Small Flame Ignitability - Lab Report Example

Experiment 1 Introduction By subjecting samples to various fire tests it is possible to determine whether or not a product meets minimum fire performance criteria set out in building codes or other applicable legislation. Protecting against fire hazard and assessing the reaction to fire as well as fire resistance is seen as being a fundamental presumption in planning process and in the erection of buildings and thus is mandatory requirement from national and EC regulations given e,g. in the construction products direction (CPD). Assessment of reaction to fire solely is possible on the basis of prescriptive fire model and resulting fire test methods. Plastic materials have two types of pre-selection test programs that are used in measurement of their flammability characteristics. The first test is done on the material to determine their tendency of extinguishing or spreading the flame upon the specimen being ignited. The program is given in UL 94 which is harmonized with IEC 60707, 60695-11-10 and 60695-11-20 and ISO 9772 and 9773. The second test program involves measurement of the ignition resistance of plastic to electrical ignition sources. The material’s resistance to ignition and surface tracking characteristics has its description in UL 746a, that is a test procedure that is similar to the test procedures whose description is given in IEC 60112 , 60112 and 60950. Flame classification fall into 12 classes that has been specified in UL 94 which can be assigned to a material on the basis of the results of the small scale flame tests. The classification which are listed in descending order in each of three groupings find application in distinguishing the burning characteristics of a material by use of test specimens that would be exposed to some specified test flame under controlled laboratory conditions. Six classifications are linked to materials that are commonly used in manufacture of enclosures, structural parts and insulators which can be found in consumer electronic products where the classes are 5VA, 5VB, V-O, V-1, V-2 AND HB. Three of the remaining six classifications are related to low density foam materials which find application in fabrication of speaker grills and sound deadening materials and are designated as HF-1, HF-2 and HBF. For the last three the classification is assigned to very thin films, which generally are not able to support themselves when places in horizontal position with their designation being VTN-0, VTM-1 and VTM-2. The materials in this group usually are assigned to substrates on flexible printed circuit boards. Vertical testing This involves supporting a specimen in a vertical position then a flame is applied at the bottom of it. The flame application takes 10 seconds then removed until the point when flaming stops t which point there is reapplication of the flame for 10 more seconds. Two sets of five specimens are tested where they are conditioned under different conditions. Results Set 1: flame was applied for 10 seconds, there was no ignition and when the flame was applied the second time for 10 seconds there was ignition for 3 seconds. Set 2: flame was applied for 10 seconds where ignition occurred for 3 seconds and on second application of flame ignition also occurred for 3 seconds Set 3: In applying flame for 10 seconds the first time there was no ignition but in second application of flame ignition occurred 10s Set 4: no ignition was experienced Set 5: Ignition of 3 seconds was registered in applying flame the second time. Conclusion The material tested fall under Vo. Experiment 2 Introduction Subjecting a sample of materials to a variety of fire tests, is a way of determining whether the material has the ability to withstand the set standards usually set by building codes and other relevant legislation. In the planning and construction process of buildings it is vital to ensure that there is protection against fire hazards and also assessing fire resistance and thus it is a requirement in both national and EC regulations. There are several prescriptive fire models and from which results fire test methods that are used in assessing the reaction. The system of the reaction to fire in building products given in EN 13501-1:2007, requires testing of fires being done according to the new fire test methods, where emphasis is placed on the central test method, single burn item. European reaction to fire classes setting is in conformation the national classification rules and legislations and thus products are assessed according to national building regulations. In EN ISO 11925-2:2010 ignitability test, test specimens are placed to in direct impingement of fire from a small flame. A specimen with dimensions of 250mm by 90mm is attached in a vertical position to a specimen holder that has a U shape. A gas flame with a height of about 20mm is brought into contact with the specimen at an angle of contact of 45 degrees. For the case of surface exposure the application point is 40mm above the bottom edge while edge exposure would involve application of flame at the centre of the width of the bottom edge. A filter is placed under the specimen holder as a way of monitoring the falling of flaming debris and the set up is as shown in figure 1. Figure 1 Two flames application times and test durations are used with the product class being put into consideration. For class E products flame application of 15s is used with the test being terminated 20 seconds after removal of the flame. For class B, C and D materials the flame application time is 30s and a maximum duration of 60s on removal of the flame. The test may be terminated earlier in case where there is no ignition observation after the flame has been removed, if the flame stops burning if there is a glow or in case the flame tip reaches the upper edge of the specimen. Classification of material is based on the observation on whether the flame spreads reaching 150mm with a certain time and whether there is ignition of the filter paper resulting from flaming debris. Also there is observation of occurrence and duration of flaming in addition to glow observation. Test Apparatus The combustion chamber constitutes the major apparatus used in the experiment. The chamber is basically an enclosure made of stainless steel and it has heat resistant glazed doors on both the front and the sides which are used in making observation. There is a horizontal plate of 455mm by 210mm mounted on a metal grip mesh that is close to the base of the chamber. There are two guide rails fixed on the plate and this allows the burner to being fixed at the desired position. There can be adjustment of the burner in a vertical position or it can be tilted into a 45 degrees angle with respect to the vertical axis. The burner is mounted on a plate placed horizontally it allows a to and fro motion in a horizontal position along the centreline of the chamber. This movement is effected from outside the chamber and the distance is set in advance through adjusting the external collar. The burner has a fine adjustment valve fitting that allows accurate controls of flame heights to be achieved and also it has a propane regulator, flashback arrester and tubing. A specimen holder of standard size can clamp a specimen of 250mm by 90mm and it has a double flame which is U in shape constructed in stainless steel with a 15mm width and 5mm in thickness. The frame is in a hanging position from the support bar in a manner to enable the underside of the specimen to have a direct exposure to the flame along its centre line and edges. The specimen is prevented from warping by ensuring that the two halves of the specimen holder are held together using bolts and wing nuts. Adjusting of flame height is effected by use of needle valves and gas supply regulator. The height of flame is adjustment is done by use of a device which when placed against a fixed point of the burner a flame height of 20mm achieved. Testing Operation The burner was lit in a vertical position and allowed to stabilize then there was adjustment of bulb burn so as to give a flame height of 20mm. The door was closed and the burner tilted to an angle of 450 relative to its axis and then it was moved in horizontal line up to the point the flame reached the pre-set contact point by use of a pusher rod. A stop watch was started immediately when the flame got into contact with the specimen. The flame was applied to the specimen for 15 or 30 seconds before the burner was retracted in a smooth and continuous manner. Surface exposure For surface exposure which applies for flat products, the flame was applied at at the centre line of the specimen at a point 40mm above the bottom edge with each different surface that may be exposed in practice being put to test. Edge exposure This comes to use where a flat single layer or multiple products with a total thickness of 3mm or more and the flame is applied at mid point at the point of the test specimen. Where the specimen is a flat single layer or for the case of multilayer products having total thickness of more than 3mm, the flame was applied to the centre of the width of the bottom edge of the test specimen a distance of 1.5mm behind the surface. With multilayer products of more than 10mm thickness, there are additional tests to be done involving turning specimen at 90 degrees about its axis and flame impingement at the bottom edge of the centerline of the underside for every layer. For the case where the flame application was 15s the total test duration was 20 s from the time of application of the flame. On the other hand for a flame application time of 30 seconds the test duration went up 60s from the time the flame was first applied. Results of experiment First face testing was done where fire was applied on a carpet for 15s. The burn size was 10cm with the whole size of the carpet being 23 cm. ignitions did not occur but molten drips were observed. In the second test where the same steps as in first test were followed the length of the burn was 9cm and ignition occurred for 6s. In the third test the carpet edge was held parallel along with white mark. Flame was applied for 15 second then ignition occurred for 2:12.10 seconds. (It took 1:40 to reach the White mark which is 150 mm) while the length burn is 18 cm For test 4 same steps applied as the third test and ignition occurred and it took 50 seconds to reach 150 m with length of the burn being 15 cm Discussion The test that were undertaken are useful in assessing classification according EN 13501-1in which 6-10 single test are normally performed. The criteria used would depend on the classification being targeted. For the case of classification D-B, 30s exposure is required with the flame height beyond 150mm being expected within a time of 60s after commencement of the test. For classification E and En the time of exposure requirement is 15s with the flame height required not beyond 150mm in 20s after the commencement of the test. The specimens are supposed to be an actual representative of the actual product for its end use application as far as possible. This is even more required for use in standard substrate which is clearly described in EN 13238. Product standards for specified materials usually contain prescriptions with regards to the construction of the specimens so as to achieve maximum field application, with sometimes guidance being given on test specimens for representation of a wider range of applications. The commencement of testing is after the confirmation has been done in writing, with the test specimens having been conditioned as directed in the standard. Reference Alexandre M.& Dubois P. (2000). Polymer-layered silicate nanocomposite: preparation, properties and uses of a new class of materials, Mat. Sci. Eng. 28, 1-63. Efectis Nederland (2011). The ignitability test. “ISO/DIS 12136: (2010). Reaction to fire tests – Measurement of fundamental material properties using a Fire Propagation Apparatus” Kashiwagi T (2007). “Flame retardant mechanism of the Nanotube-based nanocomposite- final report” NIST GCR 07-912. Read More