1. An Introduction to
Mineral Fillers
for Plastics

2. Before viewing this presentation, please be sure to read the following statement:
Before using, read, understand and comply with the information and precautions in the Material Safety Data Sheets, label and other product literature. The information presented herein, while not guaranteed, was prepared by technical personnel and, to the best of our knowledge and belief, is true and accurate as of the date hereof. No warranty, representation or guarantee, express or implied, is made regarding accuracy, performance, stability, reliability or use. This information is not intended to be all-inclusive, because the manner and conditions of use, handling, storage and other factors may involve other or additional safety or performance considerations. The user is responsible for determining the suitability of any material for a specific purpose and for adopting such safety precautions as may be required. R. T. Vanderbilt Company does not warrant the results to be obtained in using any material, and disclaims all liability with respect to the use, handling or further processing of any such material. No suggestion for use is intended as, and nothing herein shall be construed as, a recommendation to infringe any existing patent or to violate any federal, state or local law or regulation.

3. FILLER Filler = Something cheap to take up space?
Mineral “fillers” are actually most often used to improve one or more properties.

4. Volume Fraction in Matrix Compatibility With/Adhesion To Matrix
Effects of Mineral Fillers Depend On
Particle Shape
Particle Size
Volume Fraction in Matrix
Compatibility With/Adhesion To Matrix

5. Basic Particle Shapes Sphere Cube Needle 1 5-20+ Block Plate/Flake
Aspect Ratio 1
5-20+
Shape
Block
Plate/Flake
Fiber
Aspect Ratio
2-4
20-200

6. Particle Size Distribution Size (top and bottom) Counts

7. Particle Size?
“Particle” Size = Median (or Average) = Equivalent Spherical Diameter (ESD)
Automated particle sizers match the behavior of a particle (regardless of shape) to that of an ideal sphere of specific diameter. Compare the “particle size” of dissimilar minerals with care.
ESD!!! =

8. Aspect Ratio Ratio of mean length to mean diameter
Needle/Fiber Aspect Ratio:
Ratio of mean length to mean diameter
Plate Aspect Ratio:
Ratio of mean diameter of a circle of the same area as the face of the plate to the mean thickness of the plate

9. Aspect Ratio
For the same volume fraction, increasing the aspect ratio increases a composite’s strength and stiffness.
For tensile and flexural stresses to be transferred from polymer matrix to anisometric filler, a certain critical aspect ratio must be exceeded. Once this critical ratio is exceeded, the efficiency of stress transfer increases with increasing aspect ratio.

10. Volume Fraction Volume fraction:
The volume occupied by the filler divided by the volume of the composite (Vf / Vc).
Fillers usually have their strongest influence on composite properties and cost when the volume fraction is sufficiently high to allow for the matrix to just coat all particles and fill inter-particle voids. For some properties this may be good, but for others, not so good.

11. Matrix Compatibility/Adhesion
Intimate contact with the matrix is essential to filler functionality.
Nonpolar organics (polypropylene, mineral oil) will better “wet” hydrophobic fillers (talc). Polar organics (nylon, polyurethane) will better wet hydrophilic fillers (mica, wollastonite).
Surface treatment/modification can optimize filler-matrix compatibility and adhesion.

12. Matrix Compatibility/Adhesion Surface Treated: Filler + Process Aid
Surface treatments may not bond to the filler and do not bond to the matrix. They act like “wetting” agents to make the filler surface hydrophobic and more readily coated by the organic medium.

13. Matrix Compatibility/Adhesion
Surface Treatments:
Improve deagglomeration and dispersion.
Reduce blend viscosity, allow higher filler loading.

14. Matrix Compatibility/Adhesion
Surface Modification: Filler + Coupling Agent
Modification is the durable attachment of coupling agent to the filler and to the surrounding matrix.
Filler-Coupler: Covalent bond
Matrix-Coupler: Chemical reaction or
chain entanglement

15. Matrix Compatibility/Adhesion
Surface Modifiers:
Improve deagglomeration and dispersion.
Reduce blend viscosity, allow higher filler loading.
Improve impact, tensile, flexural and dielectric properties in polymers.
Improved properties retention in polymers after environmental exposure.

16. Matrix Compatibility/Adhesion
Surface Modifiers:
Silanes – Encapsulate filler particle in covalently bonded siloxane polymer; can condense more than one molecular layer.
Titanates – Individual molecules covalently bonded, no polymerization; monomolecular layer.
Both depend on the ability to form a bond via silanol (-Si-OH) on filler surface.

17. Matrix Compatibility/Adhesion
Silane Coupling:
Excellent to Good – glass, synthetic silica, natural silica, wollastonite.
Good to Fair – mica, aluminatrihydrate, kaolin, talc, barite, titanium dioxide, iron oxides.
Slight to None – calcium carbonate, carbon black.

18. Matrix Compatibility/Adhesion
Untreated
Silane- Treated
Photomicrographs: Union Carbide Corporation

19. Mineral Filler Effects in Plastics
Increase:
Stiffness (Tensile & Flex Modulus)
Strength (Compressive, Flexural)
Thermal Conductivity
Abrasion Resistance
Weather Resistance
Dielectric Strength
Surface Hardness
Fluid Resistance
Heat Resistance
Arc Resistance
Opacity
Density

20. Mineral Filler Effects in Plastics
Reduce:
Creep
Gloss
Flammability
Tensile Strength*
Shrinkage ex Mold
Elongation at Break
Coefficient of Thermal Expansion
*High aspect ratio fillers can increase tensile strength.

21. Mineral Filler Effects in Plastics8%
36%
32%
23%
26%
11% 7% 5%
Cost? Cost per part = part volume X cost/unit wt X density

22. Primary Mineral Fillers In Plastics
Calcium Carbonate- dry-ground, wet-ground, stearate-coated, PCC.
Kaolin- calcined, water-washed, delaminated, silane- modified.
Talc- fine-ground high purity platy.
Mica- fine wet-ground and dry-ground, silane-modified.
Wollastonite- fine-ground, acicular, silane-modified.
Silica- fine-ground quartz and novaculite, precipitated and fumed synthetics, silane-modified.

23. Calcium Carbonate Calcite CaCO3
Refractive Index:
Specific Gravity: 2.71
Mohs Hardness: 3-4
 Ground calcium carbonate  Dry-ground: nominal 200 to 325 mesh. Wet-ground: fine ground (FG; 3 to 12 m median, 44 m top), ultrafine ground (UFG; 0.7 to 2 m median, 10 m top). Wet-ground 75% solids slurry. Stearate-treated.
Precipitated calcium carbonate  Typically fine (0.7 m median) and ultrafine (0.07 m median), with and without stearate surface treatments.

24. Calcium Carbonate Rhombohedral Prismatic Aragonitic Scalenohedral
GCC/PCC
Rhombohedral
Prismatic
Aragonitic
PCC
Scalenohedral
Spherical
Clustered Aragonitic
Calcium Carbonate
Photomicrographs: Minerals Technologies

25. Kaolin Kaolinite Al2Si2O5(OH)4 Airfloat  Dry-ground, air separated.
Refractive Index: / calcined: 1.62
Specific Gravity: 2.58 / partially calcined: 2.50 / fully calcined: 2.63
Mohs Hardness: 2 / partially calcined: 4-6 / fully calcined: 6-8
Airfloat  Dry-ground, air separated.
Water-washed  Water-slurried, often bleached and/or high-intensity magnetic separated, centrifuged or hydrocycloned for high purity specific particle size fractions; dewatered and dried, or concentrated to 70% solids slurry.
Delaminated  Coarse clay fraction from water-washing, attrition milled into thin, wide individual plates.
Calcined  Water-washed soft clay calcined to either partially or totally remove surface hydroxyl groups.

26. Platy
Delaminated
Water-Washed
Airfloat
Kaolin

27. Talc
Talc Mg3Si4O10(OH)2
Refractive Index:
Specific Gravity: 2.75
Mohs Hardness: 1
Platy  Distinctly lamellar, soft talc, typically of >90% purity naturally or through beneficiation; type usually used for filler applications.
Steatitic  High purity, dense, very fine-grained talc that can be machined; usually used for ceramics applications.

28. Platy
Talc

29. Mica Muscovite KAl2(AlSi3)O10(OH,F)2 Phlogopite KMg3(AlSi3)O10(OH,F)2
Refractive Index:
Specific Gravity:
Mohs Hardness: 2-2.5
Phlogopite KMg3(AlSi3)O10(OH,F)2
Refractive Index:
Specific Gravity:
Mohs Hardness: 2.5-3
Wet-ground  Wet-milled to delaminate and grind; higher aspect ratio, sheen, and slip than dry-ground mica.  
Dry-ground  Coarse-ground, >100 mesh, are hammer milled and screened or air separated; fine-ground, <100 mesh to <325 mesh, are air milled.
Micronized  Air milled to <20 or <10 m.

30. Platy
Mica

31. Wollastonite Wollastonite CaSiO3
Refractive Index:
Specific Gravity: 2.92
Mohs Hardness: 4.5
Powder grades  Milled wollastonite with low aspect ratio (3:1 to 5:1). Typically 200, 325, 400 and 1250 mesh.
Acicular grades  Milled to very fine, needle-like particles. Typical aspect ratios in the range 12:1 to 20:1.

32. Wollastonite (Acicular)
Needle
Wollastonite (Acicular)

33. Silica Synthetic Silica SiO2 Quartz SiO2
Refractive Index: 1.45
Specific Gravity: 2-2.3
Mohs Hardness: 5-6
Quartz SiO2
Refractive Index: 1.54
Specific Gravity: 2.65
Mohs Hardness: 7
Ground silica  aka ground quartz, silica flour; <200 mesh ground high purity quartz, quartzite, sandstone, or silica sand. Typically >99% SiO2, high brightness, low moisture, chemical inertness, relatively low surface area, low vehicle demand.
Novaculite  Platy microcrystalline quartz, low moisture, >99% SiO2, brightness generally less than other ground silicas, but lower binder demand and abrasivity, wider range of particle size grades (as small as 2 m avg)

34. Low Aspect Ratio, Irregular Shape
Ground Silica

35. Platy
Novaculite (Silica)

36. Other Mineral Fillers In Plastics
Barite- dry-ground natural, precipitated as blanc fixe
Diatomite- calcined fine dry-ground
Feldspar, Nepheline Syenite- fine dry-ground
Pyrophyllite- fine dry-ground

37. Barite
Barite BaSO4
Refractive Index:
Specific Gravity: 4.5
Mohs Hardness: 3-3.5
Filler grade  High brightness, high purity, usually <325 mesh or finer; typically >95% BaSO4, <0.1% Fe2O3, <0.5% moisture.
Blanc fixe  Precipitated barium sulfate for higher brightness and purity and finer particle sizes than available with barite.

38. Blocky
Barite
Photomicrograph: Huber Engineered Materials, part of J.M. Huber Corporation

39. Diatomite Diatomite SiO2
Refractive Index: 1.401.43 / calcined 1.431.47
Specific Gravity: 2.02.1 / calcined 2.12.3
Mohs Hardness: 4.55 / calcined 5.56
Flux-calcined  Calcined at ~1200oC with a sodium carbonate or sodium chloride flux; milled, screened, and air classified; fine fraction (<325 mesh) is white filler grade; maximum void volume, can exceed 90%, and consequent high absorptivity.
Straight-calcined  Calcined between 870o and 1100oC in a rotary kiln; milled, screened, and air classified. Pink color from iron oxidation usually precludes filler use.
Natural diatomite  Gently crushed and milled ore; screened or air classified; fine fraction (<325 mesh) for some filler uses.

40. Weird
Diatomite is the microscopic skeletons of diatoms, unicellular algae found in both fresh and sea water.
Diatomite

41. Feldspar
Orthoclase KAlSi3O8
Refractive Index:
Specific Gravity: 2.57
Mohs Hardness: 6
Microcline KAlSi3O8
Specific Gravity:
Albite NaAlSi3O8
Refractive Index:
Specific Gravity: 2.62
Mohs Hardness: 6
Anorthite CaAl2Si2O8
Refractive Index:
Specific Gravity: 2.76
Filler grade – principally albite (soda spar) with a mixture of other feldspar minerals; usually produced by flotation and magnetic separation followed by milling; finest grades are air classified

42. Low Aspect Ratio, Irregular Shape
Feldspar

43. Nepheline Syenite
Nepheline (Na,K)AlSiO4
Refractive Index:
Specific Gravity: 2.57
Mohs Hardness: 5.5-6
Microcline KAlSi3O8
Refractive Index:
Specific Gravity:
Mohs Hardness: 6
Albite NaAlSi3O8
Refractive Index:
Specific Gravity: 2.62
Mohs Hardness: 6
Nepheline syenite is a rock composed of soda and potash feldspars and nepheline.
Filler grade  Filler grades are finely ground (325 mesh to 1250 mesh) and have high brightness (>93) and low vehicle demand.

44. Low Aspect Ratio, Irregular Shape
Nepheline Syenite

45. Pyrophyllite Pyrophyllite Al2Si4O10(OH)2
Refractive Index:
Specific Gravity: 2.8
Mohs Hardness: 1.5
In US: natural blends with sheet silicates, diaspore, andalusite and quartz; quartz makes them unsuitable for many filler applications.
Filler grade  Airfloat, mesh.
Refractory grade  Low in alkalis (<1%), i.e., a low mica content; fluxes (Fe2O3, FeO, TiO2) <1%.
Ceramic grade  High alkali (i.e. higher mica) for lower melting point/faster firing; low coloring oxides for white ware.
Agricultural grade  Carrier for active ingredients in pesticide dusts, selection based on fineness and bulking values.

46. Platy
Pyrophyllite

47. Web Site: www.rtvanderbilt.com e-mail: plastics@rtvanderbilt.com
R.T. Vanderbilt Company, Inc. offers a wide range of mineral fillers: wollastonite, talc, industrial talc, kaolin and pyrophyllite. For more information, contact us at:
Headquarters:
R.T. Vanderbilt Company, Inc. 30 Winfield Street, P.O. Box 5150, Norwalk, CT (203) Fax: (203)
Web Site:
West Coast Office:
6280 Manchester Boulevard, Suite 204, Buena Park, CA (714) Fax: (714)
Canadian Office:
1 Eva Road, Suite 419, Etobicoke, Ontario, M9C 4Z5, Canada (416) Fax: (416)
European Office:
32 Rue du Vieil Abreuvoir, 2eme etage
78100 Saint Germain en Laye, France
FAX: