Handbook
of Fillers
4th Edition
George Wypych
Toronto 2016
Published by ChemTec Publishing
38 Earswick Drive, Toronto, Ontario M1E 1C6, Canada
© ChemTec Publishing, 1993, 2000, 2010, 2016
ISBN 978-1-895198-91-1 (bound)
ISBN 978-1-927885-10-9 (epub)
Cover design: Anita Wypych
All rights reserved. No part of this publication may be reproduced, stored or transmitted in any form or by any means without written permission of copyright owner. No responsibility is
assumed by the Author and the Publisher for any injury or/and
damage to persons or properties as a matter of products liability, negligence, use, or operation of any methods, product ideas,
or instructions published or suggested in this book.
Library and Archives Canada Cataloguing in Publication
Wypych, George, author
Handbook of fillers / George Wypych. -- Fourth edition.
Includes bibliographical references and index.
Issued in print and electronic formats
ISBN 978-1-895198-91-1 (bound).--ISBN 978-1-927885-10-9 (epub)
1. Fillers (Materials). Fillers (Materials)--Handbooks, manuals, etc. I. Title.
TP1142.W96 2016
668.4'11
C2015-907779-6
C2015-907780-X
Printed in Australia, United Kingdom and United States of America
Table of Contents
iii
Table of Contents
1 Introduction
1.1 Expectations from fillers
1.2 Typical filler properties
1.3 Definitions
1.4 Classification
1.5 Markets and trends
References
2
2.1
2.1.1
2.1.2
2.1.3
2.1.4
2.1.5
2.1.6
2.1.7
2.1.8
2.1.9
2.1.10
2.1.11
2.1.12
2.1.13
2.1.14
2.1.15
2.1.16
2.1.17
2.1.18
2.1.19
2.1.20
2.1.21
2.1.22
2.1.23
2.1.24
2.1.25
2.1.26
2.1.27
Fillers - Origin, Chemical Composition, Properties,
and Morphology
Particulate fillers
Aluminum flakes and powders
Aluminum borate whiskers
Aluminum nitride
Aluminum oxide
Aluminum trihydroxide
Anthracite
Antimonate of sodium
Antimony pentoxide
Antimony trioxide
Ammonium octamolybdate
Apatite
Ash, fly
Attapulgite
Barium metaborate
Barium sulfate
Barium & strontium sulfates
Barium titanate
Bentonite
Beryllium oxide
Boron nitride
Calcium carbonate
Calcium fluoride
Calcium hydroxide
Calcium phosphate
Calcium silicate
Calcium sulfate
Carbon black
1
1
5
6
9
10
11
13
13
13
18
19
20
23
27
29
30
32
34
36
37
39
42
43
48
49
51
54
55
58
71
72
73
75
76
78
iv
2.1.28
2.1.29
2.1.30
2.1.31
2.1.32
2.1.33
2.1.34
2.1.35
2.1.36
2.1.37
2.1.38
2.1.39
2.1.40
2.1.41
2.1.42
2.1.43
2.1.44
2.1.45
2.1.46
2.1.47
2.1.48
2.1.49
2.1.50
2.1.51
2.1.52
2.1.53
2.1.54
2.1.55
2.1.56
2.1.57
2.1.58
2.1.59
2.1.60
2.1.61
2.1.62
2.1.63
2.1.64
2.1.65
2.1.66
2.1.67
2.1.68
2.1.69
2.1.70
Table of Contents
Carbonyl iron powder
Cellulose particles
Ceramic beads
Chitosan
Clamshell powder
Clay
Cobalt powder
Copper
Corn cob powder
Cristobalite
Diatomaceous earth
Dolomite
Eggshell filler
Ferrites
Feldspar
Gadolinium oxide
Glass beads
Gold
Graphene
Graphene oxide
Graphite
Ground tire powder
Halloysite
Huntite
Hydrous calcium silicate
Illite
Iron
Iron oxide
Kaolin
Lead oxide
Lithopone
Magnesium oxide
Magnesium hydroxide
Magnetite
Metal-containing conductive materials
Mica
Molybdenum
Molybdenum disulfide
Molybdenum oxide
Nanofillers
Nickel
Nickel oxide
Nickel zinc ferrite
94
96
97
99
100
101
103
104
106
107
109
113
114
115
117
119
120
126
127
129
131
136
137
139
140
142
143
144
146
151
152
153
154
157
159
163
167
168
169
170
179
182
183
Table of Contents
v
2.1.71 Nutshell powder
2.1.72 Perlite
2.1.73 Polymeric fillers
2.1.74 Potassium hexatitanate whisker
2.1.75 Pumice
2.1.76 Pyrophyllite
2.1.77 Rubber particles
2.1.78 Sepiolite
2.1.79 Silica
2.1.79.1 Fumed silica
2.1.79.2 Fused silica
2.1.79.3 Precipitated silica
2.1.79.4 Quartz (Tripoli)
2.1.79.5 Sand
2.1.79.6 Silica gel
2.1.80 Silicon carbide
2.1.81 Silicon nitride
2.1.82 Silver powder and flakes
2.1.83 Slate flour
2.1.84 Talc
2.1.85 Titanium dioxide
2.1.86 Tungsten
2.1.87 Vermiculite
2.1.88 Wollastonite
2.1.89 Wood flour and similar materials
2.1.90 Zeolites
2.1.91 Zinc borate
2.1.92 Zinc oxide
2.1.93 Zinc stannate
2.1.94 Zinc sulfide
2.2
Fibers
2.2.1
Aramid fibers
2.2.2
Carbon fibers
2.2.3
Carbon nanotubes
2.2.4
Cellulose fibers
2.2.5
Cellulose nanofibrils
2.2.6
Glass fibers
2.2.5
Other fibers
184
185
186
191
192
193
194
196
198
199
204
205
207
209
210
213
214
215
217
218
223
232
233
234
238
240
242
244
247
248
250
250
252
256
260
263
264
266
3
3.1
3.2
3.3
267
267
269
271
Fillers Transportation, Storage, and Processing
Filler packaging
External transportation
Filler receiving
vi
Table of Contents
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
Storage
In-plant conveying
Semi-bulk unloading systems
Bag handling equipment
Blending
Feeding
Drying
Dispersion
References
272
274
278
279
280
281
283
285
291
4
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
4.19
4.20
4.21
4.22
4.23
4.24
4.25
4.26
4.27
4.28
4.29
4.30
4.31
4.32
Quality Control of Fillers
Absorption coefficient
Acidity or alkalinity of water extract
Ash content
Brightness
Coarse particles
Color
CTAB surface area
Density
Electrical properties
Extractables
Fines content
Heating loss
Heat stability
Hegman fineness
Hiding power
Iodine absorption number
Lightening power of white pigments
Loss on ignition
Mechanical and related properties
Oil absorption
Particle size
Pellet strength
pH
Resistance to light
Resistivity of aqueous extract
Sieve residue
Soluble matter
Specific surface area
Sulfur content
Tamped volume
Tinting strength
Volatile matter
293
293
293
293
294
294
294
294
295
295
295
295
296
296
296
296
296
296
297
297
297
298
298
298
298
298
298
299
299
299
299
299
300
Table of Contents
vii
4.33
4.34
Water content
Water-soluble sulfates, chlorides & nitrates
References
300
300
300
5
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
5.15
5.16
5.17
5.18
5.19
5.20
5.21
5.22
5.23
5.24
5.25
5.26
5.27
5.28
5.29
5.30
5.31
5.32
5.33
5.34
5.35
5.36
5.37
Physical Properties of Fillers and Filled Materials
Density
Particle size
Particle size distribution
Particle shape
Particle surface morphology and roughness
Specific surface area
Porosity
Particle-particle interaction and spacing
Agglomerates
Aggregates and structure
Flocculation and sedimentation
Aspect ratio
Packing volume
pH
Zeta-potential
Surface energy
Moisture
Absorption of liquids and swelling
Permeability and barrier properties
Oil absorption
Hydrophilic/hydrophobic properties
Optical properties
Refractive index
Friction properties
Hardness
Intumescent properties
Thermal conductivity
Thermal expansion coefficient
Thermal degradation
Melting temperature
Glass transition temperature
Electrical properties
Relative permittivity
Electrical percolation
EMI shielding
Magnetic properties
Shape memory
References
303
303
306
309
313
314
316
317
318
320
322
324
327
328
332
332
334
338
340
342
343
344
345
347
348
349
351
352
353
354
354
355
355
359
359
360
361
362
363
viii
Table of Contents
6
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.11
Chemical Properties of Fillers & Filled Materials
Reactivity
Chemical groups on the filler surface
Filler surface modification
Filler modification and material properties
Resistance to various chemicals
Cure in fillers presence
Polymerization in fillers presence
Grafting
Crosslink density
Reaction kinetics
Molecular mobility
References
373
373
376
379
392
396
398
402
403
404
406
407
409
7
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.11
7.12
7.13
7.14
7.15
7.15
Organization of Interface and Matrix Containing Fillers
Particle distribution in matrix
Orientation of filler particles in a matrix
Distance between particles
Voids
Matrix-filler interaction
Chemical interactions
Other interactions
Interphase organization
Interfacial adhesion
Interphase thickness
Filler-chain links
Chain dynamics
Bound rubber
Debonding
Mechanisms of reinforcement
Benefits of organization on molecular level
References
415
415
420
426
427
428
429
432
436
439
441
443
444
445
451
454
459
461
8
The Effect of Fillers on the Mechanical Properties
of Filled Materials
Tensile strength and elongation
Tensile yield stress
Mullins’ effect
Elastic modulus
Flexural strength and modulus
Impact resistance
Hardness
Tear strength
467
467
474
479
479
482
484
488
490
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
Table of Contents
ix
8.9
8.10
8.11
8.12
8.13
8.14
8.15
8.16
8.17
8.18
8.19
8.20
8.21
8.22
8.23
8.24
Compressive strength
Fracture resistance
Wear
Friction
Abrasion
Scratch resistance
Fatigue
Failure
Adhesion
Thermal deformation
Shrinkage
Warpage
Compression set
Load transfer
Residual stress
Creep
References
491
492
499
501
503
504
506
510
512
514
515
517
518
519
521
522
523
9
9.1
9.2
9.3
9.4
9.5
9.6
9.7
9.8
9.9
9.10
9.11
The Effect of Fillers on Rheological Properties of Filled Materials
Viscosity
Flow
Flow induced filler particle orientation
Torque
Viscoelasticity
Dynamic mechanical behavior
Complex viscosity
Shear viscosity
Elongational viscosity
Melt rheology
Yield value
References
533
533
535
537
539
540
542
543
545
547
548
548
549
10
10.1
10.2
10.3
10.4
10.5
10.6
10.7
Morphology of Filled Systems
Crystallinity
Crystallization behavior
Nucleation
Crystal size
Spherulites
Transcrystallinity
Orientation
References
553
553
555
558
560
561
565
566
567
x
Table of Contents
11
11.1
11.2
11.3
11.4
11.5
11.6
Effect of Fillers on Exposure to Different Environments
Irradiation
UV radiation
Temperature
Liquids and vapors
Stabilization
Degradable materials
References
571
571
573
579
581
583
584
585
12
12.1
12.2
12.3
12.4
12.5
12.6
12.7
12.8
12.9
Flammability of Filled Materials
Definitions
Limiting oxygen index
Ignition and flame spread rate
Heat transmission rate
Decomposition and combustion
Emission of gaseous components
Smoke
Char
Recycling
References
589
589
590
591
593
595
597
597
599
599
602
13
Influence of Fillers on Performance of Other Additives
and Vice Versa
Adhesion promoters
Antistatics
Blowing agents
Catalysts
Compatibilizers
Coupling agents
Dispersing agents and surface active agents
Flame retardants
Impact modifiers
UV stabilizers
Other additives
References
605
605
607
608
609
610
613
615
617
618
619
622
623
Testing Methods in Filled Systems
Physical methods
Atomic force microscopy
Autoignition test
Bound rubber
Char formation
Cone calorimetry
627
627
627
628
629
629
630
13.1
13.2
13.3
13.4
13.5
13.6
13.7
13.8
13.9
13.10
13.11
14
14.1
14.1.1
14.1.2
14.1.3
14.1.4
14.1.5
Table of Contents
xi
14.1.6
14.1.7
14.1.8
14.1.9
14.1.10
14.1.11
14.1.12
14.1.13
14.1.14
14.1.15
14.1.16
14.1.17
14.1.18
14.1.19
14.1.20
14.1.21
14.1.22
14.1.23
14.1.24
14.1.25
14.1.26
14.1.27
14.2
14.2.1
14.2.2
14.2.3
14.2.4
14.2.5
14.2.6
14.2.7
14.2.8
14.2.9
Contact angle
Dispersing agent requirement
Dispersion tests
Dripping test
Dynamic mechanical analysis
Electric constants determination
Electron microscopy
Fiber orientation
Flame propagation test
Glow wire test
Image analysis
Limiting oxygen index
Magnetic properties
Optical microscopy
Particle size analysis
Radiant panel test
Rate of combustion
Scanning acoustic microscopy
Smoke chamber
Sonic methods
Specific surface area
Thermal analysis
Chemical and instrumental analysis
Electron spin resonance
Electron spectroscopy for chemical analysis
Inverse gas chromatography
Gas chromatography
Gel content
Infrared and Raman spectroscopy
Nuclear magnetic resonance
UV and visible spectroscopy
X-ray analysis
References
631
633
633
634
634
635
637
638
638
640
640
642
642
643
644
645
645
645
646
646
648
648
649
649
650
651
653
654
654
656
658
658
659
15
15.1
15.2
15.3
15.4
15.5
15.6
15.7
15.8
Fillers in Commercial Polymers
Acrylics
Acrylonitrile-butadiene-styrene copolymer
Acrylonitrile-styrene-acrylate
Aliphatic polyketone
Alkyd resins
Bismaleimide
Cellulose acetate
Chitosan
665
665
668
669
670
671
671
672
672
xii
15.9
15.10
15.11
15.12
15.13
15.14
15.15
15.16
15.17
15.18
15.19
15.20
15.21
15.22
15.23
15.24
15.25
15.26
15.27
15.28
15.29
15.30
15.31
15.32
15.33
15.34
15.35
15.36
15.37
15.38
15.39
15.40
15.41
15.42
15.43
15.44
15.45
15.46
15.47
15.48
15.49
15.50
15.51
Table of Contents
Elastomers, TPO
Epoxy resins
Ethylene vinyl acetate copolymer, EVA
Ethylene vinyl alcohol copolymer, EVOH
Ethylene ethyl acetate copolymer, EEA
Ethylene propylene copolymers, EPR & EPDM
Ionomers
Liquid crystalline polymers, LCP
Perfluoroalkoxy resin, PFA
Phenolic resins
Poly(acrylic acid), PAA
Polyacylonitrile, PAN
Polyamides, PA
Polyamideimide, PAI
Polyamines
Polyaniline, PANI
Polyaryletherketone, PAEK
Poly(butylene succinate), PBS
Poly(butylene terephthalate), PBT
Polycaprolactone, PCL
Polycarbonate, PC
Polydicyclopentadiene
Polyetheretherketone, PEEK
Polyetherimide, PEI
Polyethersulfone, PES
Polyethylene, PE
Polyethylene, chlorinated, CPE
Polyethylene, chlorosulfonated, CSM
Poly(ethylene oxide), PEO & PEG
Poly(ethylene terephthalate), PET
Polyimide, PI
Poly(lactic acid)
Polymethylmethacrylate, PMMA
Polyoxymethylene, POM
Poly(phenylene ether), PPO
Poly(phenylene sulfide), PPS
Polypropylene, PP
Polypyrrole
Polystyrene & high impact, PS & HIPS
Polysulfide
Polysulfone, PSO
Polytetrafluoroethylene, PTFE
Polyurethanes, PU & TPU
673
674
677
678
678
679
681
681
682
682
684
684
685
688
689
689
690
691
691
693
693
695
696
697
697
698
702
703
703
705
706
708
709
710
711
711
712
717
718
719
719
720
721
Table of Contents
xiii
15.52
15.53
15.54
15.55
15.56
15.56.1
15.56.2
15.56.3
15.56.4
15.56.5
15.56.6
15.56.7
15.56.8
15.57
15.58
15.59
15.60
15.61
Poly(vinyl acetate), PVA
Poly(vinyl alcohol), PVA
Poly(vinyl butyral), PVB
Poly(vinyl chloride), PVC
Rubbers
Natural rubber, NR
Nitrile rubber, NBR
Polybutadiene rubber, BR
Butyl rubber, HR
Polychloroprene
Polyisobutylene, PIB
Polyisoprene, IR
Styrene-butadiene rubber, SBR
Silicones, SI
Styrene-acrylonitrile copolymer, SAN
Tetrafluoroethylene-perfluoropropylene
Unsaturated polyesters
Vinylidene-fluoride terpolymer, PVDF
References
723
724
724
725
727
728
730
732
732
733
734
735
735
737
739
739
740
741
742
16
16.1
16.2
16.3
16.4
Fillers in Materials Combinations
Blends, alloys and interpenetrating networks
Composites
Nanocomposites
Laminates
References
763
763
772
776
781
783
17
Formulation with Fillers
References
787
792
18
18.1
18.2
18.3
18.4
18.5
18.6
18.7
18.8
18.9
18.10
18.11
18.12
Fillers in Different Processing Methods
Blow molding
Calendering and hot-melt coating
Compression molding
Dip coating
Dispersion
Extrusion
Foaming
Injection molding
Knife coating
Mixing
Pultrusion
Reaction injection molding
793
793
794
795
797
798
800
803
804
807
808
811
811
xiv
Table of Contents
18.13
18.14
18.15
18.16
18.17
18.18
Resin transfer molding
Rotational molding
Sheet molding
Spinning
Thermoforming
Welding and machining
References
812
813
814
815
816
816
817
19
19.1
19.2
19.3
19.4
19.5
19.6
19.7
19.8
19.9
19.10
19.11
19.12
19.13
19.14
19.15
19.16
19.17
19.18
19.19
19.20
19.21
19.22
19.23
19.24
19.25
19.26
19.27
19.28
19.29
19.30
19.31
19.32
19.33
19.34
Fillers in Different Products
Adhesives
Agriculture
Aerospace
Appliances
Automotive materials
Bottles and containers
Building components
Business machines
Cable and wire
Coated fabrics
Coatings and paints
Cosmetics and pharmaceutical products
Dental restorative composites
Electrical and electronic materials
Electromagnetic interference shielding
Fibers
Film
Foam
Food and feed
Friction materials
Geosynthetics
Hoses and pipes
Magnetic devices
Medical applications
Membranes
Noise dampening
Optical devices
Paper
Radiation shields
Railway transportation
Roofing
Telecommunication
Tires
Sealants
823
823
826
827
827
828
830
830
831
831
832
833
837
839
841
842
844
845
847
847
848
848
849
849
850
853
853
854
855
858
858
859
859
860
862
Table of Contents
xv
19.35
19.36
19.37
19.38
Siding
Sports equipment
Waterproofing
Windows
References
864
865
865
866
866
20
Hazards in Filler Use
References
873
880
Index
881
1
Introduction
This introduction:
• Lists the properties of materials which are influenced by fillers
• Lists typical properties of fillers
• Provides definition of the term “filler”
• Defines how fillers function in various applications
• Suggests how fillers may be classified
• Discusses the markets for fillers and the emerging trends in filler use
The introduction will define the scope of the book and provide a brief overview of
each chapter.
It is our intention to show how an understanding of the diverse functions of fillers in
materials can lead to a well designed material formulation.
1.1 EXPECTATIONS FROM FILLERS
What caused fillers to be added to materials in the first place was probably the quest for
lower costs. Fillers were inexpensive, thus using them would make the material cheaper.
We do not know who the inventor of the idea was but it was probably not one, but many
people in many different places. However, as the following discussion shows, cost reduction is no longer the only, or even the most important, consideration for using fillers in formulating composite materials.
These examples which follow list attributes of materials to the formulators various
objectives.
Table 1.1. Attributes of fillers
Cost reduction
Cost reduction depends on the relative cost of the polymer and the
filler. Polymer prices in May 2015 were approximately:1
US$/kg US$/l
ABS
2.02
2.10
HDPE 1.51
1.43
PET
2.00
2.76
PP
1.43
1.35
LLDPE 1.54
1.49
PVC
2.55
3.31
2
Introduction
Table 1.1. Attributes of fillers
Cost reduction
Filler prices depend greatly on the particle size but also on surface
preparation, shape, particle size distribution, purity, and many other
factors. Here are approximate prices of selected fillers (August,
2006):2
US$/kg
US$/l
calcium carbonate (ground)
0.06
0.17
calcium carbonate (precipitated) 0.26-0.95
0.73-2.66
carbon black
1.10
1.98
carbon nanotubes
250-75,000 450-135,000
kaolin
0.28
0.73
magnesium hydroxide
1.00
2.40
silver powder
892-1225
9,366-12,863
titanium dioxide
2.61
11.06
zinc borate
2.64-4.84
7.39-13.55
If we consider only cost, it is the cost per unit volume that must be
compared. The table shows that only the use of large particle size calcium carbonate ground (very crude products) can potentially contribute to savings in the manufactured cost of materials made from
commodity polymers. At the same time, these fillers decrease many
mechanical properties of the material so the cost reduction is
achieved at the expense of performance. Medium particle sized fillers
are less attractive economically because costs of processing, inventory and transportation are higher. This shows that there must be
other motives to compound polymers with fillers. These follow.
Material density3
Fillers can be used either to increase or to decrease the density of a
product. Because the density of a filler can be as high as 19.35 g/cm3
or as low as 0.03 g/cm3, there may be a large difference between the
density of the filler and the polymer. Thus a broad range of product
densities can be obtained. There are high density products (above 3 g/
cm3) required in materials used in appliances or casings for electronic
devices. More common are densities below 2 g/cm3, glass fiber filled
composites being a typical example. The effective density of the
polymer can be decreased by filling a foam with hollow polymer
spheres. In this example, the density of a material can be lower than
0.1 g/cm3.
Optical properties4-7
Optical properties of compounded materials depend on the physical
characteristics of the filler and the other major ingredients including
the polymer. Most important is the relative refractive index of the two
ingredients. Depending on how they match, one can obtain clear or
opaque materials. Light absorption by the non-polymer ingredients is
essential in preventing UV degradation. Some fillers (e.g., TiO2, ZnO
or talc) effectively absorb light but small particle size fillers (especially nanofillers) do not absorb effectively in visible region. Aluminum trihydroxide in UV curable polyurethanes is noteworthy in that
it accelerates the curing process because it is transparent to UV light.
Calcinated clay as a filler in greenhouse film at a 10% level drastically reduces infrared absorption during the day and heat loss during
the night. This application of physical principles has been an important factor in increasing the productivity of greenhouses. Specially
designed fillers, added in small quantities, can be used as product
markers because of their peculiarities in absorption of radiation.
Leafy fillers can be used to reflect radiation which decreases temperature behind a membrane (e.g., roofing) or creates special effects
(e.g., automotive paints)
1.1 Expectations from fillers
3
Table 1.1. Attributes of fillers
Color
Fillers frequently cause problems in color matching and must be
accounted for in product color design. Many fillers have a distinctive
color which is useful in material coloring. Some fillers (e.g., barium
sulfate, zinc oxide, or lithopone) help to reduce white pigment level
due to their lightening abilities. Recently metal powders have been
used in combination with pigments to make the composite appear
metal like.
Surface properties8-12
For hundreds of years sticky surfaces have been dusted with powder
(e.g., talc) to keep them separated. Talc is broadly used in cable and
profile extrusion to obtain a smooth surface. Similarly, in injection
molding, the application of aluminum trihydroxide gives a better surface finish. Talc, CaCO3, and diatomite provide anti-blocking properties. Graphite and other fillers decrease the coefficient of friction of
materials. PTFE, graphite and MoS2 permit production of self-lubricating parts. Here, PTFE, a polymer in a powder form, acts as a filler
in other polymers. Matte surfaced paint is obtained by the addition of
silica fillers. Also surface properties of fillers determine many properties of materials such as interfacial adhesion, reinforcement, crystallinity, and compatibility but also thermal stability of some
elastomers.
Product shape7,13,14
Fillers reduce shrinkage of polymer foams. Mica and glass fiber
reduce warpage and increase the heat distortion temperature. Intumescent fillers increase in volume rapidly as they degrade thermally
expanding the material and blocking fire spread.
Thermal properties15
Fillers may decrease thermal conductivity. The best insulation properties of composites are obtained with hollow spherical particles as a
filler. Conversely, metal powders and other thermally conductive
materials substantially increase the dissipation of thermal energy.
Electrical properties16
Volume resistivity, static dissipation and other electrical properties
can be influenced by the choice of filler. Conductive fillers in powder
or fiber form, metal coated plastics and metal coated ceramics will
increase the conductivity. Many fillers increase the electric resistivity.
These are used in electric cable insulations. Ionic conductivity can be
modified by silica fillers.
Magnetic properties17
Ferrites induce ferromagnetic properties and are used to make plastic
magnets.
Permeability8
Gas and liquid permeability are influenced by the choice of filler. The
platelet structure of mica or talc as a filler in paints and plastics
decreases the transmission of gases and liquids.
Mechanical properties18,19
All mechanical properties are affected by fillers. Filler combinations
may be selected to optimize a variety of mechanical properties. Fillers reinforce and provide abrasion resistance.
Chemical reactivity12,19
Many fillers can be used to influence chemical reactions occurring in
their presence. The reaction rate can be decreased or increased. Fillers such as ZnO will react with UV degradation products in PE to
limit damage. The pot-life of curing mixtures can be increased. Cure
rates can be slowed, exothermic effects can be controlled, incompatible polymers can be blended and molecular mobility reduced. Burning properties of materials can be modified by fillers and some toxic
gases normally emitted can be absorbed and reacted.
4
Introduction
Table 1.1. Attributes of fillers
Rheology8,11
The rheology of many industrial products depends on the filler addition. Examples include sealants, toothpastes, cosmetics, hotmelts,
papers, paints, etc. Normally, additions of fillers increase the viscosity and contribute to non-Newtonian flow characteristics, but there
are also combinations such as filler mixtures and specially designed
glass beads which either reduce the viscosity or do not affect it.
Morphology13,21
Polymer crystallization and structure are affected by fillers. They
may increase or decrease the nucleation rate (and thus the crystallization rate). An increase in the nucleation rate is observed in PET in the
presence of mica or polypropylene in the presence of talc. Fillers,
especially fibers, may also decrease the mechanical properties of
filled materials because of their effect on transcrystallinity. The polymer structure at the interface with fillers is different than in the bulk.
Material
durability4,7,14,20,22-24
Fillers which screen radiation and react with degrading molecules
contribute to material durability. The opposite effects may also occur
if fillers participate in photochemical reactions which decrease photostability. Some fillers are used for their absorption of highly penetrating radiation such as nuclear radiation or filler is used in neutron
shielding. Thermal degradation can be either decreased and increased
by the presence of fillers. Fillers such as borates and montmorillonite
also protect materials from biodegradation. The addition of starch
generates numerous mechanisms which increase biodegradability by
supplying nutrients and also participate in initiation of thermal and
UV degradation which reduces chain length and permits biological
conversions.
Environmental impact25-28
Fillers contribute to fire retardancy by suppressing fire, increasing
autoignition temperature, decreasing smoke formation, increasing
char formation, reducing heat transmission rate, preventing dripping,
etc. Fillers are used in combinations to balance properties. For example, antimony trioxide increases smoke whereas Al(OH)3 and
Mg(OH)2 reduce it. It is possible to make paper fire retardant through
the proper selection of fillers. Plastics recycling can be improved by
incorporating fillers which reduce thermodegradation (stabilize some
polymers). Complex mixtures of polymer waste are more easily
blended if compounded with fillers.
Performance of other
additives
Fillers are instrumental in improving the performance of other additives. Antistatics, blowing agents, catalysts, compatibilizers, coupling
agents, organic flame retardants, impact modifiers, rheology modifiers, thermal and UV stabilizers are all influenced by a fillers presence.
Health & safety
Fillers are probably the least hazardous components among additives.
The major exception here is asbestos which is seldom, if ever, used
now. Other fillers which may be hazardous are being carefully investigated although disputes still occur when data is incomplete or questionable.
Fillers produced today are manufactured by sophisticated processes. There are
numerous examples of surface modification which changes a fillers properties. Numerous
nanofillers are now synthesized as well as fillers having specific morphology as demanded
by properties of materials into which they are incorporated. Preparation of materials for
specific medical applications can be carried out using template polymerization.29 This has
become a well established discipline which has contributed to the understanding of poly-
1.2 Typical filler properties
5
mer structure. Here, the polymer is produced on organic and inorganic (e.g., fillers) templates. By choosing the template structure, polymer properties can be tailored to
requirements. Natural biological materials are formed in this manner and synthetic materials can be formed in a similar manner. Filler properties can also be tailored by synthesizing fillers in the presence of other materials. This is used in medical applications where the
filler becomes compatible with its surroundings as it forms in body fluids. Artificial bone
materials can thus be formed with surface characteristics acceptable to (compatible with)
the body’s environment. These techniques are at the most advanced levels of engineering
and design in filler synthesis.
In summary,
• Fillers usually do not reduce the cost of material manufacturing
• Fillers are not inert materials added to fill space (if they are used in this way, they
likely degrade properties of the material)
• Fillers can be modified and tailored to any application
• Fillers modify practically all properties of the material and influence the design,
manufacture, and use
• Plastics performance and the performance of other materials are highly influenced by fillers
• The plastics applications base has expanded greatly as the use of fillers has
increased
1.2 TYPICAL FILLER PROPERTIES
We have outlined the product performance characteristics of fillers. This leads us to an
identification of filler properties which permit comparison and evaluation of different fillers. When we go on to develop a definition of fillers in Section 1.3, this list will help to
make the definition inclusive yet precise. It will also assist in the classification of fillers
discussed in Section 1.4.
Table 1.2. Range of fillers properties
Physical state
All materials discussed are solids but they might be available in a predispersed state (water slurries)
Chemical composition
May be inorganic or organic and of an established chemical composition. May also be a single element, natural products, mixtures of different materials in unknown proportions (waste and recycled
materials), or materials of a proprietary composition
Particle shape30
Spherical, cubical, irregular, dendritic, block, plate, flake, fiber, mixtures of different shapes
Particle size
Range from a few nanometers to tens of millimeters (nanofillers to
fibers)
Aspect ratio30
1 (spherical or cubical) to 1,600 (fibers)
Particle size distribution
Mono disperse, designed mixture of sizes, Gaussian distribution,
irregular distribution
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