Testing of plastics and rubberPlastics and rubbersdevelopment,structureand propertiesPlasticsIn 1861, the first polymeric plasticwas patented for Alexander Parkesunder the name Parkesine. It was akind of celluloid then patented byHyatt in 1870, and in 1908, Bakelandand Lebach made the chemistry ofphenolic resins more transparent.Bakeland then discovered Bakelite,the first plastic to be broadly used,whilst Hermann Staudinger describedthe structure of polymericmaterials as macromolecules andthus discovered the basis of macromolecularchemistry. Ziegler andNatta worked on the polymerizationof ethylene. On this basis,Montedison produced polypropylenein 1957 for the first time.Today, the most important rawmaterial is petroleum which decomposedin its elements supplies thebasic material of plastics. Thesemolecules are linked to large chains:the polymers. When talking aboutplastics one can imagine a mass ofmolecule chains. Depending on howthese chains are linked to each other,different groups of plastic will result:ThermoplasticsThe molecule chains are linear andbranched. Very often a large portionof spaghetti is taken as example.At ambient temperature, thermoplasticsare often hard or even brittle.When heated, the material softensor is given plasticity because themolecule chains slide past eachother more easily. Thermoplasticsare the largest group of plastics. Thefour most important thermoplasticsare PE, PP, PVC and PS.Thermosetting plastics(thermohardening plastics)The molecule chains of thermosettingplastics are linked moreclosely. The cross-links are thermallynot soluble, so thermosetting plasticsdo not melt. The classicalthermosetting plastic material isBakelite, found in early telephonesand of many other commodities.Modern materials are unsaturatedpolyester, linked polyurethanes andepoxy resins.ElastomersElastomers are polymers which arebuilt up of macromolecules andwhich are three-dimensionallycross-linked. The elastic rubberlikeproperties of these materials are theresult of the cross-link of singlepolymer chains (vulcanization).In modern usage, elastomers aretherefore also called rubber.Testing of plasticsCAMPUS (Computer AidedMaterial Preselection by UniformStandards) supplies tested valuesfor mechanical, thermal, electricaland process-specific properties ofalmost every type of plastics. Thelist of rheological, mechanical,thermal, electrical and other propertiesto be tested are standardizedin ISO 10350 (single pointdata). Many material propertiesrequired as construction data arestandardized in ISO 11403(multipoint data). ISO 17282provides details for design data.See: www.campusplastics.comThermoplastic Elastomers Thermosettingmaterials materialsStructure of the molecule chainsSimple chains or Wide-range cross-linked Closely cross-linkedshrub-type ramifications in all directionsProperties Quite soft Molecular structure Hard and brittle Deformable under similiar to a Temperature-resistanttemperature fishing net Non-deformable Deformation process swellable Non-meltableis repeatable rubber-like elasticityTypes of plasticsPolyethylene (PE) Rubber Epoxy resinsPolystyrene (PS) Silicone Polyester resinsPolyamide (PA) Polyurethane Phenolic resinsPolyester PolyurethaneStructure of plasticsSample PreparationInjection molding andcompression moldingTo characterize thermoplastic andthermosetting materials, specimensare made by injection or direct compressionmolding. The applied processingparameters such as pressure,temperature and shear-rate stronglyinfluence the materials behavior.Thermosetting materials: Compression molding (ISO 295) Injection molding (ISO 10724-1)Thermoplastic materials: Compression molding (ISO 293) Injection molding (ISO 294, part 1-4)Multipurpose specimen,ISO 3167The local shear-rate during processingis influenced by the shape of thespecimen. This means that the resultsof specimens with different shapesare not normally comparable.For this reason a multipurpose specimenhas been defined in ISO 3167, which isto be used for a variety of different testssuch as tensile, compression, flexure,creep, hardness and impact.MachiningFor testing semi-finished and finishedparts it is generally required to knowthe materials characteristics afterhaving achieved its final shape.The specimens are then machinedin accordance to ISO 2818 or othermaterial-specific standards.Specimens made of softer materials(e.g. hardness of less than 85 ShoreA), especially rubber, elastomers, softplastics, and specimens made ofthin sheet and film are manufacturedrelatively easily with cutting pressesand special cutting tools. Higherhardness values reduce the life ofthe cutting dies.In particular, the thicker and harderthe specimen is, the more difficult itis to cut. These materials have to bemachined by milling, sawing, planingor blanking. Acrylic safety hood Use of interchangeable specimenmagazines Quick-clamping device formagazines Single-tooth polycrystallinediamond milling cutter for optimalnotching results Connection for external compressedair or nitrogen for specimen cooling Option: Digital measuring stationfor residual width.Standard Spezimen size (LxBxH)ISO179-1 80 x 10 x 4ISO180 80 x 10 x 4ISO8256-1 80 x 10 x 6ASTM D 256 2.5 x 0.5 x 0.125...0.5ASTM D 6110 5.0 x 0.5 x 0.125...0.5ISO179-1(historic)50 x 6 x 4DIN53435 15 x 10 x 1.2...4.6(Dynstat)All dimensions in [mm]Standard Shape A Shape B Shape CISO179-1 single or double notch single or double notch single or double notchISO180 single notch single notch -ISO8256-1 double notch - -ASTM D 256 single notch - -ASTM D 6110 single notch - -SketchRadius of 0.25 mm 0.05 mm 1.00 mm 0.05 mm 0.10 mm 0.02 mmnotch root