GATE (TF) Textile 2015 Question Paper Solution | GATE/2015/TF/40

FTIR stands for Fourier Transform Infrared Spectroscopy. It is a technique used in analytical chemistry to analyze and identify chemical compounds based on their infrared spectra. Infrared radiation is passed through a sample, and the absorption or reflection of the radiation by the sample at different wavelengths is measured. This information is then used to identify the functional groups and chemical bonds present in the sample, providing valuable information about its molecular structure and composition.

The basic principle of Fourier Transform Infrared Spectroscopy (FTIR) is based on the interaction between infrared radiation and chemical compounds. Infrared radiation lies in the region of the electromagnetic spectrum between visible light and microwave radiation, and it is absorbed by chemical bonds in molecules, causing them to vibrate.
When an infrared beam is passed through a sample, some of the radiation is absorbed by the sample, while the remaining radiation passes through and reaches a detector. The absorbed radiation corresponds to the specific vibrational frequencies of the chemical bonds in the sample, and it is measured as an interferogram, which is a plot of the intensity of the absorbed radiation as a function of the wavenumber or frequency.
The interferogram data obtained from the sample is then subjected to a mathematical technique called Fourier transform, which converts the interferogram from the time domain into the frequency domain. This transformation allows the separation of the different vibrational frequencies present in the sample, and the resulting spectrum, known as an infrared spectrum or IR spectrum, represents the unique fingerprint of the sample.
By comparing the peaks and patterns in the IR spectrum of the sample with reference spectra of known compounds in databases, FTIR can be used to identify functional groups, chemical bonds, and molecular structures in the sample. FTIR can also be used for quantitative analysis by measuring the intensity of the absorbed radiation, which is directly related to the concentration of the analyte in the sample.

A differential scanning calorimeter (DSC) is a type of thermal analysis instrument used to measure the heat flow associated with thermal transitions and chemical reactions in materials. It is commonly used in various fields such as materials science, chemistry, polymer science, pharmaceuticals, and food science to study the thermal properties and behavior of materials.
The main purpose of a DSC is to measure the heat flow into or out of a sample as it is subjected to controlled temperature changes. The sample is typically placed in two separate pans, one containing the sample and the other serving as a reference. Both pans are subjected to the same temperature program, but the heat flow into or out of the sample pan is compared to that of the reference pan. This differential measurement allows for accurate determination of the heat absorbed or released by the sample, which is indicative of thermal transitions and reactions occurring within the sample.

Some of the common applications of DSC include:

Determination of phase transitions: DSC can be used to study phase transitions such as melting, crystallization, glass transitions, and solid-state transitions in materials like polymers, pharmaceuticals, and chemicals.

Characterization of thermal stability: DSC can be used to determine the thermal stability of materials, including decomposition temperature, oxidation, and degradation behavior.
Evaluation of curing or polymerization reactions: DSC can be used to study the curing or polymerization behavior of materials like adhesives, coatings, and composites.
Analysis of thermal properties: DSC can provide information on specific heat capacity, heat capacity changes, enthalpy, and heat of reaction for materials.
Quality control: DSC can be used for quality control and batch-to-batch consistency testing of materials by monitoring thermal transitions and reactions.
Overall, DSC is a versatile and powerful technique for studying the thermal properties and behavior of materials, providing valuable insights into their thermal stability, phase transitions, and chemical reactions.

There are several other techniques that are commonly used to measure crystallinity in materials, such as:
X-ray diffraction (XRD): XRD is a widely used technique to determine the crystal structure and crystallinity of materials. It works by exposing a sample to X-ray radiation and measuring the diffraction pattern, which provides information about the arrangement of atoms or molecules in the material.
Differential scanning calorimetry (DSC): DSC measures the heat flow associated with changes in the thermal properties of a material, including its crystalline structure. By analyzing the heat flow during heating or cooling, DSC can provide information on the melting or crystallization behavior of a material, which can be indicative of its crystallinity.
Solid-state nuclear magnetic resonance (NMR): NMR is a powerful technique that can provide information about the molecular structure and dynamics of materials, including their crystalline structure. By analyzing the NMR spectra of a material, it is possible to obtain insights into its crystallinity.
Infrared spectroscopy (IR): IR spectroscopy measures the absorption and reflection of infrared light by a material, which can provide information about its chemical composition and molecular structure, including crystallinity. By analyzing the IR spectra, it is possible to identify characteristic features associated with crystalline or amorphous regions in a material.

These are just a few examples of commonly used techniques to measure crystallinity in materials. Each technique has its advantages and limitations, and the choice of method depends on the specific material being studied and the desired level of accuracy and precision in the measurement. It is important to use appropriate techniques and methods for accurate and reliable measurement of crystallinity in materials.

Birefringence is a phenomenon that occurs in certain textile fibers due to their molecular structure and alignment. It refers to the difference in refractive index between two perpendicular planes in a material, resulting in the material exhibiting different optical properties when viewed from different angles.
In textiles, birefringence can occur in fibers that have anisotropic molecular structures, meaning their properties vary depending on the direction. Examples of textile fibers that exhibit birefringence include cellulose-based fibers such as cotton, viscose, and lyocell, as well as some synthetic fibers such as polyester and nylon.
The birefringence in textile fibers can affect the appearance, performance, and processing of the fabric. When light passes through a textile fiber with birefringence, it can split into two waves that travel at different speeds and refract at different angles, resulting in changes in the polarization, intensity, and color of the transmitted light. This can lead to optical effects such as pleochroism, where the fabric appears to have different colors when viewed from different angles, or stress-induced birefringence, where the fiber alignment is altered during processing, leading to changes in the fabric’s optical properties.
Textile manufacturers and researchers may use birefringence as a property to characterize and analyze textile fibers, as it can provide information about their molecular orientation, crystallinity, and mechanical properties. For example, polarized light microscopy is a common technique used to visualize and measure birefringence in textiles.
Controlling and managing birefringence in textiles can also be important for achieving desired optical properties in the final fabric. This can be done through various processing techniques, such as controlling the fiber alignment during spinning or weaving, or by applying heat, pressure, or chemicals to induce changes in the fiber’s molecular orientation. Understanding and manipulating birefringence in textiles can be useful in developing fabrics with specific optical effects, such as in the production of specialty textiles for applications like automotive interiors, sports apparel, and outdoor gear.