uct. In the automotive market, com-panies are developing newpolypropylene copolymers toincrease their impact resistance forapplications such as car bumpers."Each time a process is changed ora new product is developed, it isimportant to check the microstruc-ture of the resulting polymer," hesays.The individual polymer chains ofpolyolefins typically have differentdegrees of polymerization. Thusanalysis of the molar mass distribu-tion of polyolefins is important.Polymer Char's polyolefins-dedicat-ed Gel Permeation Chromatograph(GPC-IR) offers fully automatedsample preparation and filtrationwith optimum infrared detection fordetermining concentration and com-position. The chemical distributionof copolymers can be analyzedusing the company's CRYSTAF orTREF instruments. For even moredetailed polyolefin analysis, theinterplay of molecular and chemicalcomposition can be examined withthe Cross-FractionationChromatograph (CFC) instrument,which combines Temperature RisingElution Fractionation (TREF) andGPC to provide highly detailed 3-Dbivariate distribution analysis.Monrabal says that the company'sanalytical instruments have beentraditionally used in R&D labs, butthat Polymer Char has recentlystarted making instruments for qual-ity-control applications in manufac-turing plants. This year it will intro-duce new instruments designed formanufacturing plants, particularlyfor the analysis of xylene solublesin polypropylene-manufacturingplants and for measurements ofintrinsic viscosity. These instru-ments perform the same types ofanalysis as the company's otherinstruments but in a robust, faster,and simpler-to-use package. "I thinkour contribution in this area will besignificant," Monrabal says.Automotive PlasticsMaterials used in the automotivemarket must meet several require-ments, depending on the applica-tion. Automotive materials have tocomply with specific safety and per-formance standards as well asmatch the consumer's perception interms of design and quality. IntertekGroup plc tests, certifies, and char-acterizes materials and products in avariety of industries, including auto-motive plastics. "Intertek can inde-pendently investigate, test, and ana-lyze materials during the earlystages of development, so that mate-rials are qualified before they moveto the next part of the automotivepolymer value chain," says MorrisGeissler, director, AutomotiveIndustry, at Intertek. This meansthat manufacturers know at a veryearly stage that the material willmeet the requirements for an intend-ed application.Recently, Intertek assistedPolyscope Polymers B.V. by pro-viding extensive laboratory supportfor development of automotivematerials for use in car interiorparts, such as the dashboard carrier.Polyscope decided to develop animproved range of styrene maleicanhydride (SMA) products calledXiran® after Nova Chemicals dis-continued production of its Dylark®SMA engineering resins, importantmaterials for dashboard carriers andother car components. "Polyscopehad the material expertise, and weassisted them with their activities tofine-tune the material so it couldmeet the requirements of the auto-motive market" Geissler says.Intertek performed physical andchemical analyses such as shrinkageand impact resistance testing, whichhelped Polyscope achieve the prop-erties it required from the material.For example, a carrier must with-stand external impact and achieveoptimal assembly characteristics. "In the automotive business, sus-tainability, comfort, and design aredriving innovation," Geissler says."Cars need to be lightweight toreduce carbon emissions." It isimportant to investigate the weightand performance characteristics ofnew materials to make sure theyperform the same as, or even betterthan, currently used materials. Asthe application of new automotivematerials-such as composites-grows, Intertek is extending its lab-oratory, processing, and knowledgecapabilities to study these materials."These innovative materials arewww.4spe.org | OCTOBER 2011 | PLASTICS ENGINEERING |11Polymer Char specializes in instrumentation analysisof polyolefins.
12| PLASTICS ENGINEERING | OCTOBER 2011| www.4spe.orgstronger and more resistant toimpact, so specialized equipmentand expertise are needed for charac-terization," Geissler says. Failure AnalysisWhen a problem with a plastic partarises-whether experienced by theconsumer or noticed after a part ismolded-it is important to analyzewhy the failure occurred. Failureanalysis can also be used to antici-pate problems or to find out whyprototype parts may have failed.The Madison Group in Madison,Wisconsin, USA, provides failureanalysis for plastics. Engineeringmanager Jeffrey A. Jansen says thatcompanies sometimes think theydon't have the time or resources forfailure analysis, but a scientificapproach to addressing a problem ismore cost- and time-effective thanguessing at the problem and tryingsolutions that might not work.During an analysis, engineers fromthe Madison Group aim to find outboth how and why a failureoccurred. In general, five factors areinvolved in failure: material, pro-cessing, design, installation, andservice conditions. The company begins an analysisby gathering backgroundinformation on the failedcomponent, such as howthe part was made andits service history. Theythen perform a visualexamination, checkingto see if the failure ishappening in the sameplace on all the parts orwhether discoloration ispresent, for example.Microscopic analysis isused to examine thefracture surface, whichshows how and where a crack beganand where it spread.Analytical characterization of thepolymer's molecular weight, com-position, and mechanical propertiesis required to understand why thefailures occurred. "Ideally we cancompare the characteristics of afailed part to a control that didn'tfail to show if some type of degra-dation, contamination, or materialanomaly was involved," Jansensays.All this information is used topiece together the primary cause ofthe failure as well as other con-tributing factors. "It is usually notjust one factor; usually two or threethings overlap," Jansen says, "par-ticularly if only 0.1 percent of theparts made are failing." For exam-ple, consider a part with sharp cor-ners and notches that focus forces.During molding, molecular degrada-tion occurs that compromises thematerial. Then during use, it under-goes strong impact. The failurewouldn't have happened if any ofthose things weren't present-thesharp corners and notches that con-centrate the force, the compromisedmaterial, or the strong impact dur-ing use. Viscoelastic MeasurementsTimothy A. Cassell, national salesmanager for rheology and solid sur-face analysis at Anton Paar USA,says there is a wider range of addi-tives on the market today for use inplastics. "With each additive it isimportant to characterize the materi-al. The goal is to understand howthe product will behave under man-ufacturing conditions and underSometimes the site of a failure is obvioussuch as in the plastic pipe on top.However, a closer look with microscopy(above) can reveal where a crack began.The Madison Group.A processed real-size automotive com-ponent for material characterization.Intertek.