Differential scanning calorimetry, and specifically modulated-temperature differential scanning calorimetry, is one of the most useful and commonly-applied forms of material testing applied to polymers across industries. Let us explore what it is, how it works, and what it can do for you.
What is Differential Scanning Calorimetry (DSC)?
DSC is a type of thermal analysis that measures the energy transferred to or from a sample undergoing a physical or chemical change—such as transitioning from a solid to a liquid. DSC accomplishes this by heating both the sample material (in order to induce the initial phase change) and a control substance at a consistent rate.
As the sample being tested undergoes phase transition, it releases or absorbs heat differently than the control sample. Therefore, the temperature of the pan containing the test sample will change at a different rate than the control pan. By measuring and comparing the heat flow difference between the two pans, DSC can demonstrate how much heat is absorbed or released by the transitioning sample being tested.
There are multiple types of DSC. The type of DSC most commonly used for polymer testing is called Modulated-temperature DSC.
What is Modulated-temperature DSC?
Modulated-temperature DSC works very similarly to conventional DSC, but in Modulated-temperature DSC, testers can overlay a small-amplitude modulation over the usual, linear temperature increase.
Modulated-temperature DSC allows users to obtain more information in a single test than they could using conventional DSC. For instance, modulated-temperature DSC can be used to find both heat capacity and heat flow in a single experiment. By carefully modulating temperature during experimentation, it’s also possible to use modulated-temperature DSC to separate, identify, and measure complex transitions which would be very difficult to tell apart otherwise.
Why is the Modulated-temperature DSC Technique Right for Polymer Testing?
DSC is frequently used as a quality control instrument for polymer products in the plastic and medication manufacturing industries. As part of their quality control process, analysts need to evaluate several crucial physical properties of these polymers simultaneously, including their glass transition point, melting point, , and/or crystallization and oxidation rates.
However, many of the most pertinent phase transitions polymers undergo can be difficult to observe and measure using only conventional DSC.
The Problem with Conventional DSC for Polymer Testing
Isolating, identifying, and measuring the heat produced or absorbed by each of these polymer phase transitions can be quite difficult using conventional DSC. Many of these transitions actually involve several processes occurring simultaneously. For example, the endothermic process enthalpic relaxation can occur during a glass transition. This can make a polymer’s glass transition look like a melting point in conventional DSC. Similarly, melting and crystallization of polymers may look very similar and occur at similar times, which can make them hard to tell apart in conventional DSC.
Fortunately, modulated-temperature DSC allows analysts to overcome these challenges.
How Modulated-temperature DSC Solves the Conventional DSC Challenge
The modulation capability of modulated-temperature DSC allows analysts to more accurately isolate each phase transition individually by modulating the temperatures they expose the sample to in real time. This increased level of control allows analysts to separate the total heat flow signal (measured by conventional DSC) into both its reversing and non-reversing components.
Via the separation of total heat flow, analysts can use modulated-temperature DSC to isolate and identify all phase transitions occurring within a sample at a given time, no matter how weak they are or how simultaneously they occur. This makes modulated-temperature DSC crucial for determining, for instance, the exact degree of crystallinity in polymers, the direct determination of the polymer’s thermal conductivity, or the polymer’s true melting point.
What Can Modulated-temperature DSC Techniques Tell Us About Polymers?
Modulated-temperature DSC is used for a broad range of applications in polymer manufacturing industries. A few of the most common practical applications we use DSC techniques for include:
Durability of Plastics
Modulated-temperature DSC can be used to determine not only how plastics react to temperature over time, but also how they will react to extreme temperature fluctuations, as well as how the phase transitions during and after these fluctuations will affect their composition and overall durability. This makes modulated-temperature DSC a go-to test for assessing the quality and durability of plastics vs. different environments they will be exposed to.
Effects of Heating and Aging
Modulated-temperature DSC is frequently applied to medical tests in order to clarify the efficacy of medications following compositional phase transitions brought about by heat exposure and/or time. These tests are used to determine the ideal storage and transportation parameters for sensitive medications.
Modulated-temperature DSC may also be used to determine the effect of heating and aging on non-medical products, including glass, rubber, synthetic polymers, and more. Applied this way, modulated-temperature DSC is a very popular means of determining general storage, transportation, and usage parameters.
Degree and Effects of Crystallinity
Many polymer-based materials may crystallize upon cooling after melting, stretching, or having some of their additive components evaporate. This crystallization has a serious impact on the material’s optical, mechanical, thermal, and chemical properties, and may affect how it behaves or performs.
Modulated-temperature DSC can reliably recreate and measure crystallization reactions in polymers and even identify the size and orientation of molecular chains created by it, allowing users to understand when their materials may crystallize and how it will affect their performance.
Processing Temperature Optimization
Modulated-temperature DSC allows testers to determine the effects of a wide range of heat and cooling variations on a material.
By analyzing how polymers respond to these temperature fluctuations, analysts can determine the best operative temperatures for a wide variety of manufacturing processes, including polymer curing, injection molding, extrusion, and heat welding.
If you think modulated-temperature DSC is the right fit for your polymer testing, the experts at Innovatech are ready to help.
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