CALCULATIONS ON PAINT FORMULAS

1. Density

Density paint is:

Total sum by weight of each ingredient in paint
Total sum by volume of each ingredient in paint

2. Solid content

Solid content by weight of paint is:

Total sum by weight of each solid ingredient in paint x 100%
Total sum by weight of each ingredient in paint

Solid content by volume of paint is:

Total sum by volume of each solid ingredient in paint x 100%
Total sum by volume of each ingredient in paint

3. Pigment Volume Concentration

PVC paint is:

Total sum by volume of all pigments + extenders in paint x 100%
Total sum by volume of each solid ingredient in paint

4. Critical Pigment Volume Concentration

The best way to determine the critical PVC of a paint is to measure the volume of the dry pigment/extender mix of a paint in a centrifuge and to calculate the CPVC as follows:

CPVC = (calculated volume pigment/extender mix / volume after centrifuge) x 100

CPVC = ( f x G x 100) / (dPi x Va)

f           = ratio weight pigments and total weight solid content paint
G         = weight of dry film
dPi      = density of pigment/extender mix
Va       = geometric volume of paintfilm (e.g. 250 micron wet filmthicknes x length x width)

A theoretical calculation which estimates the approximate CPVC is:

CPVC = (volume pigment+extender x 100) / (volume pigment+extender) + ((average o.a. pigment+extender) / 0,93)

5. Extender replacement

To calculate an extender replacement by weight by another extender and maintaining PVC:

E = A1 x D2
A2 x D1

E = factor to multiply with original extender weight to calculate weight substituting extender
A1 = OA of original extender
A2 = OA of substituting extender
D1 = density of original extender
D2 = density of substituting extender

6. Crosslinking percentage of two component products

· Epoxies

Equivalent weight epoxy component base paint is:

Weight base paint
Weight epoxy resin (1)   +   Weight epoxy resin (2) +
Eq.w.epoxy resin (1)           Eq.w. epoxy resin(2)

Equivalent weight amine component harder is:

Weight harder
Weight amine (1)          +     Weight amine (2)   +
Eq.w. amine (1)                   Eq.w.amine (2)

Crosslinking percentage = Weight harder x Eq.w. base component x 100%
Weight base x Eq.w. harder component

Polyurethanes

Equivalent weight polyol component base paint is:

Weight base paint
Weight polyol resin (1)   +   Weight polyol resin (2) +
Eq.w.polyol resin (1)           Eq.w. polyol resin(2)

Equivalent weight isocyanate component harder is:

Weight harder
Weight isocyanate (1)             +     Weight isocyanate (2)   +
Eq.w. isocyanate (1)                       Eq.w.isocyanate (2)

Crosslinking percentage =

Weight harder x Eq.w. base component x 100%
Weight base x Eq.w. harder component

7. Calculation the amount of amine to neutralize water-reducible resins

Equation: A = R (AN) E
56.100
Where:

A = weight of amine
R = weight of resin, non volatile
AN = acid number resin, non volatile
E = equivalent weight of amine

8. Starting point amounts of hydroxy / carboxy / amide containing resins in melamine / urea resins combinations in oven cured systems

Let:
x = hydroxyl number (mg of KOH to neutralize the organic acid required to esterify the hydroxyl groups present)
y = acid number (mg of KOH required to neutralize one gram of resin)
z = amide number (mg of KOH equivalent to reactivity of the amide groups present-by calculation)

Then: 56 grams (mol.wt. KOH) = gram mol. of resin to be crosslinked
x + y + z (mg)

Example: the equivalent weight of a melamine resin is 130

If a polyester resin has a hydroxy number of 60, an acid number of 5 and an amide number of 0, the gram-mol weight of the polyester is:

56 grams = 861,5 grams
60+5+0 mg

Or the starting levels for the binder may be polyester / melamine resin = 861,5 / 130
Or polyester / amino = 87 /13 by weight on solids

9.Volatile Organic Compounds (VOC’s with vapour pressure > 0,01 kPa at 20 C)

VOC = weight volatile organic material (g/l)
Volume paint (without water

VOC = 100 – NV% - water% x 1000 (g/l)
(100/density) – water%

For solvent based coatings the formula simplifies to:

VOC = (100 – NV%) x 10 x density (g/l)

10.Theoretical spreading rate paint at given filmthickness:

Volume solids = liters/m2
Filmthickness in microns : 10

Volume solids = kg/m2
(Filmthickness : 10) x density solids paint

Price per m2 at given filmthickness:

Price per liter
Theoretical spreading rate in liters

Relation thickness steel construction and surface:

Thicknes s of steel in mm

1

2

3

4

5

6

7

8

9

10

15

25

50

Surface in m / tonne steel

254

127

85

63

51

42

36

32

28

25

17

10,1

5,1

11. Required air quantities to stay below MAC levels:
∑ ( TLV per ingredient x weight %)

12.Required air quantities to stay below lowest explosion limits:
∑ ( LEL per ingredient x weight %)

13.General formulae for mixing liquids

A = C – B

B = C (a – c)
a – b

C = B (a – b)
a – c

Where:
A = weight of original liquid            a = its content in % by weight
B – weight of diluent                      b = its content in % by weight
C = weight of prepared mixture       c = its content in % by weight
For water as diluent, b = 0

14. HLB (hydrophylic – lipophylic – balance) of surfactants and their activity features

0 – 4               = defoaming
3 – 7               = emulsifying
7 – 15             = penetrating
7 – 20             = emulsifying
12 – 20           = detergency
15 – 20           = solubilising

15.Mixing rules by using mixture-cross

How much of each solution has to be mixed to get a 62% solid solution of a 54% solids solution with a 92% solids solution?

30 parts by weight of 54% solid solution must be mixed with 8 parts by weight of 92% solid solution to yield a 62% solid solution.

92 - 62 = 30 pbw 54% solution

62 - 54 = 8 pbw 92% solution