Research on Anti-icing Coatings for High-cold Train Bogies

High-speed trains running in cold, snow and ice environments are prone to ice, such as the Shinkansen in Japan and the Kazakhstan High-speed Railway in China. High-speed train steering frame mainly includes frame, wheel pair, brake clamp, brake disc, air spring, shock reducer and various lines and other components, is one of the most important components of high-speed train, once the occurrence of ice will cause safety hazards to the normal operation of the train. For example, icing in the steering frame area, falling ice can damage under-car components and equipment, air springs and shock reducers freeze, which can affect the vehicle's dynamics, and it is easy to scratch the brake disc when mixed with debris such as ice particles between the brake pads and brake discs, which greatly shortens the life of the brake disc, and brake clamp icing can affect its normal operation, preventing the train from effectively applying the underlying brake . After the freezing of the steering frame, the train needs to be de-icing, usually using artificial mechanical de-icing, high-pressure water gun de-icing, hot wind de-icing and other ways, high energy consumption, low efficiency, labor intensity. Therefore, the application of anti-ice coating in the steering frame part is not only beneficial to reduce the safety hazard caused by ice, but also can greatly reduce the labor intensity of the staff de-icing operation.
most widely studied anti-ice material is ultra-hydrophobic surfaces with low surface energy properties. Ultra-hydrophobic surface has micron, nano or micron composite microstructure, can form an air layer by binding air, avoid the immersion of water droplets, reduce the actual contact area between ice and substrate after water droplets freeze. However, ultra-hydrophobicity will fail in high humidity or high overcoord environment, resulting in mechanical locking of ice and microstructurs and increased ice adhesion strength. In addition, the structured surface wear resistance is poor, can not take into account the basic protective properties of the coating, lack of practicality. The research shows that for smooth surface, reducing the contact angle lag of water droplets can reduce the strength of ice adhesion, which indicates the direction for the development of practical anti-ice materials. This paper is guided by the anti-ice application of the high-cold train hem, and by comparing three kinds of fluorine-containing hydroxyl resins with low surface energy characteristics, it evaluates its role in reducing the strength of ice adhesion and provides experimental guidance for the preparation and application of practical anti-ice coatings under the premise of realizing the basic protective function of the coating.
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Experimental part
1.1 Main raw materials and equipment
fluorocarbon resin 1, fluorocarbon resin 2, fluorosilicon resin: commercially available; polycyanate curing agent: N3390, Coxtron; Titanium white powder: R960 goldstone type, DuPont; Light powder: PERGOPAKM2, Beijing Tianhengjian; PTFE wax powder: CerOnas, Germany; Dispersant BYK170, leveling agent BYK300, desmoticant BYK088, thickener BYK411: Bick Chemical; Butyl acetate: Chemical Purity, Beijing Chemical Plant.
sanding dispersion machine, paint film wearer, pencil hardness meter, paint film flexibility tester, lacquer film impactor: Standard Gerda Precision Instrument (Guangzhou) Co., Ltd.;
1.2 coating preparation
1.2.1 varnish coating preparation
according to the formula shown in Table 1, add desolation agent, leveling agent, thickener and butyl acetate to the resin, using a high-speed dispersion machine dispersed 1h, to obtain component A. Part B is obtained by diluting N3390 to a solid content of 50% using butyl acetate.
the varnish A, B parts in accordance with the amount of - NCO and - OH and other substances to be prepared, fully mixed and mixed evenly. Iwata W-71-2G spray gun spray preparation varnish coating, air pressure 0.4MPa, spray distance of 200mm, room temperature after placing curing 7d performance test.
Table 1 Varnish Group A Dispenser
1.2.2 White Paint Coating Preparation
According to the formula shown in Table 2, add dispersants to fluorosilica resin, mix well, then add titanium dioxide, PTFE wax Powder, anti-light powder, de-foaming agent, leveling agent, and then to the system to add a moderate amount of glass microbeads, the use of a high-speed dispersion machine installed with sanding disc for grinding dispersion 1h, and finally add butyl acetate to adjust the solid content, filtration to obtain white paint A components. Part B is obtained by diluting N3390 to a solid content of 50% using butyl acetate.
table 2 white paint group A distribution party
white paint A, B parts in accordance with the amount of - NCO and - OH and other substances to be prepared, fully stirred and mixed evenly. Iwata W-71-2G spray gun spray preparation white paint coating, air pressure 0.4MPa, spray distance of 200mm, room temperature after placing curing 7d performance test.
1.3 Performance Test
1.3.1 Coating Basic Performance Test
Coating Hardness Test by GB/T6739-2006; 8 tests; flexibility tested according to GB/T1731-381993; impact resistance tested by GB/T1732-1993; wear resistance by GB/T1768-2006 Tested for acid and alkali resistance according to GB/T9274-1988, water-resistant performance according to GB/T1733-1993 test, oil-resistant performance according to GB/T9274-1988 test; Wet and thermal performance is tested according to GB/T1740-2007, salt spray resistance performance is tested according to ISO9227:2012, and artificial climate aging performance is tested according to GB/T23987-2009.
1.3.2 coating hydrophobic performance test
the use of JM2000DM contact angle gauge for the coating contact angle and contact angle lag test. The test droplet volume was 2 μL.
1.3.3 anti-ice performance test
the anti-ice performance of the above three resin coatings is indicated by a homemade ice adhesion strength test device. The test device, as shown in Figure 1, fixes the coating model to the precision temperature control table, fills the titular container with an internal diameter of 1cm on the coating surface, is 1cm high, freezes into ice at -20C and maintains 5h, during which high purity nitrogen is inserted into the device cover to avoid frosting of the coating surface and affects the test results. Then through the mobile platform control force meter at the speed of 5mm/s, close to the coating surface in a horizontal direction to push the sample off, the maximum thrust recorded by the meter is ice adhesion force F, and then according to the formula (1) calculated ice adhesion strength:
of which, τ-ice adhesion strength;
Figure 1 Ice Adhesion Strength Test Device Schematic
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Results and Discussion
2.1 Selection of Anti-Ice Coating Substation Resins
The study shows that improving the hydrophobicity of the coating surface is beneficial to reduce the adhesion strength of ice and improve its anti-ice properties. The ice adhesion strength of smooth solid surface is related to its hydrophobicity, the larger the contact angle of the water droplet and the smaller the contact angle of the water droplet, the lower the ice adhesion strength. Compared with traditional hydroxypropyl acrylic or saturated polyester resin-based two-component polyurethane coating, the coating prepared with fluorine-containing, silicon-containing hydroxy-resin can improve surface hydrophobicity due to the low surface of the fluorosilic silicone chain segment and the ease of migration and aggregation to the coating surface. Based on the study of coating hydrophobic and anti-ice properties, the feasibility of applying 3 kinds of commercialized fluorine-containing resins to anti-ice coatings on the steering frame of high-chill trains is discussed, and the basic properties of the 3 kinds of resins are shown in Table 3.
the basic properties of different types of fluorohydroxy resins
the basic properties of varnish coatings are shown in Table 4.
Table 4 Varnish coating basic performance test results
As can be seen from Table 4, the hardness of the varnish coating prepared with 3 different resins can reach 2H, adhesion level 0, and has good flexibility and impact resistance. However, due to the differences in the molecular structure of the resin, the coating hydrophobicity is different, of which, the coating surface prepared by fluorocarbon resin 1 has the smallest static contact angle of water droplets, which is only 83 degrees. Fluorocarbon resin 2 is obtained by tetluoroethylene monomer and vinyl ether, vinyl ester monomer co-polymerization, the molecule is not chlorine, its coating surface contact angle is 91 degrees. The introduction of silicone units in fluoro-silicone resins further improves the hydrophobicity of the coating, with a surface contact angle of up to 98 degrees and a contact angle lag of only 28 degrees, which is lower than the 37 degrees of fluorocarbon resin 1 varnish coating and 33 degrees of fluorocarbon resin 2 varnish coating.
2.2 Comprehensive performance test of anti-ice coatings
In view of the best hydrophobic surface of varnish coating prepared by fluorosilicon resin, and the lowest adhesion strength of ice, a white anti-ice coating finish was further prepared with fluorosilicon resin, and the coating performance test results are shown in Table 5.
5 train hem white paint coating performance test results
As can be found from Table 5, the mechanical properties and chemical stability of the coating basically meet the performance requirements of the train set steering frame coating.
3
Conclusion
This paper compares the hydrophobic and ice adhesion strength of fluorocarbon resin 1, fluorocarbon resin 2 and fluorosilica resin coating surface, among which, the varnish coating surface prepared with fluorosilic resin has the best hydrophobicity, the contact angle is 98 degrees, and the contact angle lag is 28 degrees. At the same time, the anti-ice performance of the fluorosilicon varnish coating is optimal, and the ice adhesion strength of the coating surface at -20 degrees C is only 141kPa, well below the 536kPa of fluorocarbon resin 1 and 468kPa of fluorocarbon resin 2. After further adding pigments to fluorosilicon resins and other preparations into white anti-ice paint, the coating shows excellent comprehensive performance and is expected to be applied to high-cold train hem anti-ice.
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