Differential scanning calorimetry (DSC) is an excellent tool for evaluating the thermal properties of rubber and polymer products. DSC data can be used to gain a deeper understanding of a compound, evaluate how its thermal properties change with the addition of new materials, and determine its compliance with industry or OEM standards.
What is Calorimetry?
Calorimetry is an analytical method that quantifies the heat that is released or absorbed during a given chemical reaction. Exothermic and endothermic reaction data can be incredibly valuable for understanding the performance of rubber and polymer products.
The most common calorimetry method used in rubber testing laboratories is differential scanning calorimetry (DSC).
How Does Differential Scanning Calorimetry (DSC) Work?
There are two primary components to a DSC testing instrument: A measurement chamber and a computer.
The sample under test is placed inside a test container, usually a pan, and placed in its own cell in the measurement chamber. A second test container is placed in a separate cell to serve as a control. Both pans are heated at a controlled rate and observed closely by a technician. The temperature of each cell is monitored throughout the test, and all data is recorded by the computer.
What Does DSC Measure?
DSC measures several different thermal property values of a given material. This includes the magnitude and rate of heat flow and captures data on glass transition temperature (Tg), melt point, heat of fusion, and crystallization performance.
What is DSC Used For?
There are many potential applications of DSC testing. Specific examples include:
- Measuring the glass transition temperature (Tg) of a mixed rubber compound to determine whether the material is appropriate for the temperature range it may encounter in its intended service environment.
- Verifying the proper state of cure of a material by building a crosslink density trend line between different cure systems.
- Verifying melt flow temperature of inbound raw materials for auditing, qualification, and quality control purposes.
DSC is especially valuable for materials that will be melted and cooled during the production process and materials that will encounter a range of temperatures, especially cold temperatures, while in service.
DSC can also be used to study fusion, oxidation, and other chemical reactions, as well as purity and polymer curing. Because of this, differential scanning calorimetry is often an integral part of quality control and industry standard testing.
Differential Scanning Calorimetry Testing Benefits
While there are multiple ways to observe and quantify the thermal properties of a given material, there are several key advantages of using DSC instrumentation as opposed to other methods.
Ease and speed. DSC instrumentation allows for fast, easy observation of thermal properties and transitions of materials, especially when compared to manual methods.
Repeatability. Precision is vital when capturing thermal properties data of any material. One single degree—even one-tenth of a degree—of error can lead to problems in manufacturing and in service. Modern DSC instrumentation provides incredibly precise and repeatable thermal properties data, eliminating the guesswork and uncertainty of manual methods.
Versatility. The thermal properties of a rubber material can change with the addition of another polymer or raw material. DSC is excellent for benchmarking the thermal properties of raw polymers, mixed polymer compounds, and many raw material additives, such as plasticizers and waxes.
Differential Scanning Calorimetry Test Methods
Because DSC is such a precise and valuable test method, many industry standard protocols include differential scanning calorimetry. Two of the most common DSC test methods are ASTM D7426 and ASTM D3418.
ASTM D7426—Standard Test Method for Assignment of the DSC Procedure for Determining Tg of a Polymer or an Elastomeric Compound
ASTM D7426 is a common industry standard for determining the glass transition temperature (Tg) of a rubber material. If a material is exposed to conditions colder than its glass transition temperature, it will become brittle and glass-like. If the material or product is dropped or experiences other trauma at this stage, its performance is likely to suffer. In some cases, it may even break or shatter. This makes ASTM D7426 especially vital for rubber products and materials that will be exposed to extreme cold in its production or service environment.
ASTM D3418—Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry
ASTM D3418 uses DSC methods to determine three thermal property data points for rubber and polymer materials:
Melting point. DSC testing offers highly detailed insight into the melt properties of a material, including the onset of melting temperature, the peak temperature, and the complete melting point. DSC instrumentation also provides more precise, accurate, and reproducible melt point data than a traditional melting-point apparatus.
Heat of fusion. Heat of fusion is the amount of energy needed to melt a predetermined mass of a given material sample at its melting point temperature. Heat of fusion data provides vital information about the sample’s properties and behavior when exposed to extreme heat for an extended period of time.
Crystallization. DSC data can provide insight into the effect of crystallization on the mechanical, thermal, and chemical properties of a rubber or polymer material. When a rubber or polymer material is cooling and nearing its glass transition temperature, its polymer chains have greater mobility than at other temperatures. DSC instrumentation can pinpoint the temperature at which these polymer changes have the energy needed to form ordered arrangements and crystallize.
There are several other industry test specifications that may rely on DSC data to evaluate a material, including:
- ASTM D3895—Standard Test Method for Oxidative-Induction Time of Polyolefins by Differential Scanning Calorimetry
- ASTM E1269—Standard Test Method for Determining Specific Heat Capacity by Differential Scanning Calorimetry
Differential Scanning Calorimetry (DSC) Testing from ACE Laboratories
ACE Laboratories has invested in cutting-edge DSC instrumentation to ensure accurate, repeatable thermal properties data. Our team has significant experience evaluating thermal properties in both industry and laboratory settings. Whether you’re in the research and development stage, testing for regulatory compliance, or investigating an issue post-launch, you can count on ACE for expert guidance and the fastest turnaround times in the industry.