The Japanese standard and classification of cone calorimeter test are shown in Table 4.3. The incident heat flux is set at 50kW/m2 and heating time in the test is determined according to the classification level of each material. For class 1, the noncombustible material shall be tested for twenty minutes, for class 2, the semi noncombustible material for ten minutes, and for class 3, the fire retardant material for five minutes.
4.1.1 HRR of cone calorimeter tested in vertical orientation
The results of cone calorimeter tested in vertical orientation are summarized in Tables 4.4 and values are the average of three test results.
All detailed quantities can be referred Appendix B1. It finds that M06, M07, M12, M13, M14 and M15 were able to be ignited. Note that the ignited time of M06 was over 600s and it was marked “N.I.” in the Table 4.4. The reason is discussed in Section 4.1.2. Among these materials, M06 and M07 were added flame retardants of Phosphorus by using the way of soak. As they were subjected to the heat flux of 50kW/m2, their HRR increased slowly because of adding of flame retardants. After a period of heating, the flame retardants were decomposed and volatilized to become inert gases, which dilute the flammable gases. According to the chemical reaction, it would control the burning process of wood.
Therefore, the THR average value of M06 could be controlled less than 8MJ/m2, about 5.12 MJ/m2. So M06 was classified as the rank of class 2.
On the other hand, M07 was not qualified as class 2, even if class 3, since its average value of total heat release rate was 10.96 MJ/m2 in 300 seconds. There are two major reasons: one is the thickness of material and the other is the content of flame retardants. The thicknesses of M06 and M07 were 14.5mm and 3.6mm, respectively. M07 was thinner such that its quantity of flame retardants was less. Therefore, the peak values of heat release rate of M07 were higher than that of M06.
M12, M13, M14 and M15 were flooring materials and had no flame retardants. M12 and M14 were solid wood flooring materials and M13 and M15 were laminate ones. Because the peak values of heat release rate and total heat release rates of these flooring materials were higher than required standard of Japanese classification, they could not possess any classification.
Other materials, such as M01, M02, M03, M04, M05, M08, M09, M10 and M11, responded with low values of heat release rate. The reasons are attributed to their main compositions. The main compositions for M01, M02, M04, M10 and M11 are mineral, fibers and adhesives.
The latter two can generate low values of heat release rate. M03, M08 and M09 are ceramic board, composed of clay, so that they are noncombustible without generating any heat release. The compositions of M05 included farina and pulp, consequently it has higher heat release rate.
According to the Japanese standard, they are classified as class 1, the noncombustible materials.
4.1.2 HRR of cone calorimeter tested in horizontal orientation
The corresponding results of cone calorimeter tested in horizontal orientation are shown in Table 4.5 and they are the average of three test results. All detailed ones are given in Appendix B2. Similarly, M01, M02, M03, M04, M05, M08, M09, M10 and M11 have low heat release rate values so that they were still ranked as class 1. M07, M12, M13, M14 and M15 could not be qualified for the classification. The major difference was that the rank of M06 was lowered to class 3 in horizontal orientation, whereas it was qualified as class 2 in vertical orientation. The total heat release rate average value of M06 tested in 300 seconds was 6.11 MJ/m2. However, the corresponding values tested in 600 seconds were over the limit of class 2. Apparently, the reason can be attributed to orientation effect. When the sample is tested in vertical direction, the flammable gas is not able to accumulate easily but discharged quickly by exhaust system.
On the other hand, the sample placed in horizontal orientation has a
heater on the top. The flammable gas can be concentrated on the top of sample and ignited easier than that in vertical orientation. Such situation can also be observed in the tests of the flooring materials. Their ignition times tested in vertical orientation are longer than that in the horizontal one. Besides, the average values of HRRav_180s and THR obtained in the horizontal orientation are higher than those in vertical one. It shows the classification using Cone Calorimeter test in horizontal orientation is more stringent.
In addition, the FR (flame retardants) materials have some arguments about their values of content, which can affect the ignition time and heat release. For an example, M06 tested in Cone Calorimeter showed some unusual behaviors. After being ignited, the sparker should be removed according to ISO 5660. However, the flame was extinguished within 60s after ignition. Then, the sparker should be installed once more and M06 was ignited again. The reason is mainly attributed to the flame retardants contained. The flame retardants of Phosphorus added in M06 used the way of soaking onto the plywood, layered by lauan. The flame retardants of Phosphorus was layered onto it and led to such phenomenon. According to ISO 5660, this situation is ranked as the failed result. Therefore, the sparker for the similar materials as M06 tested in Cone Calorimeter shall not removed during the test.
4.1.3 Correlation between vertical and horizontal directions of cone calorimeter test
According to ISO 5660[1], the mean heat release rate readings within 180 seconds should be compared each other for three specimens of
the same material. This parameter is selected to discuss the correlation.
The results are demonstrated in Fig. 4.1. The correlation appears relatively good and the corresponding value of R2 is about 0.95.
Therefore, it can be concluded that there still have small difference for the test results between the vertical and horizontal orientation for the same material in Cone Calorimeter.