材料科学与工程导论双语课件教学课件 ppt 作者 陈克正 王玮 刘春延 等编Chapter 3.ppt

* * * * * * * * * * * * * * * Transfer Molding A variation of compression molding The raw material is first liquefied in a heated transfer chamber, then the softened material is injected into the mold cavity. 3.5.3 Forming Techniques for Plastics 3.5.3 Forming Techniques for Plastics Injection molding Analogue of die casting for metals Fed correct amount of raw material into a cylinder from a loading hopper. A plunger pushes forward the raw material into a heating chamber to form a liquefied plastic. 3.5.3 Forming Techniques for Plastics Extrusion Similar to extrusion of metals A screw or augur push forward the raw material into a heating chamber to form a liquefied plastic. When the liquefied plastic pass through the a die orifice, “extrusion” occurs. 3.5.3 Forming Techniques for Plastics Blow molding Adapt to hollow container A parison (型坯) was firstly extruded, then placed in a two-piece mold. Maintain the parison in a semimolten state. Blow air or steam into the parison to form the hollow inner structure. 3.5.4 Forming Techniques for Elastomers The same as those for plastics Most rubbers are vulcanized and some are reinforced with carbon black SBR 3.5.5 Forming Techniques for Fibers and Films Spinning (纺丝) Heat the raw material to form a liquefied polymer Pump down the liquefied polymer through a plate containing numerous small round holes Fibers are formed as the liquefied polymer pass through the holes, then solidified by air. 3.5.5 Forming Techniques for Fibers and Films Films 1) Extruded through a die slit (缝隙模) 2) Blown Extrude continuous tubing through an annular die (环形口模) Maintain positive gas pressure inside the tube to reduce the thickness of the tube, hence to form thin cylindrical film. Mer, monomer, polymer Molecular shape Molecular structure Thermoplastics thermosettings Crystallinity Viscoelasticity SUMMARY Thank You! QUST * * * * * * * * * * * * * * * * * * * * * * * A polymer chain is like a string of noodl