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ered as protective material for compo-nents essential to public safety.In terms of bodily safety-on thebattlefield and in civilian life-improvements continue to be made interms of protective armor that resistshigh impact and flame. PBIPerformance Products of Charlotte,N.C., has produced polybenzimida-zole fiber and Celazole PBI polymerfor nearly three decades to protect sol-diers, fire and rescue personnel, andpetrochemical workers.Of course, novel projects like theU.S. Defense Advanced ResearchProject Agency's plastic-like "blackpolymer ice"-a synthetic slipperycoating unveiled in a 2007 proposalthat could used to reduce an enemy'straction in hot climes (like those inAfghanistan and Iraq)-will continueto draw mainstream media interest.Less widely discussed but vital areintensive studies such as supersonicrain erosion tests being prepared bythe U.S. Air Force ResearchLaboratory (AFRL) that will subjectplastics-based components to precipi-tation at speeds up to Mach 2 toexamine durability.Responding to NeedPBI fiber provides a classic study inhow a newly discovered technologycan suddenly find a use in safeguard-ing human lives. PBI was synthesizedby Dr. Carl Marvel in the late 1950sand refined in 1961 to exploit thepolymer's thermal stability. The deathsof astronauts Virgil Grissom, EdwardWhite, and Roger Chaffee in a flashfire during a launch-pad test on Jan.27, 1967, made clear the need formore flame-retardant material in thecommand module and astronautflight suits."If you find a polymer that doesn'tmelt, much less burn, it's commercial-ly very unfeasible because you can'tmold it into any shapes or extrude itinto any forms," says WalterLehmann, senior vice president ofsales and marketing for PBI and a vet-eran of more than 20 years as an engi-neer of resins. "But that NASA inci-dent did inspire both the engineers atNASA and the Celanese polymer sci-entists to look at some way to possiblyconvert this polymer into somethingfunctional, and indeed did figure outhow to spin it into a fiber (in researchconducted throughout the 1970s)."With the majority of PBI's fibersbeing used in firefighting gear, thecompany is seeing a rapid growth indemand from police units around theworld and gearing up to meet thatdemand. "In many countries, policeand military are one and the same,"Lehmann notes. As the August riotsin London demonstrated, police crews"need not only something that's com-fortable but something that's flame-resistant."PBI's flexibility is likely to offersafety options down the road, addsPBI's Mike Gruender, whose marketsare primarily compression-molded bil-lets from which machine parts aremade for industrial applications."We've delved into [larger applica-tions for thin coatings]. We do have avery high-temperature material, andthere are a number of chemicalprocess industries-oil and gas in par-ticular-where they're looking forhigher-temperature coating materialsto line pipes with. It's still a littleearly; getting good adhesion and suffi-cient thickness for the lifecycle expec-tations of the product are challenging.Their applications are fairly limitedright now but can offer electrical insu-lation, thermal insulation, chemicalprotection for steel, copper, and alu-minum. We're developing wire coat-ings with the material right now, butwe don't have any commercial appli-cations (yet)." The Science of Safety"There's been more in terms of appli-cation in terms of making polymersintrinsically tougher than there hasbeen in making polymers that canheal themselves, but there has been alot of work in the latter in the labora-tory," notes Michael R. Kessler, PhD,with the Department of MaterialsScience and Engineering at Iowa StateUniversity in Ames, Iowa, USA."There have been a lot of researchpapers, but not a lot of self-healingmaterials have transitioned from thelab scale to actual application."In terms of making materialstougher, "that's continually happen-ing," he says. "One area is in theblock copolymers-polymers thathave multiple polymers attachedtogether and phase separate to create amorphology that has a lot of energy-absorbing capabilities."Composites-using conventionaland nanoscale reinforcement-arealso an area of significant develop-www.4spe.org | OCTOBER 2011| PLASTICS ENGINEERING | 29miller-stephensonchemicalcompany,inc.California-Illinois-Connecticut-Canada203743.4447Fax203791.8702e-mail:support@miller-stephenson.comwww.miller-stephenson.commsPERFORMANCEPTFERELEASEAGENTS/DRYLUBRICANTSMiller-StephensonspecializesinPTFERe-leaseAgents/DryLubricantsthatcreateasuperiorreleaseforplastics,elastomers,andresins-includingacrylics,urethanes,rubber,nylons,epoxy,polycarbonates,andpoly-styrene.Thisfamilyofreleaseagentsisdesignedtogivemultiplereleasesbetweenapplications!Nodiscernibletransfer.Nomigration.Containsnosilicones.msReleaseAgentDryLubricantMS-122ADFortechnicalinformationandsamplecall203-743-4447

30| PLASTICS ENGINEERING | OCTOBER 2011| www.4spe.orgment of tougher plastics and poly-mers."We had a paper published abouttwo years ago where we added carbonnanotubes that were functionalizedinto a polydicyclopentadiene matrixthat showed a 900% increase in thetensile toughness by adding less thana few percent of modified carbonnanotubes," Kessler notes.Polymer synthesis has facilitated thecreation of heretofore hard-to-producecomposites, thanks to the recentlydeveloped ruthenium catalyst thatpolymerizes that polymer, he adds.Polydicyclopentadiene "is a materialpolymerized by a ring-openingmetathesis polymerization that onlyreally was done in the late '90s whenthe Grubbs catalyst was developed,"Kessler explains. "That polymer isreally tough. It's a crosslinked ther-moset polymer. You can shoot a bul-let, and it may just get lodged into athick block of that thermoset. It's alsogot good toughness at lower tempera-tures, so it's used in snowmobile cowl-ings and hoods or parts of machinerythat used to be made out of maybe afiberglass composite, but now it's justmade out of a pure polymer becausethe polymer's tough enough and theycan make it without needing the fiberreinforcement." Meantime, the U.S. Army is doinga lot of work in composite armor,Kessler notes. "These are very com-plex composite systems that includeceramic tiles and polymer compositesand adhesives between the tiles tohave function where they can absorbhuge amounts of energy from a ballis-tic impact but be light enough to be adeployable force, (for example) a tankthat can be flown in an airplane."With self-healing polymers, "interms of applications there's beenmore in the area of coatings that healfrom a scratch," he says.One of Kessler's priorities is civilinfrastructure, primarily repairingsome of the thousands of miles ofaging pipeline crisscrossing the U.S."The traditional way to repair apipeline is to take that pipe offline,"Kessler notes. "The damaged sectionis cut out, and a new section is weld-ed into the spot. What we've devel-oped are external composite wraps.You can restore the structural integrityand strength of the pipeline."Some of the same technology isapplied to bridges and docks, hepoints out, with crews retrofittingdeteriorating infrastructure. Supersonic StrengthThe U.S. Department of Defense(DoD) has assembled so-called ero-sion working groups and indicatedthe need for a test facility for super-sonic rain erosion testing. Before thisyear, the only means of such testinghad been the "rocket sled" atHolloman Air Force Base in NewMexico, says Mike Spicer, programmanager for the AFRL's coatings lab."That's a very expensive test,"Spicer says. "They needed a less-expensive test facility that can weedout some of the poor polymer per-formers prior to going to the rocketsled."Using a Small Business InnovativeResearch program, the AFRL devel-oped a one-of-a-kind prototype fortesting materials against raindrops attwice the speed of sound. Such testingis primarily intended to evaluate thedurability of the leading edges of air-craft, "whether it's fixed-wing aircraft,missiles, or rockets," Spicer notes. "It'sjust about anything that could seerain droplets at supersonic speeds."The AFRL soon will develop a testprocedure and evaluate a number ofmaterials. "The main thing we test iscoatings: organic coatings or inorganiccoatings," he says. "Some of the sub-strates are polymers such as canopies,windshields, and things of thatnature."Prior to venturing into supersonictesting, the AFRL had engaged inplenty of subsonic testing-up toabout 650 mph-"that simulates aone-inch rainfall, and there are somemilitary specifications written aroundthat method." Heal ThyselfIn the early to mid-2000s, Arkemabegan exploring the idea of elastomersMichael R. Kessler