1. T HE 11 TH A SIAN T EXTILE C ONFERENCE Influences of Knitted Fabric Construction & Color on Ultraviolet Protection Presenter: Wong Wai Yin Dr. Jimmy Lam, Dr. C.W. Kan EXCO, Daegu, Korea Nov 1-4, 2011

2. O VERVIEW  Introduction  Literature Review  Background  Previous Findings  Experimental Details  Results & Discussions  Conclusion  Future Study  References 2

3. I NTRODUCTION  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 3

4. L ITERATURE R EVIEW  Parameters affecting UV protection are well researched  Many studies have concentrated on:  Woven fabrics  Chemical approaches to enhance UV protection  UV absorbers: TiO 2, 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 4

5. B ACKGROUND  Aim: Improve UV protection of summer knitwear by modifying the fabric construction  Chemical Approach by using UV absorbers (ZnO,TiO 2 ):  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 5

6. P REVIOUS F INDINGS  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 6

7. E XPERIMENTAL D ETAILS 7 Machine Gauge Length Materials used Single Knitted Fabric constructions Stoll CMS 822 14G Computer Flat Knitting Machine 14G 100% Cotton 40s x 3 (42 Tex) 1.All Knit (Plain) 2.Knit & Tuck 3.Knit & Miss 25% 4.Knit & Miss 50% Notation: Single Knit Structures 1. Fabric Specimens Production:

8. E XPERIMENTAL D ETAILS 8 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%

9. M EASUREMENTS OF UPF 9 Ultraviolet Protection Factor (UPF) indicates how much UVR is blocked by a textile materials (e.g. UPF 20 allows 1/20 th 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

10. M EASUREMENTS OF C OLOR Y IELD (K/S SUM ) 10 Measured by a Macbeth Color Eye 7000A spectrophotometer Acquired at CIE standard observer 10° viewing angle Under CIE standard illuminant D 65 (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

11. R ESULTS & D ISCUSSIONS 11 K/S Sum 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

12. R ESULTS & D ISCUSSIONS 12 K/S Sum 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)

13. C ONCLUSION 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 13

14. F UTURE W ORKS 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 14

15. R EFERENCES 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). 15 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. A CKNOWLEDGEMENT