Question 29 (Textile Technology & Fibre Science)
Techniques used to determine the glass transition temperature of textile fibres are
P. X-ray diffraction (XRD)
Q. Differential scanning calorimetry (DSC)
R. Thermogravimetric analysis (TGA)
S. Dynamic mechanical analysis (DMA)
| (A) | P & Q only |
| (B) | Q & R only |
| (C) | Q & S only |
| (D) | R & S only |
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Frequently Asked Questions | FAQs
What is glass transition temperature TC?
Glass transition temperature (Tg) is a property of amorphous materials, including many plastics, that defines the temperature at which the material transitions from a hard, brittle state to a softer, more pliable state.
At temperatures below Tg, the molecules of the material are locked in place, and the material is rigid and brittle, behaving like a glass. Above Tg, the molecules become more mobile and the material becomes softer, more flexible, and more prone to deformation. This transition occurs without any significant change in the material’s crystalline structure, unlike melting in crystalline materials.
The glass transition temperature is affected by a variety of factors, including the chemical composition of the material, the degree of cross-linking or branching in the polymer chain, and the presence of plasticizers or other additives.
The glass transition temperature is an important property to consider in the design and selection of materials for various applications. For example, in the production of plastic products, the Tg of the material must be below the intended use temperature to prevent deformation or failure of the product. In addition, understanding the Tg of a material is essential for predicting its behavior under different conditions, such as during processing or in response to changes in temperature or stress.
How to measure glass transition temperature DSC?
There are several methods for measuring the glass transition temperature (Tg) of a material, depending on the type of material and the level of accuracy required. Here are some common techniques:
Differential Scanning Calorimetry (DSC): This is the most common method for measuring Tg. It involves heating a sample of the material and measuring the heat flow as it transitions from a solid to a liquid. Tg is determined by the inflection point of the plot of the heat flow versus temperature.
Dynamic Mechanical Analysis (DMA): DMA measures the mechanical properties of a material as a function of temperature, including its elastic modulus, loss modulus, and damping coefficient. Tg is typically determined by the peak in the damping coefficient.
Thermomechanical Analysis (TMA): TMA measures the change in dimensions of a material as it is heated or cooled. Tg is determined by the change in the rate of thermal expansion as the material transitions from a glassy to a rubbery state.
Differential Thermal Analysis (DTA): DTA measures the temperature difference between a sample and a reference material as they are both heated or cooled. Tg is determined by the change in the heat capacity of the sample as it transitions from a glassy to a rubbery state.
Fourier Transform Infrared Spectroscopy (FTIR): FTIR can be used to monitor the changes in the molecular structure of a material as it undergoes a phase transition. Tg is determined by the change in the absorption spectrum of the material as it transitions from a glassy to a rubbery state.
Each method has its advantages and disadvantages, and the choice of method depends on the type of material and the level of accuracy required.