Preparation of Self-Cleaning Polyester Fabrics by Chemical Vapor Deposition of Methyltrichlorosilane/Dimethyldichlorosilane

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Zhenrong Zheng1,2,*, Hongmei Wang1, Preparation of Self-cleaning Nannan Zhang1, Xiaoming Zhao1 Polyester Fabrics by Chemical Vapor Deposition of Methyltrichlorosilane/ Dimethyldichlorosilane DOI: 10.5604/12303666.1227892

1 College of Textiles, Abstract Tianjin Polytechnic University, Self-cleaning polyester fabrics were prepared by a simple gas phase deposition procedure in Tel.: +86 22 83955355 which a layer of polydimethylsiloxane nanofilaments was grown onto textile fibers. Superhy- * E-mail: [email protected] drophobic and self-cleaning properties, tensile breaking strength, mechanical stability and 2 Key Laboratory of Advanced Textile Composites permeability of polyester fabrics were investigated. The results showed that the fabrics deposited of Ministry of Education, had superhydrophobicity, and the contact angle and sliding angle of the fabric surface were Tianjin Polytechnic University, 159° and 1.7°, respectively. The self-cleaning test showed that dust particles adhere to rolling Tianjin, 300387,China water and shed from the surface of polyester fabric, leaving an extremely clean surface. In addition, the polyester fabric deposited still has excellent breaking strength and permeability. This approach is simple, inexpensive and has little effect on the mechanical properties of the fabric. Key words: superhydrophobic, polyester fabric, self-cleaning, permeability.

Introduction Firstly polyester fabric was treated with the DDS/MTS gas for grafting for 90-180 alkali solution to increase the surface min under 80% relative humidity at 25°C. A surface with a contact angle greater roughness. Methyltrichlorosilane (MTS) than 150° and sliding angle lower than and dimethyldichlorosilane (DDS) be- Characterization 10° is usually called a superhydro-� long to volatile organic chemicals. More- phobic surface [1-2]. Many surfaces over volatile gases have a self-hydrolysis Water contact angle measurements were in nature are highly hydrophobic and property due to their molecule structure. carried out with a 50μl droplet at room have a self-cleaning property, such as The silicon-chlorine groups of DDS and temperature by means of a contact angle the lotus leaf [3-5], cabbage [6-7] and MTS can easily hydrolyse to form silanol goniometer (JY-82, Hebei Chengde Test- the wings of a butterfly [8-10]. - Nu groups. The interaction and condensation ing Machine Co. Ltd, China). To illus- merous studies have validated that this of silanol groups are attributed to the for- trate the self-cleaning property of polyes- combination of micro-and nano-scale mation of silicon-oxygen-silicon bonds. ter fabric, carbon dust was sprayed onto roughness, along with a low surface en- Under different conditions, organosilane the surface of the fabric. Subsequently ergy material leads to the self-cleaning structures obtained by self-assembly are 0.3 ml water droplets were sprayed onto property of a surface [11-14]. At pres- different. Hence the react condition is fabric, and the fabric surface was tilted ent, great interest has been focused on critical to the surface roughness of the at a certain angle to the horizontal to test the preparation of self-cleaning fabrics. polyester fabric. the sliding angle and self-cleaning prop- Preparation technologies are reported erty of the fabric. Surface morphologies such as the sol-gel process, electros- of the polyester fabrics were investigat- pinning, the wet chemical process and Experimental ed with a scanning electron microscope (SEM, TM-1000 Hitachi High-technol- coatings [15-18]. Polyester fabric is one Treating with alkali solution of the most significant and extensively ogies Co. Ltd, Japan) and field emis- used fabrics which would greatly benefit To increase the surface roughness of pol- sion environmental scanning electron from possessing superhydrophobic and yester fibers, polyester fabrics (Jiaxing microscope (FESEM, Hitachi S-4800 self-cleaning properties. These polyester Rongsheng Textile Co. Ltd, China) with Hitachi High-technologies Co. Ltd, Ja- fabrics have significant potential practi- a plain weave (450 ends/270 picks, yarn pan). The surface chemical compositions cal application in high performance tex- number 12 tex) were immersed in 20 g/l of the fabrics were measured by X-ray tiles such as superhydrophobic fabrics, NaOH solution for 60 min at 90°C. Then photoelectron spectroscopy (XPS, Kra- self-cleaning fabrics, frictionless flow the polyester fabrics were rinsed with tos Axis Ultra DLD, Japan). The tensile water pipes, snowsuits, tents, decorative water and dried at 100°C. breaking strength and permeability of the materials and so on [19-23]. polyester fabrics were tested according Chemical vapour deposition to the China National Standards GB/T

In this work, gas phase deposition from (CH3)2SiCl2 (DDS) and CH3SiCl3 (MTS) 3923.1-1997 and GB/T5453-97, respec- a mixture of MTS/DDS solution was (Tianjin Guangfu Chemical Research In- tively. The abrasion resistance of the used to fabricate self-cleaning textiles. stitute, China) were mixed and placed in polyester fabric was measured by a rub- Based on fabric roughness woven from a closed container. Because of the strong bing-crock meter. After the fabrics were yarns, low surface energy material can volatility, DDS and MTS gases can diffuse rubbed 20 times with cotton fabric under be fabricated on a fabric surface with mi- in the container (glass desiccator from a certain pressure, the contact angles of cro-and nano-scale roughness by a chem- Tianjin Tianbo Instrument Manufacturing the fabrics were tested to investigate the ical method to obtain a superhydropho- Co. Ltd, China). After treating with alkali mechanical stability of the self-cleaning bic and self-cleaning fabric. solution, polyester fabrics were placed in fabric obtained.

Zheng Z, Wang H, Zhang N, Zhao X. Preparation of Self-cleaning Polyester Fabrics by Chemical Vapor Deposition of Methyltrichlorosilane/Dimethyldichlorosilane. 121 FIBRES & TEXTILES in Eastern Europe 2017; 25, 1(121): 121-124. DOI: 10.5604/12303666.1227892 Contact angle, ° Contact angle, ° Contact angle, °

Ratio of MTS to DDS Deposition time, min Totall volume fo DDS and MTS

Figure 1. Effects of major influence factors on contact angle of polyester fabric.

Results and discussions the contact angle decreased to 153.6° to DDS was increased, more MTS gas- when the ratio of MTS to DDS was 7:1. es were introduced and more depositon Influential factors of chemical vapour MTS can hydrolyze with water to form materials were formed; consequently, the deposition three silanol groups, which can graft in contact angle of the fabric increased. But A total volume of MTS and DDS of 6ml three dimensions with the fabric or oth- when the ratio of MTS to DDS was 7:1, and deposition time of 150 min were kept er silanol groups to form filaments on there was not enough DDS to inhibite the constant. Figure 1.a shows that the wa- the fabric surface. However, DDS was silanol groups hydrolyzed from MTS; ter contact angle of polyester fabric rose used as an end-capping agent, and its di- some silanol groups (-Si-OH) were ex- from 151° to 156.2° at a ratio of MTS to methyl groups inhibited further reaction posed on the fabric, and hence the con- DDS increasing from 3:1 to 5:1, and then near them [25]. When the ratio of MTS tact angle decreased.

Table 1. Factors and levels. In order to explore the influence of the deposition time on the hydrophobicity Factors of the fabric, a total volume of MTS and Levels Ratio of MTS to DDS Deposition time, min Total volume of MTS and DDS DDS of 6ml and a ratio of MTS to DDS 1 4:1 120 8 of 5:1 were kept constant. Figure 1.b 2 5:1 150 10 shows that the water contact angle of 3 6:1 180 12 the polyester fabric gradually rose from 152.4° to 156.2° as the deposition time increased from 90 to 150 min, and then the contact angle decreased to 154.8° a) b) when the deposition time was prolonged to 180 min. Therefore the optimum deposition time is 150 min.

A deposition time of 150 min and ratio of MTS to DDS of 5:1 were applied to investigate the influence of the total volume of MTS and DDS on the hydrophobicity of fabric. As shown in Figure 1.c, the water contact angle of polyester fabric was 158.3° when the total volume of MTS and DDS was 10 ml. The contact c) d) angle decreased to 155.3° when the total volume of MTS and DDS was increased to 15 ml. The materials deposited on the fabric surface may be too dense and cover the fabric roughness woven from yarns. When water dropped on this fabric surface, the air entrapped between the water and fabric surface decreased, lead- ing to a decrease in the contact angle.

Furthermore the orthogonal design of 4 Figure 2. SEM images of (a) original polyester fabric(3000×); (b) fabric treated with alkali experiment (L9 (3 )) was performed to (8000×); (c) deposited fabric (5000×); FESEM image of (d) deposited fabric (18000×). optimise the chemical vapour deposition

122 FIBRES & TEXTILES in Eastern Europe 2017, Vol. 25, 1(121) conditions. The three factors mentioned Figure 3. XPS spec- above were chosen as shown in Table 1. trum of the polyester fabric deposited O1s with MTS/DDS. The results of this experiment show that when the ratio of MTS to DDS was 6:1, the deposition time was 180 min, the total volume of MTS and DDS 12 ml, the C1s water contact angle of polyester fabric Si2sSi2p 159°, and the sliding angle of the fabric Count / s surface was 1.7°.

Surface morphology of polyester fabric The surface morphology of polyester fabric was investigated by SEM and FE- Binding Energy, eV SEM. It can be seen from Figure 2.a that the surfaces of fibers from the original polyester fabric were smooth. However, Figure 2.b shows that there are many cracks in the surface of the alkali treated fibers, and the surface roughness of the polyester fibers has been enhanced. Fig- ure 2.c shows that many pellets of 1-5 μm diameter were distributed over the fabric deposited. The enlarged views in Figure 2.d display clearly that the surfaces of the fabric deposited were well wrapped by filaments of nano-scale size. Hence, filaments, pellets and fabric roughness Figure 4. Water droplets resided on the deposited polyester fabric. woven by yarns constructed the multiple surface roughness of the polyester fabric. it. However, when water droplets were as small as possible. For the polyester XPS spectrum of deposited materials dripped on the polyester fabric deposited, fabric deposited, the contact angle of the The composition of materials deposit- they jumped up as balls immediately and fabric surface (θCB ) was as high as 159°, ed on polyester fabric was investigated rolled on the surface. The water contact validating that the solid part coming into by XPS. Figure 3 shows that three ele- angle of the fabric deposited was 159°, contact with water was very small and ments (Si2s at 153eV, Si2p at 102.4 eV, and the sliding angle was 1.7°. that lots of air was trapped between the C1s at 284.8 eV, and O1s at 530.4 eV) fabric and water. Therefore the adherence were observed. The Si2s, Si2p, C1s and Since polyester fabric is a porous sub- strength between the water and fabric O1s components originated from the Si- strate, and the organosilane deposited on surface was greatly reduced, and hence this fabric were filaments of nano-scale the sliding angle of the fabric deposit- O, Si-(CH3)2, CH3-Si and O-Si groups, respectively. Combined with the conden- size, as shown in Figure 2.c and Fig- ed was only 1.7°. At the same time, the sation theory of silanol groups, it was de- ure 2.d, the polyester fabrics deposited fabric surface area in contact with dirty duced that the deposition materials were are considered as conforming to the Cas- particles was also small. Because organo- polymethysiloxane and polydimethyl- sie model (air pockets at the interface). silanes are low surface energy materials, siloxane. Because DDS was used as the In the Cassie model, the apparent contact the adherence strength between dirty par- end-capping agent, the surface material angle (θCB) is the sum of all the contribu- ticles and the fabric surface is lower than of the fabric deposited was mainly poly- tions of solid and air phases, as described that between water and dirty particles. dimethylsiloxane. in the following Equation (1) [26]. Hence the dirty particles will be easily taken away by rolling water droplets. cos θ = f cos θ + f cos θ (1) Superhydrophobicity of polyester CB 1 1 2 2 Self-cleaning property of polyester fabric Where f1 and f2 are the surface fractions fabric The wetting angle is used to characterise of solid and air and θ1 & θ2 are the con- the hydrophobic properties of a fabric tact angles of solid and air on the corre- The self-cleaning test of the original surface. A surface with a contact an- sponding smooth surfaces, respectively. polyester fabric is shown in Figure 5.a gle greater than 150°and sliding angle Given f is the solid fraction, then the air (see page 124). Water droplets were ab- lower than 10° is usually called super- fraction is (1 – f). With θ2 = 180° for air, sorbed by this fabric and carbon dust hydrophobic. And this surface has a self- the resulting θCB can be calculated by the was adhered to it. However, when water cleaning property. Figure 4 displays following Equation (2): droplets dripped on the polyester fab- water droplets residing on the polyester ric deposited, they formed spheres and cos θ = f (cos θ + 1) – 1 (2) fabric deposited. When water droplets CB 1 could easily roll off with dirty particles were dripped on the original polyester In this model, to obtain a superhydropho- when tilting 1.7°, leaving an extremely fabric, they were absorbed completely by bic surface, the solid part ( f ) should be clean surface, as shown in Figure 5.b.

FIBRES & TEXTILES in Eastern Europe 2017, Vol. 25, 1(121) 123 Tianjin (No. 13JCQNJC03000) and Techni- a) b) cal Guidance Project of China National Tex- tile And Apparel Council (No. 2012002).

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