Development of a high-strength polyurethane waterproof coating for railway

The performance test is carried out in accordance with TB/T2965-2011 "Technical Conditions of Railway Concrete Bridge Waterproof Layer" for physical performance test.

2.
Results and discussion

2.
1 The main performance test results of coatings

The high-strength polyurethane waterproof coating was synthesized according to the basic formula of the above A and B components, and the physical properties were tested in accordance with TB/T2965-2011.
The results are shown in Table 2.

The test results in Table 2 show that the physical properties of the coating meet the standard requirements, and the performance is good.

2.
2 The influence of NCO content on coating performance

The formula of component B is fixed, and component A with different NCO content is prepared, mixed with component B in a mass ratio of 1:1 to form a film, 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 segment in the A material increases, the polar groups increase, and hydrogen bonds are easily formed.
After coating, the crosslinking density increases, the sample is harder, and the tensile strength is relatively large.
However, the increase of the rigid segment limits the movement of the molecular chain during the stretching process, which reduces the elongation rate after coating.
In order to make the overall performance of the coating outstanding, the NCO content of component A in the test should be controlled at 8.
0%~8.
5%.

2.
3 The influence of polyether polyol on coating performance

Under the condition that the amount of polyether glycol DL-1000D and DL-2000D is constant, the amount of different glycols and triols is compared to synthesize material A, keeping the NCO content in the prepolymer unchanged, See Table 4 for the influence of the ratio of the amount of the two polyether substances on the coating film performance.

It can be seen from Table 4 that the increase in the amount ratio of the substance, the decrease in the strength of the coating film, and the increase in the elongation at break.
The reason is that the polyether glycol is mainly linear, which mainly improves the elongation performance.
When the polyether triol reacts with TDI, it acts as a cross-linking function and mainly increases the strength of the coating 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 of the obtained coating is good.

2.
4 The effect of MOCA content of curing agent in component B on coating performance

MOCA can be used as a chain extender and curing agent in the production of polyurethane and polyurea products.
The B component prepared with different MOCA content and the A component with an NCO content of 8.
0% were made into a film at a ratio of 1:1.
The measured coating film performance results are shown in Table 5.

It can be seen from Table 5 that the increase in MOCA content speeds up the reaction, which shortens the surface drying time and increases the tensile strength, while the elongation at break first increases and then decreases.
The reason is that the modified MOCA cross-linking agent contains 4 active hydrogen atoms, which has high activity and high cross-linking density after the reaction, and the benzene ring with it is a rigid segment.
As the dosage increases, the rigid segment increases and the strength increases.
The elongation at break starts to decrease after increasing to a certain extent.
As a formulation preference, the content of MOCA should be controlled at 12% to 14%, and the coating film obtained has excellent properties.

The influence of antioxidant content in 2.
5B component on the thermal aging properties of coatings

After the polyurethane waterproof coating is formed into a film, under the action of light and heat, part of the linear chains and groups in the molecule will decompose and break, resulting in a decrease in the performance of the coating film.
Adding a certain amount of antioxidants to the formula can effectively slow down the aging process of performance.
At present, the commonly used antioxidants for polyurethane coatings are hindered phenols.
The influence of the content of antioxidant BHT264 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 the antioxidant content, the heat treatment strength retention and heat treatment elongation of the coating film increase, which greatly improves the heat resistance of the polyurethane coating film.
When it is increased to 2.
0% , The heat treatment performance does not change much, as a formula optimization, BHT264 should be controlled at 1.
5%~2.
0%.

2.
6 The influence of the viscosity change of polyurethane waterproof coating on the construction performance

During the construction of polyurethane waterproof coating, it is necessary to mix and stir components A and B according to a certain ratio before applying.
After the components A and B are mixed, they will start to react.
The viscosity increases with time, and the viscosity increases over time.
Faster, it will affect the scratching 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 the catalyst, the viscosity change of the tested paint at room temperature (25°C) after mixing the A and B components for 30 minutes is shown in Figure 1.

It can be seen from Figure 1 that when the content of the catalyst T-9 is 0.
05%~0.
10%, the viscosity of the A and B components will be 20000~30000mP·s after 30 minutes of mixing, and the viscosity will change smoothly and will not increase sharply.
The scratchability is good.
When the content of T-9 is greater than 0.
1%, the viscosity of the coating will increase sharply, which is not conducive to construction.
Therefore, the content of T-9 in this system should be controlled at 0.
05% to 0.
10%.

3.
Conclusion

This test focuses on analyzing the influence of NCO content, glycol and triol substance ratio, MOCA content, and antioxidant content on the coating performance.
It also discusses the effect of catalyst T-9 content on the mixing of A and B components.
The effect of viscosity.
Compared with the test results, the NCO content of the high-strength polyurethane waterproof coating for railways is 8.
0%~8.
5%, the amount ratio of n (diol)/n (triol) is 14~15, and the MOCA content The physical properties and construction performance of polyurethane waterproof coatings obtained when the content of antioxidant BTH264 is between 1.
5% and 2.
0%, and the content of catalyst T-9 is between 0.
05% and 0.
10% are between 12% and 14%.
(Source: Global Coatings Network) (For more information, please log in: Global Coatings Network http:// )