Technology Trends: Additives

Promise of compounds containing nanoclays becoming reality?

Nanocomposites have been the Next Big Thing in the plastics industry for several years now. What has been lacking in all that time is the killer application to prove out the hype.

W hat has appeared instead is a slow trickle of relatively modest applications, mostly in automotive, along with a realization that the best way forward for the technology may be through ''hybrid'' compounds that contain nanofillers—minerals, mostly clay but also talc and others—and conventional fillers.

Because they are so small, nanofillers have a much larger surface/volume ratio than more conventional additives, so any mechanical property enhancements they provide through surface effects can be achieved at much lower addition levels. But it takes a lot of know-how and expertise to disperse and distribute nanofillers in the compound.

This at least partly explains why various players in the development chain are working together more closely than they have in the past. Typical examples are PolyOne''s strategic alliance with Nanocor, which has yielded Nanoblend concentrates and, more recently, Maxxam LST compounds; and collaborative work involving polymer supplier Basell, additive supplier Southern Clay, and end-user General Motors, that has led to the world''s largest applications for nanocomposites. In all cases, the host polymers are polyolefins.

Here is a not-untypical claim by PolyOne (Cleveland, OH) for Maxxam LST: "Compared with many other engineered materials...Maxxam LST compounds require lower processing temperatures, flow easier and cool faster. As a result, with Maxxam LST compounds, customers often use less material, improve cycle times, and lower their energy and equipment costs."

Applications targeted by PolyOne and others include auto interior and exterior trim; small appliance and power tool housings; packaging liners, containers and closures; pipe, conduit, fittings and fascia used in construction; and consumer goods.

Maxxam LST nanoclay compounds are said to offer a combination of light, stiff, and tough attributes and are designed to meet or exceed the capabilities of many engineered thermoplastics, while offering the processing advantages that are inherent to polyolefins.

"We have enhanced the exfoliation process [for separating individual leaflike particles that tend to cling together in stacks], which has enabled us to maximize the performance of the product and make it easy to use," says George Zollos, nanocomposites market development manager.

"This is a significant accomplishment, in that early industry efforts to compound and process nanopolymers failed to achieve significant property improvement and were extremely difficult to process due to improper exfoliation."

GM leading the way

The 2005 version of the Hummer H2 SUT truck is the latest vehicle in General Motors'' lineup to incorporate nanocomposites. Its cargo bed uses more than 3 kg of a Basell compound for its trim, center bridge, sail panel, and box rail protector. H2 program Engineering Manager Bill Knapp says GM designed the vehicle to use the nanocomposite parts for their low weight and dimensional stability.

GM introduced the first commercial automotive exterior application of nanocomposites on the step assist of the 2002 GMC Safari and Chevrolet Astro vans. This January, they debuted on the body side molding for the 2004 Chevrolet Impala. GM is now using about 660,000 lb of nanocomposite material per year, which is the highest volume of olefin-based nanocomposite material used in the world.

"The virtue of using a nanocomposite for automotive applications is that less filler material is required to provide the same or better performance characteristics when compared to conventional materials," says Will Rodgers, staff scientist at GM Research and Development. "Our next applications will be in exterior claddings, interior parts, and in non-support trim."

GM has an exclusive development agreement with polymer supplier Basell USA Inc. and nanoclay supplier Southern Clay Products Inc. (SCP; Gonzales, TX). The parts are molded at Sport Rack Automotive (Sterling Heights, MI). SCP provides Cloisite nanoclay.

Karl Kamena, commercial manager for Cloisite nanoclays at SCP says: "While it may seem a rather modest objective to replace a conventional talc TPO with a nano-TPO, the GM approach was designed to encourage the development of nanotechnology one ''nanostep'' at a time. Rather than targeting ambitious, breakthrough, order-of-magnitude improvement in polymer performance, the objective was to get started. Get a nano-TPO into a commercial application and on to a car."

Nanova LLC (North Huntingdon, PA), a production company spun off from nanotechnology developer Nanomat Inc., is building a demonstration plant for its Nanotalc surface-modified nanotalc. It says the filler should improve barrier and other physical properties such as scratch resistance, stiffness, and toughness. Surface area/volume ratio is close to 25 times greater than normal talc. The company expects applications in moldings and film applications.

Nanomat boasts that it can manufacture "virtually any nanomaterial that you may require—all custom-made to your specifications. Any size, any distribution."

Hybrid approach paying off

Henrik Eriksson, development manager for compounder Polykemi AB in Ystad, Sweden, says business for its Scancomp polypropylene-based nanocomposites (March 2003 MPI) "is progressing just fine." He says the most successful example of commercialization of these grades is the inner door handle for the "smart forfour" saloon made by DaimlerChrysler. Grade used is PP BN140T5, which contains nanofillers to increase performance and conventional fillers to keep the price down.

Eriksson says all grades traditionally used for automotive interiors that had been tried for the door handle had fallen short of requirements.

"Immediately on testing of the nanocomposite it was seen that previous problems with sink-marks and poor surface had disappeared. The combination of superior scratch resistance, excellent impact strength and low weight were also especially appreciated."

Eriksson says Scancomp is also finding use in several (unidentified) products such as medical devices for dental treatment and household equipment. And the company has developed nylon-based nanocomposites for single-layer automobile fuel tanks, where the key advantage is their high barrier to hydrocarbons. "Replacing a seven-layer material with a Scancomp nanocomposite has obvious cost benefits," says Eriksson.

"The development of the fuel tank is near a breakthrough. When it comes to tanks for personal cars we still need to balance some antagonistic properties to fulfill all the requirements. We are confident in succeeding in this effort." Eriksson cannot say exactly what the cost savings may be.

"It seems obvious, however, that a thermoplastic compound with its comparably simple production, moderate raw material costs, and flexibility regarding the final molding technique makes an economically superior alternative to multilayer technology."

Eriksson concedes that the number of commercial applications is still restricted to a handful. "As all the technical benefits become widely known, we think that the orders will multiply.

"An important factor is also the volumes for the expensive nanoclay raw materials. As these increase, their prices will fall, with consequent impact on final composite costs. Rumors have it that Chinese suppliers are also entering the market. This may be making way for a pricing of nanoclay that enables the large-scale market penetration for nanocomposites that has been anticipated for [so] long."

A. Schulman Inc. has a similar philosophy to Polykemi. It, too, is developing compounds containing combinations of nanofillers and more conventional fillers. "The simple approach is not working," says one of the company''s managers at its European headquarters in Wurselen, Germany, referring to the slow take-up of "pure" nanocomposites.

He notes, for example, that pure nanocomposites do not provide sufficient flame retardance for many electrical applications and so addition of specific flame retardants is still necessary. The company is said to be close to obtaining contracts for technical moldings using some of these new compounds. PM

Getting through to processors

Nanoparticles in high-performance plastics and the methods of processing them were discussed at the "Nanotechnology in Plastic Materials" conference at the Wurzburg-based South German Plastics Center (SKZ) earlier this year. What became apparent was that the processing technology, as well as the still unresolved issues surrounding the measuring techniques for quality controls, tend to be a source of confusion for medium-sized plastics processors. Some processors are simply not fully convinced of the advantages of crossing into nano territory. On top of that, there''s the cost to consider: special nanoparticles already cost roughly $100/kg; additives for scratch-resistant, antistatic, transparent coatings go for as much as $1000/kg.

Contact information

A. Schulman
Southern Clay Products

Transition from lead is swifter than predicted

Tin will remain the PVC heat stabilizer of choice in North America. Elsewhere, the transition from lead is happening faster than many anticipated.

PVC suppliers are ahead of their own schedule for phasing out lead stabilizers. In a bid to pre-empt legislation banning the heavy metal for environmental, health, and safety reasons, the industry voluntarily pledged to cut its use of lead stabilizers (based on 2000 consumption levels) 15% by 2005, 50% by 2010, and 100% by 2015, and move to leading alternatives calcium/zinc (Ca/Zn) or organic stabilizers.

But the transition is happening faster, and not only in Europe, says Michael Calicchio, global business manager for plastics at additives supplier Honeywell (Morristown, NJ). He predicts that by the end of 2004 more than 20% of PVC processed in Europe will include Ca/Zn stabilizers, exceeding 80% by 2010. Honeywell supplies lubricants to help extruders make the transition without losing productivity, and will reveal new developments for Ca/Zn stabilized compounds at the K show this October.

In North America, tin stabilizers were the best alternative in the 1970s as lead ones were phased out there. How the transition in Europe plays out for those active in both markets—will a Chinese processor shipping product to North America and Europe use a single stabilizer or one for each market?—has yet to be determined, say observers.

Additives supplier Crompton (Greenwich, CT) has tin, Ca/Zn, and organic stabilizers, but outside North America it is betting on the success of its OBS organic types, says plastics additives VP Sean O''Connor. Crompton is trying to drive down the cost of their use, something that has been a decided drawback (July 2002 MP/MPI). O''Connor says OBS grades are only slightly more costly to use than lead and often cost less to use than Ca/Zn, depending on the application. "We think OBS, especially for rigid applications such as pipe, offers great potential." Crompton estimates the lead heat stabilizers market is currently worth about $580 million.

Crompton is also developing OBS grades suitable for use in flexible PVC and in PVC injection molding compounds, and is looking beyond Europe. Connor says the firm has already had success in South America, and is now strongly pursuing the Asian market.

Beyond material transitions

There has been a surge of M&A activity among suppliers. Early this year the German subsidiary of Chemson AG (Arnoldstein, Austria) acquired Allstab (Duren, Germany), making Chemson Europe''s largest PVC stabilizer supplier with over €200 million in annual sales (some €60 million coming from Allstab).

Then in June, Chemson formed a strategic alliance with Akcros Chemicals (Roermond, Netherlands) for flexible PVC solid stabilizers. Chemson took over Akcros'' production, while Akcros does sales and marketing. Chemson once made OBS organic stabilizers under license from Crompton. Crompton officials decline to say whether that agreement continues.

In the spring, Reagens SpA of Bologna, Italy and Singapore-based Sun Ace Kakoh Pte. Ltd. acquired the PVC stabilizers business of Cognis (Dusseldorf, Germany). That purchase will help both further their Ca/Zn stabilizer programs and strengthen Reagens'' market presence in Northern Europe. MD

Penny-pinching with dispersants can backfire

Cutting costs by scrimping on important additives is false economy, say suppliers.

An increasing number of injection molders feel they can save on dispersing colorants for thicker-walled applications by using cheaper imported pigments from Asia, and stearates instead of waxes. But Reiner Hess, head of application technology, Clariant (Gersthofen, Germany) cautions: "Many dispersing agents on the market today, are unfortunately, only price driven. Major sectors in the processing industry are looking to save money and you can''t blame them when their profits are squeezed. But the tendency to cut corners on the quality of pigment, additives, or dispersing agents could result in more product problems than money saved."

As the wall thickness of injection molded products continues to diminish, Hess believes molders will have to pay closer attention to how color masterbatches are dispersed. In packaging films, especially biaxially oriented polypropylene (BOPP) in the 10 to 14 µm range, the market is moving in the opposite direction, with more attention being directed to dispersion quality to ensure color yield, he says.

Mid-sized color masterbatchers are more particular about quality today than in the past, says Isolda Bachert, end-use manager at rival additive supplier BYK-Chemie (Wesel, Germany) because they are under pressure to avoid taking back masterbatches that don''t meet customer standards. She says by upping quality, masterbatchers should be able to target value-added markets and obtain better prices for their product.

The main market for dispersing agents remains colorants, especially organic pigments, which tend to be difficult to disperse, but the agents are also used for other poor dispersing additives such as anti-stats and surfactants.

Organic pigments tend to form agglomerates, and the higher the pigment concentration in masterbatches, the more likely the formation of more and larger agglomerates. Dispersing agents wet the particle surface, help break up agglomerates through mechanical energy in the barrel, and stabilize the particles to prevent re-agglomeration.

Several exhibitors at K 2004 will show advanced products for color dispersion aimed at high-end markets. Clariant has three, two of which are polypropylene waxes made using metallocene catalysts. Hess says that unlike Ziegler-Natta waxes, catalyst ash levels are so low that the company can eliminate residue filtering, thereby producing a cleaner more efficient product for the masterbatcher. "The masterbatcher can also create a more tailor-made molecular-weight distribution than before. This results in better wettability and more surface penetration," he says.

Although masterbatchers may already be able to test these products, they probably will have to wait until Clariant finishes its production-scale plant in Frankfurt in 2006 before they get commercial quantities.

BYK-Chemie is tackling the dispersion market with products that are neither low-molecular-weight waxes nor stearates, says Buchert. Although it has a history in dispersants for paints and thermosets, BYK is a new entrant to the thermoplastics field. At K 2004, the company introduces three grades of Disper Plast, a proprietary polyolefin copolymer-based dispersant which has no lubricating effect, unlike a wax in the barrel. This better overcomes binding forces between pigment particles, Buchert says. Compared to waxes, these powders are said to provide better color strength.

Markus Weimann, in Degussa Goldschmidt''s technical services department (Essen, Germany), says his company''s Tegomer P141 polyolefin wax includes polyacrylates with hydrophilic and hydrophobic groups to improve dispersion. The hydrophilic part integrates with the polar surface of the organic pigment, while the hydrophobic element provides a compatibilizer with the polymer matrix, which prevents re-agglomeration during masterbatch production. RC

Contact information

Clariant Gmb
Degussa Goldschmidt AG

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