Alloys & blends: the promise remains, but so do the challenges.
Now comes the hard part for alloying and blending technology.
Establishing itself in the late 1980s as a premier field for the development of new engineering thermoplastics, alloying/blending promised virtually unlimited combinations of resins that could target specific market applications while taming the processing difficulties (and prohibitive cost) of exotic polymers.
Alloys and blends widely were predicted to be the dominant force for new material development in the 1990s (see PT, June '90, p. 72) and hailed as a lower-cost alternative to inventing all-new polymer species.
However, the reality for this technology in 1992 shows a different hue. Materials suppliers admit many aspects of resin compatibilization still aren't fully understood or commercially viable, despite the reams of technical literature published in recent years. They say perfecting stable alloy morphologies that can consistently withstand the high-shear/high-throughput rigors of commercial molding and extrusion remains a daunting task, and the time and investment required to successfully develop and commercialize these materials is far greater than previously imagined.
Recent interviews with custom compounders and resin producers indicate a period of quiet, cautious reassessment of the commercial realities now exists for this field. While they agree alloying/blending still has a place in the vanguard of new material development, there is far greater scrutiny given to its cost/performance profile in actual applications. And a host of other factors, including recyclability, will challenge alloys and blends to differentiate themselves from existing single-resin products.
As a result, manufacturers of plastic products will find full commercial deployment of new alloys and blends proceeding at a much slower pace in the 1990s than originally anticipated. Research and development toward new alloys will be strongly driven by market/application considerations rather than the individual polymer technology strengths of a material supplier. And there will be a deeper appreciation of how the "real-world" processing characteristics of new alloys figure in their overall cost/performance equation.
It's also clear alloying and blending technology will not replace future research into inventing all-new polymers or supplant work to optimize existing single-resin grades. What emerges are distinct, parallel technology paths to future material developments, each with a role that is not mutually exclusive of the others.
EXPLODING THE 'LOW-COST' MYTH
The main fallacy concerning alloys and blends has been the notion they are a "low-cost" alternative for developing new materials, compared with inventing entirely new resins. Many materials producers now confess the time, money and technical expertise required to develop a successful new alloy virtually mirrors the commitment necessary to invent a single new polymer.
It's true alloys and blends don't require the heavy capital investment of a new monomer production facility or polymerization unit. However, few materials companies were able to fully anticipate the level of investment required to make this technology a success for the 1990s. The message for processors: It's unlikely there will be any new commodity-priced, engineering TP super alloys in the near future.
Victoria M. Franchetti, director of technology for the Plastics Div. of Monsanto's Chemical Group, recalls that in the 1980s many materials suppliers viewed the field of alloys and blends much like a gold rush: the promise was that anyone could jump in and make a "quick buck." She says it's now apparent "the idea that alloys and blends are anybody's game has been oversold. The suppliers that will survive are the ones that can do the hard work in formulation, understand the structure/property relationship of polymers, and can address specific customer needs. The name of the game for alloys and blends in the 1990s is being applications driven."
"The technology required for alloys is no less complex than what is needed to develop a totally new polymer," says Robert J. Pangborn, business director of blends & elastomers for Dow Plastics. "There was a naivete in the industry several years ago when we thought we could get highly engineered alloyed materials 'on the cheap.' Today we know blends and alloys clearly are not a way to develop new materials 'cheaper.' The key is to have a technology that allows us to make better new materials."
"During the 1980s, there was an empirical blending frenzy," recalls George Niznik, v.p. and director of R&D for LNP Engineering Plastics. "That work was trial-and-error and, for the most part, unsuccessful. In the 1990s, the research work will be much harder and more expensive, as we try to scientifically understand ways to compatibilize resins and create predictable, stable morphologies."
Some executives still see the cost advantages in alloying. "No new material development effort is ever cheap," says John E. Quinn, general manager of Noryl & Ultem Resin Products for GE Plastics. "But the cost risk of developing alloys from existing materials stocks is still less than inventing a new polymer."
Quinn says the true challenge lies not in the economics of alloy versus all-new polymer, but rather in the ability of a material supplier to be agile and astute in responding to customer/market needs while reducing the new-product development cycle--and many other materials producers agree. Quinn says the goal for GE in the 1990s is to reduce its product cycle time for all new commercial resins by 50%, developing new materials for customers in one to two years rather than three to four.
DIRECTIONS FOR THE '90s
New alloy and blend development for the rest of the decade is expected to fall into these three categories, according to Niznik of LNP:
* Upgrading lower-cost "commodity" resins like PVC and PP. This would create cost-effective alternatives to engineering resins that could compete for niche applications and fill market gaps. As an example, many producers are developing olefin/nylon alloys, which seek to replace higher-cost, "overengineered" polymers in a variety of applications.
* Enhancing properties of engineering thermoplastics. One key current theme is to match the respective benefits of amorphous and crystalline resins in a single material. An example is combining chemical resistance with low shrinkage and good dimensional stability.
* Making higher-performance engineering polymers more cost-competitive. By "diluting" or extending high-cost/high-performance resins with a lower-cost partner and improving the high-tech resin's processability (usually meaning lowering viscosity), new alloys could be used in larger parts or higher-volume applications. However, Niznik points out the addition of a lower-priced resin as an alloy partner doesn't necessarily offset the costs associated with grafting and compatibilizing.
In pursuit of these goals, the main challenges will be to develop more "robust" polymer alloy morphologies with expanded processing windows; create a wider selection of compatibilizing agents; and maintain a competitive cost/performance profile. More long-term test data from materials suppliers, which documents both the processing characteristics and end-use performance properties of new alloys, also is cited as necessary for future growth.
Pangborn of Dow says alloys and blends in the 1990s will have to overcome the "bad rap" of being "touchy" materials that are difficult to process. The hurdle for the future is developing new alloys and blends with a consistent, stable morphology that doesn't "unravel" or phase-separate under industrial molding conditions (a "robust" morphology) and offers greater lot-to-lot consistency. Nearly all material suppliers say a common error in recent years was to trumpet the success of a new alloy or blend based mainly upon its performance under laboratory test conditions. They admit many of these lab grades were unable to withstand the high-shear, high-pressure, rigors of commercial molding into complex-shapes.
Dan Kelly, business manager for GE Plastics' Cycoloy PC/ABS alloy line, agrees, adding that processors in the future will see alloying and blending technology that provides better yields of good parts, less scrap, improved flow, faster cycles, and ultimately lower per-part manufacturing cost. "The overall processing window for processors is given as much consideration as anything when we're developing new alloys," Kelly says. "That's a standard part of our product development cycle."
Nancy C. Eickman, technology manager for the High Performance Polymers unit of Hoechst Celanese, says the concept of creating new high-performance engineering thermoplastics through the synergy of two medium-performance resins has been greatly oversold. Using alloy technology to enhance the processability and lower the cost of high-end thermoplastics will be the primary challenge for the 1990s, she says.
Accordingly, her company is conducting research on potential alloys of its Vectra liquid-crystal polymer (LCP) and Fortron polyphenylene sulfide (PPS). In its self-described "conservative" approach toward alloys and blends, Hoechst Celanese says it seeks to concentrate first on extending the limits of existing single, engineering resins.
Robert A. Weiss, associate director of the University of Connecticut's Institute of Materials Science, says much work still remains to be done in order to fully optimize polymer compatibilizers and to understand the science of alloying at the molecular level. Weiss says materials suppliers are now just beginning to grasp the underlying mechanics of polymer compatibility and the structure/property relationship of a robust, predictable morphology (see PT, Feb. '89, p. 60).
However, existing compatibilizers, such as styrenic diblock copolymers, ionomers and maleated resins, still require substantial technical improvements, he says. They remain very expensive, technically complex materials, and often must comprise a relatively large percentage of the overall alloy mix (up to 10% or more) in order to work properly, he explains. The reason for this "overkill" is that many dynamics of polymeric compatibilization cannot be controlled precisely, requiring a surplus of compatibilizer in order to get the necessary amount at the molecular interface where it's needed. Compatibilizers also tend to increase the viscosity of the overall blend, usually making the alloy more difficult to process.
Paraloid EXL-4151, a new polyglutarimide copolymer from Rohm & Haas, is among the new breed of compatibilizers, specifically engineered for that purpose rather than adapted from another use, which hold the promise of alleviating some of the former difficulties. Company officials say EXL-4151 demonstrates the ability to compatibilize nylon 6 and polycarbonate, as well as nylon 6 and ABS, using either single- or twin-screw extruders. It incorporates acid and anhydride functionalities that react spontaneously with nylon and are miscible or highly compatible with resins like ABS and PC.
This one product development illustrates two factors that together could be important trends for the future. One is off-the-shelf availability of compatibilizers that, according to Rohm and Haas, can simply be dropped into a compounding extruder together with the resin blend components and result in materials comparable to current commercial alloys. Second and equally important, suppliers of compatibilizers will, like Rohm and Haas, have their own extensive background of knowledge of what the compatibilizer can do and how to achieve good results with it in different blends. Those two factors together could in future significantly lower the hurdles for a compounder wishing to develop new commercial blends.
As suggested by Rohm and Haas' latest development, materials suppliers agree that "functionalized" resins, which incorporate "in-situ" reactive end groups grafted onto their polymer chains will be the leading alloy technology in the 1990s. In functionalized resins, the respective compatibilizing agents are grafted or built into the structure of the alloy partners through reactive extrusion. These graft copolymers, in effect, become their own compatibilizing agents, "locking in" a desired morphology while eliminating the need for additional compounding steps.
Franchetti says Monsanto's Triax 1000 is an example of a "true" molecularly engineered alloy. She explains that a functionalized styrene acrylonitrile (SAN) is prepared by forming a terpolymer containing a designated number of maleic anhydride sites and reactively extruding it with ABS and nylon. Highly miscible with the ABS, the functionalized SAN compatibilizer reacts to form a graft between the maleic anhydride sites and the amide groups in the nylon, forming a chemically bonded alloy. The result is a true synergy between the polymer components, as evidenced by notched Izod impact resistance of the blend that is three times greater than ABS and nine times greater than nylon.
Franchetti states functionalized alloys, while encompassing several technical approaches, involve three primary elements: a skill base in extrusion chemistry; ability to develop, or access to, functionalized polymer molecules or precursors; and a comprehensive understanding of the relationship between blend microstructure (morphology) and both processability and end-use properties.
Susan Ward, a technical director for ComAlloy International, says functionalized polymers represent one of the major benefits of her firm's relationship with its corporate parent and resin supplier Exxon. George H. Senkler, technical director of engineering polymers for Du Pont, says his firm's major alloying thrust will continue to be functionalizing thermoset rubbers as a dispersed phase to toughen functionalized nylons and polyesters. Senkler notes, for example, that a controlled degree of immiscibility serves as the key force to determine the size of rubber domains and their placement in the thermoplastic matrix.
Another alloying technology that continues to spread across a wide range of polymers--thermoplastics and thermosets--is interpenetrating polymer networks or IPNs (see PT, Aug. '85, p. 57). Dr. Kurt C. Frisch, professor of polymer engineering at the University of Detroit (Mercy) and the president and director of research at Polymer Technologies Inc., a subsidiary of the University, says numerous resin producers make use of IPN technology, though the fact is often secret or unannounced.
A typical IPN profile is the alloying of a glassy polymer and an elastomer, such as in certain grades of Shell Chemical's Kraton thermoplastic rubber alloys. Modar, a thermoset acrylic/polyurethane alloy from ICI Acrylics, St. Louis, used for body panels in the Chrysler Corp.'s new Viper sports car, is another example of an IPN. LNP has produced a variety of thermoplastic/thermoset IPNs, combining thermosetting silicone rubber with a number of nylons, acetal, ABS, PBT, PP and polyetherimide (GE's Ultem).
Frisch says the technology involves bonding two or more resins through reactive extrusion or a reactive molding process such as RIM, which creates a molecular structure much like the interlocking links of a chain. The phases of the resin remain distinct, lacking covalent bonds, while enhancing mechanical properties.
RECYCLED RESIN: VIABLE FEEDSTOCK?
There is a wide variety of opinion on the question of post-consumer/post-industrial resin recycling and the impact it will have on alloying technology. There are two separate components to the issue: the viability of recycled resin as a potential feedstock for alloys; and whether alloyed and blended materials can be as readily segregated and reprocessed as single polymers.
Some firms, like Allied-Signal Inc., already embrace the post-consumer recycled resin feedstock stream. The company says it's launching a new resin line known as "Impact," consisting of PET/PC alloys that will contain up to 80% total recycled content (PT, March '92, p. 33).
Suppliers such as Ferro Corp. see recycled resins as a potential solution to softening the high cost of specialized resin alloys, says technical director Deen Chundury. Others, such as Du Pont, wonder whether mixing of various polymers will only complicate and add cost to the already delicate process of identifying and separating different materials for recycling.
Du Pont's Senkler observes recycled materials clearly will have some future role as a feedstock that can be modified to add value to alloys and blends. But that role may be limited as he also notes end users seem to be consolidating their choices of resins, looking to simplify material content of components for recycling purposes. "A real question for the 1990s is whether parts made from alloys will be as recyclable as a single polymer system," he says.
Who Will Make Alloys & Blends?
Custom compounders and resin producers acknowledge their respective strengths, and it appears both will continue to compete in this growing field along traditional business lines in the 1990s. The scope of the particular market niches they pursue will depend on the strategy and resources of each material supplier.
"Custom compounders will continue to be a force in the marketplace for new alloys and blends, given their speed of execution," observes George H. Senkler, technical director of engineering polymers for Du Pont. "Compounders often have more market agility than large resin producers and can seek out smaller niches." Senkler adds the strength of resin producers lies in their "wealth of knowledge" in the art and science of alloying. Du Pont is coming on-stream with a new compounding facility in Parkersburg, W.Va., which will spearhead the company's primary alloy thrust--developing toughened nylon and polyester grades.
Besides quick reaction time, independent compounders claim wider freedom to draw on the entire spectrum of polymers as blend ingredients. "As a buyer of resins, we apply our technology after the polymer comes in the door," says George Niznik, v.p. and director of research and development for LNP Engineering Plastics Inc. "Large resin companies are driven by investment in their large production plants and are looking to develop alloys to utilize their existing capacity."
Robert J. Pangborn, business director of blends & elastomers for Dow Plastics, says another strength of prime resin producers is in their ability to work closely with processors and major OEMs to develop materials on the front-end specifications of a program, in order to harmonize design, manufacturing, assembly and end-use variables.
There has been a minor trend in recent years for resin producers and compounders to combine their strengths in the alloy/blend field. One method is through joint ventures, such as Solvay Polymers with Dexter Corp. in D&S Plastics International, Auburn Hills, Mich. Another approach is through outright purchase--such as Exxon buying ComAlloy International, Nippon Steel Chemical acquiring Thermofil, and DSM Engineering Plastics North America Inc. buying the former Wilson Fiberfil plant in Evansville, Ind., from Akzo nv. Still another route is alloying on a toll basis by custom compounders for major resin producers. Examples of the latter include North Coast Compounders Inc., North Ridgeville, Ohio, and Ametek Inc.'s Westchester Plastics Div. in Nesquehoning, Pa., two of the first to offer reactive compounding on a toll basis.
Alloys & Blends: What's the Difference?
While definitions of alloys and blends vary greatly among material suppliers, Robert Schaefer, manager of new business development for the Plastics Div. of Monsanto's Chemical Group, offers one way of distinguishing between the terms.
According to Schaefer, a blend can be characterized as a physical mixture of two miscible resins. The result is a material that offers a compromise of properties (and price) in between those of each "parent" polymer, depending on the percentage of the mix.
An alloy, says Schaefer, is a far more advanced, engineered material containing two or more compatibilized polymers that are chemically bonded in a way that creates properties exceeding those of either individual ingredient (synergy). The result is a controlled, stable morphology with a unified thermodynamic profile.
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|Title Annotation:||includes related article|
|Author:||Gabrielle, Michael C.|
|Article Type:||Cover Story|
|Date:||Jun 1, 1992|
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