Finishing of technical textiles Description of different techniques used in wet processing to develop Technical Textiles Dr Muhammad Mushtaq Mangat www.mushtaqmangat.org Dec 31, 2012
Finishing of technical textiles
Textile Finishing: A process to improve the performance and
appearance of textile It may be mechanical or chemicals processes It could be temporary or permanent examples:
Calendering Peaching Raising Coating Deposition of chemicals (fire retarding)
Mechanical finishes
Calendering
Modification of fabric surface by passing fabric through hot roller
Rollers may be engraved or polished
Purposes of calendering smoothing the surface of the fabric,
increasing the fabric lustre
closing the threads of a woven fabric
decreasing the air permeability
increasing the fabric opacity
improving the handle of a fabric, i.e. softening
flattening slubs
obtaining silk-like to high gloss finishes
surface patterning by embossing
consolidation of nonwovens. [1]
Flattening effect on fabric of calendering
Calender definition and process
A mechanical process to impart certain temporary or permanent effects on web, fabric or batt
Material is passed through a nip of rollers, normally hot
Rollers may be plane, polished, covered with fabric, engraved, embossed
Calender parameters Calender speed (dwell time in nips)
Temperature of calender
Pressure of rollers (pressure per linear inch)
Surface of rollers (polished, covered)
Speed variation between bottom and top rollers
Number of passes
Over Feeding or under feeding
Calendering and Application of finishes
Dry Calendering without application of finishes
Drying and Calendering together
Pad Mangle and Calendering
[1]
Calendering of fabrics made by natural and synthetic fibers
Natural fibers
Need high pressure to defeat the physical memory and get a new shape, temperature role is less important than pressure
Strength of web depends upon the cohesion of fibers, need high pressure to achieve a certain homogeneity
Synthetic fibers
Synthetic fibers require the presence of heat to defeat the physical & thermal memory of the fiber
High temperature and low pressure are commonly in practice
Speed of rollers should be same to avoid any un-wanted luster [2]
Rolling Calender for synthetic fibers [2]
Rolling Calender It provides:
smooth or gloss fabric surface Reshape fibers, make them flatten and increase
cohesion by more tightly stack around (nestle effect) Composed of three rollers 100-150 meter per minute for normal fabric and 30-35
for nonwoven Can be run at 3000 PSI Four or five rolls Alternative rolls (polished and filled) The intermediate resilient roll is of wool felt paper,
cotton, khaki wool and resilient wool and cotton blends which affords the extension of the webs [2].
SILK FINISHING CALENDER
It provides a smooth fabric surface, light
luster and improved hand
Provides comparatively soft
Combination of small and big roller, provides wide nip. It will break any stiffness on the surface due to auxiliaries or weaving or knitting
Silk Calender [2]
FRICTION CALENDER - NOT FOR MOST NONWOVENS
To give highly polished surface
Also creates water repellency
Normally used for apparel fabric
Friction calender can be operated at different speeds
Set of three rollers,; one filled and two polished
Friction calender [2]
SCHREINER CALENDER
Used to obtain a controlled opacity, a desired softness luster and translucency
Light reflection is changed due to changes on surface
Pattern is engraved on the heated steel roll
Name derived from the pattern which is 260 lines per inch at a 26 ó degree angle and only .001” of an inch deep
It can consolidate the fibers by as much as 4% to 16%
Can be used for natural, synthetic and blended or coated fabrics that are both knit and woven or non woven [2]
SCHREINER CALENDER [2]
EMBOSSING CALENDER
Rollers with embossed patterns
Can be used for types of fabrics including woven, non-woven and knitted cloth
Desired shapes can be achieved by having certain patterns on calender rollers
Other properties are similar to normal calender
Can be used for all sorts of fabrics
There are forged steel top roll and a filled bottom roll with the filling of wool felt [2]
Embossed Calender [2]
CIRÉ CALENDER
The Ciré calender is used for glazing and glossing fabric surfaces using both high temperatures >425 F and high pressures >1500 PLI
Porosity reduction and compaction is done
Various types of fabrics can be processed
CIRÉ CALENDER
HI-DWELL - HEAT TRANSFER PRINTING CALENDER
Also called paper printing machines
Purpose is to transfer print from paper to fabric
Hot rollers are used for paper printing
Mostly used for polyester fabric
Disperse dyes are used
Paper printing rollers
RESILIENT ROLLS
Also called calender bowls
Made by using high tonnage of pressure; 120,000 tons of pressure the cotton rings to be able to use as calender
Rollers are quite hard in nature
RESILIENT ROLLS
[2]
Raising (Brushing)
Raising is a process in which fabric is brushed with the help of wired rolls to give a brushed (napped) look
Fibers are pulled from the yarn to make a soft feel and increased thickness
It gives a hairy surface
More air is trapped and thermal resistance increased
Rotating rolls fitted with wires are used
Fabric Brushing Machine
Raising Methods
Hooked or bent steel wires are used for brushing
Angle, speed and pressure are main factors
Number of rotating rollers, width of rollers define the capacity of machine
More than one pass is normally require for uniform surface
[1]
Shearing
A process in which piles of fabric are cut to
have a uniform and smooth surface
Lawn mover (grass cutter) machine principle is applied
Compressive Shrinkage
(Compaction)
Shrinkage on washing is a common phenomenon
It is due to residual stress or strain in fabric during process
Very common use
Makes fabric more stable and minimize the shrinkage
[2]
Sueding (Peaching)
Sueding Technique
Sueding
To give a peach look
Brush or zero sand paper is used
Improve hand feel
Better thermal resistance
Currently much demanded and in practice
Heat setting
To make a stable fabric
Used to ensure that there will be no change in dimensions
Only used for synthetic fibers
Required temperature is above the softening temperature of fibers
Certain temperature and time is required for heat setting
Heat-setting mechanisms
1. chain stiffness
2. strong dipole links
3. hydrogen bonds
4. crystallization [1]
Influencing factors Temperature, Moisture, stress.
PET fabric is passed through stenter at 180-190 C for 30-60 seconds
Sudden cooling effect, called decatizing is done for better setting
Little moisture helps for better heat setting
In general heat setting temperature is with in 20-20–40 °C of the fiber melting point.
Hold at this temperature under tension for approximately 20 s.
Cool fabric before removing tension
After heat setting shrinkage should be less than 1% [1]
Transition temperatures
Glass transition temperature:
Molecules tarts moving in amorphous region
Substance starts changing from a glassy solid to a rubbery solid
Loosening starts and dyeing is possible
Melting point Thermal energy increases than holding
energy
Pleated Fabric
Permanent Pleats
To give better look
Increase usability
Some special purpose fabric is made
Common for ladies clothing
Bags are produced for more space
Pleat Making Machine
Chemical Treatment Fire retarding
Water repellant
Stain proof
Ant bacteria, moth proof
Self cleaning
Flavored
Anti pilling
Anti slippery
Stiffening and filling process
Polymers are used to create stiffness
Stiff effect is required for certain purpose e.g. collar lining, curtain lining etc.
Most common are poly vinyl acetate and poly vinyl chloride
Applied on padding
High Wicking
Wetting agents are used to increase wicking power of fabric
Towels, T shirts, shorts are treated with wetting agents
Applied on exhaust and padding
Anti-static finish
PE is much popular to reduce the static effect
Improve comfort of clothing
Much required for sensitive skin
Anti-pilling finish
Mostly enzymes are used to remove protruding fibers
Also called bio-polishing
Cleans the surface
Reduces the chances
Non-slip finishes
To have better grip
Rough surface is developed
Silica gel is commonly used
Gives a crispy hand feel
Fire Resistant or Flame Retardant
Flame retardants are materials which can minimize the spread of fire
For better safety, becoming popular in every area,
Many laws are being formulated to have Fire-retardant items at work event at homes
Two techniques: Application of chemicals on fabric surface Making changes in fiber to make them fire
retardant
Anti-microbial finish Microbes are the tiniest creatures, Cannot seen by the
naked eye
Bacteria, Fungi, Algae and viruses are part of this group
Bacteria are uni-cellular organisms, it grows rapidly under wet and warm conditions [3]
Ant-microbial finishes are required to improve safety and comfort
Brominated phenols, quaternary ammonium compounds, organo-silver and tin compounds, are used
Pad or exhaust methods are used
Conti… It controls the odor due to bacteria reproducing
Finishes will stop bacteria reproducing
It will minimize the amount of odor
Stops cross infection by pathogenic micro organisms and control the infestation by microbes
Arrest arrest metabolism in microbes in order to reduce the formation odour
Protects the textile products from staining, discoloration and quality deterioration.
[3]
[3]
Self Cleaning Fabric To make clothing cleaner – permanently
Possible by a polymer film of polyglycicidyl methacrylate sprinkled with silver nanoparticle
Not actually self-cleaning
High resistance to dirt
Concept is based on the lotus plant
Lotus leaves are well-known for their ability to ‘self-clean due to repelling properties of water and dirt
Some water to rinse away dirt and stains, but cleaning will be quicker [5]
Hybrid Polymer Nanolayers [5]
Lotus Leaf
References [1] Hall, M.E., Finishing of technical textiles, in Handbook of Technical Textiles A.R. Horrocks, Anand, S. C., Editor 2000, Woodhead Publishing Ltd Cambridge.
[2] Gunter, D.S., Perkins, B. F. . THE BASIC MECHANICS OF CALENDERING AND EMBOSSING NONWOVEN WEBS. 2012; Available from: http://www.idspackaging.com/common/paper/Paper_320/calendering_wp.pdf.
[3] Aravin, P. , and Myvizhirajeswari, G. SILVER BASED ANTI‐ ?MICROBIAL FINISHING ON COTTON
[4] Tanveer Malik, T. and Nogja, S., Goyal, P. Self cleaning textile - an overview http://www.fibre2fashion.com/industry-article/4/389/self-cleaning-textile-an-overview2.asp
[5] http://www.technovelgy.com/ct/Science-Fiction-News.asp?NewsNum=271