Calculations on Paint Formulas

# 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
 Total sum by volume of all pigments + extenders in paint x 100% Total sum by volume of each 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
or
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)

 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)

 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 film thickness:
Price per liter                              Theoretical spreading rate in liters
Relation thickness steel construction and surface:
 Thickness 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 