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Hub AI
Rheological weldability AI simulator
(@Rheological weldability_simulator)
Hub AI
Rheological weldability AI simulator
(@Rheological weldability_simulator)
Rheological weldability
Rheological weldability (RW) of thermoplastics considers the materials flow characteristics in determining the weldability of the given material. The process of welding thermal plastics requires three general steps, first is surface preparation. The second step is the application of heat and pressure to create intimate contact between the components being joined and initiate inter-molecular diffusion across the joint and the third step is cooling. RW can be used to determine the effectiveness of the second step of the process for given materials.
Rheology is the study of material flow as well as how a material deforms under an applied force. Rheological properties are typically applied to non-Newtonian fluids but can also be applied to soft solids such as thermoplastics at elevated temperatures experienced during the welding process. The material properties associated with the rheological behavior include viscosity, elasticity, plasticity, viscoelasticity, and the material's activation energy as a function of temperature.
To understand the rheological properties of a material it is also important to recognize the stress strain relationship for that material at varying temperatures. This relationship is attained through experimental measurement of the resultant deformation as a function of an applied force.
A material's rheological behavior is influenced by a combination of the material's microstructure, its composition, the temperature and pressure acting on the material at a given time. The rheological and viscoelastic properties of a polymer melt are sensitive to the material's molecular structure, including molecular weight distribution and effects of branching. As a result, rheology can be used to develop relationships between differing material combinations.
Melt rheology has shown to be an accurate method in determining the polymer's molecular structure. This is beneficial in determining weld compatibility between materials; as materials with drastically different flow characteristics will be more difficult to join compared to those with more closely matched viscosity and melting temperature properties. This information can also be used to help determine weld parameters for the given welding process to be used.
Regarding sessile drop technique, wetting is characterized by degree of interfacial contact and quantified via contact angle (θc) of a liquid on a solid surface at equilibrium, as shown in Fig. 1. Interrelation between contact angle and surface tensions at equilibrium is given by the Young equation:
Where:
For perfectly good wetting, contact angle (θc) at equilibrium should be minimized. However, it is valid only at equilibrium, and rate of the equilibrium depends on the balance between driving force of wetting and viscosity of the liquid. In the case of polymer melts, viscosity can be very high and it may take a long time to reach the equilibrium contact angle (dynamic contact angle is likely higher than the contact angle at equilibrium).
Rheological weldability
Rheological weldability (RW) of thermoplastics considers the materials flow characteristics in determining the weldability of the given material. The process of welding thermal plastics requires three general steps, first is surface preparation. The second step is the application of heat and pressure to create intimate contact between the components being joined and initiate inter-molecular diffusion across the joint and the third step is cooling. RW can be used to determine the effectiveness of the second step of the process for given materials.
Rheology is the study of material flow as well as how a material deforms under an applied force. Rheological properties are typically applied to non-Newtonian fluids but can also be applied to soft solids such as thermoplastics at elevated temperatures experienced during the welding process. The material properties associated with the rheological behavior include viscosity, elasticity, plasticity, viscoelasticity, and the material's activation energy as a function of temperature.
To understand the rheological properties of a material it is also important to recognize the stress strain relationship for that material at varying temperatures. This relationship is attained through experimental measurement of the resultant deformation as a function of an applied force.
A material's rheological behavior is influenced by a combination of the material's microstructure, its composition, the temperature and pressure acting on the material at a given time. The rheological and viscoelastic properties of a polymer melt are sensitive to the material's molecular structure, including molecular weight distribution and effects of branching. As a result, rheology can be used to develop relationships between differing material combinations.
Melt rheology has shown to be an accurate method in determining the polymer's molecular structure. This is beneficial in determining weld compatibility between materials; as materials with drastically different flow characteristics will be more difficult to join compared to those with more closely matched viscosity and melting temperature properties. This information can also be used to help determine weld parameters for the given welding process to be used.
Regarding sessile drop technique, wetting is characterized by degree of interfacial contact and quantified via contact angle (θc) of a liquid on a solid surface at equilibrium, as shown in Fig. 1. Interrelation between contact angle and surface tensions at equilibrium is given by the Young equation:
Where:
For perfectly good wetting, contact angle (θc) at equilibrium should be minimized. However, it is valid only at equilibrium, and rate of the equilibrium depends on the balance between driving force of wetting and viscosity of the liquid. In the case of polymer melts, viscosity can be very high and it may take a long time to reach the equilibrium contact angle (dynamic contact angle is likely higher than the contact angle at equilibrium).