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Combustible UL94 rating is the most widely used plastic material inflammable performance standards. It is used to evaluate the ability of a material after being lit out. According to the combustion rate, burning time, resistance ability and drops bead is burning can have many kinds of evaluation method. Each material to be tested according to the color or thickness can be many values. Elected a product materials, their level of UL should meet the requirements of part of the plastic parts wall thickness. UL level should be reported with the thickness value, only UL report level without thickness is not enough. Plastic flame retardant grade by HB, V - 2, to V V - 1-0 incremental step by step: 1, HB: UL94 standard in the bottom of the flame retardant grade. Request for samples of 3 to 13 mm thick, burning speed is less than 40 mm per minute; Less than 3 mm thick samples, the burning speed is less than 70 mm per minute; Or out in front of the sign of 100 mm. The samples - 2:2, V to 10 seconds after the combustion test twice, flame extinguished in 60 seconds. There can be so drop down. The samples: 3, V - 1 to 10 seconds twice after combustion test, flame extinguished in 60 seconds. There can be so drop down. The samples - 0:4, V to 10 seconds after the combustion test twice, flame extinguished within 30 seconds. There can be so drop down.