.150 parts pure solid Fluorine resin OHV=45mg KOH/gNCO/OH=1.15NCO%=19.5%then

                                         45×42×150×1.15

Curing dosage (supply form: weight parts =                           = 29.8

                                          561×19.5

Note: NCO/OH will raise as the water content in the solvents rises; curing agent must be diluted to a suitable viscosity before being added to the coatings, or they maybe not easy to mix to uniform.

(3) Diluting Agent

The solvents in diluting agent can adapt xylene, butyl acetate, propylene glycol mono-ether acetate, cyclohexanone, MIBK, Solvesso 100. The solvents that react with curing agent such as alcohol (glycol) and alcoholic ether and so on must not be added.

(4)  Application Parameters

Usually, spray method is selected as the application method when painting fluorocarbon coatings.

The parameters of spray application are as following:

Viscosity (23±2, Ford-4# cup), s          18~20      (solid color)

                                     15~18      (metallic )

Pressure, MPa                         0.2~0.4

Dilution proportion (mass): coating: curing agent: dilution agent =100:10:20~40

Note: when adjust curing agent concentration, usually the mass proportion of coating to curing agent takes integer for convenience (for example: 100: 10 or 10: 1).

 

Application of Fluorocarbon Coatings Cross Linking at normal Temperature to outdoor walls of buildings

Fluorocarbon coatings cure at normal temperature have unexampled durability, weathering than traditional latex and solvent-type acrylic polyurethane coatings. Therefore, they specially suit for architecture area. Architects can design audaciously many kinds of colorful effect architectural works and not be afraid of losing color and gloss problem. Also maintenance cost can be reduced greatly because of fluorocarbon coatings’ superior dirt-proof.

Fluorocarbon coatings cure at normal temperature used for mainly exterior architecture decoration, for example, high buildings, aerodromes, houses, plants, hospitals and hotels and so on. They also can be used for decoration of balconies, roofs, scuttles, ceilings and awnings. Actually, any architecture exterior surfaces that need long-term weathering can all be applicable.

 

Painting requirements:

To the exterior wall of buildings, the dust on the surface must be wiped off as soon as possible, the moisture proportion must not be higher than 8% and pH not be higher than 8. You can spread a layer of putty followed by painting a primer-surfacer and fluorocarbon coating at last. If an imitated effect of aluminum plate (metallic coatings) is required, you had better paint a clear coat (can be low gloss to high gloss according to customers’ requirements).

 

At present, compress cement wall plate painted with fluorocarbon coatings can past to the wall directly. It adopts the technique that painted in shop and baked at about 80 for 30 min. Therefore the problems that brought crack and damage the appearance by wall body or putty can be solved. Now, this technique has been attentive.

 

Note:

Fluorocarbon coating can only be used as topcoat (solid color, metallic coat or clear coat) and cannot be as primer or primer and topcoat two-in-one. Therefore, it must be mated with primer when test the performances of the fluorocarbon coating.

Application of Fluorocarbon Coatings Cross Linking at normal Temperature to outdoors Steel Constructions

In our country, the cost used for preventing the outdoor steel structures from corrosion is quite high every year. The one of reasons is that cost of maintenance is too high. The long-term anti-corrosive coatings such as epoxy coatings have been adapted. However, the correspond finishes such as alkyd, chloride rubber or polyurethane coatings have short-term weathering resistance. The makes the primer with no weatherability exposure to the sunlight directly and therefore easy to chalk too early. In order to attain long-term anti-corrosive effect, fluorocarbon topcoat is the best choice.

When corrosion resistance is a primary concern, primers must be capable of not only good adhesion to the substrate but corrosion protection effect as well. Highly corrosion resistant epoxy zinc-rich primers, along with epoxy mica ferric oxide mid-coats, can be used under fluorocarbon polymers topcoats if superior corrosion protection of outdoor steel substrates in required.

 

Application requirements of outdoor steel structure paint with fluorocarbon coatings

The surface of outdoor steel structure is treated to Sa 2.5, get out of dust followed by epoxy zinc-rich primers 2 coats, then spread a layer of putty, sand after it has been dried and get rid of dust, paint epoxy mica ferric oxide mid coat then paint fluorocarbon topcoat after being dried.

 

Note:

Fluorocarbon coating can only be used as topcoat (solid color, metallic coat or clear coat) and cannot be as primer or primer and topcoat two-in-one. Therefore, it must be mated with primer when test the performances of the fluorocarbon coating.

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