Journal On: “Influence of sheath structure on twist and diameter of dref- III polyester-wool blended friction-spun yarn ” By, S K Sinha & R Chattopadhyay Indian Jounal of Fibre & Textile Research Vol. 31, June 2006, pp. 286-292 Presented By: Md. Niloy Rahman MSc. 4 th Batch Dept: Y.M.E ID:2015-2-1-010 Presentation Date:22April2016
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Dref iii polyester-wool blended friction-spun yarn
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Journal On: “Influence of sheath structure on twist and diameter of dref-III polyester-wool
Introduction: > Torque between friction drum and fibers. > Polyester in Core & Sheath(Wool/Polyester/both) > Core fibers false twist & Sheath wrap the core fibers. > Twist depends(Drum speed/Del speed). > Dref-III-sheath may lay different layers.
Materials & Method:>Rieter C 1 /3 card and RSB 851 draw frame >Polyester: Staple length 48mm & fineness 11
Micron sliver 3.45gm/m.
>Wool: 54 mm mean length and fineness 25 micron sliver 2.18 gm/m
Materials & Method: Cont….Drafting Unit 1: Polyester Fibers(Core)Drafting Unit 2: Wool+Polyester Fibers(Sheath)Sheath fibers and its relative position:I. Sheath containing polyester and wool in the
inner and outer layer respectively is designated as structure A.
II. Sheath containing polyester, wool and polyester in alternate layers is designated as structure B.
III. All wool sheath is designated as structure C.
Materials & Method: Cont….
Fig: direction of sheath fiber approach
Materials & Method: Cont….
Total 81 yarn samples of 33Tex were spunDifferent friction drum speeds:
3500,4000,4500 rpmDifferent delivery speeds:
120,150,180m/minDifferent core sheath ratio:
50:50,60:40,70:30
Materials & Method: Cont….
Table: Different Sheath layers(P - Polyester fiber and W - Wool fiber.
Materials & Method: Cont….
Fig. Pictorial representation of the cross-section of yarn structures [Dark and light bands represent wool and polyester fibres respectively.]
Measurement of yarn twist & dia
Twist (turns / m) = (N2 - N1 ) x 39.37N1=Req. twist to break yarn same direction.N2=Req. twist to break yarn opposite direction
To measure yarn diameter:Yarn wound loosely on a board and microscopic test. At least 100 readings were taken per sample
Results and Discussion:(TWIST)Cont....The twist in structure A is always maximum,
whereas in structure C it is minimum.589-826 turns/m for structure A, 368-507
turns/m for structure B and 181 to 339 turns/m for structure C.
This friction, in turn, depends upon (i) the coefficient of friction between the fibres in the outer layer of the yarn tail & the friction drum and (ii) the normal force acting on it as a result of pressure difference due to suction acting through the perforations of the friction drums.
Results and Discussion:(TWIST)Cont....
The relationship of pressure difference (∆p) and airflow (F) is
k is the factor of form; η, the viscosity of air; s, the mean specific surface of fibers; m, the total mass of fibers; y, the fiber density; L, the length of the section of the chamber in which fibers are packed; and A, the area of the section.
Influence of friction ratio:Friction ratio is defined as the ratio of surface speed of friction drum and delivery speed. in this research the different ratios ranging between 2.7
and 5.3.
Fig:Effect of friction ratio on yarn twist A higher friction ratio indicates a higher drum speed
relative to delivery and hence a higher twist is expected.
Results and Discussion:(Yarn Diameter)• It is observed that the yarn diameter changes
with the change in sheath composition and structure.
Table: Diameter of yarn
Results and Discussion:(Yarn Diameter)Cont…The diameter is minimum for structure A
and maximum for structure C.The diameter increases marginally with the
increase in delivery speed for all the core sheath ratios.
Wool fibres being stiffer (due to being coarser) more crimpy and resilient are difficult to wrap around the core tightly.
The effective wrapping consolidates the core, thereby showing lesser yarn diameter.
Conclusions:
Higher the delivery speed reduction of twist.
Higher the friction ratio higher the twist.Stiffer character of wool less wraping
tendency less twist and higher the diameter.
Thanks to allThanks to all
Objectives of Kevlar & Properties Kevlar is a type of aramid that consists of
long polymeric chains with a parallel orientation. Kevlar derives its strength from inter-molecular hydrogen bonds and aromatic stacking interactions between aromatic groups in neighbouring strands.
Several grades of Kevlar are available: [1] Kevlar K-29 – in industrial applications, such as cables, asbestos replacement, brake linings, and body/vehicle armour.[2] Kevlar K49 – high modulus used in cable and rope products. [3] Kevlar K100 – coloured version of Kevlar [4] Kevlar K119 – higher-elongation, flexible and more fatigue resistant. [5] Kevlar K129–higher tenacity for ballistic applications. [6] Kevlar AP – has 15% higher tensile strength than [1] Kevlar KM2 – enhanced ballistic resistance for armour applications. The ultraviolet component of sunlight degrades and decomposes Kevlar
Figure 4. Molecular structure of Kevlar Superb Properties of Superb Properties of Kevlar ●It is strong but relatively light. ●Unlike most plastics it does not melt: it's reasonably good at withstanding temperatures and decomposes only at ~450°C (850°F). ●Kevlar can be ignited but burning usually stops when the heat source is removed. ●Very low temperatures have no effect on Kevlar. There is no appreciable embrittlement or degradation down to -196°C (-320°F), which makes it excellent for Arctic conditions. ●Like other plastics, long exposure to ultraviolet light (in sunlight, for example) causes discoloration and some degradation of the fibres. Kevlar can resist attacks from many different chemicals, though long exposure to strong acids or bases will degrade it over time. ●Kevlar remains virtually unchanged after exposure to hot water for more than 200 days and its properties are virtually unaffected by moisture.
Figure 11. Fibre Optics by Kevlar Figure 12. Different use of ropes & cables in different fields
Uses & Applications Military Body Armor & Jackets Protection Vests Military Helmets Automotive Uses Kevlar as a Composite Mass Transportation Figure 7. Jacket by Kevlar in Military Uniform
Kevlar in Fiber Optics Ropes and Cables Consumer Applications Other Uses
Figure 9. Kevlar in Automobile Cars
Figure: Military Helmets Figure 10. Kevlar in Aircraft
Conclusions Kevlar mainly use for two
reasons, and both are about performance: It’s lightweight and easy to integrate. A thin blanket can serve as structural reinforcement or ballistic protection, everywhere from seismic shear walls to bank counters. Sprinkle the fibres into carbon composites to cut weight and boost strength.