Thermal Stability - Thermal Hazards

Background

Thermogravimetric Analysis (TGA) measures the change in mass of a sample under controlled heating conditions.  A small amount of sample (1-10 mg) is contained within an open crucible and placed into a temperature controlled furnace.  A second crucible is used as a reference.  The sample is then heated by the temperature controlled furnace.  The most commonly used method of temperature control is dynamic (or scanning) mode and is used to increase the furnace temperature at a constant heating rate.  Another mode of operation is isothermal mode and is used to maintain the furnace at a constant temperature.  In both of these modes, the mass loss (or gain) of the sample is measured as a function of time and temperature.

Benefits

TGA data can be used to assess the thermal hazard potential as well as evaluate material properties of a given sample.  ASTM Standards commonly used for such evaluations are as follows:

• ASTM E 1131-08: Standard Test Method for Compositional Analysis by Thermogravimetry
• ASTM E 1641-07: Standard Test Method for Decomposition Kinetics by Thermogravimetry
• ASTM E 1868-10: Standard Test Method for Loss-On-Drying by Thermogravimetry
• ASTM E 2008-08: Standard Test Method for Volatility Rate by Thermogravimetry
• ASTM E 2550-11: Standard Test Method for Thermal Stability by Thermogravimetry

Background

The Accelerating Rate Calorimeter (ARC) is a high thermal inertia adiabatic calorimeter that is used to obtain data regarding the relationships between time, temperature, and pressure for exothermic reactions.  The ARC utilizes a 10 ml spherical test cell constructed of stainless steel, Hastelloy C, titanium, or tantalum.  The pressure generated by a sample must be contained within the test cell.  To accomplish this, ARC test cells use heavy walled test cells capable of withstanding pressures up to 3,000 psi or more.  As a consequence, the thermal inertia, or phi-factor, of the system is relatively high.  The combined mass of the sample and the test cell are kept adiabatic, not just the sample itself.  For this reason, care must be taken when applying this data to large scale hazard evaluations.

The ARC can be run in two modes of operation.  The first, and most common mode of operation, is heat-wait-search mode.  In this mode, the exothermic activity of the sample is monitored through a series of preprogrammed temperature steps.  When a reaction is detected, the heaters are programmed to match the temperature of the system.  The ARC can also be run in isothermal mode.  In this mode, the system is heated to the desired initial temperature.  The instrument can then be programmed to track a reaction if exothermic activity is detected or maintain the desired temperature.

 Benefits

Data obtained using this calorimeter can be applied to evaluate the thermal hazard potential of reagents, reaction mixtures, intermediates, and products. The following safety parameters are attained, or can be evaluated, from Accelerating Rate Calorimetery:

• Onset temperature
• Temperature rise rate as a function of temperature
• Pressure rise rate as a function of temperature
• Adiabatic temperature rise
• Heat of reaction
• Adiabatic time to maximum rate
• Temperature of no return
• Self-accelerating decomposition temperature

Expertise/Solutions

Fauske & Associates, LLC (FAI) Accelerating Rate Calorimetry (ARC) contract testing service test protocol conforms to ASTM E 1981, “Standard Guide for Assessing the Thermal Stability of Materials by Methods of Accelerating Rate Calorimetry”.  A sample size of 0.5 to 10 grams is typically required for each test.

Background

The Thermal Activity Monitor (TAM) is an isothermal microcalorimeter designed to monitor a wide range of chemical and biological reactions.  The system can quantify exothermic and endothermic processes at a chosen test temperature between 5 and 90°C.  The TAM utilizes 4 ml test cells constructed of glass, stainless steel, or Hastelloy C.  Stainless steel and Hastelloy C test cells allow for pressure generation up to 8 bar. 

Benefits

Through the use of a sophisticated heat leakage principle, the TAM is capable of measuring heat flows as low as 0.1 µW.  Because of its sensitivity, it is often use to study reactions that traditional calorimeters such as the DSC, ARC, or VSP2^TM cannot.  The TAM is commonly used in the following studies:

Kinetics of Chemical Reaction

• Activation Energy
• Rate Law
• Autocatalytic Behavior

Chemical Transportation and Storage

• Assure Safe Transport- Self Accelerating Decomposition Temperature
• Quantify Shelf Life 

Biological Reactions

• Evaluation of Fermentation Rates

Metabolism of Living Systems

Compatibility Studies

• Oxidation or Corrosion Rates
• Interaction Tests

Expertise/Solutions

Fauske & Associates, LLC (FAI) Thermal Activity Monitor (TAM) contract testing service test protocol conforms to the operational recommendations made by the instruments manufacturer.  A sample size of 0.5 to 2 grams is typically required for each test.

Background

Critical process safety and thermal stability parameters (TMRad, SADT, etc.) can be determined quickly and reliably from a modest amount of calorimetry data by using AKTS-Thermokinetics software.  This software utilizes an advanced differential is conversional kinetic technique for the precise modeling of runaway chemical reactions.  From just a few DSC tests, run in either dynamic or isothermal mode, model-free kinetics can be extracted.  The model-free kinetics can then be used to predict reactivity of varying quantities of material in different thermal environments. Verification of the model can be completed by a comparison of the measured and calculated reaction profiles, either rates or conversion, under both non-isothermal and isothermal conditions.  Further validation can be performed using a single adiabatic calorimetry experiment.

Benefits

• A series of Differential Scanning Calorimetry (DSC) tests on a small sample size (roughly 1-10 mg per test) can be sufficient to provide data for analysis
• The use of AKTS-Thermokinetics software does not require knowledge of the reaction mechanism.  The model-free approach to kinetics ensures proper modeling of materials subject to autocatalytic or multi-stage reactions

Features

AKTS-Thermokinetics software package facilitates kinetic analysis of DSC, DTA, TGA, and TAM data for the study of raw materials and products within the scope of research, development and quality assurance.

Advanced kinetic analysis:

• Automatic baseline construction and use of the differential isoconversional method of Friedman (model-free) for advanced baseline optimization
• Smoothing of data (Savitzky-Golay)
• Differential isoconversional method of Friedman (model-free)
• Integral isoconversional method of Ozawa-Flynn-Wall (model free)
• Standard ASTM E698 procedure
• Model fitting method applying common reaction models

Prediction of the reaction progress and thermal stability of materials under any temperature mode:

• Isothermal and non-isothermal, stepwise
• Modulated temperature or periodic temperature variations
• Rapid temperature increase (temperature shock)
• Real world temperature profiles (up to 7000 climates)

Fauske & Associates, LLC (FAI) has experience utilizing AKTS-Thermokinetics software for kinetic analysis and is also an authorized distributor. 

Some of the key benefits the C80 include:

• The C80 is a reaction, thermal and scanning calorimeter that operates like a larger version of a DSC which accommodates a larger sample size and bigger test cells  -  10 ml test cells, as opposed to 20-50 µl test cells. This is especially advantageous when dealing with heterogeneous or multi-component samples that come in and are not uniformly mixed and cannot be uniformly mixed (think different colored M&Ms) as the larger size allows a more representative sample to be tested. 

• It has a wide range of vessels that can be used with it which makes it flexible

• A lot of the other instruments primarily use metal cells, but the C80 can use glass-lined cells which is beneficial when dealing with peroxides or other chemicals that are highly sensitive/reactive to metals

• The C80 offers a unique level of sensitivity to thermal events and also the ability to design cells and vessels to simulate almost any potential condition

• Temperature ramp measures heat flow as a function of time and temperature 

• Temperature range is from ambient to 300mC

As you can see, the C80 is a fantastic addition to our toolkit here at FAI as it nicely complements other instruments in our lab and enhances the ability of our engineers to offer practical and customized solutions to unique process safety issues dealing with thermal hazards and thermal stability. When you are considering a provider for your own process safety needs in this area make sure that they too have a robust toolkit with which to effectively address your concerns.

Our team is happy to help train your staff in the understanding of technical issues, process safety programs or audits, regulations and more.  We perform process safety audits as part of a comprehensive hazards analysis and can work with you to make sure your staff is supplied with skills training needs in many ways including: 

Level I - Gap Analysis
Level II - training & consulting
Level III - Program Development and Implementation

Partial List of Services Offered:
• Reviews and upgrades of all your safety process systems and regulatory requirements
• VPP Consulting
• Audits, reviews, and upgrades of all your Operating, Safety, and Maintenance Procedures
• Training program evaluations for both completeness and effectiveness (from technical skills to professional development) and upgrades where
needed
• Reviews and upgrades of your program elements such as Employee Participation and Process Safety Information for effectiveness and completeness
• Work process effectiveness evaluations and upgrades
• Overall organizational development (e.g., motivation, work processes)
• Stress reduction
• Evaluations of the effectiveness of communication

We design, custom develop and deliver any site specific training materials needed by your organization. Our Consultants, Engineers and Technical Specialists are available to deliver the classroom, lab or on-the-job training your staff needs. In addition, we will assist with the identification and procurement of commercially available training materials where available.