Journal of Science & Technology 100 (2014) 072-077
Effects of Loop Lenght of Hight Elastan Knitted Fabric on Dimension Stability and Pressure on Surface Simulating
the Human Body Surface
Bui Van Huan^\ Vu Thi Hong Khanh^, Nguyen Thanh Nhan'^^
' Hanoi University ofScience and Technology, No. 1 Dal Co Viet Str.. Ha Noi, Viet Nam
^ Tien Giang University
Received: February 28, 2014, accepted: April 22, 2014
Abstract
This article presents the method and results of researching the loop length effect of high elastic knitted fabrics on their dimensional stability and pressure on surface simulating human body suriace. The studied fabrics were a single weave, knitted from PA textured yarn; P/VPU core yam and PU yarn with five variances of different loop lengths. The fabrics were tested by 5 cycles simulating thier use process. For each cycle, the fabric is stretched in course direction with elongation 50% (keep the same dimension in wale direction) for 24 hour. Then it is relaxed for 4 hours, washed, dried and stabilized for 4 hours. The results show that, loop length significantly affects on the dimensional stability and pressure of studied fabrics. The fabric pressure Is inversely proportional to loop length. The fabric with small loop length is more elastic and more dimensional stability than that with large loop length.
Keywords: Pressure fabric, High elastic knitted fabric, Clothing pressure.
1. Introduction
Dimensional stability and stabilized pressure on surface are the important quality criteria of knitted fabrics, especially hight elastic fabrics used for body shape clothing, as well as the special costumes such as compression body-shappmg clothing, medical thrombosis prophylaxis hosiery. These characteristics of knitted fabrics are influenced by factors: fabric stmcture (yams, weave, fabric density, loop length, thickness ...), finishing (pre-tteatment, dyeing, finishing, etc.). Recently, demands for high elastic knitted fabrics are on the rise in Vietnam and in the world, and their application scope is increasingly expanding. Therefore, there are many researches around the world have been interested in designing and manufacturing this kind of fabric [I-], in studying pressure of the fabrics on body surface [4-6] for a purpose of manufacturing products using mechanical mechanism (defined and stabilized pressure on the body surface), as well as for three dimensional garment design. By this time, in Vietnam, there is very little research on the elastic characteristics of knitted fabrics and there is no published work on elasticity of high elastic kiutted fabric. This study aimed to investigate the effects of loop length on dimensional stability and pressure on body surface of high elastic knitted fabric during use process. That is the base for choosing the appropriate loop length to
• Correspondmg author: (-^84) 989.890.521 Email: huan.bmvan@hust edu,vn
produce fabrics that can create stabilized pressure on the human body surface and have good dimensional stability.
i.. Experiment 2.1. Materials
For the study, single knitted fabric with five variances of calculating course density 220, 240, 260, 280 and 295 courses/100 mm (follow, sample notation is' M220, M240, M260, M280, M295) was made. The yarns for making the fabrics are PU (210DT1723L), PA texttired (78dtex/48f), PA/PU core yam (2040/351). Grey fabnc was knitted on circular knitting machine in Phu Vinh Hung Company. The grey fabrics were pretteated and dyed to give them good colour fastness, but to minimize the impact hurt PU components as follow: wash with soap and surface-active substance at 60 °C for 55 minutes, wash normally for 10 minutes, dye with acid dyestiiff at 95 "C for 45 minutes, wash at 60 "C for 30 minutes, wash at room temperature for 20 minutes and dry. Dyed fabrics are relaxed without heat setting. The finish fabrics have good colour fasttiess (colour change: 4-5 grade, staining: 5 grade according to TCVN 4537-88),
2.2. Experiment method
In this study, fabric is tested simulating it behaviour during use (fabric is stretched mailly in course direction, being washed and dried repeatedly).
Five test cycles were done. For each cycle, to sttetch
Journal of Science & Technology 100 (2014) 072-077 fabric in course direction for 24 hours, then to relax
tiiem for 4 hours, wash and dry. Following standard D4964-96, the sample is sttetched with elongations 30, 50 and 70%. In this study, the samples were sttetching in course dttection witii elongation 50%, in accordance witii the extension of fabnc on clothing in fact. Fabric sttetched over the PVC pipe 16 cm diameter, 110 cm length, washed at room temperahire by TCVN 4537-88. The course demensions of tiie sample are measured by gauge in millimeters.
Pressure of fabnc on the surface is measuredby eqmpment that can determine clothing pressure [7].
Preparation of samples. In order to get consistent test and correct results of 5 test cycles (sttetching, washing and drymg, stabilizing sample), as well as convement and time saving, to cut samples with 100 cm length. So, to the end of each test cycle can cut the part of samples for pressure determination, meanwhile the rest part can continue doing the next test cycle. The samples have course dimension is 356 mm (elongation of baric is 50%), From that the work part is 336 nun, the rest 20 mm for sewing sample edges. The samples are sewed along lenght edges to get tubular form.
Experiment procedure: Each test cycle is carried out as follows'
Sewed fabric samples were worn on PVC pipe, keepmg not change sample length, for 24 hours at room temperature and humidity. After 24 hours, the samples were removed from the pipes, and to measure their course dimension at the time: 0 minutes (thesampleisjust taken out of the PVC pipe), 15, 30, 60, 120, 180 and 240 minutes. The dimension change H, %, of the fabric samples is detennined by the Table 2 The structural characteristics of the finish fabric
formula:
H = (Li-LQ)/Lo*IOO,%
Where: L;[ - Dimension of sttetch sample after a period of relax time, mm;
LQ Initial sample dimension before sttetching, mm
Fabnc samples are washed. After drying, relaxing for 4 hours at room temperature and hiunidity, to measure thett course dimenssion
To cut a piece (15 cm length) from the samples to determine pressure. The rest part of samples are wom on the PVC pipe for the next test cycle. To measure the fabric pressure with elongations 10, 20, 30, 40, 50, 60, 70 and 80% in course dttection, keeping no change in test f length. Test three times (samples) and get i value.
To measure the relaxation time of pressure: To sttetch and keep the fabncs m course direction with elongation 50% on the expenmental apparatus [7] and define their pressure after each minute until the pressure value not changes for 5 minutes.
3. Results and discussion
3.1. Effect of loop length on the fabric dimensional stability
The results of determining an increase of fabric dimension for five test cycles by relaxation time, and after washing and drymg, shown in table 3 and figure 1.
i ample
Stmctural characteristics Loop length (measured by PA textured vam), mm Weight, g/m2
Horizontal density, wales/IOO mm Vertical density, courses/100 mm
Standard for identifying TCVN 5799 1994 TCVN 8042:2009 TCVN 5794-1994
Praish fabnc M220
3,18 372.67 226.00 264.67
M240 3 10 379.67 232,00 266.00
M260 3 01 378 25 232 00 264.00
M280 2.87 368,58 228 67 279 33
M295 2.73 361.75 227.33 300,00
14,00 1100
laoo m
Demciision increase. %
k
-4-M22D -I-M240
^ ^ C S " — -*-M250
^fe ""^
30 60 50 120 19) 180 210 240 time, min
F i g . 1 . G r a p h o f t h e r e l a t i o n s h i p b e t i w e e n tiie a v e r a g e d i m e n s i o n i n c r e a s e o f five t e s t c y c l e s a n d r e l a x a t i o n t i m e of fabric samples
Journal ofScience & Technology 100 (2014) 072-077 Table 3. The results ofdetcrm
Fabric length, ram)
M220 (3.18)
M240 (3.10)
M260 (3.01)
M280 (2.87)
M295 (2.73)
Cycle test
Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average Cycle 1 Cycie 2 Cycle 3 Cycle 4 Cycle 5 Average Cycle I Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average
ning an increase of fabric dimension
Increase the course dimensi an of febric, % After relaxation time, min
0 13.88 12.70 13.80 14.94 15.30 14,12 12.23 lasi 11.90 14.45 13.54 12.58 12 73 12.65 10.59 11.23 13.06 12.05 12.21 12.51 12.79 12.65 13.76 12.79 11.80 10.25 11.36 11.54 12,18 11,43
15 11.48 11.61 12.30 12.75 13.93 12,41 10 04 9.31 10.53 12.45 12 17 10.90 10.10 lOjsH
9.36 9.77 11.42 10.16 9.54 9.74 1140 11.17 l l 54 10.68
9.26 8.19 10.12 9.98 11.63 9.83
30 10.60
9.70 10.66 11.93 12.84 11,15 9.17 8.35 9.03
60 8.85 9.15 9.97 10.84 11.75 10.11 7.53 7.67 8.22 10.63 9.72 10.81 1 9.72
9.60 8.57 9 44 7.57 9.50 ' 8.81 7.85 1 7.16 8,85 1 8,40 10.87 r 9.77 9.30 8,34 8.99 , 7.32 8.91 1 8.35 10.29 1 9.46 10.53 1 9.60 10.99 • 10.16
9,94 8,98 8.71
7.22 6.95 6,81 9.29 8.60 9.33 1 8.51 10.80 10.25
9.07 1 8,22 120
8.09 8.40 9.43 9.84 9.29 9.01 6.99 6.78 7.67 9.26 9.17 7.97 6.92 8.12 6.27 7.67 8.12 7,42 6.44 7.94 8.77 9.05 8 4 9 8,13 5.95 6.39 7.64 7.86 8.60 7.29
180 7.49 7.86 8.47 9.11 9.29 8,44 6.50 6.58 7.67 9.26 9.17 7.83 6.42 7.57 5.72 7.21 7.57 6,90 6.10 7.17 8.00 8.31 8.49 7.62 5 79 5.91 7.29 7 4 1 7.77 6,83
240 7.10 7.51 8.13 9.02 9.29 8,21 6,22 6.44 7.40 9.08 9.17 7,66 6.26 7.30 5.45 7.12 7.57 6,74 5.77 6.83 7.66 8.21 8.49 7,39 5.51 5.57 6.88 7.31 7.50 6,55
After relaxing, washing and
drying 0.24 2.02 2.38 2.50 3.01 0.00 2.16 2 1 6 2.78 3.27 0.00 0.22 0.67 1.19 1.80 0.00 0.74 1.80 2.57 2.38 0.06 0.96 1.56 1.59 2.08
The results in table 3 and figure 1 show that, for all test cycles, the course dimension of al! samples after removing from the PVC pipe increases m the range from 11,43% (sample M295) to 14.12%
(sample M220). By the time of relaxing, the increase level of fabnc dimension will be reduced to be stable.
Figure 1 shows that, the main decrease of sample dimensions happens within the first 30 minutes after removing load. After 150 minutes, the reduction of fabric dimension did not significantly changes and approaches to be stable. Some samples were relaxed more for 8 hours and 24 hours, so their course dimension continues reducing less than 0.3%.
Dimensions of samples M220 and M240 after removing load and after relaxing 240 minutes, especially sample M220, increase more than rest samples. For all test cycles, course dimension of fabnc samples after relaxing for 240 minutes, washing, drying and stabilizing, increased not so
much. Increasingly the number of test cycles, the sample dimension increases. After the 5th cycle, the fabric dimension increases from 1.80% (sample M260) to 3.27% (sample M240). Thus, the fabric samples, that stretched after 5 cycles (total stietch time is 120 hours and has been washing and drying in 5 times) have a good dimensional stability, especially samples M260 and M295 (the fabric dimension increases respectively 1.8% and 2.08%). It was concluded that, in the process of washing, the moisture and mechanical impact help the the fabrics to recover their dimension, such as the sample M220 (table 3) was recovered dimension up to 6.28%.
3.2. Effect of loop length on pressure relaxation of fabrics
Table 4 and figure 2 show the pressure value and pressure relaxation time of the fabrics with 50%
extension in course direction.
Journal of Science & Technology 100 (2014) 072-077 It can be seen from table 4 and figure 2 that the fabnc
pressure reduces by the time as a result of process tension relaxation. Sample M260 have bigest relaxation time of pressure, is about 30 minutes.
Mean while in the 5th cycle, the pressure relaxation time of sample M295 is about one minute. Normally, the fabric stretching time increases (the number of test cycles increase), the value and relaxation time of pressure reduce. The biggest pressure reduction by time is 13.2% (sample M240 in cycle 1) and the lowest is 0% (sample M220 in cycles 3 and 4), Degradation of knitted fabrics tension includes shape change of the yam, a change of yam onentation and stress (the yam elasticity). Tension evenness can reduce average tension of the fabric. The tension evenness is in close relationship with the deformation of the fabric, the shift of the yams and their contact points. In addition, shape and direction change of yam sectors also result to reduce fabric tension.
Fabric IS kept in stretching state for longer time, its stmctural components are more stable in the new state. The tension unevenness of the fabric will be over come, so value and relaxation time of fabric pressure decrease markedly It can be noted that, after bemg sttetched for period, pressure of elastic knitted fabnc significantly reduced. For all studied samples, steady pressure after the 5th cycle is about 79.8 to 82.4% of pressure ofthe original sample (fabric after finishing). This should be considered when calculating the pressure to design body shape costumes. Data in table 4 shows the relationship between the relaxation time and reduction of pressure by test cycles. It can be said that the better elasticity sample has more relaxation time and more reduction of pressure, especially when the number of test cycles increase. According to this criterion, sample M260 is more elastic than rest samples.
3.3. Effect of loop length on the fabric pressure The results of detennining fabric pressure with different elongations m course direction after test cycles are shown in table 5 and figure 3.
It can be seen from table 5 and curves in figin^e 3 that the fabric elongation up to 80% is elastic. It presents through the very tight linear relationship (r ~ l ) between the fabric pressure and elongation. Generally, the fabric pressure decreases as the number of test cycles increases. After 5 test cycles, the fabric pressure can be reduced to 19.13%
(table 6). There are good relationships between loop length and pressure of knitted fabric with elongation 50% in course direction (table 7), All coefficients of the regression equation are negative, so the pressure is inversely proportional to loop length
Table 4. The pressure value and pressure relaxation lime of the fabrics with 50% extension in course direction
Test cycle
Cycle 0*
Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
Pressure, mmHg Initial
9.11 8 2 8 8.03 7 66 7.65 7.48
„. ,..|... Reduction, Stability 0/
M220 8.13 7.63 7.53 7.66 7.65 7.26
10.74 7.91 6.22 0 0 2.92
Time to steady pressure,
min
25 25 12 1 1 9 M240
Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
9,37 8.17 8.05 8.04 7.94 7.94
8.71 7.10 7.63 7.71 7.86 7,79
7.00 13.12 5.30 4.14 1.05 1.83
13 29 11 17 6 2 M260
Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
9,73 9.09 8.43 8.46 8.20 8.18
8 92 8.11 7.81 7.96 7.97 7,88
8.34 10.87 7.28 5 90 2.79 3.69
26 29 17 29 11 10 M280
Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
10,75 10.28 10 03 9.66 9.29 9.22
10.08 9.71 9.84 9.42 9.18 8,85
6.20 5.57 1.87 2.48 1.23 4.06
12 16 9 9 8 14 M295
Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
10,77 10.50 9.91 9.90 9.32 8.97
10.17 9.89 9.38 9.56 8.81 8,87
5.60 5.85 5.36 3.36 5.47 1.16
17 20 9 19 16 1 Note: Cycle
stretching or,
0* denotes the lest of fabric sample PVC pipe.
Journal ofScience & Technology 100 (2014) 072-077
Fig. 2. The pressure valine - relaxation time curves of Fig. 3. Graph of the relationship between the pressure fabnc sample M260 and elongation of fabric M260
Table 5. The results of determining fabric pressure with different elongations in course direction
Sample fabric
M220
M240
M260
M280
M295
Test cycle Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average
10 1.99 2.03 1.90 1.87 1.75 1.65 1,87 2.15 2.06 1.90 1.80 1.88 1.92 1,95 2.18 2.11 2.03 1.76 2.05 2.09 2.04 2.36 2.36 2.21 2.34 2.04 2.16 2,25 2.53 2.72 2.37 2.53 2.13 2 28 2,43
Pressure on the sur 20
3.89 3 68 3.56 3.39 3.37 3.05 3,49 4.05 3 70 3.57 3.60 3.69 3.66 3.71 4.15 4.13 3.79 3.60 3.73 3.60 3,83 4.81 4.56 4.42 4.45 4.15 4.19 4.43 4.81 4.80 4.53 4.47 4.30 4.24 4,53
30 fac 5.76 5.27 5.09 4.81 4.63 4.28 4,97 5.96 5.12 5.17 4.92 5.02 4.99 5,20 6.22 5.70 5.46 5.33 5.20 5.29 5.53 6.98 6.44 6.26 6.47 5.86 5.83 6.30 6.90 6.89 6.37 6.50 6.03 5.88 6,43
c ofthe 40
7.42 6.65 6.57 6.07 6.22 5.96 6,48 7.36 6.59 6.45 6.42 6.48 6.33 6,60 7.86 7.32 6.66 6.87 6.63 6.64 7,00 8.78 8.19 7.93 7.96 7.53 7.41 7,97 8.69 8.53 7.98 7.91 7.49 7.41 8,00
ample, mmHg,with elongation,%
50 9,14 8.35 8,10 7.63 7,69 7,39 8.05 9,26 8,18 8.03 8,01 7.96 7.98 8,24 9,78 9,02 8,39 8,44 8.20 8.39 8,70 10.85 10.14 10,01 9.90 9,46 9,26 9.94 10,77 10,54 9.93 9,78 9,45 9,04 9.92
60 10.57
9.73 9.51 8.99 9.08 8.75 9.44 10.56 9.57 9.47 9.33 9.16 9.40 9.58 11.30 10.25 9.90 9.60 9.68 9.55 10.05 12.28 11.65 10.87 11.44 11.03 10.83 11,35 12.20 12.51 11.66 11.24 10.87 10.65 11,52
70 12.23 11.37 11.06 10.52 10.50 9.99 10.94 12.15 11.24 11.15 10.96 10,69 10.90 11,18 13.06 11.99 11.40 11.24 11.39 11.46 11,76 14.62 13.81 13.81 13.48 13.17 12.90 13.63 14.37 14.37 13.91 13.37 13.02 12.58 13,60
80 13.55 12.79 12.44 11.98 12.01 11.71 12,41 13.58 12.66 12,57 12.57 12.09 1244 12,65 14.52 13.48 13.32 12.80 13.07 12.84 13,34 16.51 15.93 15.71 15.47 15.05 14.98 15.61 16.44 16.30 15.55 15.28 14,63 14.37 15,43
Journal ofScience & Technology 100 (2014) 072-077 Table 6.
Test cycle Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
Fabric pressure with elongation 50% in course direction
Pressitre, imnHg, ofthe fabric with (loop length), nmi, with elongation 50% in cotu'se M220
(3.18) 9.14 8,35 8.10 7.63 7.69 7.39
Reduction,
%
0 8 63 11.42 16.55 15.86 19.13M240 (3.10)
9.26 8,18 8.03 8.01 7.96 7.98
Reduction,
%
0 11.67 13.30 13.47M260 'Reduction, (3.01) ' i
9.78 9.02 8.39 8.44 14.08 8.20 13.81 1 8.39
0 7.75 14.24 13.71
M280 (2.87) 10.85 10.14 10.01 9.90 16 16 9.46
Reduction,
%
0 6.59 7.78 8.74 12.77 14.24 1 9.26 ! 14.64M295 (2.73) 10.77 10,24 9 93 9.78 9.45 9.04
direction Reduction,%
0 4.89 7.82 9.18 12.22 16.09 ILOO
10 50 10 00 950 900 3.50 800 750 7.00 2
Pressure, mmHs Ya = -4283i + 22 71S Y|^-5.6736s+26143
» - • R'=0.893 R= = 09285 { - . Y, = -5.107'1x + 24.!
^ " • • - - V - . / - " . M " T,..5.4ES.,5.0.1 f. "*~'-*>....,^^ * " • . . ' ' " » • - R.= = 089K5
^~ C" — I.*^^'^^-^" " - •""---.•
^ - ^ " T t ^ ^ ^ i ^ O - - .
l i - - J yjix + 0) in * - ' * s - ^ ~ - ^
• Cyde 0
• Cydel ACyde2 X Cvde 3 XCyde i
• CydeS
70 3ED J.M 300 310 3 30
Fig, 4. Graph ofthe relationship between loop length and fabnc pressure with elongation 50% in course direction
Table 7. The Jitted equations of relationship between loop length and pressure of knitted fabric with elongation 50%
Test cycie Cycle 0 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
Regression equation Yi, = -4.283x +22.710 Y i = - 5 . 6 7 3 6 x + 26.14 Y2 = -5.1074x + 24.IO Y] = -5.4827X + 25.08 Y. =-4.501 l x +21.96 Yj = -3.932x + 20.120
r2 0.893 0.928 0.848 0.898 0.906 0.847 X denotes fabric elongation Note: Yn denotes prei
4. Conclusion
Loop length can greatly effects on dimension stability and stabilized pressure of the high elastic knitted fabric. For studied knitted fabrics, their pressure is inversely proportional to loop length. The knitted fabric with short loop length can more stabilize dimension after test cycles (after stretching, washing and drying repeatedly) than the fabric with large loop length. In case of studied fabrics, reasonable loop length of finished products firom 2.75 to 3.0 mm is recommendable. These research results are primary basis for designing and manufacturing knitted fabrics and products, especially knitted products such as compression body-shapping clothing, medical thrombosis prophylaxis hosiery.
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