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Your location: Home > Related Articles > Testing Polyurethane with a Limiting Oxygen Index Tester

Testing Polyurethane with a Limiting Oxygen Index Tester

Author:QINSUN Released in:2023-08 Click:27

The Limit Oxygen Index Tester is a test instrument for measuring the oxygen index of polyurethane. It is a test equipment independently developed and produced by our company qisnun Precision Electromechanical Technology Co., Ltd. This is a cost-effective and comprehensive after-sales service. Welcome customers who need to inquire.

Polyurethane is the abbreviation of polyurethane. However, due to the special structure of polyurethane foam itself, it is extremely flammable, and its oxygen index is only about 17%, which is one of the signs to judge its flame retardancy.

Main parameters:

01. Flow adjustment range: 0-10 L/min (60-600 L/h);

02. Response time: <5S;

03. Flow meter: 1-15L/min (60-900L/H) adjustable;

04. Propane (butane) ignition system, flame length 5mm-60mm It can be adjusted freely;

05. Lengthr of flame: 16±4mm, height adjustable.

06. Combustion tube: inner diameter ≥ 75㎜, height 400mm;

07. Gas flow in the combustion tube: 40mm±2mm/s.

In addition, the research and development engineer of our standard group (Hong Kong) Co., Ltd. said that the oxygen index of polyurethane test will be affected by environmental conditions, operation Personnel impact, differences in sample preparation and other factors.

1. Effect of state adjustment time

According to the requirements of the national standard GB/T2918-1988, the state adjustment of the material of Testing is performed to minimize the impact of accidental environmental factors on Impact test results. Therefore, the prepared TDCPP flame retardant polyurethane foam sample was selected for comparison test, and the temperature and humidity of the incubator were adjustedto 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 as the sample conditioning time increases, the average value of the oxygen index obtained from the test continuously decreases. When the conditioning time satisfies a certain value*, the oxygen index remains stable. The inspection results of samples under different conditioning times are different. Therefore, the samples should be strictly adjusted according to the standard requirements and then tested, in order to obtain accurate oxygen index values ​​within the standard conditioning time.

2. The influence of the ignition method of the sample

According to GB/T2406-93, two ignition methods are used for the index test. oxygen flame retardant polyurethane foam sample TDCPP, and the ignition time is equal to 15s.

Top ignition method: make the visible part of the flame touch the top of the sample and cover the entire top surface, and prevent the flame from touching the edges and side surfaces of the sample .

Diffusion ignition method: Fully lower and move the igniter so that the visible portion of the flame is applied to the top surface of the specimen and the vertical side surface at the same time. about 6mm long.

It was found that the same material was tested under the same conditions and that different ignition methods had little or no effect on the oxygen index measurement data, which was not sufficient to alter the oxygen evaluation index sample results. Regardless of the ignition method, the timing of removing the ignition source and the timing of starting are based on the visual judgment of the ignition of the sample with the naked eye. ThisSome errors can affect inspection data. Only by increasing the number of tests can we try to reduce errors. In real operation, it is less laborious to use the tip ignition method when igniting the sample.

3. The influence of sample length

The sample length of the product tested in the national standard is 70-150 mm, the purpose is to keep the length of the glass cylinder of the test instrument consistent, make the oxygen concentration in the small ambient gas mixture in the glass cylinder uniform and 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 increasing sample length. When the sample length is short, there is still a considerable distance aboveof the combustion zone of the test sample from the top of the cylinder, so that the oxygen necessary for its flame combustion is supported only by the instrument itself and is not affected by the flow of air outside the cylinder. However, as the length of the sample increases, the distance between the combustion zone of the tested sample and the top of the cylinder becomes shorter and the flow of oxygen necessary for the combustion of the flame is gradually affected by the airflow out of the cylinder. In order to sustain the flame combustion, the instrument itself must supply more oxygen to satisfy the flame combustion and therefore the measured oxygen concentration value gradually increases. Therefore, the length of the sample tested should be specified as a specific value rather than a range value to reduce the influence of indoor ambient airflow on combustion conditions.one in the cylinder of the instrument.

4. The influence of flame retardants

As an expensive additive in polyurethane foam, flame retardants play a very important role. Well, also consider the effect of the amount of flame retardant added on the physical and mechanical properties of the foam. Considering factors such as cost, safety, compliance with flame retardant technical indicators, and the physical and mechanical properties of the foam, the use of appropriate flame retardants must be optimized to maximize their effects.

The effect of adding flame retardant: data shows that for TDCPP flame retardant, based on polyether polyol, 10 Phr of TDCPP can make the oxygen index of PUF by 23%, and the oxygen index of PUF With the increase of the addition of flame retardant, the oxygen index of the sample increased very limitedly, but after the TDCPP assaywas greater than 15 Phr, increasing the dosage of TDCPP.

Effects of Different Flame Retardants: Different flame retardants have different flame retardant effects in polyurethane foam. It is affected by the difference between the types of flame retardants and the compatibility of flame retardants with polyurethane foam.