Research on high-performance water-based damping coatings

Zhang Peng, Zhao Qingjun, Yao Hailong (Shijiazhuang City Paint Factory, Shijiazhuang 050051)
Abstract: Introduced the damping method of polymer materials, using emulsion mixing method to achieve widening damping temperature domain. Through the selection of emulsion mixing method, mica powder particle size and addition, thickener and fiber, the damping coating developed has the characteristics of damping temperature width, high compound loss frequency, good vibration reduction and noise reduction, and good mechanical performance.
key words: water-based damping coatings; compound loss cause; Damping performance; Vibration reduction noise reduction
In the figure classification number: TQ 630. 7 Document identification code: A article number: 0253 - 4312 (2012) 08 - 0039 - 04
With the rapid development of China's railway industry, the operating mileage continues to increase, the operating speed continues to improve, the experimental train speed has exceeded 500 km/ h. In the course of high-speed operation, all kinds of mechanical components will produce vibration, which will produce noise, and the size of vibration is directly related to the strength of noise. According to the test and foreign data, when the railway train is running at speeds above 80 km/h, the noise in the train increases by 0. 5 ～ 1. 0 dB, i.e. if the vehicle speed is increased from 80 km/h to 300 km/h, the noise in the vehicle will increase by 11 to 22 dB. Therefore, if the vehicle manufactured according to the current standard is used for speed increase or high speed operation, the noise inside the vehicle will be significantly improved. Strong noise will affect ride comfort, so reducing vibration and noise throughout the vehicle will be even more important. These problems will become even more acute with the acceleration of the high-speed and lightweight railway process and the improvement of people's living conditions. In this study, 2 kinds of emulsion mixing method were used to achieve widening damping range.
test found that the emulsion mixed with good mixing and large difference in Tg value can obtain damping coating with wide damping temperature range and high compound loss rate. Water-based damping coatings developed by adding filtered flak fillers, fibers that enhance film properties, and thickeners that improve the epithelia of the coating have excellent features of sound insulation, shock reduction, noise reduction, insulation, flame retardant and environmental protection, and have high application value in the field of high-speed railway.
1. The experimental part
1. Raw
R1: Tg - 0 degrees C, Baoding Yanda Chemical Co., Ltd.; Emulsion R2: Tg , 42 degrees C, China Chemical Rubber Zhuzhou Research and Design Institute; Mica Powder: Hebei Lingshou; Thickener 638: Former Corning Company; Dispersant 3204: former Corning Company; Desiccant 334: Former Corning Company; Polypropylene fiber: Hebei Baoding Xinxuan synthetic fiber factory.
1. 2
water-based damping coating formula is found in Table 1.1. 3 Performance test results
1. 3. 1 Model preparation method
preparation of the model is carried out in accordance with GB/T 1727-1992. First of all, on the substrate to apply a TB/T 2260-1991 "railway vehicles with rust-proof primer supply technical conditions" or agreed by both supply and demand anti-rust primer, dry film thickness of (23 ± 3) sm, dry 48 h, the use of scraping or spraying methods to prepare damping coating coating, dry film thickness (2. 0 ± 0. 2) mm. The model is dried at room temperature by 7 d; Or place 24 h at room temperature, then bake 2 h at (60 ± 2) degrees C, remove and then place 16 to 24 h at room temperature for testing.
1. 3. 2 Detection of damping properties
Damping coating is a functional coating whose main function is to reduce shock and noise, so compound loss ηc is the main performance indicator. In this paper, the method B free suspension beam method stipulated in GB/T16406-1996 "Bend resonance test method for the damping performance of acoustic material" is used for ηc determination, which is applicable to the measurement range of 10 to 1 000 Hz, and the measurement range of the energy storage module can reach 0. 5 MPa, loss base measurement range is 10 - 2 to 10 - 1 magnitude. The measurement results are used to evaluate the vibration damping effect of various composite structural tests.
1. 3. 3 Performance test
water-based damping coating performance test results are below Table 2.
2 Results and Discussions
2. 1 Damping
polymeric materials are widely used in the development and use of damping materials because of their unique viscosity elasticity. It generally exhibits the best damping performance in the Tg area.
This is because when the temperature is in the Tg area, the polymer chain segment is just in a state of sticky bullet that can move freely, the system viscosity is very high, the frictional resistance of the chain segment movement is very large, so irreversible sliding increases, deformation lags behind the stress change, resulting in a larger consumption within the system; When the temperature is lower than Tg, the polymer chain segment is in a hard glass state (free movement is frozen), the slip phenomenon of the inter-molecular chain segment is very rare, the external force acting on the polymer material only causes the change of key length and key angle, and this shape changes very small, very fast, enough to keep up with the change of stress, so the system internal consumption is small; When the temperature is higher than Tg, the polymer chain segment is in a high-bounce state, the chain segment movement is freer, the sliding between the chain segments can be restored quickly, so the system consumption is also small.
polymeric material in the sticky state, the phenomenon of deformation behind stress under the effect of cross-variable stress is called lag phenomenon. Because of lag, in each action there is a loss of energy, called the loss of force or "internal consumption", the consumption of work in the form of "heat" released. The actual process is to change a certain amount of momentum, mechanical energy into thermal energy, thus playing a damping role in vibration reduction noise reduction.
evaluation of damping materials still lacks uniform standards, and the more common evaluation method is dynamic dynamic spectrometology. The size of the material's aesthetic loss or internal consumption is indicated by the material's loss factor or damping factor (tan) under stress, as shown in the form (1).
E" / E' type (1)
where: E' is the real module (or energy storage module); E" is the imaginary module (or loss module); δ (the force loss angle) is the phase angle at which the strain lags behind the stress. The larger the damping factor, the wider the damping range, the better the damping performance of the material.
The loss cause of the uniform material itself is represented by tan, when the sample is composed of different material composites, the measured loss force is called the composite loss force ηc, when the damping layer and substrate thickness ratio of a certain, ηc is directly compared to the damping material itself tan. The compound loss of damping coatings has a ηc of 0. There is a damping effect at 03, ηc 0. 05 when there is practical application value, Japan ηc > 0. 08［4］。
2. 2 Choice of emulsion
water-based damping coatings are usually based on emulsions. However, a single emulsion damping temperature domain is narrow, the elastic module is too low, can not meet the practical application of wide temperature domain, wide frequency damping needs. In order to widen the glass transition area of damping material and improve the damping properties and elastic mould of the material, it is the most common method to mix 2 or more lotions.
1 shows the relationship between the temperature ηc a single emulsion.as can be found from Figure 1, the peak of ηc is 0.45 at - 2. 9 degrees C, and the peak of ηc is 0.54 at 40.2 degrees C.
damping properties of R1 emulsion and R2 emulsion are shown in Figure 2, where R3 emulsion is m (R1) : m (R2) and 1: 2 co-mix emulsion; R4 emulsion is m (R1) : m (R2) , a mixed emulsion of 1:1; The R5 lotion is a mixed emulsion of m(R1) : m (R2) and 2:1. figure 2 shows that the ηc peaks have changed significantly since the two emulsions were mixed, and only 1 peak has occurred, indicating that the compatible of the two lotions is better. When R1 and R2 are mixed together, the ηc curve changes with different co-mixing ratios, and when m(R1) : m (R2) is 2:1, its damping range is widest and the ηc is greater than 0. The temperature range at 08 is - 20 to 60 degrees C. Although the damping peak is lower than the emulsion single part, it can meet the requirements for the use of high-speed railway passenger car body.
2. 3 Thickener Selection
Water-based coatings have good construction, excellent surface effect and ideal storage stability, which depends to a large extent on the choice of thickener. At present, the variety of thickeners available on the market is mainly inorganic thickeners, cellulose, acrylic-alkali swelling and polyurethane-type thickeners and other 4 categories. Different types of thickener thickening process is different, the various properties given to the coating film are not the same, see Table 3. inoranced thickeners such as bento thickening, montes rock, etc. have the advantages of strong thickening, good denaturation, good stability, etc., but the flatness of the coating film is poor, the surface is uneven. Cellulose thickener is through hydrophobic main chain and surrounding water molecules through hydrogen bonding, improve the polymer itself fluid volume, reduce the free movement of particles space, to improve the viscosity of the system. Because it is a natural polymer, it is easily degraded by microbial attack, which affects the storage stability of the coating. Acrylic-alkali swelling thickeners generally carry a larger number of carboxyl, and the alkali in the water phase, the formation of polymer salts, from granular to a large number of branch chain structure of the three-dimensional rod-like, but also because of cross-formation of the network structure. Therefore, it has a strong hydro-hydro, water resistance is not good. Polyurethane-linked thickener is a polymer with hydrophobic and hydrophobic base, hydrophobic group and coating substrate have a strong affinity, can enhance the water resistance of the coating film, with strong thickening, leveling, water resistance, good biological stability and other characteristics.
2. 4 Filler Selection
Adding fillers can effectively expand the damping temperature field, and flaky mica powder is one of the most commonly used addition fillers. When the film made of flaky mica powder in conjunction with polymer material encounters vibration or noise radiation, the flaky material of mica powder moves along the vertical direction of vibration and noise propagation, causing friction with the polymer chain and mica powder around it, converting mechanical energy into heat energy, thus acting as damping vibration reduction.
, Tan Lianghong, etc., studies suggest that with the decrease of mica particle size, the peak of ηc is increasing, and the temperature domain of glass transformation becomes narrower. With the increase of mica particle size, the high damping temperature field widens and the damping peak decreases. With the increase of mica powder dosing, the damping performance of mica at large particle size is on the rise, while the damping performance of mica at small particle size is on the decline. The effect of different particle size mica powder on damping performance can be seen in Figure 3, and the effect of addition on performance can be seen in Table 4.
with the increase of mica powder, the particle size decreases, the peak of ηc increases, the factor of low temperature damping loss decreases, and the number of high temperature damping factors increases. With the decrease of mica powder, the particle size increases, the glass transition temperature domain widens, the low temperature damping loss is increased, and the high temperature damping loss is reduced.
table 4 in the mica powder selection 60 eyes and 600 eyes mixed use, 60 eyes and 600 eyes mica powder quality ratio of 1: 2, from Figure 3 can be known to add 60 mica powder on the low temperature of the compound loss of the reason has a greater increase, add 600 mica powder on the high temperature of the compound loss coefficient is obviously helpful, because the particle size of smaller mica powder in the damping paint scattered more dense, the chance of mutual friction is greater, damping effect is obvious, so the smaller particle size of 600 mica powder accounted for a larger proportion is appropriate. As can be known from Table 4, with the increasing amount of mica powder added, the impact resistance of damping coatings is enhanced and flexibility is reduced. The addition of mica powder in damping coating is between 40% and 50%, and the comprehensive performance of the coating film is optimal.
2. 5 fiber selection
damping coating in order to achieve the effect of silence damping vibration, generally requires the thickness of the coating film is thicker, the coating film in the drying process due to internal stress is larger easy to crack phenomenon. In order to solve this phenomenon, it is necessary to add reinforcing ribs to the coating and increase the anti-stress of the coating film. The reinforcing ribs commonly used in coating films are: asbestos fibers, fiberglass fibers, steel fibers and synthetic fibers. Among them, asbestos fiber was found to have carcinogenic effects on human body, has been banned from the international use; Glass fiber can't pass alkaline resistance experiment because of poor alkaline resistance. Steel fibers have problems such as large addition, high cost, complex operation, large wear on the machine and easy corrosion. Polypropylene synthetic fiber is widely used because it is safe and environmentally friendly and has the characteristics of improving crack resistance, osmosis, impact resistance, antifreeze, seismic resistance and ability to improve film flexibility, extension and wear resistance. Table 5 shows the effect of polypropylene fibers of different fiber lengths on the performance of damping coatings.
According to Table 5, the selection of polypropylene fibers longer than 4 mm in the construction is very easy to produce fiber clump blocking the nozzle phenomenon, and when the selection is shorter than 3 mm fiber, its strengthening effect is less than the coating film drying process cohesion contraction, the phenomenon of coating surface cracking, while not playing a role in enhancing the film impact resistance and flexibility, so the choice of 4 mm fiber is more suitable.
3. Conclusion
(1) When using a variety of emulsions to expand the damping temperature domain, it is required that the Tg values of different emulsions differ as far away as possible, and compatible is better, the size of the difference between the Tg values of emulsions determines the width and narrowness of the damping temperature domain of the mixed emulsion; Compatibleity determines the size of damping peaks.
(2) by adding mica powder to achieve the purpose of regulating damping temperature region and damping peak, adding large particle size mica powder, can widen the damping temperature domain, improve the damping value of low temperature zone, but reduce the damping value of high temperature area; Adding mica powder with small particle sizes increases damping peaks but lowers damping values in low temperature zones.
(3) the selection of effective thickeners can improve the consistency of the damping system, improve the leveling, water resistance and storage stability of the coating film, and provide good construction performance.
(4) to add polypropylene fibers, choose the appropriate fiber length, improve the anti-cracking performance of the coating film, to meet the requirements of construction spraying.
water-based damping coating developed by using the above method