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Nonwovens & Technical Textiles
  Canvas fabric from high tenacity air-textured synthetic filament

Canvas fabrics are generally used in many forms to protect people and property from the elements of rain, wind, sun and moisture. The market demand for canvas fabrics in India is quite large. Cotton is popular, but it lacks strength for heavy-duty use. The proposed project aims to develop canvas fabrics from high tenacity air-textured synthetic filament yarns and compared with other canvas fabrics made of normal tenacity yarns. The objective was to develop canvas fabrics from HT air textured synthetic yarn and to assess its performance.

Properties of an ideal canvas fabric for tents or tarpaulins or like-end uses are:

a) The base cloth should have sufficient strength particularly in its resistance to tear to provide maximum resistance to mechanical damage.
b) The material should be reasonably flexible since it is conducive both to ease of handling and durability of proofing.
c) The base fabric should not be heavy as it would make the “Made-up” too heavy as to be unwieldy and difficult to lift.
d) The material should be capable of water and rot proofed with durability and should resist abrasions.
e) The seam should be leak proof.
f) It should attract as little general dirt as possible and should be capable of cleaning easily.
g) In certain conditions, there is some advantage in having covers, which are ventile, ie, capable of transmitting moisture/vapour.
h) It should be as resistant as possible to high atmospheric contaminations.

Cotton canvases

Cotton was and is popular because of:
a) Its spinnability and weavability into uniform tight textures of cloth.
b) Cheaper and abundant availability.
c) Higher wet swelling property.

However, cotton canvases do not have strength factors necessary for heavy-duty use.

The use of air-textured synthetic filament yarns is expected to give a number of benefits, some of which are as follows:

i) Lighter weight of the canvas fabric with necessary strength required for heavy-duty use.
ii) Good resistance to rot and mildew.
iii) Good resistance to dimensional changes in extreme environmental conditions achieved through the good dimensional stability of air-textured yarns.
iv) Good abrasion resistance and durability.
v) The fabrics made from air-textured synthetic filament yarns are good input feed material for coating due to spun like structure of the yarn, which provides better cover of the fabric. In addition, good dimensional stability of the air-textured yarn facilitates curing of the coating applied to the base fabric. Also coated fabric offer flexibility in functional uses compared to rigid plastics and other composite materials.

Literature review

“Canvas” has been traditionally associated with rugged, heavy-duty fabrics used for tent covers and other outdoor materials of various types. In the recent past, canvas was practically synonymous with the term “Cotton duck”. Canvases are used in many forms to protect people and property from the elements of rain, wind, sun and moisture.

Potential for coated high performance fabrics as canvas fabrics

Coating and laminating fabrics are designed to add or improve functional properties and to add value to the product. The first coated fabric likely occurred when an early ancestor spread whale oil or blubber, bear grease or some other material onto a fabric to make it waterproof. The industry that emerged from this event is diverse and highly fragmented.

Coated fabrics have wide applications, such as medical substrates, flexible membranes for civil structures, air bags, geo-textiles and industrial fabrics. Nowadays, these materials have wide applicability in protective and outwear garments. To achieve reasonably good quality and to predict durability of such textile goods, it is essential to have enough understanding of their behaviour. As a result, recently, interest in this area of research has increased. Coated fabrics behaviour differs during deformation from uncoated fabrics behaviour. Coating changes all the fabrics properties. It increases tensile modulus especially in warp direction.

In India, there is a huge potential for the growth of coated high performance fabrics for various end uses. Light weight fabrics with high tensile and mechanical properties (permeable or im-permeable) from woven or nonwoven fabrics for manufacture of protective clothing. Awnings, canopies, canvas, tarpaulin, etc, is the focal area. Apart from this, synthetic leather cloth, sail cloth, belting and ribbons, inflatable fabrics, marine specialities, poromanics, fibre laminates, soft luggages, etc are some of the emerging areas. A country with such diversified claimatic conditions as India, coated fabrics have indeed very diversified functional requirement.

High performance coated textiles are generally manufactured depending upon the end use requirements. These fabrics can be developed by two distinctive methods. Firstly, the high performance fibres (polar or non-polar), woven, nonwoven or knitted fabrics are coated with a polymer matrix by various means. In the second method, the woven, nonwoven or knitted fabrics of regular fibres are coated with high performance polymers to obtain high performance coated fabrics.

Speciality polymer coated fabrics have been very widely accepted in the field of industry and technical applications replacing cotton duck, sheet metal and asphalt. These have found very wide range use especially in truck cover, tarpaulins, tents, bulk storage containers, bags, air supported and tension membrane structures. In USA alone, coated fabrics for truck tarpaulins are used to the extent of 20 million sq mts per year. Unfortunately, in India, we are still stuck with conventional cotton duck tarpaulins, which may be cheaper in the short term, but, can be expensive if expenses over a longer period are considered.

Material and experimental method

Materials Yarns and fabrics are purchased from the market, and fabrics are purchased for comparative study. The following three types of yarns were purchased for the study:

i) High tenacity intermingled polyester.
ii) High tenacity air textured polyester filament yarn.
iii) Normal tenacity nylon filament yarn.

Above yarns are used as warp and weft and fabrics are made out of it. High tenacity polyester filament yarn was air textured at the pilot plant on the following machine. The above fabrics are then coated and its properties tested. Different fabric properties are measured before coating, after coating and before and after weathering effects. Details of the fabrics are given below:

Fabric – 8                          =   Made from HT intermingled polyester.
Fabric – 8W                      =   Fabric 8 after 3 months weathering effect.
Fabric – 8C                       =   Fabric 8 after coating of PVC.
Fabric – 8CW                   =   Fabric 8C after 3 months weathering effect.
Fabric – 10                        =  H.T. air textured polyester fabric.
Fabric – 10W                    =   Fabric 10 after weathering.
Fabric – 10C (Plain)          =  HT air textured (after coating/plain weave).
Fabric – 10C (Twill)          =   HT air textured (after coating/twill weave).
Fabric – 10CW (Plain)      =   Fabric 10 CP after weathering.
Fabric – 10CW (Twill)      =   Fabric 10 CT after weathering.
Fabric – 27                        =   Normal tenacity air textured nylon yarn.
Fabric – 27C                     =   Fabric 27 after coating.

For this study, a number of commercially available canvas (tarpaulin) fabrics were taken from outside all coated. These fabrics were analysed/tested for different properties. Fabric details are given in Annexure - I.

Experiments

Breaking force

Record the breaking force of individual specimens; that is, the maximum force to cause a specimen to rupture as read directly from the tension testing machine expressed in Newtons (pounds force) N (lbf).

Breaking tenacity

Calculate the breaking tenacity of individual specimens using Eq 1, as follows:

B = F/T        (1)
where:
B              = breaking tenacity, cN (gf, lbf) per tex or cN (gf, lbf) per denier,
F              = breaking force, CN (gf, lbf), and
T              = linear density, tex (denier).

Elongation

Calculate the elongation of individual specimens from XY-type recorders using Equaton 2, as follows:

εp = (E x R x 100)/(C x L2)          (2)
where:

εp = elongation per cent.
E = distance along the zero force axis from the point corresponding to the point wherethe force elongation curve passes the pre-tension force to a point of corresponding force, mm (in.).
R = testing speed rate, mm/min (in/min).
C = recording chart speed, mm/min (in/min).
Lg = nominal gage length, mm (in.).

Tearing strength of fabric

This test method covers the measurement of the tearing strength of textile fabrics by the tongue (single rip) procedure using a recording constant-rate-of-extension-type (CRE) tensile testing machine.

Peak force, in tear testing of fabrics

The maximum force required to break one or more yarn components in a woven or knitted fabric specimen, or break the fibre, the fibre bonds, or fibre interlocks in other manufactured fabric forms.

The peak force may consist of a single peak or a series of peaks depending upon the nature of the fabric. Typically for woven fabrics, if a small decrease in force occurs at a time when the force is increasing, it is not considered to peak unless the indicated force exceeds the force required to break a yarn. Lower shifts corresponding to yarn movement do not qualify as peaks since no yarns are broken.

Tearing force, in fabric

The force required propagating a tear initiated under specified conditions.
The tongue tearing force may be calculated from a single peak or a multiple-peak force-extension curve.

Tearing strength, in fabrics

The capacity of a fabric to withstand the tearing force required propagating a tear after its initiation.

Weathering

All the uncoated and coated samples were put on the roof for 3 months and afterwards they were tested for breaking and tearing strength to see the effect of weathering on the canvas.

Results and Discussions

The following conclusions can be drawn from the results obtained from the fabric made from HT PET intermingled yarn:

Fabric 8: High tenacity polyester intermingled yarn base fabric.
Fabric 8W: Fabric 8 after 3 months weathering effect.
Fabric 8C: Fabric 8 after PVC coating.
Fabric 8CW: Fabric 8C after 3 months weathering effect.

Comparison of breaking strength

Warp way

When the grey fabric is exposed to weathering effect for 3 months, there is a reduction in warp way breaking strength (approximately 48.0%).

When the grey fabric is coated, the warp way breaking strength increases (approximately 21.89%) and it has been found that when the same coated fabric is exposed to weathering effect for 3 months, there is no reduction in warp way breaking strength.

This clearly justifies the general understanding that, when a fabric is used for covering purpose, it should always be coated with suitable materials.

Weft way

When the grey fabric is exposed to weathering effect for 3 months, there is reduction in weft way breaking strength (approximately 25.2%).

When the grey fabric is coated, the weft way breaking strength increases (approximately 20.72%) and it has been found that when the fabric is exposed to weathering effect for 3 months, there is no reduction in weft way breaking strength.

This clearly justifies the general understanding that, when a fabric is used for covering purpose, it should always be coated with suitable materials.

Breaking strength (Newtons/100 GSM)

When the grey fabric is exposed to weathering effect for 3 months, there is reduction in breaking strength (Newtons/100 gsm) (approximately 45.06%).

When the grey fabric is coated, the breaking strength (Newtons/100 gsm) has reduced (approximately 49.97%). Reason may be that although there is increase in breaking strength of fabric in warp way (approximately 21.89%) and weft way direction (approximately 20.72%), but it has not increased in proportion to the increase in GSM (approximately 142.79%) due to coating. So, it shows reduction in breaking strength (Newtons/100 GSM).

Comparison of tearing strength

Warp way

When the grey fabric is exposed to weathering effect for 3 months, there is reduction in warp way tearing strength (approximately 65.83%).

When the grey fabric is coated, the warp way tearing strength in kgs/mm reduces (approx. 36.91%) and it has been found that when the fabric is exposed to weathering effect for 3 months, there is no significant reduction in warp way tearing strength compared to same coated fabric strength.

Weft way

When the grey fabric is exposed to weathering effect for 3 months, there is reduction in weft way tearing strength (approx 75.55%).

When the grey fabric is coated, the weft way tearing strength in kgs/mm reduces (approximately 31.43%) and it has been found that when the fabric is exposed to weathering effect for 3 months, there is no significant reduction in weft way tearing strength compared to same coated fabric strength.

Tearing strength (Newtons/100 GSM)

When the grey fabric is exposed to weathering effect for 3 months, there is reduction in tearing strength (Newtons/100 gsm) (approximately 73.36%).

When the grey fabric is coated, the tearing strength (Newtons/100 gsm) has reduced (approximately 71.79%). Reason may be there is decrease in warp way tearing strength (approximately 65.83%) and weft way tearing strength (approximately 75.55%)

The following conclusions can be drawn from the results obtained from the fabric made from HT PET air textured yarn:

Fabric 10:                    HT air textured polyester yarn fabric.
Fabric 10C (Plain):      HT air textured (after coating/plain weave).
Fabric 10C (Twill):      HT air textured (after coating/twill weave).
Fabric 10W:                Fabric 10 after weathering.
Fabric 10CW (Plain):  Fabric 10CP after weathering.
Fabric 10CW (Twill):  Fabric 10CT after weathering.

Comparison of air textured base fabric and coated fabric (plain weave)

Comparison of breaking strength

Warpway

When the grey fabric is exposed to weathering effect for 3 months, there is a reduction in warp way breaking strength (approximately 51.8%). When the grey fabric is coated, the warp way breaking strength increases (approximately 9.14%) and it has been found that when the same coated fabric is exposed to weathering effect, there is no reduction in warp way breaking strength.

Weft way

When the grey fabric is exposed to weathering effect for 3 months, there is a reduction in weft way breaking strength (approximately 21.5%). When the grey fabric is coated, the weft way breaking strength is not increased and it has been found that when the same coated fabric is exposed to weathering effect for 3 months, there is no reduction in weft way breaking strength.

Breaking strength (Newtons/100 GSM)

When the grey fabric is exposed to weathering effect for 3 months there is reduction in breaking strength (Newtons/100 GSM) (approximately 40.34%).

When the grey fabric is coated the breaking strength (Newtons/100 GSM) has reduced (approx 55.62%). Reason may be that although there is increase in breaking strength in warp way (51.8%) and weft way direction (21.5%), but it has not increased in proportion to the increase in GSM (approximately 137.1) due to coating. So, it shows reduction in breaking strength (Newtons/100 GSM).

Comparison of tearing strength

Warpway

When the grey fabric is exposed to weathering effect for 3 months, there is a reduction in warp way tearing strength (approximately 32.57%). When the grey fabric is coated the warp way tearing strength has reduced little and it has been found that when the same coated fabric is exposed to weathering effect for 3 months, there is no reduction in warp way direction.

Weft way

When the grey fabric is exposed to weathering effect for 3 months there is a reduction in weft way tearing strength (approximately 47.18%). When the grey fabric is coated the weft way tearing strength has reduced little and it has been found that when the same coated fabric is exposed to weathering effect for 3 months there is no reduction in weft way direction.

Tearing strength (Newtons/100 GSM)

When the grey fabric is exposed to weathering effect for 3 months, there is reduction in tearing strength (Newtons/100 gsm) (approximately 33.91%). When the grey fabric is coated there is reduction in tearing strength (Newtons/100 gsm) (approximately 63.56%).

Comparison between plain woven and twill woven (coated fabrics)

From Figure 1 to Figure 6 and from Table 3 of Annexure - I we can draw the following inference:

Warp way breaking strength of coated twill weave fabric is noted 9.32% higher than coated plain weave fabric.

Weft way breaking strength of coated twill weave fabric is noted 23.15% higher than coated plain weave fabric.

Warp way tearing strength found 10.96% less in coated plain fabric compared to coated twill weave fabric.

Weft way tearing strength found 11.86% less in coated plain fabric compared to coated twill weave fabric.

Breaking strength (Newtons/100 GSM) found 6.38% less in coated plain fabric compared to coated twill weave fabric.

Tearing strength (Newtons/100 GSM) found 16.09% less in coated plain fabric compared to coated twill weave fabric.

The following conclusions can be drawn from the results obtained from the fabric made from normal tenacity nylon yarn.

Fabric 27: Normal tenacity nylon yarn fabric
Fabric 27 C: Fabric 27 after coating.

Comparison of breaking strength

Warpway

There is approximately 44.43% increase in warp way breaking strength after coating of the same fabric.

Weft way

There is approximately 22.87% increase in weft way breaking strength after coating of the same fabric.

Breaking strength (Newtons/100 GSM)

Although breaking strength in warp way direction has increased upto 44.43% and in weft way direction upto 38.36%, but there is no in terms of Newtons/100 gsm shows reduction up to 64.27%. This reduction can be justified as the strength of coated fabric has increased but not in proportion to the GSM increased due to coating 278.96%.

Comparison of tearing strength

Warpway

Reduction in warp way tearing strength (kgf/mm) approximately 38.24% after coating the same fabric.

Weft way

Reduction in weft way tearing strength (kgf/mm) approximately 33.61% after coating the same fabric.

Tearing strength (Newtons/100 GSM)

Tearing strength in warp way direction has reduced to 38.24% and in weft way direction reduced to 33.61%. Fabric tearing strength/100 GSM (Newton) reduced to 82.48% as coating increased to 278.96%.

Overall comparison of all purchased and project fabrics

Looking to the results, all the cotton based purchased fabrics show lower breaking strength (Newtons/100 GSM) than high tenacity air textured polyester fabrics. Also same is the case with tearing strength (Newtons/100 GSM)

Conclusion

From the above study, we come to the following conclusions:

1. When the fabric is exposed to atmospheric exposure its warp way as well as weft way breaking strength decrease even in fabric made of high tenacity and normal tenacity textured yarn.
2. After coating, breaking strength in both the direction (warp & weft) increases.
3. When coated fabric is exposed to atmospheric condition its warp way & weft way strength is not getting affected. Hence, proper coating on fabric may give protection against atmospheric degradation.
4. In all cases tearing strength is reduced when exposed to weathering.
5. After coating, tearing strength gets reduced in both weft and warp direction. This phenomenon requires further investigation.
6. But when the same coated fabric is exposed to atmospheric condition, its warp way and weft way strength remains almost same. Hence, proper coating on fabric may give protection against atmospheric degradation.
7. There is a benefit of use of high tenacity yarn in place of normal tenacity. The fabric also gives almost same breaking strength after weathering as coated fabric. Hence, the yarn itself contributes in strength and coating may be required only just to get protection against atmospheric degradation. But in case normal tenacita nylon yarn, breaking strength/100 gsm coated fabric is less than the coated fabric of high tenacity PET intermingled and air textured fabric. Therefore, we may say that the substrate yarn is contributing some strength towards the coated fabric.

References

1. Y K Kusumgar and Dr M K Talukdar: Application of Coated Textiles – An Opportunity for Indian Textile Industry, Journal of the Textile Association, Mar-Apr 2000, pp 275.
2. Dr S U Kulkarni: Coated Textiles, Entremande Polycoates, Mumbai.
3. R M Samdandam & K N Chandrasekhar: Quality Upgradation of Canvases for Defence End-uses, Coats Viyella India Ltd, Madurai.
4. D B Ajgaonkar: Designing of Coated Textiles, The Silk & Art Silk Mills’ Research Association, Mumbai.
5. Y Chen, D W Lloyd and S C Harlock: Mechanical Characteristics of Coated Fabrics, J Textile Inst, 1995, 86 No 4, pp 690.
6. V Masteikaite and V Saceviciene: Study on Tensile Properties of Coated Fabrics and Laminates, Indian Journal of Fibre & Textile Research, Vol 30, Sept 2005, pp 267 - 272.
7. Lt Col Y B Deshpande: Application and Quality Assurance of Engineering Fabrics, CQAE (E), Pune.

Note: For detailed version of this article please refer the print version of The Indian Textile Journal November 2008 issue.

Dr S K Basu, Director
Man Made Textile Research Association, S
urat, Gujarat.
Email: director@mantrasurat.org.

M Dalal
Man Made Textile Research Association, S
urat, Gujarat.

published November , 2008
 
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