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Non-surface-treated mica minerals for polypropylene (Nolte-Ernsting 2007).

Phlogopite Mica

Due to the brownish color, phlogopite mica is not that common in polypropylene, although the reinforcing properties which are in a good equilibrium between modulus and IZOD strength (impact strength) as well as a high HDT (heat distortion temperature) reveal the benefits for the compound.

Table 1 Composition and properties of muscovite and phlogopite mica minerals

Property

Muscovite

Phlogopite

Chemical analysis

SiO 2 [wt%]

52

42

Al 2 O 3 [wt%]

27

11

K 2 O [wt%]

10

11

Fe 2 O 3 [wt%]

3

7

MgO [wt%]

3

26

LOI [wt%]

5

3

Structural

formula

KAl2 [6][Si3Al[4]O10/(OH,F)2]

KMg3 [6][Si3Al[4]O10/(OH,F)2]

Crystal system

Monoclinic prismatic

Monoclinic prismatic

Color

White to light gray

Beige to brownish

Diaphaneity

Transparent to translucent

Transparent to translucent

Cleavage

[001] perfect

[001] perfect

Fracture habit

Fracture rare (brittle) mostly cleavage

Fracture rare (brittle) mostly cleavage

Mohs hardness

2-2.5

2.5-3

Density [g/cm 3]

2.8-2.9

2.8-2.9

Streak

White

White

Refractive index

1.55-1.62

1.53-1.62

pH

9-10

9-10

Chemical

Excellent against water, most

Excellent against water, most acids,

resistance

acids, bases, oil, solvents; weak

bases, oil, solvents; weak against

against fluoric acid

fluoric and sulfuric acid

Thermal resistance [°C]

Up to 900

Up to 900

Dielectric constant [ at104Hz]

2.0-2.6

5-8

Linear thermal expansion coeff. [1/K*10-6]

7.1-12.5

21-34

Thermal

conductivity

parallel*

[W/m*K]

30 °C: 3.89

33 °C: 3.14

Thermal

conductivity

normal*

[W/m*K]

32-45 °C: 0.62

32 °C: 0.52

Table 2 summarizes the behavior of a series of non-surface-treated phlogopite mica products in polypropylene at 20% filler load.

Advantages of using phlogopite mica of the TREFIL™ type at 20% load compared to the unfilled polymer are:

  • • An increase of up to 10% in tensile strength
  • • An increase of up to 126% in elastic modulus
  • • Moderate to no decrease in IZOD strength
  • • An increase up to 49% of HDT
  • • Reduction of the absolute shrinkage up to 31% in all dimensions
  • • Isotropic behavior (reduction of warpage)

Fig. 1 SEM of a typical muscovite mica

Microphotograph of a typical muscovite mica (500 x polarized reflected light). Market data of mica minerals

Fig. 2 Microphotograph of a typical muscovite mica (500 x polarized reflected light). Market data of mica minerals

Split of ground mica use in the USA in % in 2004 (94,000 metric tons total)

Fig. 3 Split of ground mica use in the USA in % in 2004 (94,000 metric tons total)

Table 2 Properties of phlogopite mica products at 20% filler load in PP copolymer Daplen KSR 4525

Mica

functional

filler

d 50 sedigraph

[um]

BET

[nr/g]

Tensile

strength

[MPa]

Elongation at max. [%]

Elastic

modulus

[GPa]

IZOD strength

HDT-B

[°C]

Shrinkage

Unnotched

Notched

Parallel

Nomral

Delta

[J/nr]

[%]

TREFIL™

1232-400

12

2.3

18.3

3.4

1.79

56.8

21.5

103

1.39

1.45

0.06

TREFIL™

  • 1232-
  • 04333

10

3.3

18.3

3.5

1.69

76.2

22.7

101

1.48

1.56

0.08

TREFIL™

  • 1232-
  • 04155

6

5.9

18.1

4.1

1.51

NB

30.5

96

1.52

1.61

0.09

Unfilled PP

-

-

16.7

7.2

0.79

NB

55.2

69

2.03

2.1

0.07

Talc

10

3.1

18

4.5

1.47

NB

22.4

98

1.53

1.66

0.13

The properties of the filled compound clearly correlate with the average particle size and BET of the TREFIL™ products and give a nice structure-property relationship.

Advantages over typically used talcum type used in this polymer at the same filler load are:

  • • Up to 22% higher elastic modulus
  • • Depending on the particle size comparable to better IZOD strength
  • • Up to 5% higher HDT
  • • Up to 12% reduction in shrinkage (perpendicular, up to 9% parallel)
  • • Fifty-three percent better isotropic behavior (reduction of warpage)
  • • Better scratch resistance in dark compounds due to higher Mohs hardness
 
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