MODAL: FIBRE TO FABRIC
Vasant Kothari, Assistant Professor, Department of Fashion Technology
喜耀粤西学校
防暑降温措施管理办法Prashant Verma, Master of Fashion Technology
ABSTARCT
The purpo of this article is to introduce the reader with Modal fibers; there properties, applications etc and why at all there is a need to introduce this fiber. Herein Modal acts as a cond‐generation visco rayon fiber fulfilling humans’ eternal quest for a fiber combining both aesthetics and utility performance.
HISTORY
To dissolve and spin the cellulo, method developed by English men3.5 “Cross bad Bevan” became most popular and was adopted exclusively by Lenzing. During the First World War, with shortage of raw material, visco rayon manufacturers discovered that it was possible not only to produce filament fibres but also by cutting the fibres into short staples, to create a substitute over cotton. The visco rayon staple fibres thus continued to be recognized as substitute for cotton until t
he Second World War.
Considerable improvements to the fibre, which Lenzing make, boosted fibre prestige leading to its classification as a distinct species. Modal fibers’ staple versions were initially developed in 1930s for industrial textiles (in tires, conveyor belts and ho pipes), and for blending with rapidly growing synthetics. Changes in visco rayon processing such as spin conditions; chemical solutions and stretching quences produced visco rayon fibers with incread crystallinity and thus greater strength. Additional developments in Japan in 1951 by S. Tachikawa led to the production of Modal fiber with high wet modulus called polynosic fiber.
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INTRODUCTION
Modal is a wood pulp bad cellulosic fiber, made out of pure wooden chips from the beech tree, technically as the European Schneider Zelkova3.2 tree. While visco rayon can be obtained from the wood pulp from a number of different trees, Modal us only beech wood, thus it is esntially a variety of visco rayon; a generic name for modified visco rayon fiber that has high tenacity and high wet modulus.换位思考的名人素材
Modal was first developed by Austria bad Lenzing AG Company who trademarked the fabrics’ nam
e, but now many manufacturers make their own versions. It was initially imported from Czech Republic, Slovakia, Hungary and Germany; but now for Indian market, it is catered to by Lenzing, Austria, which has tied up with Rajasthan Textile Mills.
What is Modal: Definition
Modal fibers are defined in International Standard ISO 206: 999 (E) as high wet modulus, high breaking strength regenerated cellulo fibers produced by using particular visco rayon, and regeneration bath compositions which allows greater molecular orientation during stretch and coagulation of the fibers.
Again, Modal as defined by the International Bureau for Standardization of Manmade Fibres (BISFA) is a distinct visco rayon fibre genre, which has a higher wet modulus and satisfies a minimum value of tenacity in the wet stage at 5% elongation.
MANUFACTURING PROCESS
The process of Tachikawa patent, following wet spinning, manufactures modal fiber. It is considered as bio bad3.1 rather than natural becau though the raw materials ud to make it are natural, th
ey are heavily procesd using a number of chemicals. The process followed for the manufacturing of Modal is similar to that of visco rayon except slight modification in one or two steps. The basic steps followed are:请示报告范文
1. Steeping and Pressing
卓文君的诗The objective of this process is to convert cellulo to its alkoxide derivative (alkcell). Here pulp is steeped in an aqueous solution of sodium hydroxide 17%, causing fibers to swell and converting cellulo to sodium cellulosate. The slurry so obtained is presd to remove excess soda from the alkcell slurry.
2. Shredding
Alkcell here contains 30‐ 36% cellulo and 13‐ 17% soda. To assist subquent mercerizing and xanthation reactions, alkcell slurry is opened to facilitate the penetration of oxygen and CS2.
曲多音字3. Mercerizing
HWM visco rayon can also be mercerized, like cotton, for incread strength and luster. The reduction in DP is achieved by oxidative depolymerisation or can also be achieved by irradiative dep
olymerisation1.1.
4. Xanthation
Here mercerized alkcell reacts with CS2 vapor, under vacuum, to form sodium cellulo xanthate. To form the solution, xanthate is dissolved in dilute sodium hydroxide solution to give final composition in terms of percentage cellulo and soda in visco rayon.
5. Filtration and Deaeration
The impurities prent (substantial) must be removed prior to spinning to prevent blockage of spinneret holes. Lenzing KKF1.4 is exclusively using automatic mechanical filters of sintered metal screens with automatic back flush. Then it is de‐aerated, by applying vacuum, to remove any disperd air forming bubbles.
6. Spinning
Very high modulus and tenacity is achieved when cellulo is spun from liquid crystalline solution1.2. Unlike visco rayon, the u of zinc in the spin bath is eliminated completely, and only short period immersion in cold low acid‐low salt bath is followed. Jets ud to spin the fibers are fabricated fro
m platinum/gold alloy.
: Typical layout of wet spinning process:
7. Coagulation Bath
In Modal process, coagulation and stretch occur together and are followed by regeneration, leading to high wet modulus. Unlike visco rayon, filaments in the bath are stretched 3 times their spun length before regeneration, thus forming a structure with fibrillar texture. This stretch orients the cellulo molecule to a very high degree resulting in very high dry and wet strength ratio1.5.花朵图片大全
8. After Treatment
Modal fabric is given a clean soft touch finish by impregnating the fabric with an acid donor; heat treating in gaous atmosphere to activate the acid and subquently dyeing, washing and drying it. The resulting fabric has a sheen and glossy peach touch finish
STRUCTURE
The “all skin” high tenacity yarns consist of finer and more uniform texture. When coagulation and stretch occur together, before regeneration and crystallization of cellulo, structure has a fibrillar texture1.3. The Cross ction is either circular or bean shaped.
: Microscopic view of Modal Fibers:
The cross ction analysis of both Modal and Visco rayon fibers are analyzed 3.3 and are shown in figure below:
: Regular Visco rayon:
: Modal Fiber:
PROPERTIES AND COMPARISON
In brief, Modal poss lower elongation and higher wet modulus as it has high rate of polymerization. Its exceptional similarity to cotton/silk in terms of texture (luster, sheen and gloss) results in a surface smoother than mercerized cotton.
A typical comparison of properties of High wet modulus visco rayon with commonly ud convectional fibers is as follows:
PROPERTIES
HIGH ‐WET MODULUS
COMMONLY USED
Modal
Visco rayon Cotton
Polyester
Wool
Density (g/cm 3) 1.53 1.51 1.55 1.39 1.31 Moisture Regain (%) 11.8% 12.5% 8.5% 0.4% 13.5% Tenacity (GPD) 2.2‐4.0 dry 1.2‐3.0 3.0‐5.0 3.0‐5.8 0.8‐2.0
3.8‐5.0 wet 0.5‐0.8
4.0 2.4‐3.0 1.0 Bkng Elongation (%) 7.0% dry 15‐30% 3‐10% 19‐55% 20‐40%
8.5% wet
30%
10%
47%
31%
