Physical Properties of Plastics（2）
Physical Properties of Plastics （2）
Thermodynamic three states of plastics
In nature, we divide the aggregation state of matter at room temperature into three kinds: gaseous, liquid and solid.
High molecular polymers represented by amorphous linear polymers, due to the continuity of molecular structure and their huge molecular weight, their aggregation state is different from general low molecular compounds, but exists in three unique forms under different thermal conditions: glass state, high elastic state and viscous flow state.
High molecular polymers do not exist in gaseous state. Before heating and possible gasification, the molecular structure has been completely destroyed and become low molecular gasified substances or carbides.
The glassy state of polymer is actually a form of solid state. It is characterized by the common properties of solid substances in a certain temperature range, which is similar to ordinary glass in some mechanical properties.
The viscous flow state of polymer is a unique "liquid". In a certain temperature range, it has the mechanical properties that can flow and different from ordinary low molecular liquid.
The high elastic state of polymer is a unique form in the temperature range between glass state and viscous flow state. Like other substances, polymers have a relatively stable form under specific temperature and pressure conditions. For example, under normal service conditions, plexiglass can be regarded as the representative of glassy state and liquid resin as the representative of viscous flow state.
When the external temperature and pressure change and reach a certain level, the polymer will change the original state into another state. The task of the injection molding plant is to provide these changing conditions. In the processing process, when the plastic raw materials (based on high molecular polymers) are affected by temperature, pressure and shear, their viscosity, physical structure and morphology will change, among which the temperature has the greatest influence, which is the theoretical basis of plastic thermoforming.
In nature, we divide the aggregation state of matter at room temperature into three kinds: gaseous, liquid and solid.
High molecular polymers represented by amorphous linear polymers, due to the continuity of molecular structure and their huge molecular weight, their aggregation state is different from general low molecular compounds, but exists in three unique forms under different thermal conditions: glass state, high elastic state and viscous flow state.
High molecular polymers do not exist in gaseous state. Before heating and possible gasification, the molecular structure has been completely destroyed and become low molecular gasified substances or carbides.
The glassy state of polymer is actually a form of solid state. It is characterized by the common properties of solid substances in a certain temperature range, which is similar to ordinary glass in some mechanical properties.
The viscous flow state of polymer is a unique "liquid". In a certain temperature range, it has the mechanical properties that can flow and different from ordinary low molecular liquid.
The high elastic state of polymer is a unique form in the temperature range between glass state and viscous flow state. Like other substances, polymers have a relatively stable form under specific temperature and pressure conditions. For example, under normal service conditions, plexiglass can be regarded as the representative of glassy state and liquid resin as the representative of viscous flow state.
When the external temperature and pressure change and reach a certain level, the polymer will change the original state into another state. The task of the injection molding plant is to provide these changing conditions. In the processing process, when the plastic raw materials (based on high molecular polymers) are affected by temperature, pressure and shear, their viscosity, physical structure and morphology will change, among which the temperature has the greatest influence, which is the theoretical basis of plastic thermoforming.
