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1, design requirements determine the basic scope of the rate
Because the efficacy of the building is different, the design requirements for insolution and energy saving are also different, the density design requirements for polyurethane are not the same, so talk about the rate first look at the design requirements. For example, the design requires a weight (core density) at 30KG/m3, and the theory (without any loss) of one ton is at 33 squares. The design density is 40KG/m3, and the theoretical yield should be 25. According to many years of engineering experience, the actual loss due to many factors in the construction process is about 15%-25%, resulting in higher costs.
2, the effect of material ratio deviation on the
the density of machine bubbles and manual bubbles is larger. Usually, the fixed ratio of the machine is 1:1, but because the calculation of the equipment is calculated by volume, and equipment failure and other factors, the actual ratio does not sometimes match the fixed ratio of the machine. When the excess white material is shown as low foam density, white color, foam intensity decline, soft feel, low temperature easy to shrink; When the black material is excessive, it is shown as high foam density, dark color, high foam strength, hard and brittle feel. In these cases, the ratio should be checked immediately to see if the filter is blocked, the pressure, temperature indication is correct, to ensure the accuracy of the black and white ratio. The deviation of material ratio has certain influence on the yield rate and construction quality.
3, the influence of ambient temperature on the
, polyurethane foaming is greatly affected by temperature. Foaming depends on heat, and without heat, the foaming agent in the system cannot evaporate, making it impossible to produce foam. Heat comes from both chemical reaction generation and environmental provision. Chemical reaction heat is not affected by external factors, and the heat provided by the environment varies with the ambient temperature. When the ambient temperature is high, the environment can provide heat to the reaction system, which can increase the reaction speed and shorten the reaction time. The foam foam foaming is sufficient and the foam surface and core density are close. When the ambient temperature is low (e.g. below 15 degrees C), some of the reaction heat is emitted into the environment. The loss of heat, on the one hand, causes the foam ripe period to be prolonged, increasing the shrinkage rate of foam molding (the lower the temperature, the higher the shrinkage of molding); On the other hand, the amount of foam material has been increased. Experiments show that the foaming volume of the same foaming material at ambient temperature of 15 degrees C is 25% smaller than that at 25 degrees C, thus increasing the production cost of foam. When the ambient temperature is below 15 degrees, the construction should pay attention to the temperature control device by adjusting the spray equipment to compensate for the temperature drop to the reaction limit of raw materials, so as to simulate the best temperature required for polyurethane reaction as far as possible.
spraying operations, the wind speed is required to be below 5m/s. Wind speed of more than 5m/s will blow out the heat generated by the reaction, affecting the rapid foaming reaction of polyurethane foam, making the surface of the product brittle. At the same time, because the spray foaming machine will mix raw materials, sprayed out in a atomized state, such as wind speed is too large, will blow away the atomized particles, increase the loss of raw materials, pollution of the environment.
5, grass temperature and humidity
from the engineering practice can be seen that the temperature of the grass wall on the foaming efficiency of polyurethane also has a great impact. During the spraying process, if the ambient temperature and the base wall temperature of the building are very low, after the first spray of hard foam polyurethane, the reaction heat will be quickly absorbed by the grass, thereby reducing the foaming amount of the material. Therefore, in the construction should try to shorten the noon break time, in the construction arrangement process should be reasonable arrangements for the process to ensure the foaming rate of hard foam polyurethane. Hard polyurethane foam is a polymer product produced by a mixture of isocyanate and combined polyether components. Where isocyanate parts are easy to react with water to produce arbonds, if the content of arbond bonds in polyurethane increases, then the foam will become brittle, foam and substrate bonding force is reduced. Therefore, it is required to spray the surface of the substrate clean and dry, relative humidity is less than 80%, and no rust, no dust, no pollution, no moisture, rainy days must not be constructed. If exposed or frosted, it should be removed and dried.
6, the thickness of the spray coating on the rate of the impact
spraying according to the thickness of different, different use of the environment, usually using multi-layer spraying methods, in accordance with the requirements of the national standard of the first layer of thickness and thickness of each layer have certain provisions, on the one hand, to ensure the thermal performance of polyurethane, on the other hand, along the polyurethane reaction curve to work reasonably. However, because each layer will have the presence of skin, so the thickness of each layer will be the larger the out-of-the-way rate relatively more, but in order to improve the rate of the party in violation of the polyurethane spraying process requirements of the party is not desirable, which requires construction personnel based on experience in ensuring quality in the case of site treatment.
7, construction in the face of the impact of the rate
polyurethane spraying construction in the construction of building corner lines, decorative lines, roofs, beam structures, daughter walls and other construction material waste is extremely serious. For example, in the construction of large corner construction, there are nearly 1/2 of the material can not be sprayed on the wall, in the roof construction because of the small surface of the construction, material waste phenomenon is inevitable. Therefore, the construction of special parts in the construction process should pay more attention to the unity of construction technology and construction conditions.
8, the impact of flatness on the rate of
in the construction process, should also effectively control the grass-roots flatness. The flatness of the grass-roots wall is too poor, which also causes a certain amount of material waste. In addition, if the flatness error of the base wall in the polyurethane spraying process is too large, it is necessary to saw off the part where the local positive deviation is too large, thus wasting the polyurethane material and labor costs, but also to the subsequent construction of difficulties.