lasisiniirtymän

Lasisinirtymä, often translated as glass transition, is a phenomenon observed in amorphous solids and polymers. It represents a reversible transition in these materials from a hard, glassy state to a rubbery or viscous state. This transition does not involve a change in phase in the thermodynamic sense, meaning it is not a first-order phase transition like melting or boiling, but rather a second-order transition.

The glass transition temperature, denoted as Tg, is the temperature range where this transition occurs. Below Tg, the material is rigid and brittle, with limited molecular motion. Above Tg, polymer chains gain mobility, allowing for segmental motion and leading to increased flexibility and elasticity. This change in mechanical properties is crucial for the processing and application of many materials, especially plastics and elastomers.

The exact temperature of the glass transition is influenced by several factors, including the chemical structure of the polymer, molecular weight, the presence of plasticizers, and the rate of heating or cooling. Techniques such as differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) are commonly used to determine the Tg of a material. Understanding the glass transition is fundamental in materials science for predicting the behavior and performance of amorphous materials under different temperature conditions.