Testing of plastics and rubber - Zwick - #4

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4 Plastics and rubbersdevelopment, structure and properties Plastics In 1861, the first polymeric plastic was patented for Alexander Parkes under the name Parkesine. It was a kind of celluloid then patented by Hyatt in 1870, and in 1908, Bakeland and Lebach made the chemistry of phenolic resins more transparent. Bakeland then discovered Bakelite, the first plastic to be broadly used, whilst Hermann Staudinger described the structure of polymeric materials as macromolecules and thus discovered the basis of macromolecular chemistry. Ziegler and Natta worked on the polymerization of ethylene. On this basis, Montedison produced polypropylene in 1957 for the first time. Today, the most important raw material is petroleum which – decomposed in its elements – supplies the basic material of plastics. These molecules are linked to large chains: the polymers. When talking about plastics one can imagine a mass of molecule chains. Depending on how these chains are linked to each other, different groups of plastic will result: Thermoplastics The molecule chains are linear and branched. Very often a large portion of spaghetti is taken as example. At ambient temperature, thermoplastics are often hard or even brittle. When heated, the material softens or is given plasticity because the molecule chains slide past each other more easily. Thermoplastics are the largest group of plastics. The four most important thermoplastics are PE, PP, PVC and PS. Thermosetting plastics (thermohardening plastics) The molecule chains of thermosetting plastics are linked more closely. The cross-links are thermally not soluble, so thermosetting plastics do not melt. The classical thermosetting plastic material is Bakelite, found in early telephones and of many other commodities. Modern materials are unsaturated polyester, linked polyurethanes and epoxy resins. Elastomers Elastomers are polymers which are built up of macromolecules and which are three-dimensionally cross-linked. The elastic rubberlike properties of these materials are the result of the cross-link of single polymer chains (vulcanization). In modern usage, elastomers are therefore also called rubber. Testing of plastics CAMPUS® (Computer Aided Material Preselection by Uniform Standards) supplies tested values for mechanical, thermal, electrical and process-specific properties of almost every type of plastics. The list of rheological, mechanical, thermal, electrical and other properties to be tested are standardized in ISO 10350 (single point data). Many material properties required as construction data are standardized in ISO 11403 (multipoint data). ISO 17282 provides details for design data. See: www.campusplastics.com Thermoplastic Elastomers Thermosetting materials materials Structure of the molecule chains Simple chains or Wide-range cross-linked Closely cross-linked shrub-type ramifications in all directions Properties • Quite soft • Molecular structure • Hard and brittle • Deformable under similiar to a • Temperature-resistant temperature fishing net • Non-deformable • Deformation process • swellable • Non-meltable is repeatable • rubber-like elasticity Types of plastics Polyethylene (PE) Rubber Epoxy resins Polystyrene (PS) Silicone Polyester resins Polyamide (PA) Polyurethane Phenolic resins Polyester Polyurethane Structure of plastics