Frequently Asked Questions in Process House

1.                   What are dyes?

2.                   What are pigments?

3.                   Define % Shade.

4.                   Define Absorption and desorption.

5.                   Define Substantivity/Affinity.

6.                   Define Exhaustion.

7.                   Define Material-to-Liquor Ratio.

8.                   Define % Expression.

9.                   Define % Shade.

10.                What are Exhausting Agents?

11. What are Auxochrome?
12. What is Chromogen.
13. What are Chromophore
14. Define any one of Modern theory of color and constitution:
15. What are Nitro Dyes?
16. What are Nitroso Dyes?
17. What are Azo Dyes?
18. What are Diphenyl methane dyes?
19. What are Triphenyl methane dyes?
20. What are Heterocyclic Dyes?
21. What are Anthraquinone dyes?
22. What are Indigoid dyes?
23. What are Phthlocyanines.
24. What are Acid dyes.
25. What are Basic dyes.
26. What are Mordant dyes.
27. What are direct dyes.
28. What are azoic dyes.
29. What are Vat dyes.
30. What are Disperse dyes.
31. What are Reactive dyes.
32. What are Sulphur dyes.
33. How to dye polyester nylon blends.
34. What are all the Problems caused by piling?
35. Which plasma used for desizing?
36. Which plasma used for hydrophilic finishing?
37. Why more degradation in Acid desizing than enzymatic     desizing.
38. What are methods of Reduction bleaching.
39. Factors Affecting Pilling tendency.
40. Physical and chemical methods to reduce the pilling.
41. The factors that facilities the static charge on fiber.
42. Define Antistatic agents.
43. Define Wetting agent.
44. Define Peroxide killer.
45. Define Dispersing Agents.
46. Define Retarding Agents.
47. Define Sequestring agents.
48. Define pH regulator.
49. Define Anti foaming agent. 
50. Define Dye fixing agent.
51. Define Dye bath conditioning agents.
52. Define Migration inhibitor.
53. Define Levelling agents.
54. Indigosal O is suitable for wool since..........
55. Solamine Black is..........
56. Astrazon Blue GL is recommended..........

57.                  O-Nitrodiphenyl amine disperses dyes have better light fastness due to..........

58.                The term degumming is associated with__________ fibre while retting with________ fibres.

59. A spin finish formulation contains...........
60. Gas-singeing machine is operated at a speed of..........
61. The desizing process mainly removes..........
62. Batch-wise scouring can be carried out in..........

63.                The most important ingredient of a scouring composition is..........

64. What is saponification?
65. What is emulsification?
66. What is Barium Activity Number?
67. Define Ring Dyeing on denim
68. What is souring?
69. Wool and silk can be bleached with..........
70. Polyester and acrylic fibers can be bleached with..........
71. Mercerization is carried out with NaOH at concentration..........
72. An optical brightener is..........

73.                Damage caused to cotton during bleaching can be assessed by measuring..........

74. Efficiency of Desizing can be assessed by..........
75. Efficiency of Scouring can be assessed by..........
76. Efficiency of Bleaching can be assessed by..........
77. Efficiency of mercerization can be assessed by..........
78. Cross-section of NaOH swollen cotton fibres shows rings in the   secondary wall which are better known as..........
79. The hollow space in cotton fibres is known as Lumen while         that in wool is called..........
80. How to dye cotton/lyocell by using of reactive dyes.....
81. The sulphur containing amino acids in wool are cystine      and..........
82. Stem fiber are also known as..........
83. ..........colors can be prepared on the substrate.
84. Indigo is a .......... dye.
85. Reactive dyes form a .......... bond with the fibre.
86. Pigments are applied along with a..........
87. Acrylic fibers are dyed with ..........dyes.
88. Rapidogen colors are a mixture of a .......... base and a..........

89.                A low-temperature catalyst for curing pigment colors is...........

90.                The most preferred chemical used in discharge printing for reducing the dye is ..........

91.                Steaming of printed polyester fabrics is carried out in a loop ager at.........ºC.

92.                Carbonization treatment is given to printed polyester/viscose rayon fabric to dissolve..........

93.                When cloth gets soaked in water, it looks transparent because of..........

94.                Sodium hypoclorite bleaching of cotton is carried out at what temperature..........

95.                Commercially, scouring of cotton is carried out by using..........

96.                Dyeing of silk is carried out by using which dyes..........

97.                Monchloro triazine reactive dyes are applied on cotton under which p H and temperature..........

98.                Modified cationic dyes on acrylic are held by which bonds..........

99.                Cylindrical design screens are used in the technique of..........

100.            Discharge printing of polyester is carried out by using..........

101.            Sublimation transfers printing of polyester with disperse dyes is carried out at..........

102. Swelling agent used during printing of nylon is..........
103. Stone wash finish is more commonly given to..........
104. Weight reduction finish is more commonly given to..........
105. Heat-setting of polyester is carried out on..........
106. Rot Proof finish is given to..........
107. Dimethylol dihydroxy ethylene urea is used to improve..........

108.            Which fibre dissolves at room temperature in methylene chloride..........?

109. Which fibre is generally dyed with cationic dye..........?
110. Resist salt is..........
111. THPC is a..........
112. Special luster of silk is related to..........
113. Crystallinity percent of wool fibre is approximately..........
114. Alkali resistance is highest in case of..........
115. Polyvinyl alcohol (PVA) is used for sizing........

116.            Boiling-off of cellulosic fibrous material during scouring in air may result in the formation of.......

117. For bleaching of cotton, amount of H₂O₂(50% required is).....
118. Sodium chlorite is used for the bleaching of......
119. Material to liquor ratio in a Jigger dyeing machine is......
120. Peracetic acid is used for the bleaching of......
121. Indigo is a......
122. For pigment printing following type of thickener system is          preferably used......
123. For wash-n-wear finish the crease recovery angle should be....
124. Nylon can be dyed with...
125. Heat setting of synthetic filaments is done to
126. Acid-alkali resistance is the highest for
127. Most dominant synthetic fibre used in the world is....
128. In the case of hypochlorite bleaching, the species responsible    for bleaching is.....
129. Reaction of vinyl sulphone dyes with cellulose is......
130. ‘Batik’ printing is carried out using.....
131. Flame retardancy is primarily obtained by.....
132. In printing Sodium sulphoxylate formaldehyde is used for....
133. British gum is derivative of......
134. Gum Indalca is derivative of......
135. CMC is derivative of......
136. Malachite Green is belongs to......
137. Velan PF is......
138. Why enzyme desizing of cotton is safer compared to desizing     with mineral acids?
139. Why quenching of cotton fabric is essential after singeing?  
140. What is the role of sodium silicate in bleaching of cotton with     hydrogen peroxide?
141. Sublimation transfer printing with disperse dyes is suitable for    printing of polyester and not for acrylic. Explain briefly
142. Justify why ionic dyes cannot be used for sublimation transfer    printing
143. In the case of vat dyes,sodium hydrosulphite is not suitable       for printing while sodium sulphoxylate formaldehyde is not        suitable for dyeing. Explain?
144. Why soaping at boil is absolutely essential after dyeing of cotton with reactive dyes?
145. Differentiate between wash-n-wear and durable press       finishing of cotton
146. Define water Proof.
147. Define water repellent.
148. The angle of wind of a cone meant for dyeing is
149. Singeing of polyester is carried out to
150. Identify the machine that works on the principle of both fabric   and liquor moving  during the dyeing operation
151. The most suitable thickener for reactive by printing on cotton    is.......
152. Extremely good wash fastness of reactive dyes on cotton is       due to the formation of.......
153. Soil release finishes are most effective on......
154. Enzyme desizing of cotton is carried out with the help of
155. Molecular weight of dyes suitable for sublimation transfer printing of polyester is in the range of.........
156. Reduction potential of sodium hydrosulphite under alkaline        condition at room temperature is.........
157. Resist printing on cotton under reactive dyes is carried out        at.........
158. Compounds based on nitrogen and phosphorous are used of.........
159. The disperse reactive dyes were developed for.........
160. Compared to the untreated fabric,the water repellent treated     fabric will.........
161. The presence of metal ions during H₂0₂ bleaching.........
162. Thermodynamically, dyeing is.........
163. The reactive dyes are designed to have
164. One Remazol brand and one basic dye have been given to a     printer for                  producing a discharge printed silk sari. For      this (which one ground)
165. On treating with NaOH solution, the flame retardancy of the         phosphorylated cotton  fabric
166. Distinguish between vapour phase and condensed phase   mechanism of flame
167. The main object of singeing is,
168. The main object of souring is,
169. The main object of desizing is,
170. The main object of bleaching is,
171. Which  fibres to vat dyes were usually applied
172. Identify the fibres to which disperse dyes are usually applied
173. Identify the fibres to which reactive dyes are usually applied
174. Identify the fibres to which pigments can be  applied
175. Pick out the synthetic polyamide fibres from the following
176. Pick out the package dying machine/a from the following
177. An optical brightening agent (OBA) is a colourless dye that        gives a bright white appearance to a fabric because,
178. If cotton material is to be  dyed to give good all-round      fastness, you would use a
179. Identify the dye that has colour fastness properties to       hypochlorite bleaching
180. The dye that typically shows poor colour fastness properties      to washing and light is …
181. The test conditions for the BIS wash Fastness Test No. 1 are …
182. Sanforising is a process to…
183. Calendaring is a process  to…
184. Mercerization is a chemical process to make a cotton fabric
185. Denim clothes can be quickly given a faded look at selected      places  by means of … In transfer printing..
186. Explain different types of softener
187. Name out the different types of resins

Write with reasons, whether the following statements are true or false:

188. The visible region is from 300 nm to 700 nm
189. The light fastness is assessed with the help of a grey scale.
190. Wool dissolves in sulphuric acid.
191. Cellulose acetate can be melt spun.
192. Cotton behaves as a cross-linked polymer
193. The colors that are on the textile fabrics are due to subtractive colour mixing.
194. Toluene on sulphonation gives Meta substituted sulphonic acid.
195. Hydroxyl and amino groups do not influence the colour and       dyeing properties of azo dyes
196. Silk a highly sensitive to alkali while wool is not
197. Silk a smooth while wool has scales on the surface
198. Silk is mostly composed of a few amino acids while wool has     many more
199. Silk has higher crystallinity than wool.
200. Mixture of titanium chloride and antimony oxide is used for       producing flame Retardant cotton.

MICRO-ENCAPSULATION

1. Introduction:

“Small is beautiful” would be an appropriate slogan for the many people studying micro-encapsulation, a process in which tiny particles or droplets are surrounded by a coating to give small capsules with many useful properties. The material inside the microcapsule is referred to as the core, internal phase or fill, whereas the wall is sometimes called a shell, coating or membrane. Most microcapsules have diameters of few micrometres.

The reasons for micro-encapsulation are countless. In some cases, the core must be separated from its surroundings, as in isolating vitamins from the deteriorating effects of oxygen, retarding evaporation of a volatile core, improving the handling properties of a sticky material, or isolating a reactive core from chemical attack. In other cases the objective is not to separate the core completely but to control the rate at which it leaves the microcapsules as in the controlled release of drugs or pesticides [7]. Manufacturing costs are based on coating material, solvent, equipment and labour. Coating-material prices vary greatly, and as a rule, the cheapest acceptable material is used. Coatings that can be applied without solvent or water are preferred. Environmental and safety regulations greatly increase the cost of process that use volatile organic solvents.

2. Classification:

A classification of encapsulation processes is given below:

Category I

Liquid suspending media

Water-in-oil (W/O) Oil-in-water (O/W)

Complex coacervation

Polymer-polymer incompatibility

Interfacial and in situ polymerization

Desolvation

Solvent evaporation from emulsion

Gelation

Pressure extrusion

In Category-I, a liquid is used as the suspending medium throughout. Emulsification or dispersion of two or more immiscible phases is a key step in these processes. In Category-II, a gas is the suspending medium in which the capsules are formed, and atomization of a liquid phase is the key step. Some authors refer to Category-I processes as chemical processes and Category-II processes as physical or mechanical processes. According to this classification, processes such as solvent evaporation, gelation and polymer-polymer incompatibility are termed chemical processes even if no chemical reaction occurs. A spray drying process in which reactive components are polymerized during the drying step to form microcapsules would be called a physical process, even though a chemical reaction clearly occurs during capsule formation. Many Category-I and Category-II processes are similar. For example, solvent evaporation is a key step in spray-dry encapsulation and in processes involving solvent evaporation from an emulsion. The only difference is that evaporation in the former case occurs directly from the liquid phase to the gas phase. In the latter case, evaporation involves transfer of a volatile liquid to an immiscible liquid from which it is subsequently removed. Another example is gelation encapsulation. The droplets, which are gelled to form capsules, can be formed by emulsification or atomization [1].                       Figure 1: Microencapsulation process

Figure 2: Schematic description of the microencapsulation system

3. Application of Microcapsules in Textiles:

          The consumer demands for textiles with new characteristics and added value into medical and technical fields have encouraged the industry to use micro-encapsulation processes as a means of imparting finishes and properties to fabrics which were not possible or cost-effective using other technology. Textile manufacturers are demonstrating increasing interest in the application of durable fragrances to textile as well as skin softeners; other potential applications include, for example, insect repellents, dyes, antimicrobials, phase change materials.

3.1 Phase-change materials

Micro-encapsulation technology was utilised in the early 1980s by the US National Aeronautics and Space Administration (NASA) with the aim of managing the thermal barrier properties of garments, in particular for use in space suits. They encapsulated phase-change materials (PCMs) (e.g.nonadecane) with the hope of reducing the impact of extreme variations in temperature encountered by astronauts during their missions in space. Ultimately the technology was not taken up within the space programme. However, the potential was recognised and after further development the work was licensed by the inventor. Outlast Technologies has exploited the technology in textile fibres and fabric coatings [Fig.1]. PCM capsules are now applied to all manner of materials [2, 3], particularly outdoor wear (parkas, vests, thermals, snowsuits and trousers) and in the house in blankets, duvets, mattresses and pillowcases. As well as being designed to combat cold, textiles containing PCMs also helps to combat overheating, so overall the effect can be described as thermoregulation. The microcapsules have walls less than 1 μm thick and are typically 20–40 μm in diameter, with a PCM loading of 80–85%. The small capsule size provides a relatively large surface area for heat transfer. Thus the rate at which the PCM reacts to an external temperature changes is very rapid [4].

Figure  3:  (a) PCM microcapsules coated on the surface of fabric and (b) embedded within fibres

The late injection technology processes allow the in-fiber incorporation of Outlast microcapsules, loading the fiber with 5–10% of microcapsules. In this way the PCM is permanently locked within the fiber; there is no change necessary in subsequent fiber processing (spinning, knitting, dyeing, etc.) and the fiber exhibits its normal properties of drape, softness and strength.

3.2 Fragrance finishes:

The addition of fragrances to textiles has been carried out for many years in the form of fabric conditioners in the wash and during tumble-drying to impart a fresh aroma. However, no matter the quality of the technology used, the effect is relatively short-lived. Numerous attempts have been made at adding fragrances directly to fiber and fabrics but all fail to survive one or two wash cycles. Only through micro-encapsulation are fragrances able to remain on a garment during a significant part of its lifetime. Micro-encapsulation of essential oil flavours has led to many novelty applications, particularly for children’s garments, but it has also allowed utilization at home and in the work place to the beneficial effects of aromatherapy.

In recent years several companies have gained much experience in the provision of microcapsules for textiles. The majority of the work has been in microencapsulated “scratch and sniff” T-shirts and in women’s hosiery: it is claimed that the shirts survive washing (typically 8–20 cycles), depending on the active agent encapsulated, and the hosiery up to 10 washes. The capsules also survive drying in conventional tumble-dryers. Well-established techniques such as in situ and interfacial polymerisation are used to manufacture the capsules.

Celessence International of Hatch End, Middlesex, has been investigating and manufacturing microencapsulated fragrant-smelling compounds for a number of years.

In the early days the applications included paper handkerchiefs, gift wrapping, ornaments, greeting cards, advertising brochures, books, cartons and labels. The company has now turned its attention to textiles, using its basic technology of encapsulating fragrances in gelatin or synthetic capsules, which protects the contents from evaporation, oxidization and contamination. The capsules range in size from 1 to 20 μm. In practice, the smaller the capsules the greater the covering of the product and the longer the fragrance will last, as it takes longer for the capsules to be ruptured by physical pressure. Larger capsules release more fragrance when ruptured. Traditionally the “scratch and sniff” application of microcapsules used screen-printing, but now litho and web printing techniques have been adopted, initially in paper products and now in textiles.

Celessence TXT capsule systems comprise aqueous dispersions of encapsulates, which can be applied by pad, exhaustion or hydroextraction techniques to a wide variety of textile substrates. Durability to washing and handle may be further improved by incorporating suitable formaldehyde free binders and softeners. All applied products are blended from natural and synthetic materials that conform to legislative guidelines for cosmetic products[5]. For screen-printed application the encapsulates are simply mixed with water-based, solvent-free inks or binders. The capsule printing must be the last step to avoid damage of microcapsules walls, once printed; the fabric is then cured as with standard textile inks to achieve a good bond to the fibres.

The Matsui Shikiso Chemical Co of Kyoto has also developed a way of fixing aroma compounds to fabric using microcapsules. The fabric is first treated with a nitrogenous cationic compound and the microcapsule wall is manufactured to adhere to this layer. The capsules can range in size from 0.1 to 100 μm and are made using interfacial or in situ polymerisation techniques.

In Korea the Eldorado International Co of Seoul and a number of other companies offer new fabrics that emit the natural aroma of flowers, fruit, herbs and perfumes. Emulsified microcapsules containing a natural aroma or essential oil are attached to the fabric after dyeing. The capsules break on movement of the wearer, releasing the aroma. In general the capsules continue to emit aroma for up to 25 wash cycles and on the shelf the finish will remain ready for action for between 3 and 5 years. So far the company has applied the technology to curtains, sofas, cushions and sheets, as well as some toys. Silk ties have also been produced that release fragrant oils during normal wear, and if rubbed they produce a large burst of fragrance.

Also in Korea, workers at Pusan National University were able to prepare microcapsules using melamine-formaldehyde systems containing fragrant oil [6]. When attached to cotton these capsules were able to survive over 15 wash cycles. Scanning electron microscopy indicated that the smaller of the capsules in the range survived more effectively after laundering. This phenomenon may simply be due to the relative thickness of a capsule within an adhesive film binding the capsules to the textile substrate [Fig.2].

Euracli, a company based in Chasse-sur-Rhone in France, has produced microcapsules containing perfumes or cosmetic moisturisers that can be padded, coated or sprayed onto a textile and held in place using an acrylic or polyurethane binder.

Figure 4:  example of microcapsules application on fabrics

3.3 Polychromic and thermo-chromic microcapsules

Colour-changing technology has been for a number of years generally applied to stress testers, forehead thermometers and battery testers. New applications are now beginning to be seen in textiles, such as product labelling, and medical and security flexible displays. In addition there is continued interest in novelty textiles for purposes such as swimwear and T-shirts. There are two major types of colour-changing systems: thermochromatic which alter colour in response to temperature, and photochromatic which alter colour in response to UV light. Both forms of colour-change material are produced in an encapsulated form as micro-encapsulation helps to protect these sensitive chemicals from the external environment.

Today manufacturers are able to make dyes that change colour at specific temperatures for a given application, e.g. colour changes can be initiated from the heat generated in response to human contact. Physico-chemical and chemical processes such as coacervation and interfacial polymerisation have been used to microencapsulate photochromic and thermo-chromic systems. However, to obtain satisfactory shelf-life and durability on textiles, interfacial polymerisation techniques are nearly always adopted. The most widely used system for micro-encapsulation of thermochromic and photochromic inks involves urea or melamine formaldehyde systems [7].

4. Micro-encapsulation: the future

The ideal feature for most textile applications using microcapsules would be a system that is easy to apply, does not effect the existing textile properties and has a shelf-life on a garment that allows normal fabric-care processes to take place. Currently, although capsules can survive 25–30 wash cycles, conventional ironing and other heat-input processes such as tumble-drying can cause a dramatic reduction in the desired effect. The micro-encapsulation industry must take more notice of the possibilities within the textile industry and specifically design microcapsules that overcome these problems. For the future, the consumers desire that novel and unique effects will always be present. But more importantly, in an ever-increasing desire for convenience, the consumer will require that fabric properties are inherent in the garment, e.g. fresh odour and softness. Consumers will expect these properties to last the lifetime of the garment, and not involve routine intervention in the form of the never-ending addition of washing aids and fabric conditioners. Micro-encapsulation may deliver these long-term goals. The desire for a healthier and more productive lifestyle will continue to generate a market for textiles that promote “well-being”. Textiles that “interact” with the consumer, reducing stress, promoting comfort and relaxation, are possible through active delivery from microcapsules. In the last decade the textile industries have concentrated on developing performance fabrics with added value for sports and outdoor application, as well as novel medical textiles. Micro-encapsulation can play a part in this continued development, for example by allowing sensing chemicals to be attached to sports clothing and medical products; these will be able towarn of damage or hazard to the wearer. Systems can also be developed that deliver measured dosages of chemicals to combat muscle pain or other more serious injuries.

The potential applications of micro-encapsulation in textiles are as wide as the imagination of textile designers and manufacturers. Early success for some companies in producing microencapsulated finishes for textiles have come about from collaboration and adaptation of technology from other industrial sectors [8].

6. References:

1. H. F. Mark, D. F. Othmer, C. G. Overberger, G. T. Seaborg, Micro-encapsulation, Encyclopedia of Chemical Technology (III ed.), vol.15, 470-493, Wiley Interscience publication
2. H. F. Mark, N. M. Bikales, C. G. Overberger, G. Menges, Microencapsulaion, Encyclopedia of Polymer Science and Engineering (II ed.), vol.9, 724-745, Wiley Interscience publication
3. N. S. Zubkova, Thermal Insulation, Knit. Int. 102 (1216), 1995a, 50
4. N. S. Zubkova, Phase change technology outlasts lofted fabrics, Tech. Text. Int. 4 (7), 1995b, 28-29
5. D. P. Colvin and G. Y. Bryant, Protective clothing containing phase change materials, Advances in heat and mass transfer in biotechnology (HTD), New York: ASME 362, 1998, 123-132
6. B. Pause, Measuring the thermal barrier function of phase change materials in textiles, Tech. Text.. Int. 9 (3), 2000, 20-21
7. K. Yamada and Y. Yamada, A scent of the Unusual, Int. Dyer, 2000 (june), 26
8. K. Hong and S. Park, Melamine resin microcapsules containing fragrant oil: synthesisand characterization, Mat. Chem. Phys.,1999, 58, 128-131