About this previous year paper
COATING OF TEXTILES (EC602)
Time: 3 Hours Max. Marks: 100
SECTION – A (Short Answer Questions)
(10 × 2 = 20 Marks)
(a) Polymeric material
Polymeric materials are substances made up of long-chain molecules (polymers) formed by repeating structural units. They are widely used in textile coating due to flexibility, durability, and chemical resistance.
(b) Acrylic polymer
Acrylic polymers are synthetic polymers derived from acrylic acid or its derivatives. They are commonly used in textile coatings for weather resistance, transparency, and softness.
(c) Coating
Coating is the process of applying a polymer layer on fabric surface to improve properties such as water resistance, durability, abrasion resistance, and appearance.
(d) Calendaring
Calendaring is a finishing process where fabric passes through heated rollers to improve smoothness, gloss, thickness control, and surface uniformity.
(e) Rheology
Rheology is the study of flow and deformation behavior of materials, especially polymer compounds during coating and processing.
(f) Fabric
Fabric is a flexible textile structure formed by interlacing yarns through weaving, knitting, or nonwoven processes, used as a base for coating.
(g) Clothing comfort
Clothing comfort refers to the thermal, moisture, and tactile comfort experienced by a wearer while using a textile product.
(h) Breathable fabric
Breathable fabrics allow air and moisture vapor to pass through while restricting water penetration, enhancing comfort.
(i) Abrasion resistance
Abrasion resistance is the ability of a coated fabric to withstand surface wear caused by friction.
(j) Low temperature impact test
This test evaluates the resistance of coated fabric to cracking or damage at low temperatures, indicating cold-weather performance.
SECTION – B (Long Answer Questions)
(Attempt any FIVE – 5 × 10 = 50 Marks)
2(a) Concept of curing and curing of rubber coating
Curing is the process of cross-linking polymer chains to improve strength, elasticity, and durability.
In rubber coating, curing is achieved by heat or chemical agents (sulphur), converting soft rubber into a stable elastic material with improved mechanical properties.
2(b) Screen printing method for coating
In screen printing coating, a polymer paste is forced through a patterned screen onto fabric.
Advantages: Controlled coating thickness
Design flexibility Suitable for functional and decorative coatings
Used for protective and specialty textile coatings.
2(c) Roller coating process
Roller coating involves transferring coating material from rotating rollers onto fabric.
Examples include:
Forward roller coating
Reverse roller coating
It provides uniform coating thickness and is widely used for large-scale production.
2(d) Knife as a coating head
Knife coating uses a metal blade (knife) to control the amount of coating applied.
The fabric passes under the knife, and excess coating is scraped off, giving precise thickness control.
2(e) Relation between coating thickness and knife gap
Coating thickness is directly proportional to the distance between fabric and knife.
As the gap increases, coating thickness increases; reducing gap gives thinner coatings.
2(f) Plastisols and apparent viscosity
Plastisols are dispersions of PVC resin in plasticizers.
They remain liquid at room temperature and solidify upon heating.
Apparent viscosity refers to viscosity measured under specific shear conditions during processing.
2(g) Resistance to water penetration and testing
Water penetration resistance measures a fabric’s ability to prevent water from passing through.
Testing is done using:
Hydrostatic pressure test
Spray test
Higher resistance indicates better waterproofing.
2(h) Thermochromic vs Temperature Adaptable Fabric
| Thermochromic Fabric | Temperature Adaptable Fabric |
|---|---|
| Changes color with temperature | Adjusts insulation with temperature |
| Visual response | Functional response |
| Used in fashion | Used in performance wear |
SECTION – C (Very Long Answer Questions)
(Attempt any TWO – 2 × 15 = 30 Marks)
3. Estimation of GSM of coating
GSM (grams per square meter) of coating is calculated by:
Measuring fabric area
Weighing fabric before coating
Weighing fabric after coating
Coating GSM=Coated fabric GSM−Uncoated fabric GSM\text{Coating GSM} = \text{Coated fabric GSM} - \text{Uncoated fabric GSM}Coating GSM=Coated fabric GSM−Uncoated fabric GSM
This helps control coating weight and quality.
4. Rheological behavior of coating compounds
Rheological behavior depends on: Polymer type
Filler content Temperature
Shear rate Materials may show:
Newtonian behavior Pseudoplastic behavior
Thixotropic behavior
Proper rheology ensures uniform coating and defect-free surfaces.
5. Short notes
(a) Impermeable coating
Impermeable coatings completely block air and water penetration, used in rainwear and protective textiles.
(b) Camouflage nets
Camouflage nets are coated textiles used for concealment, providing visual and infrared masking.
(c) Radiation cured coating
Radiation curing uses UV or electron beam radiation to instantly cure coatings, offering fast processing and low energy consumption.