Effect of (TiO2) Titanium Dioxide on Polyester

Effect of (TiO2) Titanium Dioxide on Polyester

Rushikesh Digambar Patil
Department of Textiles (Textile Chemistry)
DKTE’S Textile and Engineering Institute, Ichalkaranji, India
Intern at Textile Learner
Email: rushikeshpatil23052002@gmail.com

 

Introduction:
TiO2 was added in varying weight percentages to polyethylene terephthalate (PET) filaments at draw ratios of 3.5 and 4.0, respectively. Using spectroscopy measurements, it was determined how TiO2 affected the PET filaments’ ability to shield the eye from light. The findings reveal that as TiO2 weight percentage increases at both draw ratios, light transmittance falls and the light reflectance of PET filaments increases, which makes it easier to effectively improve the optical shielding feature.

Additionally, the variations in light reflectance and light transmittance are more pronounced in the TiO2, weight percentage range of 0-3 wt% compared to those within the TiO2, weight percentage of 3-9 wt%, indicating that the improvement of the visual shielding property slows down as the weight percentage of TiO2, increases.

The visual shielding of materials relates to the avoidance of revealing the human body, underwear, or anything else underneath. Excellent visual shielding is more crucial for military uniforms, whereas adequate visual shielding is a minimum necessity for everyday wear. An effective method to retain the optical shielding feature of the materials with light weight and light color is urgently needed given the trend toward high count yarns, light and ultralight fabrics. Currently, the use of opaque fibers, alterations to yarn or fabric structures, and finishing can be used to create fabrics that have strong visual shielding capabilities as well as light colour and weight [1-3]. However, the improvement of fabric visual shielding property is very limited since the structure change could not often be that great so as to satisfy other design objections, while finishing would always deteriorate the fabric comfort.

For this reason, the application of opaque fibers has become the most feasible and efficient method. Opaque fibers can be prepared by regulating cross-section shape of the fibers, increasing the slack porosity or surface coarseness [4, 5]. In order to further intensify fiber opacity, mineral pigment fillers, such as titanium dioxide, amorphous silica and silicates, aluminum trihydrate, zinc oxide and mixtures of the above are often used to impart opacity to fibers [6, 7]. In this research, the PET filaments added with different weight percentages of TiO2 and different draw ratios were produced by melt spinning. The visual shielding properties of the filaments were measured by spectrophotometer. The data obtained from this study may be helpful in understanding the effect of TiO2, on visual shielding characteristics of PET filaments and facilitate parameter prediction on the production line.

Experiment:

Preparation of the polyester filaments:
The commercially available PET chips and the opacity fiber master batch were applied to spin filaments containing TiO2, weight percentages of 0, 3, 6 and 9 wt. %.

sample preparation
Figure 1: Sample preparation

Production parameters of the PET filaments are shown in the table:

Production parameters Values
Intrinsic viscosity 0.68
Spinning speed 800
Spinneret temperature 290
Hot disc temperature 80
Hot plate temperature 160
Draw ratio 3.5

Measurements:
The PET filaments were wound on the slide by 90 circles within the width of 3.5 cm as shown in Fig. 1. The reflection and transmission spectra of the PET filaments were scanned by U-4100 UV visible near-infrared spectrophotometer in the range of 350 800 nm with a 5 nm interval.

Results and Discussion:
Compensation testing method of the visual shielding property: The light reflectance and light transmittance of the PET filaments with 6 wt. % TiO2 at the draw ratio of 3.5 were tested by 2 methods. One is the compensation method using a slide without filaments as the reference substance and taking into account its effect; the other is to test the slide with filaments directly without compensation of the slide.

influence of slide on light reflectance and light transmittance of the PET filaments, respectively
Figure 2: Influence of slide on light reflectance and light transmittance of the PET filaments a) light reflectance, b) light transmittance

Fig. 2 shows the influence of slide on light reflectance and light transmittance of the PET filaments, respectively. It can be seen in Fig. 2 (a) that the light reflectances measured with and without compensation are almost the same. However, the light transmittances obtained by the 2 methods demonstrate obvious difference as in Fig. 2 (b). The light transmittance is mainly dependent on the incident light intensity, the light absorption co efficient and the straight distance for the light bundle to get through the material. For the slide wounded with the PET filaments, not only the filaments but also the slide could absorb the = incident light, leading to the decrease in light transmittance regardless of the compensation. As for light reflectance of the PET filaments, surface reflectance is the primary mechanism which is affected by the polarization status of the incident light, the incident angle and the difference of the refractive index be the particle and the matrix. Therefore, the slide not ex posed on the surface but behind the PET filaments has little influence on the light reflectance. The following light reflection and light transmission spectra of the PET filaments were all tested by the compensation method to ensure the accuracy.

Light reflection spectra of the PET filaments:
The light reflection spectra of the PET filaments with different weight percentages of TiO2, at the draw ratios of 3.5 and 4.0 are shown in Fig. 3. It can be found that the light reflectance of the PET filaments increases with the increasing weight percentage of TiO2, no matter the draw ratios are 3.5 or 4.0. Supposing the PET matrix and TiO2, particles are mixed uniformly to produce the PET filaments, the refractive index difference between the PET filaments and air increases as the weight percentage of TiO2 augments, attributed to the larger refractive index of TiO2 (with a value of 2.5) than that of the PET matrix (with a value of 1.5). As a result, the light reflectance of the PET filaments maintains a continuous growth with the increase of the TiO2 weight percentage at both the draw ratios of 3.5 and 4.0. Moreover, the enhancement of the light reflectance is more obvious when the weight percent age of TiO2 ranges from 0-3 wt.% compared with the change when the weight percentage of TiO2 is within 3-9 wt.%.

The light reflection spectra of the PET filaments
Figure 3: The light reflection spectra of the PET filaments with different weight percentages of TiO2. The draw ratio is respectively: a) 3.5 and b) 4.0

If the weight percentage of TiO2 is “0” and the incident light perpendicular to the PET filaments, the reflection factor of the filaments can be calculated according to Fenier’s Law by Eq. (1) [8].

……(n2 – n1)2
n = ————————     …… (1)
……(n1 + n2)2

Where n is the reflection factor of the PET filaments, and n, are the refractive indices of air and PET matrix, respectively. Taking the refractive indices of air, PET matrix and TiO2 as 1.0, 1.5 and 2.5, the reflection factor of pure PET filaments should be 0.04.

Under the condition that the weight percentage of TiO2 is 100 wt. %, meaning that the light reflection interface is formed by pure TiO2 and air, then the reflection factor would increase to 0.18367 by replacing the refractive index of PET matrix with that of TiO2.

Light transmission spectra of the PET filaments:
The light transmission spectra of the PET filaments with different weight percentages of TiO2 at the draw ratios of 3.5 and 4.0 are shown in Fig. 4. When no TiO2 and optically inhomogeneous impurities such as crack, hole or dye pigments exist in the PET filaments, the incident light goes directly inside the filaments. If the incident light could not be absorbed completely, the rest of the light would transmit through the filaments. As TiO2 particles are added into the PET filaments, inter face between TiO2 and PET molecular chains expands, rendering more light reflection and scattering, and the path through which the incident light transmit ting would extend correspondingly.

The light transmission spectra of the PET filaments with different weight percentages of TiO2. The draw ratio is respectively: a) 3.5 and b) 4.0
Figure 4: The light transmission spectra of the PET filaments with different weight percentages of TiO2. The draw ratio is respectively: a) 3.5 and b) 4.0

Therefore, light transmittance of the PET filaments reduces with the increasing weight percentage of TiO2.

The transmittance of the PET filaments decreases sharply as the weight percent age of TiO2, increases from 0-3 wt. %, suggesting that the overall visual shielding effect is significantly improved by adding a tiny amount of TiO2. When the weight percentage of TiO2, increases further, the variation in light transmittance becomes slight, making the enhancement of opaqueness slow down. The diameter of the PET filament is not thick enough for the TiO2 particles to disperse without interrelationship as the TiO₂ weight percentage increases, thus aggregation of the TiO2 particles inevitably occurs, leading to decline of the effective optical interface and deterioration of the light scattering extinction effect.

References:

[1] Wang, N.; Liu, Z.; Shi, M.; Yu, J.: Effect of the filled titanium dioxide particulates on optical properties of polyester films, Jour nal of the Textile Institute 108 (2017) 776-782

[2] Wang, N.; Liu, Z.; Tang, C.; Zhao, S.; Shi, M.; Yu, J.: Study of the near-infrared light transmission of woven fabrics based on statistical analysis, Fibers and Polymers 15 (2014) 2013-2018

[3] Pan, W.; Wang, N.; Shi, M.; Yu, J.; Hu, J.; Chen, J.: Factor analysis of effect of basic parameters of fabric on the light shading property, Journal of Donghua University (Natural Science) 37 (2011) 153-157, 159

[4] Yu, Y.; Hurren, C.; Millington, K.; Sun, L.; Wang, X.: UV protection performance of textiles affected by fiber cross-sectional shape, Textile Research Journal 85 (2015)1946-1960

[5] Wang, Z.: Transparency preventing white swimming suit, Chemical Fiber Textile 4 (1996) 44-45

[6] Wang, N.; Pan, W.; Shi, M.; Yu, J.: Theo retical analysis on the development of opaque fibers based on Mie scattering, Textile Research Journal 83 (2012) 355 362

[7] Shi, M.; Zhang, Y.: Study of the visual masking synthetic fibre and its knitted fabric, Knitting Industries 261 (2010) 6-8

[8] Wang, N.: Ph. D Dissertation, Donghua University, Shanghai/China, 2010

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