The use of minerals in plastics as
functional fillers is one of the primary consuming market
sectors for the industrial minerals business. A wide range of
minerals perform specific functions to enhance the desired
properties of the plastic end product.
While mineral filler use has been
around since the advent of plastics, advances in plastic
manufacturing technology and the increasing and changing
demands from the plastic end user industries have dictated that
mineral filler producers also keep pace with market
Electroluxs total European demand for GCC
filled PP used in its washing machines and
dishwashers equates to about 55,000 tpa,
which is about 20% of the European market.
This has led to increased sophistication in mineral filler
processing and surface treatment methods in order to produce
higher performance mineral grades to satisfy the stringent
demand requirements in manufacturing modern plastic components
The accompanying table shows some
of the key industrial minerals used and their main
Mineral fillers are consumed in
both thermoplastics, especially in polypropylene (PP) and
polyvinyl chloride (PVC) products, and elastomers, mainly in
rubber tyre formulations.
In Europe, the most recent
estimates available reveal that elastomers consume 3-3.5m. tpa
fillers, thermoplastics, 1.4-1.6m. tpa, and thermosets, 0.6m.
European plastic filler consumption 2007
* ie. certain sophisticated processed grades further
categorised as high performance
||Consumption (000s tonnes)
||Estimated % as high performance*
|Ground calcium carbonate
|Precipitated calcium carbonate
Source: Roger Rothon (2009)
Filler and filler modifier markets and trends at
High Performance Fillers for Polymer Composites, Barcelona, 4-5
The point where industrial minerals
meet polymers is at the compounding stage of plastics
manufacture (see flow chart). Here the chosen polymer
or resin, the most expensive component of the plastic, is mixed
with fillers and additives.
The majority of fillers are
industrial minerals, although there are also some synthetic
materials and organic materials, such as wood flour. They
perform a range of functions (see table), but above
all they help reduce costs by reducing the volume of
polymer/resin used if at all possible.
Additives include pigments and dyes
(also comprising industrial minerals and derived compounds),
antioxidants, slip/release agents, coupling agents, and
Most compounding is now undertaken
using a twin-screw extruder machine. This conveys, melts,
mixes, injects additives, degases and pressurises to form a
wide range of plastic compounds.
One of the main costs in plastics
manufacture is at that of the compounding facility, ie. power,
water, and machine wear and tear. So manufacturers strive to
attain the optimum compounding facilities for their
For high mineral filler loadings in
plastics, ie. >50%, a continuous mixer combined with a
single screw extruder has been demonstrated to be a potential
alternative. The result is excellent dispersion and energy
savings when compared with a twin-screw extruder.
Tests carried out by US processing
equipment supplier Farrel Corp. (acquired by HF Machinery Group
division of L. Possehl & Co., mbH, Germany in 2009) and
carbonate filler leader Omya AG, have shown that such a set-up
can handle compounds with up to 84% filler loadings.
Industrial minerals used in plastics
Source: adapted from tables by Sara Robinson, RT Vanderbilt
||ABS, TPES, LDPE, PVC, Epoxy, Phenolics, PU
||Smoke suppressant; extender
||Inert; Increases specific gravity; noise
||PVC, ABS, Fluoroplastics, Polyolefins, PP, PS, Epoxy,
Phenolics, TPES, PU
||Most widely used filler
||PVC, Acrylic, PP, PS, Epoxy PEU,
||Used to provide weather and chemical resistance
||TPES, Nylon, Polyolefins, PU, PVC, PEU
||Platy shape; Largest use in wire and cable,
||PP, ABS, Fluoroplastics, Nylon , PC, TPES,
||Dimensional reinforcement; thermal and mechanical
||Epoxy, ABS, Polyolefins, PS, PVC, TPES, PU
||Filler and reinforcement
||PP, Nylon, Polyolefins, PVC, Phenolic, PU, PS
||Platy shape; Stiffness; creep resistance; tensile
||Nylon, PC, TPES, PP, PS, Polyolefins, Thermoset
||Needle shape; improves strength; high heat &
dimensional stability; improved electrical
Trends in filler use
From the accompanying table on
European consumption of fillers, it can be seen that ground
calcium carbonate (GCC) at 2m. tonnes is by far and away the
dominant mineral filler, used at loading levels of 15-80% in a
wide range of plastics, but particularly in PVC.
Talc, kaolin, precipitated silica,
and the flame retardant minerals aluminium trihydrate (ATH) and
magnesium hydroxide (MHD) come next by volume in the
200-300,000 tonne range.
At 100,000 tonnes and less are
barium sulphate, crystalline silica, precipitated calcium
carbonate (PCC), calcined kaolin, fumed silica, and
The market sectors using these
mineral filled plastic are automotive (includes rubber in
tyres), wire and cable, flooring, domestic appliances, and
Roger Rothon, of Rothon
Consultants, UK, further categorises a high
performance range of filler grades within the overall
range of fillers consumed. These include fumed and precipitated
silicas, PCC, flame retardants, calcined clays, and special
grades of talc and wollastonite (see table).
Rothon estimates the European
consumption of high performance fillers to be 3.3m. tonnes or
about 60% of the total. Primary markets include automotive
(especially in tyres), wire and cable (a key area for flame
retardants), sealants, and in breathable films.
There has been increased use of
surface coating of filler minerals in order to modify their
characteristics and enhance their performance when compounded
with the polymer and other additives.
The main surface treatments are
fatty acids and organo-silanes, of which 6,500 tonnes and
13,500 tonnes, respectively, are consumed in Europe. Most high
performance minerals, with the exception of talc, use these
Organo-silanes for coated
precipitated silica in tyre tread formulations is the leading
surface treatment market, while flame retardants (ATH, MHD) in
wire and cable and GCC in breathable film are also important
and growing applications.
Indeed, world speciality silica
demand (for all grades) stood at 1.9m. tonnes in 2009, and is
expected to grow 6.3% annually to 2.7m. tonnes in 2014, with
precipitated silica in rubber looking to take 45% of the market
by that time.
As a rule of thumb, when oil prices
are high or rising, then filler loading levels tend to
increase, as the price of polymers increase, and vice versa.
However, it really depends on the end product performance
Other trends in the mineral filler
Almost complete substitution of carbon black by silane
coated precipitated silica in the move to green tyre
Growth in breathable films, eg. for disposable nappies,
has driven demand for fatty acid coated GCC
Polyolefin films, eg. rubbish bags, using increased
loadings, eg. typically 20-30% GCC, and up to 50%.
Substitution of steel with lighter weight mineral filled
Increased use of recycled plastics using reinforcement
Thermoplastic polyolefins requiring more reinforcement
using platy minerals such as talc
Increased use of talc replacing glass fibre in
engineering resins eg. ABS, PC, PET, and PA.
Continued development of speciality masterbatches based
on higher loading levels of filler minerals, eg. 75-80%
GCC or talc
Development and emerging use of nanominerals, eg.
Use of high aspect ratio kaolins for gas barrier
applications to reduce permeability in polyolefins, PET,
and other plastic films
Development of surface treated diatomite fillers (already
used in silicone rubber applications) for thermoplastics
In 2008, Europe produced about 60m.
tonnes of plastics, of which some 48m. tonnes were consumed by
converters. Of this figure, PP accounted for the largest share,
18%, and PVC, 12%.
Just over a third of Europes
PP compound consumption comprises mineral filled PP, followed
by glass fibre filled PP (also using industrial minerals in
glass fibre production), and impact modified PP (see pie
PP compound consumption in Europe by product type
Source: Applied Market Information Ltd
Simplified flow chart of plastic manufacturing
showing the compounding stage where mineral fillers
are mixed to form the plastic compound.