WELCOME TO RHEOLOGY TESTING SERVICES
FEES FOR MOST ASSAYS LISTED BELOW:
$500 minimum per submitted set since involves running performance standards and report.
-1 to 10 assays $175/assay
-11 to 25 assays $150/assay
->26 assays $125/assay
*$250 for longer assays such as temperature cycling and single frequency sweep 1-2hrs, then $100/hr for assays >2hrs.
-Summary of results and experimental details
-Summary tables listing primary results to highlight trends.
-Excel files of results
-Follow-up discussions to review results and answer questions
•Below are the most commonly requested assays that can be performed with a broad array of parameters to meet your particular rheology needs. These and other assays not listed may be performed in various combinations.
•Overview and application of proposed assays below can be found in more detail at https://www.rheologytestingservices.com.
1. ROTATION - Yield Stress Ramp (“flow curve”)
Description: Shear stress controlled, non-equilibrium ramp. Measures viscosity vs shear stress. Determine yield stress and yield viscosity to quantify initiation of sample flow. Helpful to identify impact of stress during manufacturing, application (spreadability, pumpability, syringability) and performance, as well as for sample handling for testing.
2. ROTATION – Increasing/Decreasing Shear Rate Ramp
Description: Shear rate controlled. Measures viscosity vs shear rate increase, then decrease as a continuous ramp to screen for post-shear (ir)reversibility (hysteresis). Helpful to identify impact of shear rate during manufacturing, application (spreadability, pumpability, syringability) and performance, as well as for sample handling for testing. For reference, pouring and dripping are approx 1-10sec-1.
3. ROTATION – Stepwise Increasing/Decreasing Shear Rate
Description: Shear rate controlled. Measures viscosity with stepwise shear rate change as next step criteria are met to provide a more stabilized viscosity result rather than acquiring data across a continuous ramp. Quantify viscosity vs shear rate and determine post-shear (ir)reversibility (hysteresis). Helpful to model impact of shear rate during manufacturing, application (spreadability, pumpability, syringability) and performance, as well as for sample handling for testing. For reference, pouring and dripping are approx 1-10sec-1.
4. ROTATION: 3-Step Thixotropy (post-shear rebuilding)
Description: Step 1 measures viscosity at low shear (baseline). Evaluate rebuild time and extent (Step 3) after exposure to shear thinning (Step 2). Helpful to identify impact of shear forces during sample handling for testing as well as for product manufacturing, delivery and performance. For reference, pouring and dripping are approx 1-10sec-1.
5. ROTATIONAL: Heat/Cool Ramp Cycle at Single Shear Rate
(single sample loading per cycle)
Description: Measure viscosity vs increasing/decreasing temperature cycles while typically applying a low as possible fixed shear rate having acceptable signal/noise. Helpful for process development and stability screen by evaluating potential for (ir)reversible changes (hysteresis).
6. ROTATION: Creep-Recovery
Description: Evaluate viscoelastic properties by measuring sample recovery over time following an applied, then released shear stress often over multiple stress-release cycles.
7. OSCILLATION: Amplitude (Strain) Sweep
Description: Apply an increasing strain (force) at a constant frequency until sample rheologically “breaks” to determine upper LVER (Linear Viscoelastic Region) as % strain. Using %strain within the LVER is a critical input for frequency assay to ensure rheological integrity. Upper LVER limit is defined as 5% decrease in G’ (elastic modulus) indicating start of structural breakdown with increasing amplitude. LVER tends to correlate with physical stability and strength of intermolecular interactions.
8. OSCILLATION: Single Frequency over Time (typically strain controlled)
Description: Measure changes in G’ (elastic modulus), G” (viscous modulus), phase angle, n* (complex viscosity), and G* (complex modulus) vs over time at a constant frequency (typically 1Hz) and % strain within the LVER determined from amplitude sweep. Identify potential for rheological change over time and temperature used for other assays. Unaccounted for changes may confound interpretation results of assays.
9. OSCILLATION: Frequency Sweep (typically strain controlled)
Description: Measure G’ (elastic modulus), G” (viscous modulus), phase angle, n* (complex viscosity), G* (complex modulus), G’-G” crossover (if observed, typically not observed for gels) vs frequency at a constant % strain determined from an amplitude sweep. Generates a rheological “fingerprint”. Helpful to evaluate properties to support Q3. Quantifies solid/liquid nature of material to model processes having short- and long-timeframes corresponding to high and low frequency, respectively.
10. VERTICAL: Squeeze Pull-Away
Description: Compress sample between lower and upper plates, then pull plate apart at define rate. Quantifies the force (stickiness, adhesion, cohesion) required to vertically separate sample between plates. These values can correlate with human sensory panel results.
11. VERTICAL: Surface Tension (requires 4mL minimum)
Description: A DuNouy ring is slowly raised through the sample to quantify the liquid-liquid or liquid-air interface tension due to the attraction force (Newtons) exerted from asymmetric intermolecular interactions that can appreciably differ from the more balanced interactions within the sample.
12. ROTATIONAL: Tribology (friction, lubricity)
Description: Measures resistance as torque (N-m) as sample is exposed to a bearing rotating with increasing velocity under a defined normal force.
GENERAL CONSIDERATIONS (may not be applicable to all sample types)
• Overview and application of proposed assays can be found at https://www.rheologytestingservices.com.
• Assays are performed under non-GMP.
• Multiple assays per sample may be helpful depending on desired precision.
• Since this study is a basic comparative screen, specific test parameters are not optimized for each sample and are based on best estimates from experience.
• Ideally at least 2mL per sample per assay is requested, especially for low viscosity samples. If sample is scarce, many assays can be performed with 200uL (transferrable) using a small plate with small gap between plates although accuracy and precision may decrease. Having extra samples would be very helpful in case method refinement and repeat analyses are necessary.
• Unless requested otherwise, samples will be stored at ambient conditions prior to and after analysis. Please communicate any special hazard, handling, preparation or storage needs prior to finalization of the quote.
• Please note if sample contains volatiles at assay temperatures. Loss of volatiles may affect results if not accommodated with use of a solvent trap to saturate the sample test environment.
• Assays can be performed with sample under low-flow N2 to reduce potential for degradation. Request if needed.
• Samples will be handled and applied to the rheometer with a high level of consistency and care so as to minimize potential shear force that could bias results.
• Unless requested, samples will not be pre-sheared. Pre-shearing can be helpful to rheologically normalize samples that may undergo shear thinning during sample handling. However, depending on the material sensitivity to pre-shearing, some rheological properties may be erased. It is recommended to consider pre-shearing if deemed necessary based on observed rheologicial sensitivities of sample.
• Lower viscosity samples may generate variable results at suggested lower shear rates and may necessitate adjusting if poor signal to noise response is observed.
• Unless specified, assays are typically performed with 25mm diameter roughened parallel plates to reduce potential for slippage and minimize sample usage. Low viscosity samples or samples requiring highly accurate viscosity measurements will be assayed with a 40mm 4deg cone (smooth) assuming adequate sample is provided.
• Assays performed with high shear rates may require using a flat plate with narrow sample gap (200um) to retain sample within plates. Low viscosity samples are more prone to spin out from plates at high shear rate.
• While a cone may provide better rheological resolution, it is not suggested for working for wide ranging temperature ramp due to potential sample expansion.
• Unless otherwise stated, all analysis will be performed with samples equilibrated at 25C.
• A draft report will be submitted for review. The report will be considered finalized after 1 week with no response and invoice for payment will be submitted (30 days net upon receipt of invoice).
Indicate any safety, handling, or disposal considerations prior to sample shipment in case Rheology Testing Services cannot properly accommodate.
• Samples are to be clearly labeled with unique IDs and accompanied by appropriate Safety Data Sheets (SDS), along with any special handling and storage information.
• A screw-top glass or plastic vial, bottle or jar is preferable to crimp-top container/closures. If samples are submitted in crimp-top containers, please provide additional several caps per sample to reseal.
• Arrange for sample delivery to occur on a weekday since no one may be present to receive on weekends.
• Please forward shipment tracking information. You will be notified when samples arrive.
Ship samples to: Provided in actual quote
• Unless specifically requested otherwise, samples will be retained for 30 days after report is approved and then properly disposed according to local Environmental requirements.
• If unused samples are to be returned to client, unless prepaid by requestor or is local (RTP area North Carolina) sample return will incur a pass-through cost plus $50 for handling.
With coordination of sample shipment with Rheology Testing Services, work is typically initiated within 2 business days upon receipt of samples and approved purchase order with a signed quote or via email response with quote stating approval. Approximate duration of the project is typically 3-5 days depending on number of samples and type of testing.
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I have known the owner - Mark Patrick - for many years and I recommend Rheology Testing Services very highly. He has an impressive expert understanding of the science of rheology. I worked with Mark for many years during our time with GlaxoSmithKline and saw first-hand the exceptional quality of his work. He conducts his work with great rigor and professionalism.