Application of the hottest polyurethane waterproof

Application of polyurethane waterproof coating in high-speed railway projects

introduction

polyurethane materials have excellent physical and chemical properties and meet the requirements of high-speed railway materials. Based on polyurethane, the products that can be made include foamed plastics, elastomers, coatings, adhesives, etc., which are widely used in the seismic and noise reduction, waterproof, potting and other aspects of rail transit []

with the rapid development of high-speed railway in recent years, polyurethane waterproof coating is more and more widely used in high-speed railway engineering projects [3]. The technical conditions for waterproof layer of railway concrete bridge deck strictly stipulates that the tensile strength of polyurethane waterproof coating directly used as waterproof layer is ≥ 6.0MPa, and the elongation at break is ≥ 450%. Based on this standard requirement, this paper discusses the influence of polyether, isocyanate, crosslinking agent and additives in polyurethane coating on polyurethane waterproof coating, and prepares a high-strength polyurethane waterproof coating that meets the standard requirements

1. Test part

1.1 raw materials

Polyether Polyols (dl-1000d, dl-2000d, ep-330ng): industrial grade, Shandong Bluestar Dongda Chemical Co., Ltd; Toluene diisocyanate (TDI): industrial grade, Bayer materials technology (China) Co., Ltd; Chlorinated paraffin (52#): industrial grade, Nanjing Rongji Chemical Co., Ltd; Calcined talc powder (1250 mesh): industrial products, Yangshan Huaxing fine powder factory; Dibutyl phthalate (DBP): industrial products, Guangzhou Zhuangda Chemical Co., Ltd; 3,3 '- dichloro-4,4' - diaminodiphenylmethane (MoCA): industrial products, Xiangyuan special Fine Chemical Co., Ltd; Stannous octanoate (T-9): industrial grade, Shanghai Yutian Chemical Co., Ltd; Antioxidant bht264: industrial grade, Germany younging group

1.2 basic formula

the basic formula of components a and B is shown in Table 1

1.3 preparation process

component A: add polyether dl-1000d, dl-2000d and ep-330ng into a four port flask in a certain proportion, raise the temperature to 110 ℃; ③ separate the power line and the signal line, keep the pressure below -0.085mpa, dehydrate for 2h, lower the temperature to 80 ℃, add TDI reaction for 3h, lower the temperature and discharge the material

b component: disperse chlorinated paraffin, DBP, ep-330ng, Moca, talc powder, etc. in a certain proportion, add them to a four port flask, raise the temperature to 110 ℃ for dehydration 2h, lower the temperature to 50 ℃, add T-12 and bht264, stir evenly, and then discharge

1.4 main instruments

electric blast drying oven: dhg-9070, Shanghai Pudong Rongfeng Scientific Instruments Co., Ltd; Low temperature test chamber: dx-40, Tianjin Gangyuan test instrument factory; Standard curing box: jby-30b, Cangzhou Keda road and bridge test instrument factory; Electronic universal tensile testing machine: WDW-5, Guangzhou AOJIN Industrial Automation System Co., Ltd

1.5 performance test

mix and stir components a and B according to the mass ratio of 1:1 for 3~5min to prepare the film, and cure and test under standard test conditions (temperature (23 ° 2) ℃, relative humidity (60 ° 15)%)

the physical performance test shall be carried out in accordance with tb/t2965-2011 technical conditions for waterproof layer of railway concrete bridge deck

2. Results and discussion

2.1 test results of main properties of coating

high strength polyurethane waterproof coating is synthesized according to the above basic formula of component A and B, and the physical properties are tested according to tb/t2965-2011. The results are shown in Table 2

the test results in Table 2 show that all physical performance indexes of the coating meet the standard requirements, and the performance is good

2.2 effect of NCO content on coating performance

the formula of component B is fixed, and component A with different NCO content is prepared. The film is mixed with component B at the mass ratio of 1:1, and its strength and elongation are tested. The results are shown in Table 3

it can be seen from table 3 that when the NCO content increases, the rigid chain segments in material a increase, the polar groups increase, it is easy to form hydrogen bonds, the crosslinking density increases after coating, the sample is hard, and the tensile strength is relatively large. However, the increase of rigid chain segment limits the movement of molecular chain in the stretching process, which reduces the elongation after coating. In order to make the comprehensive performance of the coating outstanding, the NCO content of component A in the test should be controlled at 8.0% - 8.5%

2.3 effect of polyether polyol on coating performance

under the condition that the amount ratio of polyether diol dl-1000d and dl-2000d is certain, different amount ratios of diol and triol are used to synthesize material a, keeping the NCO content in the prepolymer unchanged. The effect of the amount ratio of two polyether substances on the coating performance is shown in Table 4

it can be seen from table 4 that if the amount ratio of substances increases, if the microcomputer function is strong, it can be printed directly, the film strength decreases, and the elongation at break increases. The reason is that polyether diols are mainly linear, which mainly improves the elongation performance. When polyether triols react with TDI, they play a cross-linking role, which mainly increases the strength of the film. Therefore, when the formula is optimized, the mass ratio of n (diol)/n (triol) is controlled at 14~15, and the coating film performance is good

2.4b effect of the content of curing agent MOCA in the component on the performance of the coating

moca can be used as chain extender and curing agent in the production of polyurethane and polyurea products. The film of component B with different MOCA content and component A with NCO content of 8.0% is prepared at the ratio of 1:1. The results of coating film performance measured are shown in Table 5

it can be seen from table 5 that the MOCA content increases and the reaction accelerates, which shortens the surface drying time and increases the tensile strength, while the fracture elongation first increases and then decreases. The reason is that the modified MOCA crosslinking agent contains 4 active hydrogen atoms, with high activity, high crosslinking density after reaction, and the benzene ring belongs to the rigid chain segment. With the increase of dosage, the rigid chain segment increases, the strength increases, and the fracture elongation increases to a certain extent and then begins to decline. As a formula optimization, the MOCA content should be controlled at 12%~14%, and the coating film performance is excellent

2.5b effect of antioxidant content in component on the thermal aging performance of the coating

after the film-forming of polyurethane waterproof coating, under the action of light and heat, some linear chains and groups in the molecule will decompose and break, resulting in the decline of film performance. Adding a certain amount of antioxidant to the formula can effectively slow down the aging process of performance. At present, the commonly used antioxidant for polyurethane coating JTG d30 ⑵ 015 highway subgrade design code material is hindered phenols. The influence of antioxidant bht264 content in component B on the heat treatment performance of the coating is shown in Table 6

it can be seen from table 6 that with the increase of antioxidant content, the heat treatment strength retention and heat treatment elongation of the film increase, which greatly improves the heat resistance of polyurethane film. When it increases to 2.0%, the heat treatment performance changes little. As a formula optimization, bht264 should be controlled at 1.5% - 2.0%

2.6 influence of viscosity change of polyurethane waterproof coating on the construction performance, thus ensuring the consistency of system sampling and high-speed and effective control function

during construction, the polyurethane waterproof coating needs to mix and stir components a and B according to a certain proportion before construction. After mixing, components a and B begin to react, and the viscosity increases with time. If the viscosity increases too fast, it will affect the coating and scraping performance of construction. Therefore, in the formulation development process, it is necessary to appropriately control the reaction speed to control the viscosity of the paint after mixing, so that the paint has better construction performance. By adjusting the content of catalyst, the viscosity change of the coating at room temperature (25 ℃) for 30min after the mixing of components a and B is shown in Figure 1

it can be seen from Figure 1 that when the content of catalyst T-9 is 0.05%~0.10%, the viscosity of components a and B is 20000~30000mps after mixing for 30min, and the viscosity changes smoothly without sharp increase. The coating has good scrapability. When the content of T-9 is greater than 0.1%, the viscosity of the coating increases sharply, which is not conducive to construction. Therefore, the content of T-9 in this system should be controlled at 0.05% - 0.10%

3, conclusion

this test focuses on the analysis of the influence of NCO content, the amount ratio of diol and triol, MOCA content, antioxidant content on the film performance, and also discusses the influence of catalyst T-9 content on the viscosity of a and B components after mixing. Through the comparison of test results, in the proportion of the high-strength polyurethane waterproof coating for the railway, when the NCO content is 8.0%~8.5%, the amount ratio of n (diol)/n (triol) material is 14~15, the MOCA content is 12%~14%, the antioxidant bth264 content is 1.5%~2.0%, and the catalyst T-9 content is 0.05%~0.10%, the polyurethane waterproof coating has the best physical performance and construction performance