Filament Stretching Rheometer Sagging Compensation
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Solution Overview
Problem
Current extensional rheometers face challenges in accurately measuring extensional rheological properties of complex fluids, particularly polymer melts and solutions, due to the difficulty in applying well-defined extensional flows and accounting for the sagging effect, which leads to erroneous results and limited availability of commercially viable instruments.
Innovation Solution
A filament stretching rheometer with a sample scanning unit that independently measures the sample diameter at various axial positions, including below and above the midpoint, allowing for closed-loop feedback control to determine the minimum diameter and account for sagging, enabling precise measurement of extensional rheological properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the mid-filament diameter is measured at a fixed point between plates, then the measurement setup is simple, but the sagging effect causes erroneous rheological property calculations
Solution Approach 1:
The measurement system is segmented into multiple detection points along the filament length rather than a single fixed point. The scanner divides the continuous filament into measurable segments, identifying the minimum diameter location dynamically. This segmentation allows the system to account for sagging effects by measuring diameter at multiple positions and selecting the minimum, thereby resolving the contradiction between simple setup and accurate measurement.
2Ease of operation
If the optical measuring device is linked to plate movement, then only mid-filament diameter is measured, but this prevents detection of minimum diameter location when sagging occurs
Solution Approach 1:
The measurement system transitions from a static fixed-point measurement to a dynamic scanning measurement. The optical scanner moves along with the filament, dynamically adjusting the measurement position to track the minimum diameter location. This dynamic adaptation allows the system to maintain measurement simplicity while accurately detecting the minimum diameter even when sagging causes the minimum to shift from the mid-filament position.
3Reliability
If constant extensional strain rate is applied, then the extensional flow is well-defined, but controlling cross-sectional area change in time is fundamentally difficult
Solution Approach 1:
The system implements feedback control by continuously measuring the filament diameter at the minimum point and using this information to adjust the plate movement. The measured diameter data feeds back to the control system, which modulates the extensional strain rate to maintain the desired flow conditions. This feedback mechanism resolves the contradiction by providing reliable extensional flow definition while managing the complexity of cross-sectional area control through real-time measurement and adjustment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and reliable measurement of extensional rheological properties, including transient and steady-state responses, and mechanical properties like Poisson's ratio and Young's modulus, by accounting for sagging and providing real-time feedback control, resulting in improved characterization and control of complex fluids in industrial processes.
Implementation Method 1
a light source (104) and a detector (105) configured to measure the diameter of the sample
Data Source
Figure 1a~1c
Figure 2
Figure 3
AI summary
The present disclosure relates to a filament stretching rheometer for measuring rheological and/or mechanical properties of a sample, comprising: a pair of opposed surfaces for holding the sample therebetween; an actuator configured to provide a controlled axial displacement of at least one of said opposed surfaces; and a sample scanning unit for measuring a diameter of said sample, the sample scanning unit configured for measuring said sample diameter at an axial position controlled independently of the displacement of the opposed surfaces, the sample scanning unit configured for being positioned at a starting point before said controlled axial displacement, wherein the starting point is selected from a position where a minimum diameter of the said sample is determined by said sample scanning unit.