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en:grundlagenhandbuch:materialkenngroessen [2026/09/03 11:21] – [Rheological Material Parameters] paalen:grundlagenhandbuch:materialkenngroessen [2026/09/04 08:25] (aktuell) – [Meaning] paal
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-==== Measuring Series with the High Pressure Capillary Rheometer ====+==== Measuring Series with the High-Pressure Capillary Rheometer ====
  
 To be able to define the necessary Carreau parameters, measurements have to be taken, for instance, the high pressure capillary rheometer. Usually the experimental series are performed at 3 different temperatures. To be able to define the necessary Carreau parameters, measurements have to be taken, for instance, the high pressure capillary rheometer. Usually the experimental series are performed at 3 different temperatures.
  
-In a high pressured capillary rheometer, pre-heated material flows through a capillary with a circular cross-section. During this process, practically the total area of the interesting viscosities is measured. For low viscous fluids, long thin capillaries are used and for high viscous fluids appropriately high pressures are used. By using this discontinual method, the necessary pressure through foreign gas, gravity or by means of piston is made available. The volume flow rate is imposed, by a constant piston speed. The pressure gradient at the inlet and at the outlet is not constant due to vortex formation as a result of viscoelastic effects (Bagley-Correction), due to the change of the flow speed (Hagenbach-Correction) and due to the variation of the friction at the wall (Couette-Correction). To calculate the exact viscosity of the polymer melt, the pressure gradient is measured using two probes on a designated length in the capillary, since here, there are simple rheological flow relationships.+In a high-pressured capillary rheometer, pre-heated material flows through a capillary with a circular cross-section. During this process, practically the total area of the interesting viscosities is measured. For low viscous fluids, long thin capillaries are used and for high viscous fluids appropriately high pressures are used. In the discontinuous method, the required pressure is applied by an external gas, gravity, or a piston. The volume flow rate is imposed, by a constant piston speed. The pressure gradient at the inlet and at the outlet is not constant due to vortex formation as a result of viscoelastic effects (Bagley-Correction), due to the change of the flow speed (Hagenbach-Correction) and due to the variation of the friction at the wall (Couette-Correction). To calculate the exact viscosity of the polymer melt, the pressure gradient is measured using two probes on a designated length in the capillary, since here, there are simple rheological flow relationships.
  
  
 ===== Thermodynamic Material Parameters ===== ===== Thermodynamic Material Parameters =====
  
-The calculation of both the melting behavior and the temperature development in power melts requires a comprehensive knowledge of the thermodynamic material behavior  [[en:grundlagenhandbuch:materialkenngroessen#references|[HKP89]]]. The thermodynamic properties are dependent on both pressure and temperature and show a different material property in the solid state and in the melt state.+The calculation of both the melting behavior and the temperature development in polymer melts requires a comprehensive knowledge of the thermodynamic material behavior  [[en:grundlagenhandbuch:materialkenngroessen#references|[HKP89]]]. The thermodynamic properties are dependent on both pressure and temperature and show a different material property in the solid state and in the melt state.
  
-The following data is required for SIGMA: the crystalline melting temperature, glass transition temperature, specific heat capacity and specific enthalpy. These can be detected using the DSC (Difference Scanning Calorimetry)-analysis.+The following data is required for SIGMA: the crystalline melting temperature, glass transition temperature, specific heat capacity and specific enthalpy. These can be detected using the DSC (Differential Scanning Calorimetry)-analysis.
  
 ==== General Principle of the DSC-Analysis ==== ==== General Principle of the DSC-Analysis ====
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-A heat flow $\dot{Q}$, drifts from the oven over a sensor (thermal resistor) to the sample pot and to the reference pot, which are usually very similar (equal in dimension and composed of the same material). The heat flow to the reference $\dot{Q}_R$ is caused due to the heat capacity of the pot material and the heat flow losses. This applies to equal pot materials, symmetry of the measuring cell and also to the specimen pot $\dot{Q}_S = \dot{Q}_R$. The specimen substance that is embedded in the specimen pot, causes an additional heat flow $\dot{H}$ (dH/ dt) that can be determined by the difference in heat flows:+A heat flow $\dot{Q}$, drifts from the oven over a sensor (thermal resistor) to the sample pot and to the reference pot, which are usually very similar (equal in dimension and composed of the same material). The heat flow to the reference $\dot{Q}_R$ is caused due to the heat capacity of the pot material and the heat flow losses. This applies to equal pot materials, symmetry of the measuring cell and also to the specimen pot $\dot{Q}_S = \dot{Q}_R$. The sample material enclosed in the specimen pot causes an additional heat flow $\dot{H}$ (dH/ dt) that can be determined by the difference in heat flows:
  
 $$\dot{H} = \dot{Q}_S - \dot{Q}_R = \frac{T_p - T_S}{R_t} - \frac{T_p - T_R}{R_t} = \frac{T_S - T_R}{R_t} = -\frac{\Delta T}{R_t} \tag{6}$$ $$\dot{H} = \dot{Q}_S - \dot{Q}_R = \frac{T_p - T_S}{R_t} - \frac{T_p - T_R}{R_t} = \frac{T_S - T_R}{R_t} = -\frac{\Delta T}{R_t} \tag{6}$$
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 Where is $\dot{H}$ = heat flow of the specimen substance $\dot{Q}_S$, resp. $\dot{Q}_R$ = heat flow to the specimen pot and reference pot, $R_t$ = thermal resistance of the sensor, $T_p$= temperature of the oven (temperature program) and $T_S$ resp. $T_R$ = reference temperature. Where is $\dot{H}$ = heat flow of the specimen substance $\dot{Q}_S$, resp. $\dot{Q}_R$ = heat flow to the specimen pot and reference pot, $R_t$ = thermal resistance of the sensor, $T_p$= temperature of the oven (temperature program) and $T_S$ resp. $T_R$ = reference temperature.
  
-Partially crystalline thermoplastics do not have a fixed melting point but rather a melting range. This is due to them having different sized crystal lamellas in comparison to metals. Smaller, irregular crystallites melt at a lower temperature than larger crystallites. Characteristic for every partially crystalline polymer is the melting temperature resp. the crystallite peak temperature TK. The position of the peak on the temperature axis is identified by the start temperature ($T_A$), the peak temperature ($T_K$) and the final temperature ($T_E$) that is also important for other thermodynamical properties like specific enthalpy. For partially crystalline thermoplastics one obtains the heat flow ($T$) $\dot{H}$ over the temperature $T$ like shown in the figure:+Partially crystalline thermoplastics do not have a fixed melting point but rather a melting range. This is due to them having different sized crystal lamellas in comparison to metals. Smaller, irregular crystallites melt at a lower temperature than larger crystallites. Characteristic for every partially crystalline polymer is the melting temperature resp. the crystallite peak temperature TK. The position of the peak on the temperature axis is identified by the start temperature ($T_A$), the peak temperature ($T_K$) and the final temperature ($T_E$) that is also important for other thermodynamic properties like specific enthalpy. For partially crystalline thermoplastics one obtains the heat flow ($T$) $\dot{H}$ over the temperature $T$ like shown in the figure:
  
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   * $V_0$= volume of the tank.   * $V_0$= volume of the tank.
  
-The solid densities can be determined according to DIN 53 479. This method (lift method) compares the value of a certain sample mass of air with a fluid medium (here: distillate water $\rho_{H_2O}$=1,000 g/ cm³). The principle is shown in the figure.+The solid densities can be determined according to DIN 53 479. This method (buoyancy method) compares the value of a certain sample mass of air with a fluid medium (here: distillate water $\rho_{H_2O}$=1,000 g/ cm³). The principle is shown in the figure.
  
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-Another option is to determine the granule diameter $d$ from a total of $n$ samples using the solid density $r$ and the total weight of the samples $m_{total}$. The following applies to the total of $n$ samples:+Another option is to determine the granule diameter $d$ from a total of $n$ samples using the solid density $\rho$ and the total weight of the samples $m_{total}$. The following applies to the total of $n$ samples:
  
 $$V_{ges} = \frac{m_{ges}}{\rho} \tag{15}$$ $$V_{ges} = \frac{m_{ges}}{\rho} \tag{15}$$
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-The melt flows out mass is determined by the deposition of the liquid strand at predetermined time intervals and weighing. As modified melt index the increased volume flow index MVI / MVR is strongly used indicating the extruded melt volume in 10 minutes. A major advantage of the melt volume flow rate MVR is the simple measurement of the piston travel at a known piston diameter to determine the treat out melt volume. In contrast, for the melt mass-flow rate MFR the detached molten strands have to be weighed and as result it is an additional expense for the handling. For this reason, the measurement of the mass flow rate is only used when the determination of the melt volume in case of problems during the reaction is not workable.+The melt flows out mass is determined by the deposition of the liquid strand at predetermined time intervals and weighing. As modified melt index the increased volume flow index MVI / MVR is strongly used indicating the extruded melt volume in 10 minutes. A major advantage of the melt volume flow rate MVR is the simple measurement of the piston travel at a known piston diameter to determine the extruded melt volume. In contrast, for the melt mass-flow rate MFR the detached molten strands have to be weighed and as result it is an additional expense for the handling. For this reason, the measurement of the mass flow rate is only used when the determination of the melt volume in case of problems during the reaction is not workable.
  
 In order to compare MFI values among themselves, whose value must always be specified in addition to the weight used and the respective test temperature. Specifying MFI 190/2,16 for example, means that the melt index was determined at 190 ° C and a piston mass of 2,16 kg  [[en:grundlagenhandbuch:materialkenngroessen#references|[MHM+05]]]. In order to compare MFI values among themselves, whose value must always be specified in addition to the weight used and the respective test temperature. Specifying MFI 190/2,16 for example, means that the melt index was determined at 190 ° C and a piston mass of 2,16 kg  [[en:grundlagenhandbuch:materialkenngroessen#references|[MHM+05]]].