Influencing Factors of Determination of Polyurethane Oxygen Index by Digital Oxygen Index Meter

Polyurethane is the abbreviation of polyurethane, which is a thermal insulation material widely used in construction and industrial equipment and an important material in automobile, shipbuilding, packaging and other industries. However, due to the special structure of polyurethane foam itself, it is very easy to burn, and its oxygen index is only about 17%. The oxygen index is one of the signs to determine its flame retardant performance. The digital oxygen index meter is a test instrument for measuring the oxygen index of polyurethane. Co., Ltd. is a manufacturer, and customers in need are welcome to inquire. Main parameters: 01. Flow adjustment range: 0-10L/min (60-600L/h); 02. Response time: <5S; 03. Flow meter: 1-15L/min (60-900L/H) adjustable; 04. Propane (butane) ignition system, flame length 5mm-60mm can be adjusted freely; 05. Flame length: 16±4mm, size adjustable. 06. Combustion cylinder: inner diameter≥75mm, height 400mm; 07. Gas flow rate in the combustion cylinder: 40mm±2mm/s. In addition, the R&D engineer of (Hong Kong) Co., Ltd. said that the polyurethane oxygen index test will be affected by factors such as environmental conditions, operators, and sample preparation differences. 1. Influence of state adjustment time According to the requirements of the national standard GB/T2918-1988, the state adjustment of the test material is carried out to minimize the influence of environmental accidental factors on the test results. Therefore, the prepared TDCPP flame retardant polyurethane foam sample was selected for comparison test, and the temperature and humidity of the incubator was adjusted to a certain value required by the national standard (temperature: 23°C; relative humidity: 50%; air pressure: 86-106kPa). It can be seen from the test data that with the increase of the conditioning time of the sample, the average value of the oxygen index obtained by the test continues to decrease. When the conditioning time meets a certain time limit, the oxygen index remains stable. The test results of the samples under different adjustment time are different, therefore, the sample should be strictly adjusted according to the standard requirements, and then tested, so as to obtain the accurate oxygen index value under the standard adjustment time. 2. The influence of the ignition method of the sample According to GB/T2406-93, two ignition methods were used to test the oxygen index of the TDCPP flame retardant polyurethane foam sample, and the ignition time was 15s. Top ignition method: let the lowest visible part of the flame touch the top of the sample and cover the entire top surface, do not let the flame touch the edges and side surfaces of the sample. Diffusion ignition method: Fully lower and move the igniter so that the visible part of the flame is simultaneously applied to the top surface and vertical side surface of the sample about 6mm long. It was found that under the same conditions of the same material, different ignition methods had little or no effect on the measurement data of the oxygen index, which was not enough to change the evaluation of the oxygen index of the sample. No matter what kind of ignition method is used, when to remove the ignition source and start timing is to visually judge the ignition situation of the sample with the naked eye, there is a certain error, which may cause an impact on the inspection data, only by increasing the number of tests can we try to do as much as possible. reduce errors. In practice, it is more labor-saving to use the tip ignition method when igniting the sample. 3. Influence of sample length The sample length of the tested product in the national standard is 70-150mm, the purpose is to keep the length of the glass cylinder of the test instrument consistent, so that the oxygen concentration in the small ambient mixed gas in the glass cylinder is uniform constant. It can be seen that the length of the sample has a great influence on the test data. Within the range required by the national standard, the measured oxygen index value continues to increase with the increase of the length of the sample. When the sample length is short, there is still a considerable distance above the combustion area of ​​the tested sample from the top of the cylinder, so the oxygen required for its flame combustion is completely supported by the instrument itself and is not affected by the airflow outside the cylinder. However, as the length of the sample increases, the distance between the combustion area of ​​the tested sample and the top of the cylinder becomes shorter, and the flow of oxygen required for flame combustion is gradually affected by the airflow outside the cylinder. In order to support the flame combustion, the instrument itself must provide more oxygen to meet the flame combustion, resulting in a gradual increase in the measured oxygen concentration. Therefore, the length of the test sample should be specified as a specific value rather than a range value to reduce the influence of indoor ambient air flow on the combustion conditions in the instrument cylinder. 4. Effects of flame retardants As an expensive additive in polyurethane foam, flame retardants play a very important role. The more flame retardants are added, the better, and the effect of flame retardants on foam physical properties should also be considered. effect on mechanical properties. In view of factors such as cost, safety, meeting flame retardant specifications and foam physical and mechanical properties, the use of appropriate flame retardants should be optimized to maximize their effect. Influence of flame retardant addition amount: The data shows that for TDCPP flame retardant, based on polyether polyol, 10Phr of TDCPP can make the oxygen index of PUF to be 23%, and the oxygen index of PUF increases with the amount of flame retardant added. However, after the amount of TDCPP is greater than 15 Phr, and the amount of TDCPP is increased again, the oxygen index of the sample is very limited. Influence of different flame retardants: Different flame retardants have different flame retardant effects in polyurethane foam. With the change of flame retardant content, the change rule of flame retardant effect is also different. Differences and Effects of Flame Retardant Compatibility with Polyurethane Foam.
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