Chapter 3 Plastics, Mold Materials and Management 3.1 Plastics 3.1.1 Condition for Injection and Molding The large molecular structure of polymer and the features of molecular thermodynamic movement have determined that polymer has such states of aggregation as the glassy state, highly-elastic state as well as viscous flow state etc. The transformation of aggregative state is nfluenced by chemical composition, molecular structure, the stress applied whereon and the environment temperature, and is mainly related with temperature when the composition of Membrane blow molding Calendering forming Extrusion forming Processing and molding temperature njection molding 加工与型方法的适应 Flexibility of processing (或Tm)7 and molding 熔纺 Vacuum and pressure molding Heat stretch of membrane and fiber Melting spinning 延成型 空吹塑成型 Deformation rate Cold stretch of the membrane and 空和压力成型 fiber 膜和纤维热拉伸 薄膜和纤维冷拉伸 Hollow molding Glassy state 玻璃态尚弹态黏 固体移皮状弹性体数娃 Hard solid Highly-elastic state Rubber-elastomer viscous liquid Viscous flow state Fig 3-1: relationship between polymer state and plastic molding As indicated in the Fig 3-1, when the temperature is below the vitrification temperature(T.), the polymer is under glassy state, which is hard solid, wherein energy from the molecular thermodynamic movement is low, the elastic modulus is large, and the deformation is reversible Under such aggregative state, it is not suitable for molding with large-scale deformation. When the temperature is above the vitrification temperature(T,), the plastics will become softer, andChapter 3 Plastics, Mold Materials and Management 3.1 Plastics 3.1.1 Condition for Injection and Molding The large molecular structure of polymer and the features of molecular thermodynamic movement have determined that polymer has such states of aggregation as the glassy state, highly-elastic state as well as viscous flow state etc. The transformation of aggregative state is influenced by chemical composition, molecular structure, the stress applied whereon and the environment temperature, and is mainly related with temperature when the composition of polymer is certain. Fig.3-1: relationship between polymer state and plastic molding As indicated in the Fig.3-1, when the temperature is below the vitrification temperature (Tg ), the polymer is under glassy state, which is hard solid, wherein energy from the molecular thermodynamic movement is low, the elastic modulus is large, and the deformation is reversible. Under such aggregative state, it is not suitable for molding with large-scale deformation. When the temperature is above the vitrification temperature (Tg ), the plastics will become softer, and Hollow molding Hard solid Highly-elastic state Rubber-elastomer Viscous liquid Viscous flow state Processing and molding temperature Deformation rate Heat stretch of membrane and fiber Vacuum and pressure molding Cold stretch of the membrane and fiber Extrusion forming Injection molding Membrane blow molding Calendering forming Glassy state Flexibility of processing and molding Melting spinning