THEORY EXAMINATION (SEM–VIII) 2016-17 TECHNOLOGY OF PRINTING-II

SECTION A – Basic Concepts of Printing Technology

Section A includes short questions related to textile printing processes, dye fixation, digital printing, and finishing treatments used in printing technology. 

Question (a): What is the Role of Binder in Pigment Printing?

Answer:
In pigment printing, the binder acts as an adhesive material that helps fix the pigment particles onto the fabric surface. Pigments themselves do not have chemical affinity for fibers, so they require a binder to attach them to the fabric.

During the curing process, the binder forms a thin film that holds the pigment particles firmly on the fabric surface. This improves the durability and wash resistance of the printed design.

Thus, the binder is an essential component in pigment printing because it ensures proper fixation of pigments.

Question (b): What is the Purpose of Drying and Washing-Off Treatment?

Answer:
Drying and washing-off are important post-printing treatments.

Drying removes moisture from the printed fabric after the printing process. This ensures that the printed design remains stable before further processing.

Washing-off removes excess dyes, chemicals, and impurities that remain on the fabric after printing. This improves the clarity of the printed design and prevents color bleeding.

These treatments help improve the quality and durability of the printed fabric.

Question (c): Define Steaming Process

Answer:
Steaming is a process used in textile printing to fix dyes onto the fabric fibers. In this process, the printed fabric is exposed to steam under controlled temperature and humidity conditions.

The steam provides moisture and heat, which allow the dye molecules to penetrate the fibers and form a chemical bond.

Steaming is commonly used in printing with reactive dyes, acid dyes, and disperse dyes.

Question (d): Define Ageing

Answer:
Ageing is a treatment in which printed fabrics are kept in a warm and moist environment for a certain period of time to allow the dye to react with the fiber.

This process improves dye fixation and color development. Ageing is often used in textile printing processes involving reactive dyes.

The ageing process helps produce brighter and more stable colors on fabric.

Question (e): What are Discharging Agents?

Answer:
Discharging agents are chemicals used in discharge printing to remove previously dyed colors from specific areas of the fabric.

These chemicals destroy or modify the dye molecules in selected areas, creating a pattern on the fabric.

Common discharging agents include reducing agents such as sodium formaldehyde sulfoxylate.

Discharge printing is often used to create white or colored patterns on dark fabrics.

Question (f): What is the Fixation Process in Printing?

Answer:
Fixation is the process of permanently attaching dyes or pigments to textile fibers.

During fixation, the dye molecules form chemical bonds with the fibers, ensuring that the printed design remains durable and resistant to washing and rubbing.

Different fixation methods include:

Steaming

Curing

Thermofixation

Chemical fixation

Fixation is a critical step in textile printing because it determines the color fastness of the printed fabric.

Question (g): What is Digital Printing and What are its Components?

Answer:
Digital printing is a modern printing technology that prints designs directly onto fabric using digital data.

Unlike traditional printing methods, digital printing does not require printing screens or plates.

The main components of digital printing systems include:

Computer or digital design system

Printing software

Inkjet print head

Ink supply system

Fabric feeding system

Digital printing allows high precision, fast production, and easy customization of textile designs.

Question (h): Define Curing

Answer:
Curing is a heat treatment process used in pigment printing to fix the binder and pigment onto the fabric surface.

During curing, the printed fabric is exposed to high temperatures that cause the binder to polymerize and form a durable film.

This process improves the wash fastness and durability of the printed design.

Question (i): Define Resist Style of Printing

Answer:
Resist printing is a method in which certain areas of the fabric are treated with a chemical substance that prevents dye from penetrating those areas.

When the fabric is dyed, the resist-treated areas remain undyed, forming patterns.

Resist printing is commonly used in traditional textile designs such as batik.

Question (j): What is Sublimation Transfer Printing?

Answer:
Sublimation transfer printing is a printing technique in which dye is transferred from paper to fabric using heat and pressure.

In this process, the dye sublimates (changes from solid to gas) and penetrates the fabric fibers.

This method is commonly used for printing on polyester fabrics because the dye bonds effectively with synthetic fibers.

SECTION B – Intermediate Concepts of Textile Printing

Section B questions involve detailed explanations of printing processes and techniques used in textile printing. 

Question: Printing Polyester/Cellulosic Blended Fabric with Disperse/Reactive System

Polyester/cellulosic blended fabrics require a combination of dye systems because polyester and cellulose fibers react differently to dyes.

Disperse dyes are used for polyester fibers, while reactive dyes are used for cellulosic fibers such as cotton.

The printing process typically involves preparing a printing paste containing both dye systems, followed by drying and fixation processes such as steaming and thermofixation.

This method ensures proper dye fixation on both fiber types.

Question: Discharge and Resist Style Printing with Azoic Colors

Discharge printing involves removing previously dyed colors from fabric to create patterns. Azoic dyes can be used in discharge printing by applying discharging agents that break down dye molecules.

Resist printing prevents dye penetration in certain areas of fabric by applying resist chemicals before dyeing.

Both techniques allow designers to create complex and artistic patterns on textiles.

Question: Flock Printing

Flock printing is a decorative printing technique in which short fibers are applied to the surface of fabric to create a velvet-like texture.

The process involves applying adhesive onto the fabric in the desired pattern and then depositing fibers onto the adhesive-coated areas.

After drying and curing, the fibers remain attached to the fabric, forming a raised design.

SECTION C – Advanced Printing Technology Concepts

Section C questions require detailed explanations of advanced printing processes and machinery. 

Question: Types of Steam Used for Fixation Process

Steam is used in textile printing to fix dyes onto fibers.

Different types of steam used include:

Saturated steam

Superheated steam

High-pressure steam

Each type of steam provides different levels of temperature and moisture, which influence dye fixation efficiency.

Steamers are specialized machines used to expose printed fabrics to steam under controlled conditions.

Question: Sublimation Transfer Printing Process

Sublimation transfer printing works by transferring dye from transfer paper to fabric using heat and pressure.

The mechanism involves:

Printing the design onto transfer paper using sublimation dyes.

Placing the transfer paper onto the fabric.

Applying heat and pressure using a heat press.

The dye sublimates and penetrates the fabric fibers.

This method produces high-quality prints with excellent color brightness.

Question: Continuous Ink Jet (CIJ) and Drop-on-Demand (DOD)

Continuous Ink Jet printing continuously ejects ink droplets from the nozzle, and unwanted droplets are deflected away using electrostatic fields.

Drop-on-Demand printing produces ink droplets only when needed.

CIJ is faster and suitable for high-speed printing, while DOD provides higher printing precision.

Each method has its own advantages and disadvantages depending on the printing application.

Conclusion

Technology of Printing-II focuses on advanced textile printing processes and techniques used to create high-quality designs on fabrics. Concepts such as pigment printing, steaming, curing, discharge printing, and digital printing play a crucial role in modern textile production.

Understanding these processes helps engineers and designers develop efficient printing methods that improve fabric quality, color durability, and design precision.