It is very common technical question for all technician , How to find out which yarn count should be use for which structure to achieve required GSM . It has to be calculate based on required tightness factor , So that residual Shrinkage in the finish fabric should be within control .
For this purpose we have made this calculator . Here one need to Select Knitted fabric structure , and type the required GSM, Result will be Ideal yarn count required to knit this fabric
Polyester based knitted fabric means any fabric has polyester fibre as composition in the fabric. It may vary from 5 % to 100% . Based on polyester % in the fabric the processing method will change . As fabric may have polyester in the form spun fibre or filament . Processing of the fabric will depend on this also.
Polyester knitted fabrics are used on a large scale for outer wear of all types. The main reasons for their success are the wide patterning potential, the good durability and crease resistance, and the excellent easy-care properties. Polyester knitted fabrics are composed almost exclusively of texturized yarn. To avoid creases and breakages, knitted fabric that have not been set should always be stored or treated in full width.
Polyester fabrics are made using the following yarns
Filament yarns are made in monofilament and multifilament forms.
Textured Yarns are produced of polyester multifilament. they are given a texturizing either in conjunction with the drawing process or subsequently as part of the throwing and texturizing process in producing the finished yarns.
Spun yarns , means it is made from the fibre . It may be 100% polyester or blend with any other fibre as like Viscose, Cotton , Modal etc .
Properties of polyester fabrics – Fabrics made of regular tenacity polyester filament yarns are very strong and durable. They do not have a high degree of elasticity which means it is characterized as having a high degree of stretch resistance, which means polyester fabrics are not likely to stretch out of shape too easily. This property makes polyester suited for knitted garments, sagging and stretching that would ordinarily occur are reduced.
Polyester fabrics have good dimensional stability. It has got a high degree of resilience. Polyester fabric resist wrinkling when dry, it also resists wrinkling when wet. For example, a suit of polyester will keep its pressed appearance after many wearing, even after exposure to rain or moist, humid weather. Fabrics of polyester filament yarn have satisfactory draping qualities. The trilobal filament type is more supple and imparts better drapability. spun yarns are also more flexible and softer, thereby imparting the draping quality.
Polyester fabrics are better conductors of heat than acrylic fabrics. Polyester fabrics have low absorbency as a result it will dry very rapidly since almost all the moisture will lie on the surface rather than penetrate the yarns. So polyester fabrics are well suited for water –repellent purposes, such as rain wear. This low absorbency means that polyester fabrics will not stain easily except oil which has got affinity for polyester, and it is difficult to remove.
The main disadvantage due to low absorbency is polyester fabrics are clammy and uncomfortable in humid weather because they will not absorb perspiration or atmospheric moisture. This property can be improve by using multifilament Polyester filament yarn. As it helps to evaporate water fast by spreading water in larger area .
There is essentially no water shrinkage of polyester fabrics; therefore, shirts, blouses and even slacks may be safely laundered. When ironing polyester fabrics, it is best to use low to medium heat. excessive heat will cause polyester to melt. The wrinkle resistance of polyester is extremely good. Polyester fabrics made from spun polyester yarns tend to pill.
Polyester fabrics shrink as much as 20 % during wet – finishing operations and they are generally heat –set in later treatments. Polyester fabrics are better suited for outdoor use because it has good resistance to degradation by sunlight. They are resistant to mildew.
Scouring of Polyester based fabric –
It is required for all type of polyester knitted qualities. It is carried out as Single bath Scouring & Weight Reduction in HTHP Dyeing machine. It involves following steps
1- Loading of fabric at water which is pre heated up 50 deg C, and having no chemicals . As warm wash will help to remove Knitting oils from the polyester based fabric easily . It is in general seen if we add wetting agent then it becomes some times difficult to remove oil completely . We might have listen several times from knitting oil seller that our oil is water soluble , We should focus on this line. Hence first give only 10 min warm wash .
2- Weight Reduction of Polyester fabric
PROCESS FOR LEVEL DYEING OF 100% COTTON KNIT FABRICS WITH REACTIVE DYE
CHOWDHURY JONY MOIN1 AND A.K.M. MAHABUBUZZAMAN2
1 Senior Lecturer, Department of Textile
Engineering, Southeast University, Dhaka, Bangladesh
and 2 Principal Scientific Officer,
Mechanical Processing Division, Bangladesh Jute
Research Institute (BJRI), Manik Mia Avenue, Dhaka-1207, Bangladesh.
Accepted for publication
on 17 July 2009
ABSTRACT
Moin, C.J., and Mahabubuzzaman, A.K.M. 2009. Process for level dyeing of 100% cotton knit fabrics with reactive dye.
J. innov.dev.strategy 3(4): 01- 08.
The research was carried out at Hamza Textile Mills Ltd.of Gazipur in 2007. A beige color is selected to dye in a modern knit-dyeing machine (jet type) with the capacity of 500kg; maximum load of 440kg with 88% load. Three batches are dyed and observed. The machine contains two separate feeding units and has the scope of dividing the batch into two parts, with 220 kg each. This study will enable the industry to reduce loss of reprocess and rejection of fabric. The study was identified that precision setup of cycle time, run-time, dosing time and temperature gradient can improve meter-to-meter variation from 66%- 86%; the study considers the factors namely water hardness, dyes combination and dyes levelling properties were optimum. In this study it was found that a satisfactory improvement in level dyeing of 100% cotton knit fabric with reactive dye could be ensured without additional chemicals or operational costs.
Manufacturing of knit goods is cheap and 100% cotton knit
items are very comfortable which increase the
demand of knit underwear as well as outerwear. As a result knitting, knit dyeing and finishing industries are growing very
rapidly (Biljana et al 2004). In
2006, Textile Intelligence estimated yearly production of knitted goods to be 17 millions tons,
which is one-third of global textile market, and predicted an increase by 25% over the next 10 years,
amounting 21 millions
tons/year (Booth, 1968).
New fibre will be used and that will create new markets.
Designers will get high-tech fibres to create more sophisticated items, which will reduce monopolistic use of 100% cotton knitted textile in basic apparel.But still we are in trouble for quality of knit clothing items.
Day by day the customers are going to be more conscious about quality of clothing items. As a result it became more challenging to the manufacturer. First of all cotton
determines the quality of textile, hence higher quality cotton is used for clothing and lower quality for household or industrial products (Crown, 2005). If fibre is selected as per quality, then fabric quality will depend on fabric manufacturing and processing techniques.
Generally cotton fibres are ring spun to card, combed and compact yarn, among these first one is inferior and last one is the best in quality. The properties of yarn are directly shifted to the fabrics, as fabric- manufacturing techniques define arrangement of yarn by creating loops and interlacements. After fabric manufacturing the fabric is subjected for wet processing to add values.
Jets and Winch dyeing machines are usually used as exhaust equipment for preparation, dyeing and finishing of apparel knit fabrics (David, 2005). Knit fabric wet processing is started with batching or batch preparation where fabric is weighted as per machine capacity and the fabric is turned to inside out in case of body fabric i.e. main fabric of garments. Normally in Bangladesh single jersey fabric such as plain, locust, pique etc. fabrics are widely used for body fabric of garments. Interlock, rib, fleece fabrics are also turned to inside out when those are in unbalanced structures and used as body fabric of garments. The fabrics are usually turned to keep away from the any unaccepted incident or damage on face side and remove edge marks, which are created due to formation of fabric roll.
Maximum knit fabric problems are created during preparation, dyeing and after treatment
process. Common problems of knit dyeing are edge mark, crease mark, pin hole, loss of fabric strength, shade variation of batch to batch, uneven dyeing (such as roll to roll shade variation, patchy, color spot, white spot, meter to meter shade variation), hand feel problem, fastness problems etc.
Edge mark and Crease mark
incase of edge mark fabric is turned before wet processing and for precaution gray fabric roll should not too tight and should not stored for a long time. For crease marks anti-creasing chemicals are used. However, to ensure perfect remedy, preventive measures are more convenient and prescribed. Among the precautionary measures followings are ensured like convenient machine speed (with fabric compactness), correct loading (no twisted rope and knots), relaxation of fabric; proper dyeing process (heating-cooling rates not too rapid). Simultaneously the measures like stationary fabric in a running machine, overloading which might cause mechanical frictions, rough patches in the machine, tight construction of fabric, high twisted yarns and high GSM are avoided. |
Pinhole is an interesting and very dangerous problem; it may cause rejection of full batch fabric. The reason behind this is presence of Fe+ and Cu+
ions in water and active per-oxide that is used during bleaching (Teal at
el, 2002). As there is no correction options water hardness should be
within limit or strong sequestering agent should be used and per-oxide killing
should be done properly.
Contamination of sulphuric acid with acetic
acid, longer process
with excess scouring
bleaching chemicals, delay of killing the enzymes, very high
speed of machine, too long dyeing (corrective or repairing) process are mainly responsible for loss of fabric strength
(Teal at el, 2002).
Consistency of dyeing performance mainly depends on minimum shade variation of batch to batch. Process parameters such as water hardness, M:L, time, temperature, recipe,
reproducibility of dyes, dye lot, fabric structure, GSM, fibre lot, yarn count etc. should
be same as much as possible for minimizing batch to batch
shade variation problem.
Roll to roll shade variation always confused for matching the batch with standard shade and produces a variety of shade within a batch. This is a result of mixing of fabric roll produced from different fibre lot, yarn count, GSM, structure and even sometime for different machines. So to avoid such problems one has to avoid mixing of different types of fabrics. Patchy is the real uneven dyeing; this may result of uneven absorbency, electrolytes (salt) alkaline pH, uneven and sudden alkali dosing, wrong dye combinations, improper mixing of dyes, improper neutralization after scouring-bleaching and dyeing, fabric entanglement during process etc. If above mentioned points are under controlled then possibility of patchy is very low.
Color spot is the result of improper color mixing (very serious issue in case of turquoise dyes as their dye molecules are comparatively larger), water hardness and presence
of heavy metal sulphate, sulphides, sulphites & alkali especially caustic soda. Water treatment plant (WTP), sequestering agent and proper mixing of dyes are fundamental solution of this problem. White specks are mainly yarn problem i.e. dead or immature
fibres. Moreover contamination in water, improper dissolve of alkali and presence of silica based chemical before dyeing also arise white spots. Excluding yarn quality; WTP, proper handling of caustic and de-finishing removing silica based finishes, incase processing of finished fabric with such finishing chemicals, are necessary to solve such problem.
Meter to meter shade variation is a typical shade variation problem. Very short dyeing
arise unleveled dyeing (Gordon, 2006) .United State patent 4,629,465 and 5,167,668 show that level dyeing is dependent on controlled addition of dyes and electrolytes and proper alkali dosing system for dye fixation respectively. Another United State patent 4089644 suggested controlling the rate of dye adsorption of dye on to the substrates by the number of cycles of dye liquor and/or substrates throughout the dyeing process.
Furthermore, during my job in the industry, it was found that, imbalance dosing time, run time and temperature gradient of each step with cycle time of fabric is responsible for meter-to-meter shade variation. Six batches are dyed with linear dosing system, incase of
alkali & per-oxide dosing of scouring- bleaching and dyes, salt, alkali of dyeing,
on this aspect and described in methodology and result section.
Hand feel problem is irreversible due to use of harsh metal chemicals for processing. It can be easily reduce by demineralization and can improve by the addition of softener. Fuzzy appearance comes because of fabric to fabric, fabric to chemicals and fabric to machine abrasion in presence of high temperature for a long period of time. Nowadays very popular bio polishing is practiced to improve the appearance of the fabric.
Fastness problems are result of improper washing off, presence of unfix dyes, hydrolysis of dyes, dyeing with excessive dyes, poor fastness properties of dyes, improper use of fixer and softener
(
Process for level dyeing of 100% cotton knit fabrics with reactive dye
A beige color is selected to dye in a modern knit-dyeing machine (jet type) with the capacity of 500kg; maximum load of 440kg with 88% load. Three batches are dyed and
observed. The machine contains two separate feeding units and has the scope of dividing
the batch into two parts, with 220 kg each.
Traditionally in our country technicians are habituated
for maintaining the cycle time in between 2.5 to 3 minutes as standard.
First batch is dyed with 3 minutes cycle time. The secondone is dyed with 3 minutes cycle time and synchronized to chemicals & dyes dosing time and runtime. And the third batch dyed with a cycle time of 2.5 minutes where chemicals & dyes dosing
time, run time and temperature gradients are synchronized with cycle time. Full fabrics
are inspected for meter-to-meter shade variation and ten samples are taken randomly
for each batch. Ten samples from each batch are catalogued along each other and inspected visually. Finally 3 batches are examined to identify the extent of meter-to-meter shade variation among the batches.
Furthermore, samples are measured in a spectrophotometer for each batch considering the sample-1 as standard and other nines as batches. Data for each batch are analyzed with respect to dE. And then statistical analysis is done to identify the improvements in levelness of dyeing between three batches.
Additionally, three batches of another color (Brown) are also dyed and inspected maintaining the same procedure of beige color.
For both color it is clearly observed that third batch
gives the most level dyeing and second batch gives more than the first. The reason behind these is for third batch cycle time is synchronized to dyes and chemicals dosing time, temperature gradient and run time where as at second batch cycle time is synchronized to dyes and chemicals dosing time and run time. Here cycle time means the time required for the fabric to complete one revolution.
Theoretically for uniform dyeing adsorption, absorption and fixation should be uniform. This study focused on these factors and made following adjustments (a – e as shown in Annexture-1 Table 1). a) Scouring- bleaching process determines uniform absorption properties. To get uniform absorption properties dosing time (DT) of caustic and per-oxide set in such a way that during dosing fabric can complete it’s full cycles
i.e. DT/CT= an integer. For example, in second batch
it was six minutes (6/3=2) and five minutes (5/2.5=2) for third batch.
b) Incase of scouring-bleaching run time for 2nd and 3rd batches it was 60 minutes where run time (RT) also perfect for completion of fabric cycles i.e. RT/CT== a integer (60/3=20 & 60/2.5=24). So during run time 2nd batch complete 20 cycles and 3rd batch 24 cycles. c) Similarly, salt dosing time 21 minutes for 2nd batch and 20 minutes for 3rd batch. Dyes and alkali dosing time also 30 minutes and 60 minutes, both are compatible for completion of full cycles of fabric. These DT ensures the uniform impregnation of fabric during DT, hence ensures level adsorption, absorption and fixation.d) According to b run times are also set to 51 and 50 minutes for 2nd and 3rd batch respectively. These RT
ensures the uniform impregnation of fabric during RT, hence ensures level adsorption, absorption and fixation.
e) For third batch another factor; temperature gradient (TG) for scouring-bleaching is also synchronized with cycle time. Room temperature was 38oC. The scouring-bleaching temperature was 110oC. So temperature is increased by 72oC. The temperature gradient in 3rd batch was 3oC/minute and total time required to raise temperature up to 110oC was 72/3 = 24 minutes. Within this 24 minutes fabric completed 9.6 cycles ≈ 10 cycles {24 minutes/2.5 minutes (CT) = 9.6}. So this ensures uniform absorption properties of fabric as with the increase of temperature the action of caustic and per-oxide increase rapidly.
Another factor also noticeable that batch-3 received more impregnations of fabric (due to less cycles time, 2.5 minutes) than batch-2; this more impregnation also helps to improve level dyeing. With respect to the sample 1, dE value of the rest nine samples from respective
batches, are measured by spectrophotometer. Annexture-1 Table 2 shows the dE value of beige colour and its three batches against sample 1 of corresponding batches. Similarly, Annexture-1 Table 3 shows the dE value of brown colour and its three batches against sample 1 of corresponding batches. Variance of dE which represents variance of 9 samples for each batch.
For beige colour, batch 1 shows variance of dE as 0.152. After the adjustment of the process (as mentioned in Annexture-1 Table 1), in Batch 2 and 3, variances of dE are found 0.051 and 0.021 respectively. Consequently, batch 2 and 3 shows 66.45% and 86.18% improvement against batch 1 (Annexture-1 Table 4). In case of brown colour,
batch 1 shows variance of dE as 0.075. After the adjustment of the process (as mentioned in Annexture-1 Table 1), in Batch 2 and 3, variances of dE are found 0.020 and 0.010 respectively. Consequently, batch 2 and 3 show 73.33% and 86.67% improvement against batch 1
(Annexture-1 Table 4).
The study found that a satisfactory improvement in level
dyeing of 100% cotton knit fabric with reactive dye could be ensured without additional chemicals or operational
costs. Suggested adjustments are much user-friendly as well. This study will enable the industry to reduce loss of reprocess and rejection of fabric.
Biljana,
M., Goran D. and Igor J. 2004. Structural characteristics of cotton knitted
fabrics after enzymatic
and alkaline scouring,
Bulletin of the chemists and technologists of Macedonia, vol. 23 No. 1, pp. 19-28.
Booth, J.E. 1968. Principles
of Textile Testing,
Butterwrth Heinemann Ltd. UK. 0-592-06325-9, P 101.
Crown, J. 2005. Critical
solutions in the dyeing of cotton. Textile
progress, The Textile
Institute.Dec., P- 150.
David,
T. Parkes, 2005. Dye house productivity Back to basics.
Istanbul Conference, May pp-15-21.
Gordon, R. 2006. The preparation, dyeing and finishing of
cotton knit goods. Nearchimica S.p.A. textile
auxiliaries. P-22.
Teal, S, R.T.Ervin
and R.D. Mehta, 2002. Economic
analysis of cotton textile finishing
processes, Part 2- After treatments, Texas Tech University, Lubbock, Texas, USA pp-15-20.
www.researchandmarkets.com/reports/29475/world_markets_for_knitted_textiles_and.pdf.
ANNEXTURE-1
Bleaching is the process of removing natural color from textile substrate, which yields a permanent white color of fibre, yarn or fabric. Thus, the results of coloring would be better. It is the process of destroying
natural coloring matter from the textile materials to achieve a clean white end product. This is also called as some times Ready for dyeing (RFD). This is a second step of pretreatment of textile materials as well as wet processing technology. Owing to the presence of protoplasmic residues of the protein and flavones pigments of cotton flowers, it possesses its natural grey color . As a consequence, it needs to pre-treat the cotton to produce a perfect white surface that is suitable for dyeing or any other wet process treatment. Hydrogen peroxide is the most commonly used bleaching agent among all others, since it can bleach both cellulosic and protein fibers successfully .
It is a slightly more viscous and colorless liquid whose chemical formula is H2O2, with high sensitivity to metal ions. It is primarily used as an oxidizer, bleaching agent, and disinfectant. Although there is no exact evidence in the case of the nature of bleaching action of hydrogen peroxide, it is believed that the per-hydroxyl ion is the active group. Formation of this ion happened when hydrogen peroxide cleaves into the following manner .
In the absence of any kind of hue,
high luminous color of material gives an aspect of whiteness index . White is a monochromic color, and it is categorized by constant absorption from 400 to 700 nm wave length.
Substrate
Fabric Type: Single jersey Fabric Construction Composition- 100% cotton CPI- 42;WPI-60
Yarn count- 28 Ne, Loop length-2.4mm GSM-160
Color: Grey
Recipe of bleaching
Sample weight 20gm
Wetting agent 2gm/L
Sequestering agent 2 cc/L
Detergent 3 cc/L
Caustic soda 6 cc/L
Hydrogen per oxide (25/30/35/40/45)%———– 10/8/6 cc/L
Stabilizer (Sodium silicate)————-2 cc/L
Temperature (90-100)0C Time 60 minutes
pH 11
M: L 1:10
Bleaching of grey fabric was done in a closed vessel for 1 hour at 100°C keeping the material to liquor ratio at 1:10 with hydrogen peroxide (6- 10 cc/l), sodium hydroxide (6 cc/l), sodium silicate (2 cc/l), and none ionic detergent (3 gm/L). The pH of the bath was maintained at 11. Then it was rinsed thoroughly with hot and cold water and subsequently dried in oven at 80 deg c
Measurement of Whiteness Index (WI)
The cotton bleached fabrics were tested through a spectrophotometer (data color 650, USA) in order to determine the whiteness index at D65 illuminant and 10° observer setting.
Percentage of weight loss occurred in the cotton knit fabric due to bleaching which was evaluated by oven dry-weight basis. Usually, it is calculated from the following equation which shows the difference of pretreated and treated sample weight. It is also measured in percentage of pretreated weight of the of the sample.
Absorbency Test
The absorbency test of bleached sample was performed by drop test and wicking test according to the established procedure.
v Drop Test
In a pipet, water is taken and water drops are dropped on the scoured fabric. Then the absorption of the water drop is observed visually.
v Wicking Test
In a beaker, 1% direct dye Blue color is taken and a sample (18cm x 5 cm) is cut from bleached fabric which is hung from a wood stick. This is supported by immersing that 1cm portion of fabric in the dye liquor. Then the point is measured up to which the colored solution is absorbed by the sample in 5 min time.
All the samples were tested through a bursting strength testing instrument (Auto burst, SDL Atlas, England) followed by ISO13938-1 method. Each specimen was placed beneath the ball. It must also be flat and free from creases and any kind of distortions. Then the two clamp buttons were pressed. After that, the standard flow rate was selected. It measures the speed
at which the ball will inflate. Then start button was pressed and the diaphragm was automatically inflated until the specimen bursts. The reading was then collected from the instrument as KPa unit
Whiteness Index of Bleached
Sample
Greater value of “STD CIE WI” indicates that sample is whiter. It is observed
that the sample bleached with hydrogen peroxide
at 25% concentration has higher value of STD CIE WI, while less tint
variation is achieved during
bleaching of hydrogen peroxide for 30% concentration. On the other hand, STD CIE WI is 162.5 for 30% concentration of
hydrogen peroxide bleaching which is
near to 25% concentration. Therefore, it can be said that bleaching of hydrogen peroxide at 30% concentration for 10cc/L comparatively yields
the best whiteness result.
Enormous GSM variation has been observed for bleaching of hydrogen peroxide at 45%, 40%, and 35% respectively. This is not appreciated because it means that fabric is over bleached. On the other hand, GSM loss of hydrogen peroxide bleaching is 1.1 and 1.2 for 25% and 30% concentration.
Thus, GSM fabric bleached
with 25% and 30% concentration of H2O2 is
better.
v Drop Test
From the drop test results, it has been observed that
fabric bleached with hydrogen
peroxide at 25% concentration takes
more time to absorb the droplet. At
30% and 35% concentration, 4 sec is required to absorb the drop, while 3 sec is needed for 40% and 45%
hydrogen peroxide concentration of bleached fabric.
Table 1. Test result
of drop test of all bleaching samples
The surface area of the absorption of all sample bleached with hydrogen
peroxide shows the good scouring effect at 30%, 40%, and 45% concentration. This is according to its
spot observation of dye solution as its spot are nearly round shape.
Table 2. Pictorial view of spot test of all bleaching samples
The absorbed length of 45% concentration of peroxide bleached
sample is 55 mm. This sample shows the over bleaching than other concentration of peroxide bleached sample.
On
the other hand, fabric
bleached at 35% and 45% shows very good results as they wick 43
mm and 48 mm dye solution. In addition, 30% concentrated hydrogen
peroxide gives good
bleaching effect as it can wick 37 mm dye solution
after passing through
wicking test.
Table 3. Wicking test results of bleached samples
After analyzing the bursting test of cotton bleached fabric
properly, it has been seen that
fabric bleached with 40% hydrogen peroxide shows the lower bursting strength. On the contrary, 25% concentrated
bleaching agents yield high bursting
results which is more than 410 Kpa. However, 407 kPa strength is noticed in the case of 30% and 35% concentration of
hydrogen peroxide as bleaching
agents which is acceptable.
Whiteness is defined as a measure of how closely a surface matches the properties of a perfect reflecting diffuser, i.e. an ideal reflecting surface that neither absorbs nor transmits light, but reflects it at equal intensities in all directions. For the purposes of this standard, the color of such a surface is known as preferred white.
LOT PREPARATION METHOD
Knit Fabric
| Lot No. | Party | Grey GSM | |||
| Required GSM | Required WIDTH | Grey Width | |||
| Roll No | Roll weight | Roll Length | No. of Hole/Big cut | No. of handling stain | Other |
Uneven white is very common problem in the knitted fabric , either it is processed in Soft flow or in CBR. with some precaution it can be permanently cured .
In knitted cotton fabric, as we know it is in general processed in soft flow dyeing machine , Which is running in rope form. Hence chances of unevenness is always present. For this we need to insure that
1- fabric is running properly .
2- Temperature profile of the Process.
3- Chemical concentration is as per requirement.
4- Residual of the Peroxide is not in the fabric after end of the process.
5- Oba selection is correct .
6- Application of OBA is done at correct pH.
Runnability of the knitted fabric in the soft flow depends on the rope length of the fabric . Hence it is very important that before loading the fabric we need to calculate the rope length of each tube. it should almost same with the tolerance of +/- 10 mtrs .
The loading capacity is the next thing need to be check. Loading capacity means the maximum height of the fabric in the chamber without falling here and there . This need to fix by seeing the chamber condition. As it depends on the type of plaiting arrangement inside the chamber. If plaiting is uneven then height of the plaited fabric will be uneven, and we will face lot of fabric entanglement .
In the cotton bleaching the temperature profile is very important. The addition of chemical and temperature rising should not ever together . It is based on simple physical chemistry formula. PV=nRT. So if we are adding any chemical , volume is increasing, and if increase the temperature at same time, then pressure will also increase . this will result in all factor increment together , which P, V, T. it will give uneven reaction with cotton. This unevenness can not ever corrected at later stage by any means. As here cellulose is getting uneven bleached.
In general we are using caustic and peroxide to do bleaching of the fabric . We need to insure h2o2 is not getting decompose very fast . and it is not left too much un reacted also at the end of the process.
Excess H2O2 , need to neutralise in the further washes . If H2O2 remains in the fabric after unloading in the fabric then it may give yellowing effect in the finished fabric.
If pH of the fabric at the end of the process should be 5 to 6.5 in core level.
Too acidic will also give yellowing of fabric . And little alkailne or towards neutral will give failure of phenolic yellowing . It means fabric may turned yellowing in the polythene packing condition due to storage
Residual of H2O2 should not be left out in the fabric after completion of process. It is very hard to calculate the exact amount of H2O2 needed . In general 0.5 to 0.8 % peroxide remain in the bath after completion of process.
So if we add 0.75 gpl to 1 gpl Sodium Hydro sulphite in the next hot wash , It will kill peroxide , And will improve the brightness of white . Other than this there is one more advantage of this step that some colour contamination fibre will also get reduce , and we can reduce the colour fibre level in the finished fabric also.
Warp knitting is the sequential formation and interlinking of loops in an axial direction on a lateral array of needles with at least one separate thread being supplied to each needle. The loops are joined together in a width-wise direction by moving the threads back and forth between adjacent needles.
Warp knitting represents the fastest method of producing fabric from yarns. Warp knitting differs from weft knitting in that each needle loops its own thread. The needles produce parallel rows of loops simultaneously that are interlocked in a zigzag pattern. The fabric is produced in sheet or flat form using one or more sets of warp yarns. The yarns are fed from warp beams to a row of needles extending across the width of the machine. Two common types of warp knitting machines are the Tricot and Raschel machines. Raschel machines are useful because they can process all yarn types in all forms (filament, staple, combed, carded, etc.). Warp knitting can also be used to make pile fabrics often used for upholstery.
Warp knitting is defined as a stitch forming process in which the yarns are supplied to the knitting zone parallel to the selvedge of the fabric, i.e. in the direction of the wales. In warp knitting, every knitting needle is supplied with at least one separate yarn. In order to connect the stitches to form a fabric, the yarns are deflected laterally between the needles. In this manner, a knitting needle often draws the new yarn loop through the knitted loop formed by another end of the yarn in the previous knitting cycle.
A warp knitted structure is made up of two parts. The first is the stitch itself, which is formed by wrapping the yarn around the needle and drawing it through the previously knitted loop. This wrapping of the yarn is called an overlap. The diagram shows the path taken by the eyelet of one yarn guide traveling through the needle line, making a lateral overlap (shog) and making a return swing. This movement wraps the yarn around the needle ready for the knock-over displacement.
The second part of stitch formation is the length of yarn linking together the stitches and this is termed the underlap, which is formed by the lateral movement of the yarns across the needles.
The length of the underlap is defined in terms of needle spaces. The longer the underlap, the more it lies at right angles to the fabric length axis. The longer the underlap for a given warp the greater the increase in lateral fabric stability, conversely a shorter underlap reduces the width-wise stability and strength and increases the lengthways stability of the fabric.
The length of the underlap also influences the fabric weight. When knitting with a longer underlap, more yarn has to be supplied to the knitting needles. The underlap crosses and covers more wales on its way, with the result that the fabric becomes heavier, thicker, and denser. Since the underlap is connected to the root of the stitch, it causes a lateral displacement in the root of the stitch due to the warp tension. The reciprocating movements of the yarn, therefore, cause the stitch of each knitted course to incline in the same direction, alternately to the left and to the right.
In order to control both the lateral and longitudinal properties, as well as to produce an improved fabric appearance with erect loops, the second set of yarns is usually employed. The second set is usually moved in the opposite direction to the first in order to help balance the lateral forces on the needles. The length of the underlap need not necessarily be the same for both sets of yarns.
Knitting is a method by which yarn is manipulated to create a textile or fabric; it’s used in many types of garments. Knitting may be done by hand or by machine. Knitting creates stitches: loops of yarn in a row, either flat or in the round. There are usually many active stitches on the knitting needle at one time.
Knitting can be broadly classified as two type
1- Warp Knit
2- Weft Knit
the warp knits—including tricot, raschel, and milanese.
Types of weft knitting are jersey, rib, purl, run resist, tuck stitch, and interlock.
SINCE WE KNOW THAT TODAY IN THIS GLOBAL WORLD THE COMPETITION IS EXTREMELY HIGH SO EACH AND EVERY COMPANY IS TRYING TO MINIMISE THE COST OF THE PRODUCT BY INCREASING THE PRODUCTIVITY AND THUS THE PROFITS.
A COMPANY ALWAYS NEEDS TO ACHIEVE ITS MAXIMUM POSSIBLE PRODUCTIVITY ALONG WITH EXCELLENT QUALITY AND ECONOMICS SO THAT IT CAN SURVIVE IN THE MARKET. THESE CAN ONLY BE ACHIEVED WITH PROPER PLANNING AND USAGE OF AVAILABLE RESOURCES AS MINIMUM AS POSSIBLE TO INCREASE THE PROFITS ETHICALLY.
HERE WE HAVE CARRIED OUT A STUDY ON DIFFERENT MACHINES TO KNOW THE CAUSES OF NEEDLE BREAK AND THE EFFECT OF MOISTURE CONTENT OF THE YARN ON KNITABILLITY, NEEDLE PERFORMANCE,PRODUCTIVITY AND EFFICIENY.
Sodium Carbonate is also called as Soda Ash.
Characteristics: Soda ash is a white, odorless, hygroscopic powder, with an alkaline taste. It is soluble in water and glycerin, insoluble in alcohol.
Assay: About 5 g of sample accurately weighed, is dissolved in carbon dioxide free water and made up to 1 liter. 50 ml is then titrated with 0.1 N hydrochloric acid, first in the presence of phenolphthalein till the pink color is discharged and then in the presence of methyl orange till an orange tint is obtained.
Let x = ml of 0.1 N acid used in the first titration,
y = ml of 0.1 N acid used in the second titration, and
w = wt of sample in aliquot in g.
Then if x > y, Na2CO3 and NaHCO3 are present and given by
Na2CO3, % = 2y x 0.0053 x 100
w
NaHCO3, % = (y- x) x 0.0084 x 100
w
Reactions:
Na2CO3 + HCl NaHCO3 + HCl
NaHCO3 + HCl NaCl + H2O + CO2
NaOH + HCl NaCl + H2O
Hydro Chloric Acid (HCL) Strength Calculation
Take x gm of sample dissolve in 500 ml OR 100ml of water (A) Take 10 ml of diluted solution then titrate against 0.1 NaOH .Use Phenolphthalein as a indicator.
End point ……………. Colorless to Pink.
% of HCL =0.003647 X A X BR X 100
Pipette out solution X x gm
STANDARD = 30 % + – 1