Study of copper releasing rate from vinyl copolymer/Cu₂O/Seanine 211-based anti-fouling paint coating

Cite this paper: Vietnam J. Chem., 2021, 59(1), 127-131 Article DOI: 10.1002/vjch.201900198 127 Wiley Online Library © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH Study of copper releasing rate from vinyl copolymer/Cu2O/Seanine 211-based anti-fouling paint coating Do Minh Thanh* 1,2 , Nguyen Anh Hiep 1 , Vu Dinh Sang 3 1 Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 10000, Viet Nam 2 Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 10000, Viet Nam 3 Hanoi University of Industry, Cau Dien, Tu Liem North, Hanoi 10000, Viet Nam Submitted December 29, 2019; Accepted 6 February 2020 Abstract The effects of Seanine 211 content rate on Cu releasing as well as coating properties were investigated. The process of releasing Cu has been studied in dynamic conditions with Seanine content of 0, 3, 5, 10 % and static conditions using Seanine content of 5 % (in weight). Under dynamic conditions, the Cu shall release at high speed in the first 2 days of the test, then remain stable and proportional to the time according to the linear-line equation, maintained at ≈ 3.5 µg/cm 2 /day. Under static conditions, the process of Cu releasing is studied through the reduction of coating thickness, the results show that the coating abrasion rate is also proportional to the time and according to linear-line equation. With the content of 20 % Cu2O (in proportion) and 5 % Seanine (in proportion), the coat has the following properties: relative hardness 0.5; impact resistance 65 Kg.cm; flexural strength 1 mm; adhesion cross cut at 1. Keywords. Anti-fouling paint, Seanine 211, Copper(I) oxide. 1. INTRODUCTION Vietnam has 3,260 km of coastal line, excluding islands, and over 49 seaports at various scales. Marine economy as well as sea transport plays an important role in the national economy of our country. [3] Iron and steel structures which operating offshore, such as oil rigs, ships etc. have suffered from great damage not only due to metal corrosion but also due to microbial fouling, causing large loss to the operation, maintenance and reparation. Therefore, the study of anti-fouling paints has been interested by scientists, domestic and foreign manufacturers. Scientists have worked hard to find out environmentally friendly materials to replace toxic compounds such as organotin, including compounds which are capable of killing extracted micro- organisms from natural products such as those derived from algae, resin etc. and control the release of microbiological substances to prevent emissions on a large scale. However, in fact, these organic compounds are less antifouling-active than organotin and copper compounds. [1,2,4,7,8] Because organotin compounds are currently banned from using, Cu2O is still the manufacturers’ first choice today. However, the effects of copper(I) oxide on marine life as well as human life have still been controversial. [2,4,9] Therefore, how to reduce the content of copper(I) oxide in anti-fouling paints without decreasing the paint quality is a problem raised to scientists and manufacturers. Also, the usage of copper(I) oxide with anti-fouling organic compounds is a highly concerned subject. Seanine 211 is a 30 % solution of 4.5-dichloro- 2-n-octyl-4-isothiazolin-3-one in xylene, the Seanine 211 mixture remains unchanged for at least two years at 22-25 °C and 6 months at 40 °C. Seanine 211 is an active ingredient widely used in anti- fouling paint nowadays because it meets most of the characteristics such as not containing heavy metals, having good effects against fungi, bacteria, worm algae, diatoms etc. Especially with its environmental characteristics, Seanine 211 did won the very first Green Chemistry Challenge Award in the Design of Safer Chemical Products presented by the US Environmental Protection Agency. Seanine 211 has a very broad spectrum of activity when being used with copper oxide. [1,2,4,5] Within the scope of this study, we plan to clarify Vietnam Journal of Chemistry Do Minh Thanh et al. © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH www.vjc.wiley-vch.de 128 the effect of Seanine 211 content on copper releasing ability of the coating based on vinyl copolymers and the properties of the products. 2. MATERIALS AND METHODS 2.1. Materials Cu2O Powder from Hangzhou Dayang Chem Co. Ltd, China. - Vinyl copolymers, China - Zinc acrylate copolymer, China - Modified resin, China - Anti-fouling ingredient Seanine 211 from Dow - Solvent: Xylene, acetone: Using pure grade from China. - Artificial seawater under Standard ASTM D1141. 2.2. Modulation fomula of manufacturing anti- contaminant, anti-fouling paints Modulation fomula of manufacturing anti- contaminant, anti-fouling paints is presented in Table 1. Table 1: Modulation formula of manufacturing anti-fouling paints Ingredients Weight Percentage (%) Vinyl copolymers 30 Modified Rosin (50% in xylene) 20 Zinc acrylate copolymers 20 Cu2O powder 20 Seanine 211 - Additives 5 Anti-fouling Seanine 211 is used with 0, 3, 5 and 10 % in total (which are correlative to M0, M1, M2, M3 samples). The paint mixing process is described as follows: The mixing components are respectively fed into the ball mill at a speed of 100 rpm in 8 hours. Then being filtered through a 270 mesh strainer. 2.3. Determination of the physico-mechanical properties The relative hardness of the coating is determined by ISO 1522:2006 standard; the impact resistance of the coating is determined by ISO 6272-2:2011 standard; the adhesion cross of the coating is determined by ISO 2409 standard; the flexural strength of the coating is determined by ГOCT 6806-53 standard. 2.4. Copper releasing ability assessment PVC sheets sized 55 cm are covered by such paint with a coating thickness about ≈ 150 µm. Weighing to record the initial weight of each plate at the starting point. Soaking these PVC sheets in artificial seawater (prepared according to ASTM D1141 at 40 o C). Over a fixed period of time, this PVC sheet is removed, dried at room temperature and weighted to measure the loss weight over such period. The formula for calculating the loss weight: where: Δm is the loss weight; m0 sample and sole sheet weight at starting point; mn sole sheet weight; mt sample and sole sheet weight at the specified time. The steel sheets sized 10×15 cm are covered by such paint with a coating thickness about ≈ 150 µm. The samples are attached to the shaft and stirred in brine at 100 rpm. Stirring solution is collected at different times, analyzing the concentration by AAS atomic absorption spectrum method. From which, calculating the copper releasing rate according to this formula: [10] where: T: Copper releasing speed (µg/cm 2 /day); C: Copper concentration in 1 liter of soaking solution (mg/liter); V: Volume of solution (liters); S: Testing surface painted area (cm 2 ); d: Number of immersion days. 3. RESULTS AND DISCUSSION 3.1. The morphology of the coating copolymer vinyl/Cu2O/Seanine The morphological structure of anti-fouling coating surface based on copolymer vinyl/Cu2O/Seanine is presented in figure 1. From SEM images in figure 1, we can see that the coating has heterogeneous structure, with the dispersion of the additive phases, Cu2O powder in the paint base, the size of additives as well as Cu2O widely ranged from 100 nm to 2 µm. These particles are evenly distributed in the paint base, which can explain the stability of the abrasion of the coating when being tested in artificial seawater under both static and dynamic conditions. Vietnam Journal of Chemistry Study of copper releasing rate from vinyl © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH www.vjc.wiley-vch.de 129 Figure 1: SEM images of the coating 3.2. Study on the copper release of the coating The anti-fouling ability of paint strongly depends on the Cu releasing rate, which is also the erosion speed of the coating. Within the scope of this study, we assess the abrasion rate of coating both in static and dynamic conditions. 3.2.1. Static abrasion rate of 5% Seanine The process of erosion is tracking over time and obtained results shown in figure 2. 0.00 0.04 0.08 0.12 0.16 0.20 0 10 20 30 40 50 L o st w ei gh t (g ) Time (day) Figure 2: Weight loss of the coating over experimental period Regarding experimental results after 43 days of soaking, the weight loss of coating is very small (≈ 5.3 %). This shows that the abrasion rate occurs very slowly in static conditions. Figure 2 also shows that the decrease in sample weight is proportional to the time according to the linear-line equation. This means that the abrasive speed remains constant throughout the experiment. 3.2.2. Dynamic abrasion speed Anti-fouling Seanine 211 is used with 0 %, 3 %, 5 % and 10 % percent by weight of samples M0, M1, M2, M3. The concentration of Cu released from the coating at different contents of Seanine 211 is shown in figure 3. 0 50 100 150 200 250 300 350 400 450 500 0 20 40 60 80 100 C u ( m g /l ) Time (day) Figure 3: Cu releasing concentration over time. Seanine in portion: 0 %,  3 %, ● 5 %,  10 % Figure 3 showed that samples contained Seanine will affect the ability to release Cu in the first 2 days of the experiment. In the samples with Seanine content of 0 %, 3 %, 5 % and 10 %, copper releasing concentration after 2 days, respectively, is 53.1; 90; 95.25 and 138 mg/l. This shows that when increasing Seanine content, the ability to release copper in the coating will increase respectively. However, after 2 days, this releasing concentration tended to increase slowly for M1, M2, M3 samples while still increased rapidly for M0 sample. Especially, after about 25 days of experiment, the concentrations of M0, M1, M2, M3 samples were 193.1, 129.3, 160.1, 191.2 mg/l, respectively. Also after 2 days, the copper concentrations in M0, M1, M2, M3 samples increased gradually and linearly according to the linear-line equation, or this means that the abrasion rate remained stable during the experiment. Some properties of anti-fouling paint with different Seanine contents are presented in table 2. Vietnam Journal of Chemistry Do Minh Thanh et al. © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH www.vjc.wiley-vch.de 130 Table 2: Some properties of anti-fouling paints in different Seanine contents No Properties of coating Seanine content rate/ paint weight in total (%) 0 3 5 10 1 Impact resistance (kG.cm) 40 50 65 70 2 Flexural strength (mm) 1 1 1 2 3 Adhesion (Point) 3 2 1 1 4 Relative hardness 0.48 0.50 0.50 0.53 Because Seanine has a ring structure in the molecule, increasing Seanine 211 content in such system will accordingly increase the relative hardness of the coating. In addition, chlorine atoms in the molecule also contributes to the adhesion of the membrane. This is evident in models with and without Seanine. However, increasing the Seanine content in excess of 5 % makes the flexural strength decrease. For anti-fouling paint systems, which are submerged paint systems, their adhesion and flexural properties are more concerned than relative hardness. The effect of Seanine contents on copper releasing rate is presented in figure 4. 0 5 10 15 20 25 30 35 40 0 20 40 60 80 100 C u ( µ g /c m 2 /d a y ) Time (day) Figure 4: Average Cu releasing speed over time Seanine in portion: 0 %,  3 %, ● 5 %,  10 % Figure 4 shows that in the first 2 days of testing, when Seanine content increased from 0 to 10 %, the Cu releasing rate increased accordingly, then all 4 rates of Cu releasing speed tended to decrease and remained stable. After 2 days of experiment, the average Cu releasing rate with the Seanine contents of 0 %, 3 %, 5 %, and 10 % was 19.13; 27.56; 32.50 and 36.88 µg/cm 2 /day respectively. With 0 % Seanine content, Cu releasing rate remained stable after 15 days of experiment. Meanwhile, with the Seanine content of 3 and 5 %, Cu releasing rate remained stable after 20 days of experiment. With 5 % Seanine sample on the 19 th day, the average Cu releasing speed was 5.89 µg/cm 2 /day. From the 20 th day onwards Cu releasing rate of the coating was more stable and maintained at ≈ 3.5 µg/cm2/day, this rate maintained until the 98 th day. With a stable releasing rate and within this threshold, the coating is resistant to marine microorganisms such as algae, fouling and some other microorganisms. 4. CONCLUSION It has been determined that Seanine 211 content has an effect on Cu2O releasing process but is not significant. Seanine 5 % content is suitable rate for making anti-fouling paint. The average copper releasing rate at stable stage ≈ 3.5 µg/cm2/day and this process follow the linear-line equation in both static and dynamic conditions. The coating with good properties are considered for making anti- fouling paint. Acknowledgments. The authors are grateful to Vietnam Academy Science and Technology for its financial support by grant No VAST.03.04/20-21. REFERENCES 1. International Maritime Organization, Anti-fouling systems, United Kingdom, London, 2002. 2. O. Iwao. Organotin antifouling paints and their alternatives, Appl Organomet Chem., 2003, 17, 81- 105. 3. Le Thi Thu Ha. Final report Researching on technology of manufacturing anti-fouling paint based on cashew nut shell oil to replace imported goods, Scientific and technical research subject of Ministry of Industry and Trade, 2010. 4. Y. Yonehara, H. Yamashita, C. Kawamura, K. Itoh. A new antifouling paint based on a zinc acrylate copolymer, Prog. Org. Coat., 2001, 42, 150-158. 5. M. O. Stefan. 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Chem., 1996, 15, 181- 193. 10. Standard Test Method for Determination of Copper Release Rate from Antifouling Coatings in Substitute Ocean Water, ASTM D 6442-05. Corresponding author: Do Minh Thanh Institute for Tropical Technology Vietnam Academy of Science and Technology 18 Hoang Quoc Viet, Cau Giay, Hanoi 10000, Viet Nam Email: thanhnau.vn@gmail.com; Tel: +84- 988267333.