High flame retardant performance of SiO₂-TiO₂ sol coated on polyester/cotton fabrics

Nội dung text: High flame retardant performance of SiO₂-TiO₂ sol coated on polyester/cotton fabrics

1. VNU Journal of Science: Natural Sciences and Technology, Vol. 37, No. 1 (2021) 11-18 Original Article High flame retardant performance of SiO2-TiO2 sol coated on polyester/cotton fabrics Pham Thi Thu Trang1,2, Le Ha Giang1, Nguyen Ba Manh1, Trinh Duc Cong1, Ngo Trinh Tung1 and Vu Anh Tuan1,2.* 1Institute of Chemistry, Vietnam Academy of Science and Technology. 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam. 2Graduate University of Science and Technology, Vietnam Academy of Science and Technology. 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam. Received 10 November 2020 Revised 12 January 2021; Accepted 2 February 2021 Abstract: SiO2 and TiO2 sols were successfully synthesized by using sodium silicate and titanium chloride as Si and Ti sources. SiO2-TiO2 sol coated polyester/cotton fabric was fabricated by deep- coating method and using SiO2, TiO2 sols as coating materials. SiO2-TiO2 coated fabric were characterized by XRD, FTIR, TGA, SEM and EDX. From SEM image, it showed the SiO2, TiO2 particles of 20-30 nm which well deposited on fabric surface. TGA result revealed the significant improvement of thermal resistance and stability of SiO2-TiO2 coated fabric as compared to those of uncoated fabric. Flame retardant performance of SiO2-TiO2 coated fabrics was much better than that of uncoated fabric. Thus, SiO2-TiO2 coated fabric SiO2-TiO2 content of 26wt% showed the UL-94 classification of V-0 and LOI value of 30.3 were obtained. Moreover, mechanical property (tear strength) of SiO2-TiO2 coated fabrics were also improved. Keywords: nano silica, titanium dioxide, polyester/cotton fabrics, flame retardant 1. Introduction* and ventilation of cotton yarn with high strength of polyester [1,2]. However, polyester / Polyester/cotton fabric is a blend of cotton fabric is flammable and it cannot be used polyester and cotton and it is widely used in the as flame retardancy materials. Therefore, many textile industry. The quality of blended fabric is efforts on flame retardancy improvements have improved by the combination of the comfort been devoted [3,4]. Materials of coating can be of organic or inorganic nature. Halogen-based ___ * flame retardants materials have been shown to Corresponding author. be one of the most effective materials to reduce Email address: vuanhtuan.vast@gmail.com the risk of fire, but the downside is the release of toxic and corrosive gases during combustion 11
2. 12 P.T.T. Trang et al. / VNU Journal of Science: Natural Sciences and Technology, Vol. 37, No. 1 (2021) 11-18 [5,6]. Phosphorus and nitrogen based materials 85%, Merck company), ion exchange are preferably chosen as flame retardants (AMBERLITETM IR 120 from Down Chemical because of their eco-friendly by-products, low company), H2O2 (31 wt% from Aldrich toxicity. However, their poor flame retardant company), NH4OH (30 wt% from Sigma performance and low thermal stability were company). Polyester/cotton fabric (trade mark- noted [7,8]. Flame retardants of inorganic Lacoste, 35% polyester-65 %cotton, 115 g/cm2) nature such as nanosilica, nano alumino-silica, is provided by the textile Dong Xuan-Vietnam nano clay are often used to cover the fabric company. surface to create an insulating and fireproof protective layer and simultaneously, the 2.1. Synthesis of silica sol physico-mechanical properties can be Silica sol was synthesized by ion exchange improved. Among inorganic flame retardants, method using Amberlite as ion exchange resin nano silica and nano titanium dioxide have and sodium silicate (liquid glass) as source of received a great interest because these materials silicon [11]. are environmentally friendly, non-toxic and The process of synthesizing sol silica highly effective in slowing or resisting fire [9- consists of the following steps: Step 1: 12]. El-Shafei et al. [13] modified the fabric Dissolution of sodium silicate in distilled water. with nano TiO sol gel from titanium 2 Step 2: Na+ ion exchange by using ion isopropoxide and the fire resistance of the TiO 2 exchange resin (AMBERLITETM IR 120). Step modified fabric is significantly improved (LOI 3: Adjusting pH value of 8.5-9.0 by KOH increased from 17.4% to 23%). Fei et al. [14] addition to form the Si(OH) slurry. Step 4: modified fabric with nano silica synthesized 4 Stirring the mixture until to get the from TEOS and the significant enhance of homogeneous sols. flame retardancy (LOI value from 19.0 to 23.0) is reported. Liu et al. [15] reported that fabric 2.2. Synthesis of titanium dioxide sol coated with silica nano by using the sources of organic silicon TEOS and trimethylsilane and Titanium dioxide sol was synthesized by showed that the thermal stability was using titanium tetrachloride (TiCl4) as Ti soured considerably improved. Most fabrics used for and H2O2 as an oxidizing agent. The synthesis coating are cotton fabrics. Nano silica coating procedure of TiO2 sol was described in on polyester/cotton fabric is much more [reference 16], consisting four following steps: difficult due to its high smooths and low Step 1: Titanium tetrachloride (TiCl4) was adhesion ability. In this study, we report the slowly added to the cold distilled water synthesis of SiO2, TiO2 sols using sodium container in an ice batch under strong stirring silicate and titanium chlorides as sources of Si for 30 minutes until to get a clear solution. and Ti. Polyester/cotton fabric was coated with NH4OH solution was then added to the solution SiO2-TiO2 sols by deep-coating method. to precipitate the Ti(OH)4 slurry. Step 2: Thermal resistance, flame retardancy and Ti(OH)4 hydroxide slurry was washed with mechanical property (tear strength) were tested distillated water several times to remove Cl-. and evaluated. Step 3: Ti(OH)4 slurry was oxidized by adding H2O2 (30 wt%) to obtain the titanium peroxide (Ti-OOH). Step 4: Titanium peroxide was 2. Experiments heated at 90 oC for 8h under stirring condition and then cooled down to room temperature. Chemicals and materials: Sodium silicate SiO2-TiO2 sol solution was prepared by mixing SiO sol solution (10 wt% SiO ) and TiO sol 20 wt% was from company Sigma, TiCl4 2 2 2 (purity of 99%, sigma company), KOH (purity solution (2 wt% TiO2) under stirring condition.
3. P.T.T. Trang et al. / VNU Journal of Science: Natural Sciences and Technology, Vol. 37, No. 1 (2021) 11-18 13 o This SiO2-TiO2 sol solution was used for fabrics, the intensity of the peaks at 2θ of 22.66 o coating polyester/cotton fabric. and 25.44 decreased with increasing the SiO2- TiO2 content. This clearly indicated the 2.3. SiO2-TiO2 sol coating on polyester/cotton coverage of SiO2 and TiO2 particles on fabric polyester/cotton fabrics. Typical peaks of SiO2 Polyester/cotton fabric (35 % polyester, and TiO2 phase were not detected since these 65% Cotton) was cut in small pieces of 60 x 40 particles were amorphous [20]. mm size. Polyester/cotton fabric piece was deepened in a container with 50 ml SiO2-TiO2 sol solution (10 wt% SiO2 and 2 wt% TiO2) for 2 minutes and then ultrasonically treated for 5 minutes. The SiO2-TiO2 coated fabric was dried at 80 oC for 30 minutes in an oven. This sample was denoted as S1 (one time coating sample). Fabric after 3, 5 and 7 times coating were denoted as S3, S5 and S7. 2.4. Characterization of SiO2-TiO2 coated fabrics The X-ray diffraction (XRD) measurements Fig. 1: XRD patterns of polyester/cotton fabric (a) were performed on a D8 Advance and SiO2-TiO2 coated fabrics (b-e) diffractometer (Bruker, Germany) using CuKα as radiation source, λ = 0.154 06 nm, a range of 2θ = 10°– 80°. The morphology of the samples FTIR spectra of polyester/cotton fabric and was examined on scanning electron microscopy SiO2-TiO2 coated fabrics were presented in (SEM, JEOL JSM 6500F). The FT-IR spectra figure 2. The FTIR spectrum of polyester/cotton of the samples were recorded by the KBr pellet fabric (fig 2.a) showed the band at 3430 cm-1 is method (JACOS 4700). EDX of samples were attributed to the vibration of C-OH of fabrics measured using JEOL JED-2300 spectrometer. (cellulose) [21,22]. Bands at 1690 -1700 cm-1 Thermal analyses were conducted from room and 730 cm-1 are corresponded to the vibrations temperature to 600◦C under air atmosphere of C=O and C-C bonds in fabric structure using LABSYS evo TG-DTA 1600. UL-94 [22,23]. In the FTIR spectra of SiO2-TiO2 classification and limiting oxygen index (LOI) coated fabrics (figure2, b-e), a new band were determined according the standards appeared at 3490-3500 cm-1 which assigned to ASTM D2863, BS ISO4589-2. the vibrations of Si-OH, Ti-OH groups [24,25]. Also, new bands at 780 cm-1, 480 cm-1 appeared which attributed to vibrations of Si-O-Si, Ti-O- 3. Results and discussion Ti, Si-O, Ti-O groups of SiO2, TiO2 structure. Moreover, disappearing of bands at 3430 cm-1, 3.1. Structure characterization of SiO -TiO 2 2 1730 cm-1 and 700 cm-1 which are characteristic coated fabric for fabric structure indicated the coverage of XRD pattern of polyester/cotton fabric (fig SiO2, TiO2 particles on the polyester/cotton 1a) showed the peaks at 2θ of 22.66o and 25.44o fabric surface [26,27]. As presented in figure which corresponded to string segments of small 3A, weight loss diagram of polyester/cotton crystal structure of polyester/cotton fabric [17- fabric showed 3 stages: at the first stage (50 - o 19]. In the XRD patterns of SiO2-TiO2 coated 200 C), weight loss of 10 wt% was observed.
4. 14 P.T.T. Trang et al. / VNU Journal of Science: Natural Sciences and Technology, Vol. 37, No. 1 (2021) 11-18 SEM images of polyester/cotton fabric and SiO2-TiO2 coated fabric (S7) were given in figure 4. In figure 4A, polyester/cotton fabric Fig. 2: FTIR spectra of polyester/cotton fabric (a) and SiO2-TiO2 coated fabric (b-e) This weight loss is due to the water desorption. At the second stage (250 - 350 oC), weight loss of 50 wt% is noted. This is due to the partial decomposition of fabric. At the third stage (350 - 500 oC), weight loss was 38 wt%. The weight loss in this region is due to the further decomposition of fabrics. As seen in the derivative thermogravimetry of polyester/cotton fabric (Fig 3B), the decomposition occurred at o o Tmax of 330 - 430 C and 480 C. The behavior of weight loss for SiO2-TiO2 coated fabrics was different from that of polyester/cotton fabric. Thus, in the temperature range from 50 oC to 300 oC, weight loss of 1.5-2% was observed. In Fig. 3: Weight loss (A) and derivative the range from 350 oC to 550 oC, weight loss of thermogravimetry (B) of polyester/cotton fabric and SiO2-TiO2 coated fabric SiO2-TiO2 coated fabric (S1-S7) was 65 wt%, 50 wt%, 41 wt% and 38 wt%, respectively. From showed the heterogeneous structure with this result, it clearly indicated that SiO2-TiO2 the pore system consisted of large pore (100 - coating reduced the weight loss of fabric. Thus, 150 nm), medium pore (50-60 nm) and small SiO2-TiO2 coated fabric (7 coating times) pore (20 -30 nm). In the SEM image of SiO2- showed the weight loss of 38% which was 2.5 TiO coated fabric (figure 4B), it can be seen times less than that of polyester/cotton fabric 2 SiO2, TiO2 particles of 30-40 nm size which (98 wt%). Moreover, the decomposition of filled up the pore system of polyester/cotton SiO2-TiO2 coated fabrics needed higher fabric and simultaneously covered the fabric temperature (see fig 3B). surface. 3.2. Morphology and chemical composition EDX spectra of polyester/cotton fabric and SiO2-TiO2 coated fabric-S7 were presented in figure 5 and elemental composition was given in table 1.
5. P.T.T. Trang et al. / VNU Journal of Science: Natural Sciences and Technology, Vol. 37, No. 1 (2021) 11-18 15 concentration of SiO2-TiO2 solution (10 wt% SiO2 and 2 wt% TiO2) was used. This can be explained on the basis of the competition between SiO2 and TiO2 particles since concentration of SiO2 was 5 times higher than that of TiO2 which promoted much more SiO2 deposition on fabric surface than TiO2 deposition. (B) Fig. 4: SEM image (A) polyester/cotton fabric and (B) SiO2-TiO2 coated fabric (S7) As given in Table 1, C content decreased Fig. 5: EDX spectra of polyester/cotton fabric (A) with increasing SiO2-TiO2 coating times while and SiO -TiO coated fabric-S (B) O, Si and Ti content increased with increasing 2 2 7 SiO2-TiO2 coating times (S1-S7). Thus, C Table 1: Elemental composition of polyester/cotton content decreased from 51.06 wt% to 20.45 fabric and SiO2-TiO2 coated fabrics wt%, respectively. O content of S1, S3, S5 and S7 samples was 28.38%, 33.41%, 38.7% and 45.97 wt%, respectively. N content of S1, S3, S5 and S7 samples was 14.12%, 12,42%, 10.09% and 7.58%. Si content of S1, S3, S5 and S7 samples was 5.34%, 11.06%, 18.72% and 23.99%, respectively. Ti content of S1, S3, S5 and S7 sample was 1.01%, 1.35%, 1.64% and 2.01 wt%, respectively. Interestingly, the ratio of Si/Ti increased with increasing SiO2-TiO2 coating times. Normally, this ratio Si/Ti should 3.3. Flame retardancy and mechanical property maintain unchanged since the same
6. 16 P.T.T. Trang et al. / VNU Journal of Science: Natural Sciences and Technology, Vol. 37, No. 1 (2021) 11-18 UL-94 classification and limiting oxygen fabric and SiO2-TiO2 coated fabric was shown index (LOI) of polyester/cotton fabric and SiO2- in table 3. TiO2 coated fabric were listed in the table 2 Table 3: Tear strength of polyester/cotton fabric Table 2: UL-94 classification and limiting oxygen SiO2-TiO2 coated fabrics index (LOI) of polyester/cotton fabric and SiO2-TiO2 coated fabrics Sample Tear strength (N/mm) Sample UL - 94 LOI (%) Polyester/cotton fabric 39.37 Polyester/cotton fabric V-2 17.5 SiO2-TiO2 coated fabric (S1) 41.22 SiO2-TiO2 coated fabrics (S1) V-2 19.0 SiO2-TiO2 coated fabric (S3) 43.35 SiO2-TiO2 coated fabrics (S3) V-1 23.6 SiO2-TiO2 coated fabric (S5) 45.27 SiO2-TiO2 coated fabrics (S5) V-1 25.2 SiO2-TiO2 coated fabrics (S7) V-0 30.3 SiO2-TiO2 coated fabric (S7) 37.56 As seen in table 2, polyester/cotton fabric As seen in table 3, the increase of tear and SiO2-TiO2 coated fabric-S1 had the UL-94 strength from 39.37 (polyester/cotton fabric) to of V-2 which did not satisfy the quality 45.26 N/mm (SiO2-TiO2 coated fabric-S5) was requirement for flame retardant materials. SiO2- observed. Further SiO2-TiO2 coating (SiO2- TiO2 coated fabrics (S3 and S5) showed UL-94 TiO2 coated fabric-S7) leaded to decrease the classification of V-1 which satisfied the quality tear strength (37.56 N/mm). This can be requirement for flame retardant materials. SiO2- explained by the fact that SiO2-TiO2 coated TiO2 coated fabric-S7 reached the best quality fabric with high loading, SiO2 and TiO2 requirement for flame retardant materials (UL- particles tended to the agglomeration, making 94 classification of V-0). Polyester/cotton SiO2-TiO2 coated fabric become more fragile fabric showed the LOI value of 17.5 while the and consequently decreased the tear strength. LOI value of SiO2-TiO2 coated fabrics was 19.0 (for S1), 23.6 (for S3), 25.2 (for S5) and 30.3 (for S7), respectively. It is well known that O2 4. Conclusions content in the air is ca. 19 % (v/v). Therefore, polyester/cotton fabric is easily burned in air. From the obtained results, some conclusions could be drawn: SiO2 and TiO2 sols were SiO2-TiO2 coated fabrics (S3, S5) with LOI value of 23.6-25.2 are slowly burned in air. successfully synthesized by using sodium silicate and titanium chloride as Si and Ti SiO2-TiO2 coated fabric (S7) showed the highest LOI value of 30.3 which is unburnable under sources. SiO2-TiO2 sol polyester/cotton fabric was fabricated by deep coating method and flame. Thus, the SiO2 and TiO2 nanoparticles with the size of 30-50 nm were covered on the using SiO2-TiO2 sol as coating materials. SiO2- surface of the polyester/cotton fabric to help TiO2 coated fabrics with different SiO2-TiO2 prevent contact between flame and combustible content were made by repeating the coating components (polyester/cotton fabric). times. Polyester/cotton fabric and SiO2-TiO2 Mechanical property of polyester/cotton coated fabrics were characterized by XRD, FTIR, TGA, SEM and EDX. From SEM result, fabric and SiO2-TiO2 coated fabrics One of the most important physico- it showed that SiO2, TiO2 particles of 20-30 nm mechanical properties of fabric is the tear filled up the pore system of fabric and well strength. Tear strength of polyester/cotton deposited on fabric surface. From TGA analysis of the samples, it revealed the significant
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