Performance Research of Polyester Fabric Treated by Nano Titanium Dioxide ( N ano-TiO 2 ) Anti-ultraviolet Finishing

Nano-TiO2 sol and finishing agent was prepared by sol-gel method, during which tetrabutyl titanate was used as precursor and ethanol was used as solvent. The agent was penetrated into polyester fabric through a padding method, the anti-ultraviolet performance of the fabric was analyzed and the external morphology was carefully studied afterward. The results showed that indicated that the Nano-TiO2 particles distribute evenly with fine dispersity and stability and the finished fabrics demonstrated exceptional anti-ultraviolet performance with a phenomenal UPF ascendance reaching up to 50+ without influencing the breaking strength.


Introduction
With the aggravating greenhouse effect and the getting-severer ozone depletion phenomenon emerge, the total amount of ultraviolet (UV) reached the earth surface increased year by year ( Diffey.B, 2004).When intensely interact with human skin, central nervous system and ocular region, various pathological changes would be caused which makes doing research and development on Anti-ultraviolet fabrics a focal point in recent years (Wu, Dacheng, 2003).Nanometer particles are those superfine particles with sizing range around 1-100 nm.Based on the unique characteristics demonstrated by nanometer particles such as quantum size effect, small-geometry effect, surface effect and quantum tunnel effect, wide range of application are applying nanometer technology, e.g.catalyzing, optical filtering and absorbing, pharmaceutical, magnetic medium and novel material.Nano-TiO 2 possesses a multitude of advantages like small particle size, large specific surface area, strong magnetism, photocatalytic, exceptional absorbing property especially on UV, large surface activity, remarkable heat transfer performance and stable suspension liquid.In recent years, the research of function-fabric by application of the Nano-materials and application of Nano-technology were published (such as super-amphiphobic, super-amphiphilic, UV-protection, far-infrared healthy, antistatic, anti-bacterial ) ( Xin J H, 2004, p.97-100).
There are plenty of inorganic UV-absorbing nanometer material which could be used as UV-absorber, for example, Nano-TiO 2 , Nano-ZnO, Nano-SiO 2 , Nano-Al 2 O 3 , Nano-FeO and etc, among which Nano-TiO 2 is one stable, nontoxic and tasteless UV-absorber.By uniformly distributing Nano-TiO 2 into fiber molecules, the decomposition of the macromolecule chain could be effectively inhibited and free radicals could be reduced (Wang, Shimin, 2004, p.230-234).Nano-TiO 2 shows strong UV-absorbing capability and UVA, UVB could be effectively shielded while visible light could freely penetrate through.Nano-TiO 2 finishing agents could enhance the fabrics` UV-reflection and UV-scattering capability to a good extent and they are secure and pragmatic to use (Zhao, Jiaxiang, 2002, p.31-34).Yalpani M and Johnson F(Yalpani, M, 1995) etc. have done deeply research on the preparation and performance of Nanometer Titanium Dioxide(Nano-TiO 2 ); Denghua (Deng, hua, 2007, p.40-42) have done the research about the treatment of cotton fabric using the Nanometer Titanium Dioxide(Nano-TiO 2 ), improving the performance of the anti-ultraviolet and anti-bacterial, Haixia Li (Li, Haixia, 2008, p.70-73) have discussed the performance of the Nanometer Titanium Dioxide(Nano-TiO 2 ).However most of the research is about the function treatment of cotton fabric using Nanometer Titanium Dioxide, the research about the treatment of polyester fabric was so little.Thought the function of the anti-ultraviolet of polyester fabric is better than that of cotton fabric, the performance of the anti-ultraviolet still can not satisfy the anti-ultraviolet standard(AS/NZS) of fabric when the polyester fabric made into clothing.

Nano-TiO 2 prepared by sol-gel method
Add certain quantity of Tetrabutyl titanate precursor into the anhydrous ethanol with a 1:10 ratio, sufficient stir to get a fully resolved mixed solution A. Next put the catalyst HNO 3 into distilled water to make mixed solution B and then add A into B drop by drop under quick stirring state.Maintain that state under room temperature for a certain length of time and the uniformly distributed transparent Nano-TiO 2 sol could be prepared.

Finishing process
The polyester fabric processed by plasma ion gas with power of 100KW, processing time of 10min, then dipping the fabric into the Nano-TiO 2 sol, at 60 , processing time of 40 min, then dry out under 80 .

Performance of the finishing agent
Dilute the Nano-TiO 2 Anti-ultraviolet finishing agent with 100 times of distilled water.The absorbency (A) and transmittance (T) were measured under different wave lengths by using TEC ultraviolet spectrophotometer.Test the particle distribution condition of Nano-TiO 2 sol and the surface potential characteristics of Nano-TiO 2 by using D10-BA38-1436 nanometer particle size analyzer.The crystallization phase situation of the prepared Nano-TiO 2 powder XRD diagram was characterized and analyzed by X-ray diffraction analyzer.

Performance of the finished fabric
The UV transmittance and obstructing rate in the wave section of UVA and UVB (Sliney.D.H., 2000, p.213-228) was got by using Camspec M350 SPF Spectrophometer in accordance with AATCC Test Method 183-1998), then evaluate the UV-protection effectiveness according to the value of ultraviolet protection factor (UPF) and the rate of UV-protection of fabric Use YG065/PC electronic strength tester by referring to GB/T3923.1-1997testing method section 1(which is an introduction about the breaking strength and breaking elongation rate by undertaking stripe sampling method) to test the warp-wise breaking strength.

Finishing agent's performance
The UV-Visible light absorbency spectrum and transmittance spectrum of Nano-TiO 2 anti-ultraviolet finishing agent show as fig. 1 and fig. 2.
Figure 1.shows that Nano-TiO 2 anti-ultraviolet finishing agent has a very limited UV-absorbing capability around the wavelength of 200nm with absorbency less than1, but when the wavelength surpasses 200nm, the absorbency ascends phenomenally and reaches a maximum value of 4.2 around 250nm.After that section, the absorbency gradually descends until around 320nm a precipitous decline appeared and the absorbency reaches to a minimum level of 0.1 around 360nm with no obvious absorbency change happened thereafter.In the whole visible light section, the finishing agent shows almost none absorption.
Figure 2. shows that a precipitous ultraviolet transmittance decline occurred since 200nm section and the transmittance comes almost to zero between wavelengths 250nm to 370nm.After 370nm section, the transmittance gradually ascends and around 400nm, the transmittance increases the fastest.The transmittance of visible light in all spectrums increases as the wavelengths increase.
So Nano-TiO 2 finishing agent has exceptional anti-ultraviolet effect and UVA, UVB section could be effectively shielded.
In the visible light section, the agent has good transmittance and transparence.

5.2
The finishing agent's particle size and Zeta potential Figure 3. shows that the average particle size of the nanometer particles is 23.3nm ranging uniformly between 5nm to 50nm which illustrates that high-purity Nano-TiO 2 sol could be readily prepared undertaking sol-gel method.The particle size distribution of Nano-TiO 2 could also affect the zeta potential: the smaller the Nano-TiO 2 particles are and the more uniformly they distribute, the larger the zeta potential absolute value will be and the more stable of Nano-TiO 2 sol will be.
The zeta potential of Nano-TiO 2 tested is 31.97 with positive and large absolute value.The particle size is ideally small and well-distributed, therefore obtains a good distribution stability.

The XRD of Nano-TiO 2 powder
The Nano-TiO 2 powder used for XRD is deserved under a drying condition lower than 50 Because of a low drying condition, the crystal form could be considered as intact without any breakage.Figure 4 shows that a maximum diffraction peak in the pattern appeared when the diffraction angle(2 ) reaches 25.3°, which just correspondence of the diffraction peak of the crystal plane of anatase type TiO 2 (101) .Different diffraction peaks appeared when the diffraction angle reaches 37.9°, 48°and 55°matching along separately with the crystal plane of anatase type TiO 2 ( 004), ( 200) and ( 211) which illustrates that the prepared Nano-TiO 2 has all been crystallized with phase structure of anatase crystal type.If the maximum diffraction peak of Nano-TiO 2 is narrow-and-acuate-oriented, the half-peak width would be narrow-oriented accordingly and the corresponding crystallinity would be better with comparatively intact crystal form.

Anti-ultraviolet performance of the finished fabrics
In Table1, Finished fabrics are fabrics which have prepared Nano-TiO 2 finishing agent without plasma ion; Get the polyester fabric processed by plasma ion and then impregnate the fabric into the Nano-TiO 2 finishing agent, got Finished fabrics.In Table .1,compared with the unfinished fibers, the UPF values of Finished fabrics did not increase, and the anti-ultraviolet performance of polyester fabrics did not obviously improve; Finished fabrics on the whole UV spectrum finished by Nano-TiO 2 is very high, especially for UVB reaching 98.8%.The UPF value of polyester fabrics finished elevates from 15.1 to 65.3 and UPF rate elevates from15 to 50+ belonging to exceptional protecting class which illustrates that the anti-ultraviolet performance of polyester fabrics enhanced to a good extent after being firstly pretreated by plasma and retreated by the finishing agent.

SEM analysis
Figure 5 and Figure 6 are the fiber surface topography after 1000 times of magnification.By comparing the two images, we can see that the unfinished fiber surface is smooth and sleek while the finished has deposited Nano-TiO 2 on the fiber surface ranging in an inconsecutive way with some aggregation formed due to the minimal-particle-size-led self-aggregating phenomenon of Nano-TiO 2 .Consecutive Nano-TiO 2 particles ranged in a dispersed way leading to an irregular surface.
Nano-TiO 2 anti-ultraviolet mechanism analysis: (1) the valence band of Nano-TiO 2 is formed by the electron-filled-O 2p track and the conduction band is formed by the unoccupied Ti 3d orbital, which jointly configures a typical n-type semiconductor band gap.Based on its broadband-absorption performance, the energy of photonic (UV wavelength less than 410nm) would exceed the band gap if being radiated by UV when the energy of UV would be transformed into excitation energy to overcome the band gap.e -is going to be stimulated and transit into a high-power conduction band from the valence band to form a e --h + hole and impart the TiO 2 the power of UV absorption.( 2) Nano-TiO 2 also has a remarkable capability of UV-scattering.The particle size of Nano-TiO 2 is smaller than the wavelength of UV and when the UV energy propagates into the Nano-TiO 2 particles in the form of electromagnetic wave to collide with the electrons within the Nano-TiO 2 particles, vibration would be triggered in the frequency of the incident UV thus becoming a source of propagation of the electromagnetic wave and scatter UV light in all directions (Cao, Jianjun, 2005).Due to the powerful UV absorption and scattering capability, fabrics finished by Nano-TiO 2 would be imparted with excellent UV-shielding performance.
Table 2 shows that the breaking strength of the finished polyester fabric has decreased because the surface etching when being pretreated by plasma has caused damage to the fabric.The breaking force descending magnitude is fairly slight because of a low-level etching.

Conclusions
(1) The particle size of Nano-TiO 2 prepared by sol-gel method distributed fairly evenly showing fine dispersion and stability and has a remarkable shielding performance on the ultraviolet of UVA and UVB section.

Table 1 .
Anti-ultraviolet performance of the finished and unfinished fabrics

Table 2 .
Strength comparison of fabrics