1. The design requirements determine the basic range of the output rate
Due to the different functions of the buildings, the design requirements for heat preservation and energy saving are also different, and the design requirements for the density of polyurethane are different, so when discussing the rate of delivery, first look at the design requirements. For example, the design requires the bulk density (core material density) to be 30KG/cubic meter, and the theoretical (without any loss) one-ton yield rate is 33 cubic meters. For a design density of 40KG/m3, the theoretical yield rate should be 25. According to years of engineering experience, the actual loss due to many factors during the construction process is about 15%-25%, which leads to an increase in cost.
2. The influence of material ratio deviation on the output rate
The density difference between machine bubble and manual bubble is quite big. Normally, the fixed material ratio of the machine is 1:1, but because the calculation of the equipment is calculated by the volume, and factors such as equipment failure, the actual material ratio and the fixed material ratio of the machine sometimes do not match. When the white material is excessive, the foam density is low, the color is white, the foam strength is reduced, and the hand feels soft, and it is easy to shrink when the temperature is low; when the black material is excessive, the foam density is high, the color is deep, the foam strength is high, and the hand feels hard and brittle. . Under these circumstances, the material ratio should be checked immediately to check whether the filter is clogged, and whether the pressure and temperature indicators are normal to ensure the accuracy of the ratio of black and white materials. The deviation of the material ratio has a certain impact on the output rate and construction quality.
3. The influence of ambient temperature on the output rate
Polyurethane foaming is greatly affected by temperature. Foaming relies on heat. If there is no heat, the foaming agent in the system cannot evaporate, and foam cannot be produced. Heat comes from two aspects: chemical reaction generation and environment supply. The heat of chemical reaction is not affected by external factors, and the heat provided by the environment changes with the change of 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. It shows that the foam is fully foamed, and the density of the foam surface layer and the core part are close. When the ambient temperature is low (for example, below 15°C), part of the reaction heat will be dissipated into the environment. The loss of heat, on the one hand, causes the foam maturation period to be extended and increases the foam molding shrinkage rate (the lower the temperature, the higher the molding shrinkage rate); on the other hand, it increases the amount of foam material. Experiments show that: the same foaming material, the foaming volume at 15°C is 25% smaller than the foaming volume at 25°C, which increases the production cost of the foam. When the ambient temperature is lower than 15 degrees, the construction should pay attention to adjusting the temperature control device of the spraying equipment to make up for the reaction limitation of the temperature drop to the raw materials, so as to simulate the best temperature required for the polyurethane reaction as much as possible.
When spraying, the wind speed should be below 5m/s. The wind speed exceeds 5m/s, the heat generated by the blowing reaction will be lost, which will affect the rapid foaming reaction of the polyurethane foam and make the surface of the product brittle. At the same time, since the spray foaming machine mixes the raw materials and sprays them in an atomized state, if the wind speed is too high, the atomized particles will be blown away, increasing the loss of raw materials and polluting the environment.