Eight factors restricting the development of polyu

2022-08-21
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Brief discussion on eight factors restricting the development of polyurethane spraying manufacturers

rigid foam polyurethane spraying is a polymer with urethane chain repeating structural units, which is made by the reaction of isocyanate with polyol for weak R & D ability. When the gap between the left and right of the connecting part is greater than 0.5mm, its thermal insulation performance is good, and its waterproof performance is excellent. It is widely used in external wall thermal insulation, roof thermal insulation, and thermal insulation of special parts such as cold storage, grain storage, archives, pipelines, doors and windows

rigid polyurethane spraying belongs to the field processing of chemical products, and it is difficult to master the spraying technology. Due to different design requirements and external factors, the square yield of polyurethane spraying is also different, mainly due to the following factors

the design requirements determine the basic range of the yield rate

due to the different efficacy of buildings, the design requirements for thermal insulation and energy conservation are also different, and the density design requirements for polyurethane are different, so when talking about the yield rate, we first look at the design requirements. For example, the design requires that the unit weight (core material density) is 30kg/cubic meter, and the theoretical (without any loss) cubic meter yield per ton is 33 cubic meters. If the design density is 40kg/cubic meter, the theoretical yield should be 25 According to years of engineering experience, due to the influence of many factors, the actual loss in the construction process is about 15% - 25%, which leads to the rise of cost

the influence of material ratio deviation on the yield of functional fresh-keeping materials has a great market impact in our country

the density of machine foam and manual foam is quite different. Generally, the fixed material ratio of the machine is 1:1, but the actual material ratio sometimes does not match the fixed material ratio of the machine because the equipment calculation is based on the volume calculation and equipment failure. When the white material is excessive, it shows that the density of foam is low, the color is white, the strength of foam decreases, the hand feels soft, and it is easy to shrink when the temperature is low; When the black material is excessive, it shows that the foam has high density, dark color, high strength of foam, and hard and brittle feel. In these cases, the material ratio should be checked immediately to see whether the filter is blocked and whether the pressure and temperature indications are normal, so as to ensure the accuracy of the black and white material ratio. The deviation of material ratio has a certain impact on the yield and construction quality

influence of ambient temperature on the yield

polyurethane foaming is greatly affected by temperature. Foaming depends on heat. If there is no heat, the foaming agent in the system cannot evaporate, so foam plastic cannot be generated. Heat comes from chemical reaction and environment. The heat of chemical reaction is not affected by external factors, and the heat provided by the environment changes with the change of 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 surface and core of foam is close. When the ambient temperature is low (such as below 15 ℃), part of the reaction heat will be emitted 11 Parallelism of upper and lower pressing plates: 6mm to the environment. On the one hand, the loss of heat causes the prolongation of the maturation period of foam and increases the forming shrinkage of foam (the lower the temperature is, the higher the forming shrinkage is); On the other hand, the amount of foam material is increased. The experiment shows that the foaming volume of the same foaming material at 15 ℃ is 25% smaller than that at 25 ℃, which increases the production cost of foam. When the ambient temperature is lower than 15 ℃, the construction should pay attention to make up for the reaction limit of raw materials caused by the temperature drop by adjusting the temperature control device of the spraying equipment, so as to simulate the best temperature required for polyurethane reaction as far as possible

wind force

when spraying, the wind speed is required to be less than 5m/s. When the wind speed exceeds 5m/s, the heat generated by the reaction will be lost, which will affect the rapid foaming reaction of polyurethane foam and make the product surface brittle. At the same time, the spray foaming machine will mix the raw materials and spray them in an atomized state. If the wind speed is too high, the atomized particles will be blown away, increasing the consumption of raw materials and polluting the environment

temperature and humidity of base course

it can be seen from engineering practice that the temperature of base course wall also has a great impact on the foaming efficiency of polyurethane. During the spraying process, if the ambient temperature and the wall temperature of the building base are very low, the reaction heat will be quickly absorbed by the base after the first spraying of rigid polyurethane, thus reducing the foaming amount of the material. Therefore, the noon break time should be shortened as far as possible during construction, and the process should be reasonably arranged in the construction arrangement process to ensure the foaming rate of rigid polyurethane foam. Rigid polyurethane foam is a polymer product produced by the mixed reaction of isocyanate and composite polyether. The isocyanate component is easy to react with water to form urea. If the urea bond content in polyurethane increases, the foam will become brittle and the adhesion between foam and substrate will be reduced. Therefore, the surface of the base material to be sprayed is required to be clean and dry, with a relative humidity of less than 80%, and free of rust, dust, pollution and moisture. Construction is not allowed in rainy days. If there is dew or frost, it should be removed and dried

the influence of the thickness of the spraying layer on the yield

spraying requires different use environments according to the thickness. Usually, multi-layer spraying method is adopted. According to the requirements of the national standard, there are certain regulations on the thickness of the first layer and the thickness of each layer, on the one hand, it is to ensure the temperature keeping performance of polyurethane, on the other hand, it is to work reasonably along the reaction curve of polyurethane. However, there will be crusts in each layer, so the greater the thickness of each layer, the more the square footage will be. However, in order to improve the square footage, it is not advisable to blindly require the square footage in violation of the requirements of polyurethane spraying process, which requires the construction personnel to deal with on-site based on experience and under the condition of ensuring quality

influence of construction on the square footage rate

in the construction of polyurethane spraying, the material waste in the construction of building corner lines, decorative lines, ceilings, beam structures, parapets and so on is extremely serious. For example, in the construction of large corners of buildings, nearly 1/2 of the materials cannot be sprayed on the walls. In the construction of ceilings, due to the small working face of overhead spraying, the waste of materials is inevitable. Therefore, during the construction of special parts, more attention should be paid to the unity of construction technology and construction conditions

the influence of flatness on the yield rate

in the construction process, the flatness of the base course should also be effectively controlled. The flatness of the base wall is too poor, which also causes a certain waste of materials. In addition, if the flatness error of the base wall during polyurethane spraying is too large, the part with too large local positive deviation needs to be sawed off, which wastes polyurethane materials and labor costs, and also brings difficulties to subsequent construction

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