What is the density of polyurethane foam? The density of polyurethane foam mainly has three concepts: feed density, bulk density and core density. Feeding density refers to the capacity of the foaming material in the production of cold storage panels, bulk density refers to the overall density of the foam after curing and molding, and core density refers to the density of the core foam after the foam is cured and molded and the skin is removed. The core density is the key factor that affects the physical properties of the cold version. Since a small amount of blowing agent will volatilize into the air when the foam is cured, and there is a dense skin on the edge of the polyurethane foam, the relationship between the three can be roughly converted into, the same density is equal to 1.1 times the core density, and the bulk density is equal to 1.05 times the core density.
What is the standard method for determining the density of polyurethane foams? The determination of polyurethane foam density can be based on the national standard GBT6343, the determination of the apparent density of foamed plastics and rubber. First, we need to take a regular geometric polyurethane foam at the center of the cold storage board for accurate measurement, and then weigh the mass M of the foam with a balance, then measure the length, width and height of the foam and calculate the volume force, and finally use the formula ρ=M/V to get The density of the foam can be calculated. GBT6343 needs proper size and regularity, so how can we measure for irregular samples? At this time, we can use the Archimedes drainage method. First, we also use the balance to weigh the mass m of the foam, then press the foam completely into the water in the beaker, and read the value M on the balance after it is stable. The large M is approximately equal to the volume of the foam, and finally the density of the foam is calculated using the formula ρ=m/M. There is a caveat here, considering the water absorption rate of polyurethane foam, the density measured by the Archimedes drainage method will be slightly higher than the actual density of the foam.
The influence of density on the mechanical properties of polyurethane foam mainly involves compressive strength, flexural strength, tensile strength, shear strength, etc. The relationship between them can be simply summarized as, the higher the density, the better the mechanical properties. Mechanical properties are the key properties in the use of polyurethane foam. When it is inconvenient to test the mechanical properties of the foam, the density can be used as a reference index for physical properties. The effect of density on thermal conductivity, the general trend is that the density is between 40 and 50 kilograms per cubic meter, the thermal conductivity remains at the lowest point without significant change, while the density exceeds 50, the thermal conductivity increases with the increase of density, which is also very important. It is a good explanation of why customers who have higher requirements on the insulation performance of sandwich panels in the market choose sandwich panels with a density of 40. Since polyurethane density has an effect on performance, how will foam density and performance differ when produced in different ways? The difference between the maximum density and the minimum density of the sandwich panel produced by a continuous sandwich panel line is within 10%. Compared with the products of the gap production method and the spray method, the uniformity of the foam density is excellent, so the performance of the continuously produced polyurethane sandwich panel is more stable. JINGGONG is specialized in manufacturing sandwich panel production machinery and production lines include continuous PU sandwich panel production line, rockwool production line, etc to provide you with professional sandwich panel production solutions. Get sandwich panel production line price now!