JPS6259260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for evaluating the ignitability of plastic materials, in which the surface of a sample to be measured is carbonized by a high-voltage arc to form a conductive path, and then a new low voltage is applied. The object of the present invention is to provide an ignitability evaluation test device that can accurately and reproducibly measure the ignitability of a sample to be measured by applying a voltage.

Conventionally, methods for evaluating the ignition properties of plastic materials include methods for evaluating large current arc ignition properties, track ignition properties, tracking ignition power, and the like. However, these methods have the following drawbacks.

In other words, high current arc ignitability evaluation (UL746)
The outline of the voltage 240V, current 32.7A spark discharge,
This is a test method in which the test sample is repeated 40 times per minute on the surface of the sample to be measured to see how many spark discharges will cause the sample to ignite, and each measurement can be carried out for up to 5 minutes (200 times). The disadvantage of this method is that it is necessary to simultaneously observe the flame caused by the ignition of the sample to be measured and the spark discharge, and it is very difficult to distinguish between the two, so it is difficult to determine when the sample to be measured has ignited. is difficult. For this reason, the variation in test results becomes extremely large and reproducibility is poor. In addition, the spark discharge of this test method causes relatively little damage to the sample under test, and for modern plastic materials, the spark discharge usually results in more than 200 cycles, making it meaningless as a method for evaluating flammability. It has become a test method.

The outline of the track ignitability evaluation is as follows: After forming a carbonized conductive path on the sample to be measured through a tracking resistance test (IEC-112), a constant voltage with a stepwise change in current is applied to the carbonized conductive path, and ignition is detected. This is a method to find the current. First, to explain the outline of the tracking resistance test method, in the tracking resistance test, a voltage is applied to a pair of electrodes that are in contact with the sample to be measured, and an electrolytic solution is dropped between the electrodes once every 30 seconds. This is a test method to determine at what voltage the tracking breakdown of the sample to be measured occurs and at what number of drops of electrolyte solution. Such a tracking resistance test requires a long time. As a result, the track ignition property is measured after the tracking resistance test has been completed, which has the drawback of requiring a long time, and the track ignition property test may cause the sample to be measured to be damaged by tracking during the tracking resistance test. This is the premise. As a result, materials with excellent tracking resistance have the major drawback that a tracking resistance test requires an enormous amount of time or that ignitability cannot be evaluated.

The outline of the method for evaluating tracking ignition power is the tracking resistance test (IEC-112) mentioned above.
This is a method similar to that in which a pair of electrodes in contact with a sample to be measured is supplied with conditions in which the short-circuit current and applied voltage are changed stepwise, and an electrolytic solution is dropped between the electrodes. In the process of conducting this tracking resistance test, it is a method of determining under what conditions the short circuit current and applied voltage cause the sample to be measured to ignite. However, in the test, the number of drops of electrolyte was
Measure within 50 drops. The disadvantage of this method is
Similar to the above-mentioned disadvantages of track ignition properties, it requires a long time to conduct a tracking resistance test, and it is not possible to evaluate the ignition properties of materials with excellent tracking resistance.

The present invention eliminates the conventional drawbacks as mentioned above,
The object of the present invention is to provide a testing device that can evaluate the ignitability of plastic materials in a short time, accurately, and with high reproducibility.

The present invention will be explained below with reference to Examples.

FIG. 1 shows a schematic configuration of an ignitability evaluation test device according to the present invention. 1 is a sample to be measured. 2,
2 is a pair of electrodes that make point contact, line contact, or surface contact with the sample to be measured 1;
has a shape that generates an arc near the surface of the sample 1 to be measured. The electrodes 2, 2 are connected to a changeover switch 3 such as a vacuum switch, and the changeover switch 3 switches the connection between a high voltage circuit 4 and a low voltage circuit 5. The high voltage circuit 4 includes a voltage controller 6 that can vary the voltage, for example, from 5KV to 20KV, and an arc current controller 7 that can vary the arc current, for example, from 1mA to 50mA. Reference numeral 8 denotes an arc time control circuit for controlling the supply time of the high voltage arc, which can be varied, for example, from 0 to 180 seconds. This arc time control circuit 8 is connected to the high voltage circuit 4. The low voltage circuit 5 includes an applied voltage control section 9 that can vary the voltage from, for example, 0 to 2 KV, and a short circuit current control section 10 that can vary the short circuit current from, for example, 0 to 2 A.

First, the selector switch 3 is connected to the high voltage circuit 4, the voltage is adjusted to 12.5KV by the voltage control section 6, and the arc current is adjusted to 10mA, 20mA, 30mA, 40mA by the arc current control section 7. A voltage arc is applied to the electrodes 2, 2, and the sample to be measured 1
An arc is generated on the surface of the specimen 1 to form a carbonized conductive path between the electrodes 2 and 2 on the sample 1 to be measured. At this time, the arc supply time is determined by the arc time control circuit 8.
For example, for 60 seconds, the sample to be measured is sufficiently carbonized.

Next, the changeover switch 3 is used to connect the low voltage circuit 5, and the current control section 10 and the voltage control section 9 adjust the short circuit current to, for example, 1A, and apply a voltage between the electrodes 2, 2, and at what voltage is applied? , to check whether the sample to be measured ignites.The sample to be measured 1 is formed by a high voltage arc under each condition.
The ignitability of the sample to be measured 1 is evaluated by determining the limit conditions under which voltage or current will cause the charcoal conductive path to ignite.

Figure 2 shows that using this flammability evaluation test device,
The results of measuring the ignitability of polyester resin A and noryl resin B are shown. The test conditions are as follows:
The distance between the electrodes 2, 2 in point contact with the sample to be measured 1 was set to 4 mm. The conditions for high voltage arc are voltage
Constant at 12.5KV, arc current 10mA, 20mA,
Each continuous arc of 30 mA and 40 mA was applied for 60 seconds. In addition, the voltage applied after the high voltage arc is the short circuit current 1
The voltage was set to A.

As can be seen from these results, by using the test device of the present invention, not only the noryl resin that could be evaluated using the conventional test method, but also the tracking resistance of polyester resin that could not be evaluated using the conventional test method. It has become possible to evaluate excellent materials accurately and with high reproducibility. In addition, since the test using this test device does not involve a tracking resistance test, the test time is also significantly shortened.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an ignitability evaluation test apparatus showing an embodiment of the present invention, and FIG. 2 shows measurement results of noryl resin and polyester resin using the same apparatus. DESCRIPTION OF SYMBOLS 1... Sample to be measured, 2... Electrode, 3... Changeover switch, 4... High voltage circuit, 5... Low voltage circuit, 6... High voltage control section, 7... Arc current control section, 8... Arc time control circuit, 9... Applied voltage control section, 10... Short circuit current control section.

Claims (1)

[Claims] 1 A high voltage circuit having a pair of electrodes in contact with a sample to be measured, an arc current control section and an arc voltage control section that supply a high voltage arc between the electrodes, and an arc that supplies the high voltage arc for a certain period of time. It consists of a time control section, a low voltage circuit having a voltage and current control section, and a changeover switch that switches the electrode to a high voltage circuit or a low voltage circuit. 1. An ignitability evaluation test device that evaluates the ignitability of a sample to be measured by applying a low voltage to the sample after forming a path.