The Role Of Crimp In The Textile ProcessTexturing: means bywhich luxurious bulk , greater absorbency and improved hand are combined withrugged performances through permanent introduction of crimp, loops, coils orwrinkles into an otherwise continuous filament.Fibersused in texturing: Generallythermoplastic fibers such as nylon, polyester, acetate and polypropylene areextensively used for producing textured yarns. ‘Advantages: Higher bulk Greater water absorption Increased warmth Good draping capacity Better air permeability Better dimensional stability Higher covering power Higher hygienic characteristics Pleasing hand and appearanceDisadvantages: Increased hairiness Reduced strength and abrasion resistance Crimp : is waviness introduced in staple fibers to bespun into yarn.Take UpPercentage or Crimp Rigidity: Take up percentage or crimprigidity is a measure of the ability of textured yarn to receive from stretch.It is the ratio of reduced length to original length, expressed as percentage.Thus, take up percentage T% = L – P/ L × 100.Crimp rigidity tester:There are three methods:1.
Mechanical method2. Chemical method3. By using bio components 1. Mechanical methodIn order for staple fibers to be spun into yarn,they must have a waviness, or crimp, similar to that of wool.Crimp may be introduced mechanically by passingthe filament between gear like rolls.
2. Chemical methodIt can also be produced chemically by controllingthe coagulation of a filament.3. By using bio componentsA similar effect can be produced from biocomponent fibers. When the filament is drawn, the two polymers extend todifferent degrees, producing a helical crimp when the strain is relaxed.
Types of crimping:1. Edge crimped yarns2. Stuffer box crimping3. Gear crimping1.
Edge crimped yarnsStretch and modified stretch yarns canalso be produced by a process known as “edge crimping”.The use of edge crimped yarn has beenextended to heavy denier yarns for the use in carpet, knitted outer wear, men’shosiery etc. Knife edge crimping:• In thisprocess yarn is tensioned, stretched, heated , bent and drawn around an edge ,followed by shrinking and cooling step.• Crimpdevelopment in a filament is caused by bilateral compressional deformation,extensional strain deformations inducedin the heated filament as it is being pulled over a blunt knife edge.
• Thefilament touching the knife edge is under compression where as that on theoutside experiences extension.• The regionpressed against the knife edge is deformed into a flat and a filament crosssection appears.• Finalcrimp development is thus a function of: temperature bending curvature dwell time on edge• Compressionzone : rupture of crystals, disruption of molecular orientation .
• Regionfarthest from edge : stretched todevelop a crimp in the filament.• The strainsthus induced are relaxed by subsequently relaxing and heating the yarn undercontrolled conditions.• Relaxationis carried out either in steam or in dry heat.
• Whenstrain is released crimpage takes place .• Filamentform coils in almost helical configuration. Crimpstructure:2. Stuffer box crimping The crimping unit consists of two feed rolls andbrass tube stuffer box and a brass tube stuffer box. By compressing the yarninto the heated stuffer box, the individual filaments are caused to fold orbend at a sharp angle, while being simultaneously set by a heating device. • The process oftexturing by the stuffer box method is based on the principle of heat setting filaments held in a confinedspace in compressed state and then drawing them in their crimped form.
Thechamber in which the filaments are stuffed is known as the stuffer box. Thestuffer-box method is a fast and inexpensive method for carpeting yarn.• Properties : zigzag to wavy crimp, low elasticity.• Crimp structure: • 3. Gearcrimping :· In this methodfilament is run between a pair of intermeshing gear wheel.· The resultantyarn is left with the impression of the gear wheel teeth. • Bulk can be producedin a continuous filament yarn when it is passed through closely meshed gears.• The gear head isheated so that the crinkle produced in the yarn is permanent.
• End use applications : Ladies and children knitted outer wear Sweaters Ladies blouse 4. Air jet texturing method:· · Theair jet texturing process consists of subjecting an overfed bundle of filamentsto the action of a turbulent air steam in a venture tube.· Air jet is basically a mechanical process andcan be used for both thermoplastic and non thermoplastic filament yarns as well as their blends. · Yarnsproduced by this process resemble the natural fiber spun yarn both inappearance and physical characteristics.· Yarns produced by the air-jettexturizing are totally different structures in that they much more closelysimulate spun yarn structures· Thereare two basic types of texturing jet i. Axial ii.
Radial· Properties: i. High yarn stability ii. Low and uniform package take-off tension iii. High bulk iv. Reduced boiling water shrinkage v. Improved soft hand of fabrics vi. Elimination of the Velcro effectof fabrics vii. High pilling resistance viii.
Uniform appearance of the fabric ix. Sizing of warp beams may not benecessary for slower running looms Crimp structure: 5. Knit andde knit: In thismethod, the flat yarn is first knit, then heat set and unraveled to produce acrinkle type structure.knit-de-knit yarns are available in all color shadeswhich makes them a favorite for effect or fantasy yarns for distinct designs intrendy knitwear. · Properties: i. Excellent stretch ii. Full hand iii.
Yarns are torque free iv. Wavy crimp v. Elongation vi. Crepe effect Crimp structure: