Key Words to Know Better about Adhesive (8)

14. Vicat Softening Temperature

The Vicat softening temperature is a measure of the heat resistance and thermal behavior of a material, particularly plastics and polymers. It indicates the temperature at which a specific material softens and starts to deform under a specific load.

The test to determine the Vicat softening temperature involves applying a predefined load to a small, heated sample of the material and measuring the depth of penetration of a needle or a flat-ended plunger. The test is conducted according to various standards, such as ASTM D1525 or ISO 306.

The Vicat softening temperature is reported in degrees Celsius (°C) and is often denoted as VST. It is an important parameter for assessing the suitability of a material for various applications, such as determining its ability to withstand elevated temperatures without deforming or losing its structural integrity.

It is worth noting that the Vicat softening temperature is different from the melting point or glass transition temperature of a material, as it specifically measures the softening behavior under a defined load.

15. Water Absorption

Water absorption refers to the ability of a material to take up water when exposed to a moist environment. It is a property that is particularly relevant for porous materials such as ceramics, polymers, and composites.

Water absorption can occur through various mechanisms, including diffusion of water molecules into the material's structure or capillary action through interconnected pores. The rate and extent of water absorption depend on factors such as the porosity, surface area, and intrinsic hydrophilicity/hydrophobicity of the material.

Water absorption is typically expressed as a percentage of the material's original weight or volume. The test to determine water absorption involves immersing the material in water for a specified period of time, followed by drying and weighing the material to calculate the absorbed water content.

Water absorption can have important implications for the performance and durability of a material. It can lead to dimensional changes, weakening of mechanical properties, loss of electrical insulation properties, degradation of surface finishes, and other detrimental effects. Therefore, understanding the water absorption behavior of a material is crucial for selecting appropriate materials for specific applications, such as outdoor or underwater environments.

16. OI

Oxygen Index (OI) is a measure of a material's ability to support combustion or sustain itself in an environment with a certain concentration of oxygen. It is widely used in the industry to classify and compare the flammability of combustible materials.

The Oxygen Index is expressed as the minimum percentage of oxygen required to maintain the combustion of a material. The higher the Oxygen Index value, the greater the material's resistance to burning. For example, a material with an Oxygen Index of 25% requires at least 25% oxygen to sustain a combustion.

This index is particularly relevant in determining the fire safety of various materials, such as plastics, fabrics, and insulators. It is also frequently used in classifying products into different flammability classes according to specific standards and regulations.