Liquid Handling

Materials: PlasticTechnical InformationPlasticsn ElastomersPolymers with loosely cross-linked molecules,exhibiting rubber-like elasticityat room temperature. Heating causesirreversible curing (vulcanization).The most popular elastomers arenatural rubber and silicone rubber.n ThermosetsPolymers with tightly cross-linked moleculesare very hard and brittle at room temperature;heating causes irreversible curing.These plastics are rarely used for plasticlabware. The best known thermosets arethe melamine resins. Melamine resin isproduced by polycondensation of melaminewith formaldehyde.Besides glass, plastics play a very important role in laboratories.In general, plastics can be divided into the three groups:n ThermoplasticsPolymers with a linear molecular structurewith or without side branches are transformedinto objects during molding operationswithout changing their thermoplasticproperties. Thermoplastics are the materialscommonly used in plastic labware production.Hence we provide here a brief descriptionof some individual plastics explainingtheir structural, mechanical, chemical andphysical properties. The most popular thermoplasticsare polyolefins like polyethyleneand polypropylene.PS PolystyrenePolystyrene is glass-clear, hard, brittle, anddimensionally stable due to its amorphousstructure. PS has good chemical resistanceto aqueous solutions but limited resistanceto solvents. Disadvantages include low thermalstability and its tendency to suffer fromstress-cracks.SAN Styrene-acrylonitrile copolymerThis is a glass-clear material with goodresistance to stress-cracking. It has slightlybetter chemical resistance than PS.PMMA Polymethyl methacrylateRigid, glass-clear ("organic glass"). Resistantto atmospheric agents. Replaces glassin many applications where temperaturesare below 90 °C and low chemical resistanceis required. PMMA has excellent UVradiation stability.PC PolycarbonateThese are thermoplastic linear carboxylicacid polyesters combining many of theproperties of metals, glass and plastics.The materials are transparent and havegood thermal properties between -130 to+130 °C. Note: PC may be weakened byautoclaving or exposure to alkaline detergents.PA PolyamidePolyamides are linear polymers with repeatingamide chain linkages. With theirfavorable strength characteristics and highdurability, polyamides can often be used asstructural materials and for surface coatingmetals. They have good chemical resistanceagainst organic solvents, but are easily attackedby acids and oxidizing agents.334info@brand.de