Filler minerals: Auto doom & gloom stalls market

By Jessica Roberts
Published: Friday, 20 March 2009

IM reports on the 4th High Performance Fillers for Polymer Composites conference, held 4-5 March 2009 in Barcelona, Spain, covering market outlook, new filler grades, plus developments in nanofillers and mineral processing by Jessica Roberts, Assistant Editor

 
 
The coastal city of Barcelona, Spain, played host to this year’s High Performance Fillers for Polymer Composites (HPF) conference, held 4-5 March 2009, organised by Smithers Rapra. There was a good variety of topics, covered by over 16 papers.

Kicking off the event was the keynote speech, “Filler and filler modifier markets and trends,” presented by market consultant Prof. Roger Rothon.

Rothon revealed that filler trends, using European markets as the example, were strongly skewed towards elastomers – which consumed around 3-3.5m. tpa of the 5.5m. tpa filler minerals produced in Europe in 2007. The second largest consuming sector was thermoplastics, at 1.4-1.6m. tpa, while thermosets consumed around 0.6m. tpa.

The main filler markets in Europe were stated as automotive (especially tyres); wire and cable; flooring; household appliances; and sealants. Regarding consumption in these markets, Rothon was sombre: “The alarming decrease in new car sales is a major concern as very significant amounts of filler are used in this sector.”

Rather than attempting to forecast the future market in terms of mineral tonnage and pricing, Rothon presented a unique take on the market outlook, whereby a severity rating was applied to each of the main filler minerals. The rating of each mineral thus illustrated the expected impact of the economic downturn on their production and consumption.

Under Rothon’s system, ‘0’ equated to no expected change, while ‘5’ equated to a very significant reduction. Rothon explained: “The higher the rating [of the mineral], the larger the expected fall, and the longer before [market] growth returns.”

As expected, minerals dependent on automotive end-uses were rated as performing worst, including carbon black (rating = 3), precipitated silicas (rating = 4), fumed silica (rating = 2.5), and precipitated calcium carbonate (rating = 2.5).

Flame retardant fillers were also affected under Rothon’s rating system, with aluminium hydroxide and magnesium hydroxide given a rating of 2-3.

Fillers such as natural fibres and talcs, meanwhile, were rated as 3-4.

Those fillers with less of an automotive link, such as GCC, were given a severity rating of 2. Regarding these filler minerals, Rothon stated: “Their low cost and wide range of applications will probably limit any effects [of the economic downturn]. They may also see increased replacement opportunities.”

Rounding off the presentation, Rothon predicted filler consumption by all markets to decline between 2008-2010, meanwhile for the market between 2008-2013 he proposed that it may be characterised by no or weak demand.

Filler enhancement

For the processing aspect of the market, Dr Jürgen Roth, managing director of Powder Maker Technologies (PMT) Jetmill GmbH, took the delegates through: “Jet milling technologies for enhancing the performance of functional fillers”.

The main influencing properties on the effectiveness of functional fillers, as highlighted by Roth, are particle aspect ratio, particle shape and particle size distribution. This is especially true for softer filler minerals such as graphite, mica, talc and wollastonite.

The company presented some interesting results of tests involving mica dry processed in its spiral jetmill, which was showed to effectively delaminate particles from the feed material while preserving their characteristic filler properties. In addition, the jetmill provided a method of classification by ejecting coarse material and waste particles (such as silica), while accepting successfully processed mica.

Lamellar particles with a steep particle size distribution and good top cut have been demonstrated to improve a filler’s mechanical properties; namely charpy impact strength, modulus and scratch resistance.

Roth summarised: “Due to its integrated classifier system, PMT Jetmill is able to produce steep particle size distributions with an exact top cut and [fewer] ultrafine particles.”

Plastic POSSibilities

Moving on to plastics, Polyhedral Oligomeric SilSesquioxanes (POSS) was the focus of a talk by Chris DeArmitt, chief scientist for USA-based Hybrid Plastics Inc. – superbly delivered by impromptu fill-in Roger Rothon.

POSS is essentially a hybrid compound, structurally somewhere between silica and silicone. Unlike silica, however, each molecule of POSS contains covalently bonded functionalities which make them suitable for polymerisation.

As a functional filler in thermoplastics POSS can improve melt flow while retaining mechanical properties, reducing friction and acting as a flame retardance synergist. Rothon also highlighted that, unlike nanoparticles, POSS molecules dissolve easily in solvents and polymers.

Rothon outlined some of the existing applications for POSS – including packaging, aircraft components, optical devices, and dental restoratives – although new research indicates that it could be used to accelerate healing and impart biocompatibility to implants.

At current prices, a small (100g) sample of POSS can cost an equivalent of €1,000/kg, while bulk buying of POSS (1,000kg) costs an equivalent of €50/kg. Rothon, citing these costs, warned against using POSS in applications where more traditional, cheaper filler minerals are effective.

 
Scanning electron microscope (SEM) image of KMI’s MIOX filler.  Courtesy Kärntner Montanindustrie GmbH 
Silica solutions

With automobile tyres accounting for a considerable percentage of European filler mineral consumption, it is unsurprising that this field of research continues to be very active.

In fact tyre technology has undergone a revolution over the past few years, with the demand for more fuel efficient cars leading to the development of so-called green tyres – made with silica compounds instead of carbon black.

Precipitated silica substituted for carbon black in tyre tread has been shown to provide better wet traction, better rolling resistance and an overall 5% improvement on fuel efficiency for many vehicle types.

The hydrophilic nature of silica, however, can be problematic for the production of green tyres, as it does not easily mix with non-polar hydrocarbon rubbers. Dr Martin Saewe from Rhein Chemie Rheinau GmbH outlined some interesting results from the company’s research into this mixing problem, with new work focusing on additives for silica compounds.

The first generation of green tyres was successfully produced from rubber and silica because of an additional organo-silane coupling agent, which improved the interaction between silica particles and the rubber.

However, some accelerators (such as DPG) have been highlighted as a health concern owing to their release of aniline – a carcinogenic, mutagenic, toxic substance – during decomposition.

Rhein Chemie has undertaken significant research into the types of silanes used in tyres. Saewe presented some interesting results which showed that the use of a non-mutagenic accelerator (namely Rhenocure ZBOP-S) could be achieved while preserving the desired properties of the compound.

High performance

Historically, the introduction of fillers into polymers was developed as a method of reducing material costs. In more recent years, however, the market has seen a move to developing new filler mineral grades whose incorporation in polymers actually increases polymer performance.

Mica

Christian Rupp of Kärntner Montanindustrie GmbH (KMI) presented a talk on the company’s new high performance, micaceous iron oxide grades, recently covered by IM (see IM February ’09, p.69).

Processing involves the use of PMT-Jetmill’s spiral jetmill; the subject of an earlier presentation.

MIOX comprises highly lamellar particles that can be processed to achieve an aspect ratio of up to 50:1. Although Rupp did not give an indication of prices, he outlined the filler’s benefits to performance: increased charpy impact strength, melt flow rate, e-modulus, scratch resistance, thermal conductivity, oxygen permeability and sound absorption.

Calcium carbonate

 
Cross sectional SEM image of a spunbond nonwoven fibre containing FiberLink engineered calcium carbonate at 20wt% loading.  Courtesy Imerys SA 
Julian Danvers, marketing director for Imerys subsidiary World Minerals Inc., gave an engaging talk on, “Engineered calcium carbonate adding value to polyolefin film extrusion and nonwoven spunlaid process”.

World Minerals has conducted significant research into the role of inorganic additives, such as calcium carbonate, in polymer film and sheet applications. These additives may take the form of low grade chalk material, up to engineered marbles.

Tests conducted by World Minerals indicated that the addition of calcium carbonate to polypropylene resulted in breakage of the fibres in cases where the company had used a CaCO3 with a top-cut that was more than the average fibre diameter (16-18µ).

Recognising this, the company successfully introduced its FiberLink grade – a steep engineered CaCO3 with a controlled particle size distribution – into later tests with polypropylene, with positive results. In nonwoven micron-size fibres, the addition of FiberLink at up to 20wt% processed well during the trials, and good dispersion of particles was observed.

What this means for polymer producers (using powdered resin for melt blown applications) is reduced cycle time, good web formation and cost savings.

Flame retardants

The European production of aluminium and magnesium hydroxides for flame retardant fillers accounted for some 255,000 tpa in 2007, although this market was generally dominated by aluminium hydroxide owing to its lower cost.

Although it is more expensive to produce, magnesium hydroxide is ideal for niche applications which require a flame retardant with greater thermal stability.

Gerry Spoors, development manager for Omex Environmental Ltd, gave a presentation on a promising new magnesium hydroxide grade currently under development by Omex, which could pave the way for cheaper magnesium-based flame retardant fillers.

The filler is produced via hydration of magnesium oxide, which is specially dried to give a fine, free-flowing powder, available in coated and uncoated versions.

Carbon nanotubes

Carbon nanotubes (CNT) as a filler material was the subject of two talks at this year’s conference. Dr Vincent Calard from Austrian Research Centers GmbH discussed, “Thermal and electrical properties of carbon nanotube reinforced cyanate ester polymer,” which assessed the feasibility of using CNT as a filler for lightweight spacecraft structures.

CNT has strength and stiffness properties several orders of magnitude larger than steel and conductivity superior to copper.

Also presenting the case for CNT was Marta Martins from Portugal’s Institute of Mechanical Engineering and Industrial Management (INEGI), who discussed, “Processing of carbon nanotube buckypaper/epoxy resin matrix nanocomposites”.

Martins described a new approach that the institute has used to produce highly loaded CNT nanocomposites by infiltrating CNT skeletons with an epoxy resin, which produced a CNT loading of more than 15wt% resin. The promising results may eventually lead to the production of high performance structures, with good thermal and electrical conductivity, based on CNT material.

Cost savings

All ears were primed as Kevin Breese, advanced purchasing manager for the fabric care line of Electrolux Major Appliances, presented, “Holistic cost savings: a performance/component-cost evaluation of thermoplastic-performance filler composites”.

Breese explained: “A total cost model for the complete filled polymer process, from material sourcing to forming the part, has been constructed.” The total cost model is based on volume and volume fraction of materials and compounds used, rather than using mass costs of materials – which has tended to be the norm.

Holistic cost attempts to account for all aspects of polymer processing and property variation with filler content. Illustrating this, Breese outlined the method of calculating part cost, which uses compound cost (material and compound) plus injection molding costs.

Breese believes that holistic cost can be used to “look for savings and new direction of materials” – a model that may well become very popular during the course of the current downturn.

The latest research in magnesium hydroxide flame retardant fillers will be presented by Dr Guenter Beyer, of Kabelwerk EUPEN AG, at IM’s MagMin 2009 conference, 10-12 May 2009, Amsterdam. See p.14-15.