Read Bulletin1502fürNet text version

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: 7,5 µm 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:

w% Roskydal K36 Aerosil 200 Byk W980 Styrene Bayertitan R-KB-2 Talc Omycarb 10-GU Luvotix R-RF BaSO4, EWO-powder Styrene 31,8 0,4 0,2 1,6 2,2 41,9 12,6 0,5 8,1 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 3 l. 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, TiO2, talc and CaCO3 were added. The pigments were mixed until the mixture was homogeneous. After this

2

Mondo Minerals OY · Technical Bulletin 1502

the mixing speed was increased from 1000 rpm to 2000 rpm and rheological modifier Luvotix R-RF, BaSO4 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.

Figure 2.1: Vacuum dissolver for putty preparation.

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).

Figure 3.2:

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.

Determination of pot life

Figure 3.3: Bending test

Mondo Minerals OY · Technical Bulletin 1502

3

4. Results

Figure 3.4: Sanding machine

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

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.

Figure 3.5: Test pieces for sanding test

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

Mondo Minerals OY · Technical Bulletin 1502

Sandability: the higher the value the better the result 8 7 6 Weight loss in sanding, g 5 4 3 2 1

After 0,5 h

After 2 h

After 24 h

Figure 4.1: Sandability of putties made with different talc grades

21 µm chlorite talc

15 µm chlorite talc

18 µm micro crystalline talc

8,5 µm micro crystalline talc

Westmin D50E

Adhesion on Bending 100 90 80 70 60 50 Bending degree 40 30 20 10

15 µm chlorite talc

Micro-Talc AT200

The higher the Bending degree the better the adhesion

Figure 4.2: Adhesion and elasticity

83

80

80

80

77 65 60 50 40 40 30 23

Westmin D100

10,5 µm carbonate talc

7,5 µm carbonate talc

Finntalc M40

Finntalc M50

8,5 µm chlorite talc on bending 18 µm micro crystalline talc Figure 4.3: Photo of bent panels 15 µm chlorite talc is the best and 18 µm micro crystalline talc the worst

5

0

8,5 µm chlorite talc

7,5 µm carbonate talc

10,5 µm carbonate talc

Finntalc M40

Finntalc M50

21 µm chlorite talc

Westmin D50E

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.

Mondo Minerals OY · Technical Bulletin 1502

Micro-Talc AT200

Westmin D100

8,5 µm micro crystalline talc

0

Figure 4.4: Pot life of putties with different talc grades.

Pot Life 500 450 400 350 300 250 200 150 100 Pot life 50 0

21 µm chlorite talc 8,5 µm chlorite talc 18 µm micro crystalline talc 10,5 µm carbonate talc 8,5 µm micro crystalline talc 15 µm chlorite talc Finntalc M50 Micro-Talc AT200 Westmin D100 Westmin D50E 7,5 µm carbonate talc Finntalc M40

450 380 360

350

340

330

320

310

310

310

310 270

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.

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

Br-Viscosity at Different Stirring Speeds of Spindle

Figure 4.5: Brookfield viscosity at different stirring speeds of spindle

120

8,5 µm chlorite talc Micro-Talc AT200 8,5 µm micro crystalline talc

100

80

Finntalc M40 18 µm micro crystalline talc

60

10,5 µm carbonate talc 7,5 µm carbonate talc

40 Br-Viscosity. Pas

21 µm chlorite talc Westmin D50E

20

15 µm chlorite talc Finntalc M50

0 0 20 40 60 Stirring speeds of spindle, rpm 80 100 120

Westmin D100

6

Mondo Minerals OY · Technical Bulletin 1502

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).

100 % Talc

21 µm chlorite talc 15 µm 50/50 chlorite talc 8,5 µm chlorite talc

Finntalcs, Westmin Talcs, 8,5 µm micro crystalline talc, 18 µm micro crystalline talc

50/50

AT 200, 10,5 µm carbonate talc 7,5 µm carbonate talc

100 % Chlorite

50/50

100 % Carbonates

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 21 µm 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.

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.

Mondo Minerals OY · Technical Bulletin 1502

8

Comm Ref.

Finntalc M40

Finntalc M50

Micro-Talc AT200

7,5 µm carbonate talc

8,5 µm chlorite talc

21 µm chlorite talc

10,5 µm

8,5 µm

15 µm chlorite talc

18 µm micro crystalline talc

Westmin D50E

Westmin D100

carbonate micro crystalc 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 Br-viscosity at 50 rpm, Pas Br-viscosity at 20 rpm, Pas Br-viscosity at 10 rpm, Pas

28,6 41,6 77,2 124,0

16,4 26,0 50,4 78,4

7,2 10,8 22,8 45,2

25,6 36,5 67,4 103,2

12,3 19,8 39,4 70,8

33,9 52,4 82,4 107,2

11,8 17,1 33,6 57,2

10,7 17,0 35,2 62,4

24,4 39,3 73,2 98,0

11,2 16,8 31,6 54,4

12,0 19,7 40,4 75,2

11,0 16,6 32,2 57,6

5,8 9,3 22,0 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 after 2 h after 24 h 7,6 8,4 8,6 7,6 6,9 6,9 7,5 7,1 6,8 6,1 6,3 5,5 4,5 4,5 4,0 3,9 3,8 3,6 4,6 4,4 3,8 5,3 5,0 5,3 5,6 5,9 5,5 4,1 5,8 5,1 5,3 5,7 5,4 5,6 4,4 4,9 4,7

Storage stability at room temp, months Storage stability at 50 °C, months

>6 4

>6 4

>6 4

>6 5

>6 3,5

>6 4

>6 4

>6 4

>6 6

>6 3

>6 6

>6 6

>6 6

Appendix 2, Table 2.1: Putty results

Finntalc M40

Finntalc M50

Micro-Talc AT200

7,5 µm carbonate talc

8,5 µm chlorite talc

21 µm chlorite talc

10,5 µm

8,5 µm

15 µm chlorite talc

18 µm micro crystalline tal

Westmin D50E

Westmin D100

carbonate micro crystalc talline talc

Mineralogical composition: Talc-content, w% Chlorite-content, w% Carbonate-content, w% 94 4 2

10 93 4 3

12 57 5 39

9 56 5 39

9 40 55 5

6 45 50 5

13 55

11 94 3

9 40 50 10

12 93 4 3

9 93 4 3

11 95 4 1

45

3

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 N adsorption, m2/g

2

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 < 50 µm < 40 µm < 30 µm < 20 µm < 10 µm < 5 µm < 2 µm 100 98 93 79 36 11 5 100 98 91 74 39 9 5 3 100 96 81 43 19 3 100 98 96 91 79 59 41 23 100 98 97 92 80 56 33 14 100 98 85 46 14 10 7 100 98 92 76 48 30 15 100 98 97 92 80 56 33 14 100 94 72 27 14 7 100 97 87 59 20 15 11 100 98 83 19 11 8 100 93 77 44 13 10 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

WE

TA L K

TA L C

MONDO MINERALS OY · www.mondominerals.com Kasarmikatu 22 · FI-00130 Helsinki · Phone +358 105 6211 · Fax +358 105 621 440 · E-Mail: [email protected]

The information contained in this Technical Bulletin relates only to the specific tests designated herein and does not relate to the use of our products in combination with any other material or in any process. The information provided herein is based on technical data that Mondo Minerals believes to be reliable, however Mondo Minerals makes no representation or warranty as to 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 exercise their own judgement as to the appropriateness of its use, and it is the user´s responsibility to assess the materials suitability (including safety) for a particular purpose prior to such use.

Information

Bulletin1502fürNet

10 pages

Report File (DMCA)

Our content is added by our users. We aim to remove reported files within 1 working day. Please use this link to notify us:

Report this file as copyright or inappropriate

396907


You might also be interested in

BETA
Bulletin1502fürNet