Whether you are new to the industry, just assigned to a new project or looking to brush up on your knowledge, Parker LORD’s five-part educational series delivers a thorough study of thermal management.
What is thermal management? It is the use of materials to transfer heat away from a component to avoid malfunction. Watch our first part in the series—Introduction to Thermal Management to learn more.
Our second webinar in the series, Understanding Technical Terms, provides an overview of technical terms commonly used to describe thermal management products, why they are important and how they are used. Some of the properties may sound familiar while others may not. We may not even realize that many of them can be found in our everyday lives.
When working with uncured materials, knowing the material’s properties is important. These include:
- Viscosity is the measurement of a material’s resistance to flow at a given shear rate. Water, for example, has a low viscosity. Lard, on the other hand, is very viscous.
- Specific gravity refers to the dimensionless ratio of density of one material to a reference material. Materials that are lighter (less dense) will have a lower specific gravity while heavier (denser) materials will have a higher specific gravity.
- Working time is the allowable time from when a material is mixed to when the material’s viscosity is so high that it will no longer bond.
- Pot life is the time it takes for a material’s viscosity to double. Ultimately, you should choose the material with a working time and pot life that best fits your manufacturing process.
- Time to handling strength indicates the time required, after mixing, for the adhesive to hold parts together without fixturing.
- Cure time – is the time needed after mixing for the adhesive to reach its final mechanical properties.
Thermal properties determine a material’s reaction to heat. Thermal conductivity refers to the material’s ability to conduct heat. This is important to know when you are trying to reduce thermal strain and prevent performance loss or component failure. Several factors can affect this property including density, air entrapment and temperature. Other thermal properties include thermal resistance which measures the material’s ability to resist the flow of heat and specific heat which is the amount of heat per unit mass.
Mechanical properties represent how a material will act when forces are applied and these technical terms include:
- Durometer, a device that measures material hardness
- Glass transition temperature, the point when a material transitions from firm and glassy to pliable and rubbery
- Coefficient of thermal expansion, the extent a material expands when heated
- Linear cure shrinkage, the size reduction of a material during the manufacturing process
Other mechanical properties are:
- Storage modulus, the measure a material’s stiffness and ability to store energy
- Loss modulus, a material’s ability to dissipate energy lost as heat
- Lap shear strength, the material’s strength when shear stress is applied
- T-peel, the evaluation of the strength of the bond from a T-peel test
Most everyone is at least somewhat familiar with tensile properties like tensile strength, elongation (stretch), elastic modulus (resistance to deformation) and toughness. These properties are greatly affected by test speed and specimen thickness, and when defects are present.
Electrical properties show how materials respond to electrical currents and include:
- Volume resistivity, the measurement of electrical resistance
- Dielectric strength, the voltage at which material breakdown occurs
- Dielectric constant, the measurement of thematerials’ ability to store energy
- Dissipation factor, which looks at materials’ inefficiencies in retaining energy
Thermal management materials can be dispensed, in some cases, by hand. But applications often require more accuracy. Meter Mix Dispense (MMD) equipment ensures the proper quantity and amount of mixing is applied. There are many types of dispense equipment and your material’s properties can greatly impact which you should choose. If you need help selecting MMD equipment or choosing the individual components, please contact a member of our technical service team.
Our other in-depth webinars in this educational series are on-demand so you can learn at your own pace. They include: Introduction to Thermal Management, Silicone Properties, Epoxy Properties and Urethane & Acrylic Properties.