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Durability of Paint and Varnish Coatings Depending on the Quality of
their Appearance
To cite this article: Valentina Loganina 2019 IOP Conf. Ser.: Mater. Sci. Eng. 471 022044
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WMCAUS 2018
IOP Conf. Series: Materials Science and Engineering 471 (2019) 022044 IOP Publishing
doi:10.1088/1757-899X/471/2/022044
1
Durability of Paint and Varnish Coatings Depending on the
Quality of their Appearance
Valentina Loganina 1
1 Penza State University of Architecture and Construction, Russia
loganin@mail.ru
Abstract. The aim of the work is to study the regularities of the influence of the quality of the
appearance of coatings on their durability during the operation. Object of research - paint and
varnish coatings of building products and construction. Information on the effect on the
longevity of coatings of the quality of their appearance is given. It is shown, that coatings with
a high roughness index are characterized by low durability during exploitation. Are revealed
the influence of the rheological properties of the paint, the porosity of the substrate on the
surface roughness of the coatings. Determined, that regardless of the type of paint composition,
the strength and relative deformations are reduced, the plastic deformation is increased and the
elastic deformation are reduced with increasing roughness of surfaces. A mathematical model
is obtained of the dependence of the tensile strength on the roughness of the surface of the
films. It is established, that during the moistening of the coatings in the first stage (up to 30
days), the roughness of the surface is reduced, i.e., the surface micro relief is levelled due to the
plasticizing effect of moisture (swelling of the coatings). In the future, due to the destructive
effect of moisture, the surface roughness increases, caused by the appearance of micro cracks,
rashes, and bubbles. It is established, that in the process of cyclic freezing-thawing the cracks
appear locally and are formed near defects on the surface of the coating. The researches allow
to develop recommendations for increasing the resistance of coatings and to select the optimum
rheological properties of paints depending on the porosity of the substrate.
1. Introduction
Building and conservation the working condition of buildings and structures require a large number of
paint and varnish compositions. Increasing competition in the market of finishing materials, increasing
demands of consumers require from manufacturers to obtain high-quality painted surfaces. However,
the practice of finishing works shows, that often the quality of the finish is bad. It leads to premature
unscheduled repairs and additional costs [1]. In accordance with the statistical theory of the strength of
solids, the probability of destruction of coatings is determined by the presence and concentration of
defects, including on the surface of the coatings. Consequently, the quality of the appearance of
coatings determines their stress state and resistance in the process of exploitation [2,3,4]. In [5] were
established regularities of the formation of the quality of the appearance of coatings on a metallic
substrate from the rheological properties of the paint, paint's ability to flow on surface of substrate. It
is noted in [6], that the destruction of coatings on a metal substrate begins around different defects.
Coatings on a porous cement substrate have their own peculiarities [7]. The porous structure of the
cement substrate effects on the formation of the quality of the appearance of the coatings. They are
characterized by a lower quality of appearance. This, of course, has an effect on the resistance of
coatings during operation. Meanwhile, an analysis of scientific and technical literature shows, that the
durability of coatings on a cement substrate has not been studied sufficiently
WMCAUS 2018
IOP Conf. Series: Materials Science and Engineering 471 (2019) 022044 IOP Publishing
doi:10.1088/1757-899X/471/2/022044
2
2. Materials and methods of research
In the study used the following paint: alkyd enamel PF-115 grade, oil paint brands MA-15,
polystyrene paint brands PS-160, acrylate paint Universal.
The surface quality of the paintwork was evaluated a roughness, which is determined by
profilograph TR- 100.
Assessment deformation of coating was carried out with the help of a tensile machine IR 5057-50
with the samples after 28 days of curing. The method is based on the sample stretching until it ruptures
(deformation speed of 1mm/min). The 1x1x5 cm samples were fixed in the clips of the tensile
machine so, that their longitudinal axis was in the direction of stretching, and the force was applied
equally all over the sample section. The tests were carried out at the temperature of 20° C and relative
air humidity of 60%. The ultimate tensile strength estimation was carried out for four samples [8,9].
The ultimate tensile strength Rkog for each sample was calculated by formula:
Oi
Pi
S
F
R=
kog
(1)
, where FPI - the stretching loading at the time of a rupture, N;
SOi- the initial cross-sectional area of a sample, mm2.
The modulus of elasticity was calculated according to the chart "tension-deformation".
The modulus of elasticity for each sample (Eupr) in MPa was calculated by formula:
100⋅
′
′
=
i
kogi
upr
R
Е
ε
(2)
where
kogi
R′
– the ultimate tensile strength at the time of the tangent separation from the chart
"tension-deformation", MPa;
i
ε
′
– relative lengthening at the time of rupture, %.
3. Results of researches
The presence of defects on the surface of the coatings will undoubtedly affect the physico-mechanical
properties of paint coatings. It is revealed, that coatings have the elastoplastic character of the
destruction (Tables 1, 2).
Table 1. Deformations of films based on polystyrene paint PS-160 depending on surface roughness
Coating
surface
roughness,
Ra, μm
Strength at
Stretching,
RP kgf / cm2
Relative
deformation
rel
ε
,%
Elastic
deformation
el
ε
,%
Plastic
deformation
pl
ε
%
Share of
Elastic
component
Deformation
el
ε
′
Share of
plastic
component
Deformation
pl
ε
′
0.74
69.4
3.1
2.9
0.2
0.935
0.065
0.77
62.8
1.86
1.63
0.23
0.876
0.124
0.8
56.5
1.8
1.5
0.3
0.833
0.167
0.86
50.5
1.75
1.44
0.31
0.82
0.18
1.2
47.2
1.4
1.1
0.3
0.7857
0.2143
WMCAUS 2018
IOP Conf. Series: Materials Science and Engineering 471 (2019) 022044 IOP Publishing
doi:10.1088/1757-899X/471/2/022044
3
Table 2. Deformations of films based on paint PF-115 depending on surface roughness
Coating
surface
roughness,
Ra, μm
Strength
at
Stretching,
p
R
,kgf/cm2
Relative
deformation
rel
ε
,%
Elastic
deformation
el
ε
,%
Plastic
deformation
pl
ε
,%
Share of
elastic
component
Deformation
el
ε
′
Share of
plastic
component
Deformation
pl
ε
′
1.2
57.7
44.3
21.3
23
0.481
0.519
1.37
56.1
38
13.9
24.1
0.367
0.633
1.45
54.3
28
9
19
0.321
0.679
1.54
45.9
24
7
17
0.292
0.708
1.74
44.1
23
6.44
16.56
0.281
0.719
Regardless of the type of paint, the strength and relative deformations are reduced, the plastic
deformation is increased and the elastic deformations are reduced with increasing roughness of surface
(Fig. 1, 2). Thus, when the surface of coatings roughness based on paint PS-160 is Ra = 0.74 μm, the
tensile strength RP is 69.4 kgf / cm2, the relative strain rel
ε
= 3.1%, and with a roughness Ra = 0.86 μm
- RP =50.5 kgf/cm2 and 1.75% respectively. At a roughness of the film based on the paint PF-115 Ra =
0.74 μm, the tensile strength RP is 57.7 kgf / cm2, the relative strain rel
ε
= 44.3%, at a roughness Ra =
1.74 μm - RP =44.1 kgf / cm2 and 23% respectively.
Figure 1. Dependence of the tensile strength (1) and the relative elongation (2) on the roughness of the
film surface on the basis of paint PS-160
WMCAUS 2018
IOP Conf. Series: Materials Science and Engineering 471 (2019) 022044 IOP Publishing
doi:10.1088/1757-899X/471/2/022044
4
Figure 2. Dependence of the tensile strength (1) and the relative elongation (2) on the roughness of the
film surface on the basis of paint PF-115
The dependence of the tensile strength on the roughness of the surface of the films can be
approximated by an expression of the form:
a
Rb
peaR ⋅
⋅=
(3)
where:
Ra - is the surface roughness, μm;
b - is a coefficient that takes into account the degree of reduction in strength from roughness, μm-1;
A - coefficient, characterizes the value of tensile strength, at Ra = 0 (ideal model).
The quality of the coatings is determined by the rheological properties of the paint, the porosity of
the substrate. The presence of inclusions, shagreen, streaks, waviness on the surface of coatings
determines their stress state and endurance during operation. In Fig. 3-4 shows the results of
measuring the surface roughness of coatings during the moistening process. It is established, that
irrespective from the rheological properties of the paints and the porosity of the substrates during the
moistening of the coatings in the first stage (up to 30 days), the roughness of the surface is reduced, ie,
the surface micro relief is levelled due to the plasticizing effect of moisture (swelling of the coatings).
In the future, due to the destructive effect of moisture, the surface roughness increases, caused by the
appearance of micro cracks, rashes, and bubbles.
A more stressed state of the coating in places of greater roughness contribute to destroy the coating
in these places during operation. It is established, that in the process of cyclic freezing-thawing the
cracks appear locally and are formed near defects on the surface of the coating. In particular, on a
coatings based on paint MA-15 with a roughness Ra = 0.23 μm appeared racks after 5 freeze-thaw
cycles, and on a coating with a roughness Ra = 0.14 μm - after 15 cycles tests.
Similar regularities are also characteristic for other coatings. The obtained data correlate well with
other indices of the protective and decorative properties of the coating (colour change, gloss variation,
chalking, mud retention, bronzing).
WMCAUS 2018
IOP Conf. Series: Materials Science and Engineering 471 (2019) 022044 IOP Publishing
doi:10.1088/1757-899X/471/2/022044
5
Figure 3. Change of the roughness of coatings in the process of moistening:
a. based on paint PF-115 (a method of applying- brush, porosity 24%): 1 – viscosity is 0.001.103Pа.s;
2 - viscosity is 0.00065.103Pа.s; 3- viscosity is 0.00026.103 Pа.s.
b. based on dispersion paint (a method of applying- brush, on the surface of the putty): 1 – viscosity is
0,0347.103 Pа.s; 2 - viscosity is 0,02317.103 Pа.s; 3- viscosity is 0,013.103 Pа.s.
Figure 4. Change of the roughness of coatings in the process of moistening:
a) - based on paint MA-15 (airless method, porosity 24%): 1-viscosity is
1
η
=0.0026*103 Pa⋅s;
2 - viscosity is
2
η
=0.0020*103 Pa⋅s; 3 - viscosity is
3
η
=0.0014*103 Pa⋅s
b) - based on paint PF-115 (method pouring): 1 – viscosity is 0.001.103Pа.s, porosity 24%;
2 - viscosity i 0.001.103 Pа.s , porosity 28%; 3 - viscosity is 0.001.103Pа.s, porosity 32%;
4 - viscosity is 0.001.103 Pа.s, on the surface of the putty.
4.Conclusions
The elastoplastic character of the destruction for the coatings studied are revealed. The models of the
strength of coatings depending on the roughness of surface are given. It is established, that irrespective
WMCAUS 2018
IOP Conf. Series: Materials Science and Engineering 471 (2019) 022044 IOP Publishing
doi:10.1088/1757-899X/471/2/022044
6
of the rheological properties of paint and the porosity of the substrates during the moistening of the
coatings in the first stage the roughness of the surface is reduced, the surface micro relief is leveled
due to the plasticizing effect of moisture (swelling of the coatings). In the future, due to the destructive
effect of moisture, the surface roughness increases. A more stressed state of the coating in places of
greater roughness contribute to destroy the coating in these places during exploitation. It is established,
that in the process of cyclic freezing-thawing the cracks appear locally and are formed near defects on
the surface of the coating.
The obtained data correlate well with other indices of the protective and decorative properties of
the coating (colour change, gloss variation, chalking, mud retention, bronzing).
The researches allow to develop recommendations for increasing the resistance of coatings and to
select the optimum rheological properties of paints depending on the porosity of the substrate
References
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Chemistry, 387 p.,1964
[3] P. S.Song , “Assessment of statistical variations in impact resistance of high-strength concrete
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[4] A.Fiore , “On the dispersion of data collected by in situ diagnostic of the existing concrete”
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[5] A.T.Sanzharovsky, “Physical and mechanical properties of polymer and paint coatings”.
Moscow: Chemistry, 183 p.,1978
[6] V.I.Loganina, “Maintenance of Quality of Paint and Varnish Coverings of Building Products
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2016
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