THE 11TH ASIAN TEXTILE CONFERENCE

Influences of Knitted Fabric Construction

& Color on Ultraviolet Protection

Presenter: Wong Wai Yin

Dr. Jimmy Lam, Dr. C.W. Kan

EXCO, Daegu, KoreaNov 1-4, 2011

2

OVERVIEW

Introduction

Literature Review

Background

Previous Findings

Experimental Details

Results & Discussions

Conclusion

Future Study

References

3

INTRODUCTION Increasing no. of people dying from skin cancer due to over exposure to UVR

Skin ageing, skin cancer, cataract, ↓ Effectiveness of immune system

Excessive sun exposure in childhood is likely to contribute to skin cancer in later life

Clothing provide limited protection against UV radiation

Factors affecting UV protection of clothing:

Fiber Composition

Fabric Construction: tighter structure, smaller the fabric pores for UVR transmission

Yarn twist

Fabric Thickness, Weight

End-use conditions: Wetness / Stretching

Coloration: absorption band of dye extend into invisible UV region (290-400nm)

Chemical Treatments / Additives

UVA UVR in the range of 315-400 nm

UVB UVR in the range of 280-315 nm

UVC UVR in the range of 100-280 nm(mostly absorbed by ozone layer)

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LITERATURE REVIEW

Parameters affecting UV protection are well researched

Many studies have concentrated on:

Woven fabrics

Chemical approaches to enhance UV protection

UV absorbers: TiO2, ZnO, optical brightening agents

Little work has been done on:

Influence of knitted fabric construction

Structural parameters of knitted fabric against UVR transmission

UV protection provided by stretched or wetted knitted fabrics

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BACKGROUND

Aim: Improve UV protection of summer knitwear

by modifying the fabric construction

Chemical Approach by using UV absorbers (ZnO,TiO2):

Problem of fiber & dye degradation by photo-catalytic mechanism

Challenges on wash-fastness & adhesion to fabrics

Pollution, water consumption of those chemical treatments

Engineering Approach by modifying fabric construction

Environmental friendly manufacturing process

Especially suitable for knitwear (more elastic and creates more open spaces

when stretched)

UV protection enhanced by chemicals is only sufficient when fabric structure

is closed enough

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PREVIOUS FINDINGS

Fabric construction with different types of stitches possess distinct UV protection ability

UV protection factor of greige & bleached cotton fabrics with: Miss stitch > Knit stitch > Tuck stitch Double Knitted fabrics > Single Knitted fabrics

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EXPERIMENTAL DETAILS

MachineGauge Length

Materials usedSingle Knitted Fabric

constructions

Stoll CMS 82214G Computer Flat Knitting Machine

14G100% Cotton

40s x 3 (42 Tex)

1. All Knit (Plain)2. Knit & Tuck3. Knit & Miss 25%4. Knit & Miss 50%

Notation:Single Knit Structures

1. Fabric Specimens Production:

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EXPERIMENTAL DETAILS

Greige Fabrics produced in gauge length 14G

Scouring & Bleaching

Dyeing with reactive dyes

Red

0.1%

1%

3%

Yellow

0.1%

1%

3%

Blue

0.1%

1%

3%

Black

0.1%

1%

3%

2. Coloration with Reactive Dyes:

Reactive dyes with bi-functional group for better color fastness

Temperature rise process 25-60℃ L.R. = 50:1 Four shades:

Red: Levafix Red CA (MFT-TEP) Yellow: Remazol Yellow 3RS (MCT-VS) Blue: Levafix Navy Blue E-BNA (FCP-VS) Black: Remazol Black A (VS-DCT)

Three level of depths:

0.1%, 1%, 3%

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MEASUREMENTS OF UPF

Ultraviolet Protection Factor (UPF) indicates how much UVR is blocked by a textile

materials (e.g. UPF 20 allows 1/20th of UVR passing through fabric)

Measured by Cary 300 Conc UV-Vis spectrophotometer with a schott UG 11 filter in a

dry, flat and tensionless state (un-stretched)

Australian/New Zealand Standard (AS/NZS 4399:1996)

In Vitro Method: Transmittance (T%) of UV spectrum (290-400 nm) through fabric

and calculating the ratio of erthemally weighted solar UVR irradiance measured by a

detector with and without fabric sample in place

UV protective clothing should have a minimum UPF 15

↑ UPF ≈ ↓ Transmittance

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MEASUREMENTS OF COLOR YIELD (K/S SUM)

Measured by a Macbeth Color Eye 7000A spectrophotometer

Acquired at CIE standard observer 10° viewing angle

Under CIE standard illuminant D65 (daylight illumination)

Specimens were folded into layers to ensure opacity but without stretching

K/S Sum value is calculated by summation of each K/S value within the

visible spectrum (400-700 nm) with 10 nm intervals:

↑ K/S ≈ ↑ Concentration of colorant in the medium

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RESULTS & DISCUSSIONS

K/S

S

um

K/S

S

um

No major difference in color yield (K/S sum) whereas distinct difference in UPF among

various knit structures in red & yellow colored fabrics

Knit & Miss structures have higher UPF than All Knit and Knit & Tuck structures

↑ UPF ~ ↑ dye concentration (color depth)

Although darker colored fabric provides superior UV protection, thermal comfort is a concern

especially for summer wear.

Darker shaded clothes absorb more infra-red radiation causing wearer feels hot

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RESULTS & DISCUSSIONS

K/S

S

um

K/S

S

um

No major difference in color yield (K/S sum) whereas distinct difference in UPF among

various knit structures in red & yellow colored fabrics

Color is not a reliable indicator for UV protective performance of fabrics

UV protection depends on dye’s absorption characteristics in UV region which further

controlled by their specific structural attributes rather than the chemical class of the dye

(Srinivasan et al., 2000)

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CONCLUSION

For colored cotton fabrics with the 4 single knit structures:

Knit structures have significant influence in UPF but not for Color yield (K/S

sum)

Knit & Miss structure provides better UV protection in all the 4 colors than

the All Knit and Knit & Tuck structures

↑ UPF ~ ↑ dye concentration (color depth)

Darker shaded clothing may not be suitable for summer wear

∵ higher absorption of IR radiation, feel hotter

To achieve thermo-physiological comfort, fabrics with Knit & Miss

structure are recommended for lighter shaded clothing

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FUTURE WORKS

With various knit constructions: Influence of stretching and wetting on UV

protection of knitwear with various knit constructions

Effect of fiber type Yarn structures e.g. bulkiness & hairiness Impact of laundering and abrasion affect UPF of

various knit structures

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REFERENCES Ultraviolet radiation and human health (2009). Retrieved May 10, 2011 from

http://www.who.int/mediacentre/factsheets/fs305/en/index.html Skin Cancer Facts (2010). Retrieved June 20, 2011 from

http://www.cancer.org/Cancer/CancerCauses/SunandUVExposure/skin-cancer-facts J. Fan, & L. Hunter, Engineering Apparel Fabrics and Garment, Cambridge: Woodhead:

Textile Institute; Roca Raton, Fla.: CRC, 309-338, (2009). The American Society for Testing and Materials, ASTM D1776-04, Standard Practice

for Conditioning and Testing Textiles. Australian/New Zealand Standard, AS/NZS 4399:1996, Sun protection clothing –

Evaluation and classification. M. Srinivasan and B.M. Gatewood, Textile Chemist and Colorist & American Dyestuff

Reporter, 32(4), 36-43, (2000). P.D. Dubrovski and D.Golob, Textile Research Journal, 79(4), 351-359, (2009).

The research is funded in part by the General Research Fund (A-SA21) from the University Grants Committee, Hong Kong and The Hong Kong Polytechnic University, Hong Kong.

ACKNOWLEDGEMENT

THANK YOU!