Talc in Polyester Putties - Mondo Minerals

Technical Bulletin 1502
Talc in Polyester Putties

1. Introduction
Talc is a very important functional filler in car body
polyester putties. The fraction of talc in this type of
putty can rise up to 60 w %. That is why the quality
of talc has a significant effect on the performance of
the putty. However, all talc grades are not the identical
and there is a considerable variety of different
types of talc available on the market. A large number
of these talc grades contain considerable amounts of
accessory minerals such as magnesite, dolomite, chlorite,
quartz etc. The properties of these various minerals
are dissimilar. For instance all the accessory minerals
are harder than talc. The accessory mineral content
in commercial talc grades can vary from a few
percent up to nearly 100 %. Furthermore, the properties
of pure talcs can vary: for instance, the particle
shape can be different affecting the properties of the
putty. Therefore it is not immaterial what type of talc
grade is used in the putty formulations.
The purpose of this study was to compare the performance
of different commercial talc grades in car body
polyester putties. In this study only talc grades that are
classified as coarse talc were compared.
Altogether, 12 different talc grades were tested.
The talc grades used were from major European talc
suppliers.
Talc grades of Mondo Minerals Oy:
Finntalc M40 and M50,
Westmin Talc D50E and D100,
Norwegian Talc AT 200
Talc grades from other suppliers:
7,5µm carbonate talc,
15 µm chlorite talc,
8,5 µm micro crystalline talc,
18 µm micro crystalline talc,
8,5 µm chlorite talc,
21 µm chlorite talc,
10,5 µm carbonate talc
The following putty properties were investigated:
Sandability using Wallace's sanding machine
➤ Adhesion and elasticity by bending
➤ Pot life
➤ Application properties by manual application
➤ Viscosity using a Brookfield viscometer at four
different shear rates
➤ Storage stability at room temperature and at 50°C
2. Preparation of Putty
A universal polyester car repair putty formulation of
Bayer AG was used as a model formulation. Both a
fine and a coarse talc were used in Bayer's original
formulation, however, in these tests the formulation
was modified so that only a coarse talc was used. The
same formulation was used for all the talc grades. The
formulation has the following composition:
2 Mondo Minerals OY · Technical Bulletin 1502
w%
Roskydal K36 31,8
Aerosil 200 0,4
Byk W980 0,2
Styrene 1,6
Bayertitan R-KB-2 2,2
Talc 41,9
Omycarb 10-GU 12,6
Luvotix R-RF 0,5
BaSO 4 , EWO-powder 8,1
Styrene 0,7
100 w %
The putties were prepared using Getzmann's vacuum
dissolver (Dispermat VL03-M) that is shown in Figure
2.1. The mixer was equipped with a scraper. The volume
of the mixing container was 3l. The diameter of the
mixing disc was 70 mm. The batch size was 1.98 kg.
At first the resin (Roskydal K36), thickener (Aerosil
200), wetting agent (Byk W980) and a about half of
the styrene were added to the mixing container and
the raw materials were mixed using a moderate
mixing speed (1000 rpm). The scraper system was on.
When the first batch of raw materials was well mixed,
TiO 2 , talc and CaCO 3 were added. The pigments were
mixed until the mixture was homogeneous. After this

the mixing speed was increased from 1000 rpm to
2000 rpm and rheological modifier Luvotix R-RF, BaSO 4
and the rest of styrene were added. When all the raw
materials were added, the mixing speed was increased
to 4000 rpm. The raw materials were dispersed
for such a long time that the temperature of the mixture
rose to 53° C, after which the mixing speed was
reduced to 2000 rpm and a vacuum was applied for
5 minutes. The finished product was transferred to the
metallic container.
3. Test Methods used
Viscosity
Immediately after preparation of the putty the viscosity
was measured using a Brookfield viscosity meter.
The measurement was carried out at 50° C. The viscosity
was measured at 4 different spindle stirring
speeds (4 different shear rates).
Pot Life
49 g of the putty was transferred to an aluminium
dish and 1 g of 50 w% di-benzoyl-peroxide paste was
added. The clock was started and the putty and hardener
were mixed together for 30 s. The time needed
for total gelation of the mass was measured.
Adhesion and elasticity by bending
The hardener and the putty were mixed together in
the same way as described earlier, after which the
putty was applied to the Q-Panel's metal panel (QR36)
as a layer of constant thickness (500 µm). Several
panels were prepared from each putty. The layers
were allowed to cure for 24 h, after which the panels
were bent over the table's edge until cracking occurred.
The bending angle was measured.
Sandability
The sandability was measured using Wallace's sanding
machine (Fig. 3.4). Before performing the sanding test
a sanding piece shaped like a flat cylindrical disc was
made from the putty. The ratio of hardener and putty
was the same as in the measurements of pot life. Each
sanding piece was sanded three times:
1) 30 minutes after the addition of hardener
2) 2 h after the addition of hardener
3) 24 h after the addition of hardener.
Mondo Minerals OY · Technical Bulletin 1502 3
Figure 2.1:
Vacuum dissolver
for putty
preparation.
Figure 3.2:
Determination of
pot life
Figure 3.3:
Bending test

Figure 3.4:
Sanding machine
Figure 3.5:
Test pieces
for sanding test
The hardened polyester putty is polished with sanding
paper, and the loss of weight is measured. The test is
repeated three times to get an average result. Each
sanding took 300 cycles (300 seconds). The fineness
of the sanding paper was 80' and a weight of 2,8 kg
was applied to the sanding piece. The loss of mass of
the sanding piece during sanding was measured.
Storage stability
50 g of putty was put into a tin can with volume of
50 ml. 6 samples were prepared from each putty:
three for the test at room temperature and three for
the test at 50° C. The time of onset of gelation of the
putty was recorded.
4. Results
Sandability
Sandability was measured using a Wallace sanding
machine. A round shaped sanding piece resembling a
large tablet was prepared from each putty, that was
sanded with sandpaper (fineness 80') with the application
of a weight of 2.8 kg. Each tablet was sanded
three times: 30 min, 2 h and 24 h after the addition of
hardener. During each sanding the tablet was sanded
for 300 cycles. The loss of weight of the tablet during
the sanding was measured. Sandability results are
shown in Figure 4.1.
Finntalcs yielded the best sandability results: the loss
of mass of the sanding piece during sanding was largest
with putties containing Finntalcs. The explanation
for this is that Finntalcs are pure, platy talcs and
thus very soft, which gives them good sandability.
Mistron 82 and Westmin talcs D50E and D100 are
also pure talcs, but the particle shape is less platy.
Adhesion and Elasticity by Bending
Adhesion and elasticity of putties were determined
by bending. The putties were applied to the metal
panels as a layer with constant film thickness
(~ 500 µm). The panels were left to cure for 24 h,
after which they were bent across the edge of a table
until cracking of putties occurred. The bending angle
was measured. The results are shown in Figure 4.2
and 4.3.
Pot Life
49 g of the putty was placed in an aluminium dish and
1 g of 50 w% di-benzoyl-peroxide paste was added.
The clock was started and the putty and hardener
were mixed together for 30 seconds. The time needed
for total hardening of the putty was measured. Pot
life values for different talc grades are presented in
Figure 4.4.
Finntalc M40 yielded the longest pot life. Finntalc
M40 also had the highest oil absorption value, which
might explain the long pot life. Finntalc M40 absorbed
the largest quantity of resins that contain double
bonds needed for the hardening reaction. Thus the
hardening reaction with Finntalc M40 was slower
compared with other talcs, because larger amounts of
4 Mondo Minerals OY · Technical Bulletin 1502

Weight loss in sanding, g
Bending degree
Sandability: the higher the value the better the result After 0,5 h After 2 h After 24 h
8
7
6
5
4
3
2
1
0
Adhesion on Bending The higher the Bending degree the better the adhesion
100
90
80
70
60
50
40
30
20
10
0
Finntalc M40
83
15 µm
chlorite talc
Finntalc M50
7,5 µm
carbonate talc
15 µm
chlorite talc
10,5 µm
carbonate talc
Westmin D50E
80 80 80
Westmin D50E
Micro-Talc AT200
Finntalc M40
styrene and hardener first had to migrate to the surface
of talc before they could react with the double
bonds. In the case of the other talcs the hardening
reaction occurred to a greater extent in the bulk phase
and not on the talc surface so that is why it was faster.
77
Mondo Minerals OY · Technical Bulletin 1502 5
18 µm micro
crystalline talc
65
Micro-Talc AT200
Westmin D100
60
8,5 µm
chlorite talc
10,5 µm
carbonate talc
50
Finntalc M50
8,5 µm micro
crystalline talc
40 40
21 µm
chlorite talc
7,5 µm
carbonate talc
Westmin D100
21 µm
chlorite talc
30
8,5 µm micro
crystalline talc
8,5 µm
chlorite talc
23
18 µm micro
crystalline talc
Figure 4.1:
Sandability of putties
made with different
talc grades
Figure 4.2:
Adhesion and
elasticity
on bending
Figure 4.3:
Photo of bent panels -
15 µm chlorite talc
is the best and
18 µm micro
crystalline talc
the worst

Figure 4.4:
Pot life of putties
with different talc
grades.
Figure 4.5:
Brookfield viscosity
at different stirring
speeds of spindle
Pot life
500
450
400
350
300
250
200
150
100
50
0
Pot Life
Viscosity
Viscosity was measured using a Brookfield RVF 100
viscometer at four different spindle (N:o 7) rotation
speeds. Viscosity was measured at 50° C, as it could
not be measured at room temperature, since the
putties were too viscous. The viscosity results are
presented in Figure 4.5.
Br-Viscosity. Pas
120
100
80
60
40
20
450
Finntalc M40
380
Micro-Talc AT200
360 350 340 330
Westmin D100
15 µm
chlorite talc
10,5 µm
carbonate talc
21 µm
chlorite talc
Br-Viscosity at Different Stirring Speeds of Spindle
0
0 20 40 60 80 100 120
Stirring speeds of spindle, rpm
320 310 310 310 310
The viscosity behaviour of all the putties was pseudoplastic:
the viscosity decreased with increase of shear rate.
Application by hand
The application properties of putties were also evaluated
by spreading the putties by hand. The spreading
properties of each putty were compared to the
8,5 µm chlorite talc
Micro-Talc AT200
8,5 µm micro crystalline talc
Finntalc M40
18 µm micro crystalline talc
10,5 µm carbonate talc
7,5 µm carbonate talc
21 µm chlorite talc
Westmin D50E
15 µm chlorite talc
Finntalc M50
Westmin D100
6 Mondo Minerals OY · Technical Bulletin 1502
8,5 µm
chlorite talc
Finntalc M50
18 µm micro
crystalline talc
8,5 µm micro
crystalline talc
Westmin D50E
270
7,5 µm
carbonate talc

properties of commercial car body polyester putty. If
the experimental putty spread as well as the commercial
product and the surface of the applied film had a
good appearance, then it was given the value 0 as
application rating. However, if the application of putty
was harder than with the commercial product and/or
the surface was rough, then it given an inferior rating
using the scale 0 (best) to 5 (worst). According to the
tests only three talc grades had clearly worse application
properties than the others: NT's AT200 and 10,5
µm carbonate talc were given rating 1 and 21 µm
chlorite talc rating 2 the other talc grades all attained
the top rating of 0.
Storage Stability
The storage stability of all the talc grades was quite
good. All the grades had over 6 months storage
stability at room temperature. There were some differences
in storage stability at elevated temperature.
The Westmin D-grades and 18µm micro crystalline talc
displayed the best storage stability at 50° C (6 months).
7,5 µm carbonate talc had the lowest storage stability
(3.5 months).
5. Summary
The effect of different talc grades on the properties of
car body polyester putty was evaluated. The putty
formulation was based on an universal car repair
polyester putty formulation developed by Bayer AG.
The following putty properties were evaluated:
➤ sandability using a sanding machine
➤ adhesion and elasticity by bending
➤ viscosity using a Brookfield viscometer at four
different spindle stirring speeds
➤ pot life
➤ storage stability at room temperature and at 50°C
All together 12 different commercial talc grades were
evaluated. The talc grades were from Mondo Minerals
(Finnminerals Oy, Norwegian Talc and Westmin Talc)
and from other European suppliers. The talc grades
were evaluated carefully – the properties of the talc
grades are listed in Appendix 1.
The mineralogical composition of the talc grades varied
quite a lot. The variation of composition of the different
talc grades is depicted in the following diagram.
21 µm
chlorite talc
15 µm
chlorite talc
8,5µm
chlorite talc
100 % Chlorite
100 % Talc
Finntalcs,
Westmin Talcs,
8,5 µm micro crystalline talc,
18 µm micro crystalline talc
AT 200,
10,5 µm carbonate talc
7,5 µm carbonate talc
The Finntalc and Westmin talc grades, 8,5 µm micro
crystalline talc and 18 µm micro crystalline talc are
relatively pure talcs, whereas the other talcs contained
considerable amounts of accessory minerals.
The particle size distributions of talc grades tested also
varied considerably (see Appendix 1). Finntalc M50
was the coarsest product with a relatively steep distribution
curve while the finest product was 7,5 µm carbonate
talc with the most gently sloping (broadest)
particle size distribution curve. Finntalc M50 also had
the coarsest grinding fineness measured using a grindometer,
but also 8,5 µm chlorite talc and 21 µm chlorite
talc had quite similar grinding fineness. Westmin
Talc D50E showed the best grinding fineness, and also
had the steepest (narrowest) particle size distribution
curve. There was no direct relationship between the
fraction of fines, oil absorption and specific surface
area. The reason for that was that the mineralogical
composition and the particle shape of the talc grades
were so different.
Due to different whitenesses of talc grades the colour
of putties varied from white to very grey. 8,5 µm micro
crystalline talc (78.9 %) had the highest whiteness
and the lowest 21µm chlorite talc (51.5%). Dark talc
grades like 21µm chlorite talc, 8,5µm chlorite talc,
10,5µm carbonate talc, 15µm chlorite talc and AT200
imparted a grey colour to the putties. The colour of putties
with other talc grades was very noticeably whiter.
Finntalc M40 displayed the best overall putty performance:
its sandability was the best and its adhesion
and elasticity were also very good. Finntalc M40 also
yielded the longest pot life and its manual application
properties were similar to those of commercial polyester
putty. The excellent performance of Finntalc M40
is related to its purity, platy particle form and optimised
particle size distribution.
Mondo Minerals OY · Technical Bulletin 1502 8
50/50
50/50
50/50
100 % Carbonates

Comm Finntalc Finntalc Micro-Talc 7,5 µm 8,5 µm 21 µm 10,5 µm 8,5 µm 15 µm 18 µm Westmin Westmin
Ref. M40 M50 AT200 carbonate chlorite chlorite carbonate micro crys- chlorite micro crys- D50E D100
talc talc talc talc talline talc talc talline talc
Dispersing time needed to reach 53° C, min 10 12 9 9 6 13 11 9 12 9 11 11
Br-viscosity at 100 rpm, Pas 28,6 16,4 7,2 25,6 12,3 33,9 11,8 10,7 24,4 11,2 12,0 11,0 5,8
Br-viscosity at 50 rpm, Pas 41,6 26,0 10,8 36,5 19,8 52,4 17,1 17,0 39,3 16,8 19,7 16,6 9,3
Br-viscosity at 20 rpm, Pas 77,2 50,4 22,8 67,4 39,4 82,4 33,6 35,2 73,2 31,6 40,4 32,2 22,0
Br-viscosity at 10 rpm, Pas 124,0 78,4 45,2 103,2 70,8 107,2 57,2 62,4 98,0 54,4 75,2 57,6 50,0
Application by hands, 0 ––> 5, is the best 0 0 0 1 0 0 2 1 0 0 0 0 0
Pot Life, min:s 6:30 7:30 5:10 6:20 4:30 6:19 5:30 4:10 5:10 5:50 5:10 5:10 6:00
Bending angle, ° 80 77 50 65 80 60 40 80 30 83 23 80 40
Sandability, loss of weight, g
after 30 min 7,6 7,6 7,5 6,1 4,5 3,9 4,6 5,3 5,0 5,9 5,8 5,7 4,4
after 2 h 8,4 6,9 7,1 6,3 4,5 3,8 4,4 5,3 5,5 5,1 5,4 4,9
after 24 h 8,6 6,9 6,8 5,5 4,0 3,6 3,8 5,6 4,1 5,3 5,6 4,7
Storage stability at room temp, months > 6 > 6 > 6 > 6 > 6 > 6 > 6 > 6 > 6 > 6 > 6 > 6 > 6
Storage stability at 50 °C, months 4 4 4 5 3,5 4 4 4 6 3 6 6 6
Appendix 2, Table 2.1: Putty results

Finntalc Finntalc Micro-Talc 7,5 µm 8,5 µm 21 µm 10,5 µm 8,5 µm 15 µm 18 µm Westmin Westmin
M40 M50 AT200 carbonate chlorite chlorite carbonate micro crys- chlorite micro crys- D50E D100
talc talc talc talc talline talc talc talline tal
Mineralogical composition: 10 12 9 9 6 13 11 9 12 9 11
Talc-content, w% 94 93 57 56 40 45 55 94 40 93 93 95
Chlorite-content, w% 4 4 5 5 55 50 3 50 4 4 4
Carbonate-content, w% 2 3 39 39 5 5 45 3 10 3 3 1
Loss on ignition, w% 6,1 6,6 20,7 20,0 8,3 7,7 23,1 4,8 9,3 6,5 6,0 5,6
Material soluble in 1 M HCL, w% 3,8 4,5 38,1 38,6 7,5 5,0 43,1 2,8 10,5 5,9 6,5 5,3
Oil absorption, g/100 g 24 15 18 19 20 16 19 20 18 17 20 16
Specific surface area by N2 adsorption, m 2 /g 2,3 1,7 2,6 7,2 3,9 2,9 3,5 4,5 2,2 8,8 6,2 7,4
ISO-brightness, % 76,6 74,8 66,5 70,1 64,2 51,5 69,2 78,9 69,9 77,9 77,8 76,8
Particle size distribution by Sedigraph, w%
< 60 µm 100 100 100 100
< 50 µm 100 98 98 98 100 100 98 100 100
< 40 µm 98 91 100 96 97 98 98 97 100 97 100 93
< 30 µm 93 74 96 91 92 85 92 92 94 87 98 77
< 20 µm 79 39 81 79 80 46 76 80 72 59 83 44
< 10 µm 36 9 43 59 56 14 48 56 27 20 19 13
< 5 µm 11 5 19 41 33 10 30 33 14 15 11 10
< 2 µm 5 3 3 23 14 7 15 14 7 11 8 7
Medium diameter, µm 12,3 22,7 11,5 7,3 8,5 20,9 10,5 8,5 15,2 18,1 14,8 21,5
Hegman Fineness, µm 120 140 110 100 135 130 95 110 100 95 75 110
Appendix 1, Table 1: Properties of talc grades used in Putty study

W E TALK TALC
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the completeness or accuracy thereof and Mondo Minerals assumes no liability resulting from its use for any claims, losses, or damages of any third party. Recipients using this information must
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