Flame Retardant Series Basics

Flame Retardant Series Basics

Today, we are going to discuss the topic of “Flame Retardant Series Basics”. In our daily lives, fire accidents occur frequently, causing huge property losses and casualties. Therefore, understanding the basics of flame-retardant materials is essential to raising our safety awareness and reducing the risk of fire. First, let's start with the basic definition. Flame retardancy is a property of a substance or material that reduces the incidence of fire by slowing the spread of flames or extinguishing them on its own. As technology has advanced, researchers have developed a variety of flame retardant technologies, including the application of additive flame retardants and reactive flame retardants, and their effectiveness in different materials. Next, we will discuss the classification and properties of flame retardant materials. First of all, the flame retardancy of engineering plastics can be evaluated by combustion test method, which is divided into 2 types: horizontal method and vertical method. Vertical method is through the measurement of after-flame and afterglow duration, the range of combustion and particle droplets to evaluate the flame retardancy of the material, according to the behavior of the specimen, according to the criteria shown in Table 1, the conventional we generally classify the material into V-0, V-1 and V-2 level (V that is, vertical combustion), and in the UL specification inside the content of the plastic material 94-V0 (94V0 that is, the so-called flame retardant level, divided into 5) (94V0 is the so-called flame retardant grade, which is divided into 5 grades)

94-V0: The fire goes out as soon as it leaves the room and does not ignite spontaneously.

94-V1: When burning, it will burn for 1 second and then go out immediately without spontaneous combustion.

94-V2: The fire burns for 2 seconds and then goes out without spontaneous combustion.

94-V5: Burns for 5 seconds after the fire has been removed from the burner and will not ignite spontaneously.

94-HB: Burns until only carbon remains when flame is removed.

Note: t₁, t₂ refers to the duration of the afterflame; t₃ refers to the duration of the afterglow; t_f refers to the total afterflame time.

Different plastics have different combustion properties, such as PC itself has a certain degree of flame retardancy, vertical combustion test can reach V-2 grade, while ABS itself is flammable and can not be graded. Flame retardant modification of plastics through the addition of flame retardants can delay combustion and reduce the intensity of combustion. However, plastic in the combustion process, in addition to their own combustion, but also produce droplets ignite other combustible materials, resulting in the spread of fire, resulting in serious consequences. Therefore, in flame retardant plastics, it is often necessary to add anti-dripping agents to prevent the melt from dripping during the combustion process.

I. Introduction to fire ratings for electrical cables

• CSA fire rating:

FT1: Vertical burning test (no requirement for dripping material)

FT2: Horizontal burning test

FT3: Vertical burning incendiary drop test (cannot ignite newsprint)

FT4: Vertical combustion test in a closed combustion chamber (similar to a closed building) heat energy of 70,000 btu/h

FT5: Flame-resistant test, usually used in underground operations portable CABLE

• UL Fire Rating:

A: Horizontal Fire Test

B: VW-1: Vertical fire test, drops cannot ignite cotton wool.VW-1SC: Vertical fire test, insulated core wire is tested separately from finished wire.

C: CL2 (VERTICAL TRAY FLAM TEST): Vertical fire test in a closed combustion chamber (similar to the closed building UL1581).

D: CL2R(RISET CABLE)

E: CL2P(PLENUM CABLE)

F: CM (COMMUNICATION CABLE)

G: CMR

H: CMP

• UL1581 in the wire burning mode:

1: VW-1: vertical combustion test (UL wire combustion level)

2: FT1: vertical combustion test;

3: FT2: horizontal combustion test;

4: FT4: vertical combustion test;

5: FT6: horizontal combustion and smoke test. (The FT class of flammability is the CSA standard flammability rating for electrical wiring)

Among the above levels: VW-1 and FT1 are of the same level. FT2 is the easiest to pass and has the lowest level. (FT6>FT4>FT1>FT2);

VW-1 is stricter than FT1, both of them burn vertically, judgment criteria: 1.

1. The burn mark (kraft paper) cannot be charred more than 25%;

2. five 15-second burns must not be continued for more than 60 seconds. 3;

3. burning droplets cannot ignite cotton; VW-1 requires 1, 2, 3; FT1 requires 1, 2 only.

For the wire industry: UL 94 V-2, V-1, V-0, 5VA, 5VB assessment of the materials used in the wire, the test will be used to test the material to develop a standard sample, will not be marked on the wire. VW-1 VW -2 FT-1 FT-2 test is the wire itself, after passing the test, you can mark the corresponding grade on the wire. Flame retardant wire and UL94 flame retardant are two different things, let's say an insulating material can pass UL94 V-0, but not necessarily through the VW-1; In addition, UL94 is the flame retardant insulating material, and the flame retardant requirements of the wire is generally in the UL758 62 1581; the object of the different; so the flame retardant of the UL94 V-0 V-1 and so on is not the flame retardant of the wire. V-0 V-1 and other UL94 flame retardant is not a wire flame retardant; in the AWM wire there is no print “V-0”!

VW-1/FT1 and UL94 V0 combustion test in the equipment there is a big difference:

1: The height and temperature of the flame are different

2: The methane flow used in the test is also different

3: The back pressure of methane is also different

4: The volume of the combustion box is also different: VW-1 requires more than 4 cubic meters, while V0 only requires more than 0.5 cubic meters can be

5: The number of combustion is also different

6: Combustion results: V0 requires recording the residual burning time, while VW-1 does not!

But UL94 in the 5V level combustion and VW-1 combustion test conditions and test methods are similar, closer! Reminder: Whether it is VW-1 or UL94 combustion test equipment, have to refer to ASTM5025 and ASTM5027, UL1581 and UL94 is only the test method, the requirements of the test equipment must be in accordance with ASTM standards!

II. Comparison of UL94 Plastic Flame Retardant Ratings to UL 1581 VW-1 Flame Retardant Ratings

There are 12 types in UL94: HB, V-0, V-1, V-2, 5VA, 5VB, VTM-0, VTM-1, VTM-2, HBF, HF-1, HF-2. The flammability UL94 rating is the most widely used standard for the flammability of plastic materials. It is used to evaluate the ability of a material to extinguish when ignited. A variety of judgments can be made based on burning speed, burning time, drop resistance, and whether or not the droplets burn. Many values can be obtained for each material tested, depending on color or thickness. When a material is selected for a product, the UL rating should meet the thickness requirements for the wall portion of the plastic part.The UL rating should be reported along with the thickness value; it is not sufficient to report the UL rating without the thickness.

The flame retardancy of plastics increases from HB, V-2, V-1, V-0, 5VB to 5VA:

• HB: The lowest flame retardant grade in the UL94 standard. Requires a burning rate of less than 40 mm per minute for samples 3 to 13 mm thick; less than 70 mm per minute for samples less than 3 mm thick; or extinguishment before the 100 mm mark.

• V-2: After two 10-second burn tests on the sample, the residual flame & afterburning are extinguished within 60 seconds. Dripping particles can ignite cotton.

• V-1: After two 10-second burn tests on the sample, the residual flame & afterburning are extinguished within 60 seconds. The dripping particles may not ignite the cotton.

• V-0: After two 10-second burn tests on the sample, the residual flame & afterburning are extinguished within 30 seconds. Droplets must not ignite the cotton.

• 5VB: After five 5-second burn tests, the flame & afterburning are extinguished within 60 seconds. Droplets should not ignite the cotton. Burn-through is permitted for lumpy samples.

• 5VA: After five 5-second burn tests on the sample, the flame & afterburning are extinguished within 30 seconds. Dripping particles must not ignite the cotton. No burn-through is allowed for lumpy samples.

III. Differences in equipment between UL94 and VW-1 tests

Difference between UL94 and VW-1 test in equipment.UL94 combustion test has HB, V0, V1, V2, VMT, 5VA, 5VB and other combustion tests, while UL1581 has VW-1, FT1, FT2, FT4 and other combustion tests.

• The difference between these two tests in terms of equipment is as follows:

VW-1\FT1 torch for: 125mm (500W), combustion flame: inner flame height 40±2mm, outer flame 125±10mm.

UL94 HB, V-class blowtorch for: 20mm (50W), combustion flame: blue flame without cone, height 20 ± 1mm.

UL94 5V level combustion is used 125mm (500W), combustion flame: inner flame height 40 ± 2mm, outer flame 125 ± 10mm.

• The flame temperature of the flame is also different:

20mm (50W) test flame: The time from 100±2 to 700±3℃ is 44±2S.

125mm (500W) test flame: 100±2~700±3℃ is 54±2S.

• The test space is also different:

UL94 in the HB, V, VMT its space is only required to be greater than 0.5 cubic meters can be, while the 5V requirements are greater than 0.75 cubic meters VW-1 requirements are greater than 4 cubic meters.

• Methane has different flow requirements:

Class HB, V, and VMT gas flow is 105 ml/min with a back pressure of 10 mm water column or equivalent;

Class 5V gas flow rate is 965 ml/min, 125 ± 25 mm water column or equivalent pressure.

• VW-1 has the same back pressure as Class 5V in UL94:

The gas flow rate is 965ml/min, 125±25mm water column or equivalent pressure.

(Note: At present, many domestic plastic UL94 burners are not equipped with a dedicated methane flow meter (often replaced by an air flow meter, resulting in a significant difference!) In addition, they are not equipped with U-shaped back pressure gauges! More importantly: no flame temperature measurement system, you can check your equipment!

IV. Types of Flame Retardant and Standard Grades

The main technical indicators of fire safety for cables are the flame retardancy of CO₂ cables, the density of smoke and the toxicity of gases. American fire protection standards are more concerned with the first two issues, but Europe and the United States have completely different views on fire safety. The traditional concept of the United States that: the root cause of the fire is the production of carbon monoxide (CO) gas and the subsequent combustion process of CO into CO₂ heat release. Therefore, controlling the amount of heat released during the combustion process can reduce the fire hazard. Europe has traditionally been convinced that: in the combustion of halogenated acid (HCL) release, gas corrosivity, smoke concentration and gas toxicity is to determine whether people can be safely removed from the scene of the fire is the main factor. IEC flame retardant rating in order to assess the flame retardant properties of cables and cables, the International Electrotechnical Commission formulated the IEC60332-1, IEC60332-2 and IEC60332-3 three standards. IEC60332-1 and IEC60332-2 are used to evaluate the flame retardancy of single cable when it is arranged in an inclined and vertical manner (GB12666.3 and GB12666.4 standards), while IEC60332-3 (GB12666.5-90 standards) is used to evaluate the flame retardancy of bunched cable when it is burned vertically, compared with the flame retardancy of bunched cable when it is burned vertically. IEC60332-3 (GB12666.5-90 in China) is used to assess the flame retardancy of bundled cables when burning vertically, compared with bundled cables.

• IEC60332-1/BS4066-1 Flame Retardant Rating (Flame Test On Single Vertical Insulated Wires/Cables)

This is a flame retardant standard for single cables. The test specifies that a 60cm long specimen is fixed vertically in a metal box with the front wall open, and a propane burner with a flame length of 175mm is used from the upper fixed end of the specimen at a distance of 450mm, with the flame cone in contact with the cable at an angle of 45 degrees. The test passes if the burned damaged portion of the specimen is not more than 50mm from the lower fixed end.

• IEC60332-3/BS4066-3 Flame Retardant Rating (Flame Test On BunchedWires/Cables)

This is a standard for flame retardancy of bunched cables. The test specification, bundles of 3.5m long cable specimens with wire fixed in a trapezoidal test frame, the number of specimens according to the different classifications of non-metallic materials required to determine. The specimens are hung vertically on the back wall of the combustion furnace, and air is introduced into the combustion furnace through the air inlet on the bottom plate. Propane plane burner to 750 ℃ flame and specimen contact, the specimen in the forced air blowing (air emissions 5m3 / min, wind speed 0.9m / s), must be in the vertical combustion within 20 minutes of combustion does not come up, the cable in the flame spreads 2.5 meters within the self-extinguishing. IEC60332 has a class A, class B, class C and class D of the classification, in order to assess the advantages and disadvantages of flame retardant properties.

• Pressurization level - CMP level (air supply combustion test/steiner tunnel test Plenum Flame Test/Steiner TunnelTest)

This is the most demanding cable in UL fire protection standard (Plenum Cable), the applicable safety standard is UL910, the test stipulates that several specimens are laid on the horizontal duct of the device, and burned with 87.9KW gas Bunsen burner (300,000BTU/Hr) for 20 minutes. The passing standard is that the flame must not extend more than 5 feet beyond the front of the Gas Bunsen burner flame. Optical density has a maximum peak value of 0.5 and a maximum average density value of 0.15. This CMP cable is typically installed in air return pressurization systems used in ventilation ducts or air handling equipment and is approved for use in Canada and the United States. FEP/PLENUM materials conforming to UL910 have better flame retardancy and lower smoke concentrations than low-smoke, halogen-free materials conforming to IEC60332-1 and IEC60332-3.

• Trunking Class-CMR Class (Riser Flame Test)

This is a UL Standard for Commercial Grade Cable (Riser Cable) to the applicable safety standard UL1666. The test specifies that multiple specimens are laid on a simulated upright shaft and subjected to a specified 154.5KW gas Bunsen burner (527,500 BTU/Hr) for 30 minutes. The qualifying criterion is that the flame must not spread to the upper portion of a room 12 feet in height. Trunking grade cables do not have a smoke concentration specification and are typically used for vertical and horizontal floor wiring.

• Commercial Grade-CM (Vertical Tray Flame Test)

This is a UL Standard for Commercial Grade Cable (General Purpose Cable) to UL1581, the applicable safety standard, which requires that multiple specimens be laid on a vertical 8-foot-high support and burned (70,000 BTU/Hr) for 20 minutes with a specified 20KW strip torch. The passing standard is that the flame does not spread to the top end of the cable and extinguishes itself. UL1581 is similar to IEC60332-3C except that the number of cables laid is different. Commercial grade cables do not have a smoke concentration specification and are generally only used for horizontal routing on the same floor, not for vertical routing on the floor.

• General Purpose-CMG Grade (Vertical Tray Flame Test)

This is the UL standard for General Purpose Cable (General Purpose Cable), the applicable safety standard is UL1581. The test conditions for Commercial Grade and General Purpose Grade are similar, and both are recognized for use in Canada and the United States. General Purpose Cable does not have a smoke concentration specification and is generally only used for horizontal wiring on the same floor, not vertical wiring on the floor.

• Household Grade - CMX Grade (Vertical Wire Flame Test)

This is a UL Standard for Restricted Cable, applicable safety standard UL1581, VW-1. The test specimen is kept in vertical position and burned with a test torch (30,000 TU/Hr) for 15 seconds, then stopped for 15 seconds and repeated 5 times. Passing criteria are that the residual flame must not exceed 60 seconds, the specimen must not be burned out by more than 25%, and the surgical cotton padding on the bottom must not be ignited by falling objects. UL1581-VW-1 is similar to IEC60332-1 except that it burns for a different period of time. This rating also has no smoke or toxicity specification and is intended for use only in home or small office systems where a single cable is laid. These cables should not be used in bundles and must be sleeved. Smoke density, halogen content and toxicity rating.

• IEC60754-1/BS6425-1 Determination of Halogen Gas Content (Emission Of Halogens)

This is the specification in the IEC and BS standards for the emission concentration of hydrogen chloride (HCL). Halogens contain fluorine, chlorine, bromine, iodine and the radioactive volatile element astatine, and the components are highly toxic. Experimental provisions, combustion furnace preheated to 800 ℃, a built-in 1.0g sample pushed into the furnace, the use of air emission rate so that HCL dissolved in water, and then determine the halogen acid content of the aqueous solution. If the cable material combustion haloacid (HCL) release is less than 5mg / g, can be called halogen-free cable (LSOH), if the haloacid (HCL) release is greater than 5mg / g but less than 15mg / g, can be called low-halogen cable (LSF). It is worth noting that the IEC 60754-1 method.

V. The Future of Flame Retardant

Next, we will discuss the classification and properties of flame retardant materials. Flame retardant materials can be broadly categorized into two main groups: organic flame retardants and inorganic flame retardants. Organic flame retardants mainly include phosphate esters, halogenated hydrocarbons and so on, while inorganic flame retardants include aluminum hydroxide, magnesium hydroxide and so on. Each type of flame retardant has its unique advantages and scope of application, we need to choose the right type according to the actual situation. In addition, environmental protection has become one of the key concerns of today's society, so the research and development of environmentally friendly flame retardant materials has been increasingly emphasized. Although traditional halogen-containing flame retardants have excellent flame retardant effects, they produce toxic fumes when burning, which pose a threat to the environment and human health. Therefore, the research of new flame retardant materials with high efficiency, low toxicity and easy degradation is an important task we are currently facing. In general, although we have made some progress in the research of flame retardant materials, there is still a lot of work to be done. We must continue our efforts to meet the challenges facing the flame retardant field. I hope that today's sharing will provide you with some new ideas and inspirations, and I look forward to working with you to promote the future development of this field.

(1) The flame retardant system of engineering plastics includes base resin, flame retardant, anti-drip agent, etc. Usually, the applicable flame retardant is added according to the compatibility of the flame retardant with the base resin, and whether the addition of the flame retardant will affect the original performance of the base resin, durability, and cost and other factors.

(2) At present, flame retardant engineering plastics, flame retardant PC / ABS, flame retardant PC is mainly added to organic non-halogenated phosphorus flame retardant aryl phosphate, such as RDP, etc., and add anti-dripping agent as a co-effective flame retardant in order to achieve UL94V0 flame retardant standards. Flame-retardant ABS, flame-retardant HIPS, flame-retardant PBT and flame-retardant PA, due to the halogen-free flame retardant or flame retardant efficiency or price is too high to be practically applied, organic bromine flame retardant such as DBDPE and other co-flame retardant Sb2O3 is still applied in large quantities, anti-drip agent is added selectively according to the situation or not added.

(3) As the coated PTFE anti-drip agent has excellent dispersibility and ease of operation, no agglomeration at room temperature, injection molded products do not wrinkle, black and white products without crystal, can significantly improve the surface gloss of the products, in the requirements of the surface gloss of the products in the PC, PC / ABS, ABS and HIPS flame retardant materials in the application of the proportion of the higher, and in the products do not require the surface gloss of the flame-retarded PBT or PA In the PBT or PA flame retardant materials which do not require the surface gloss of the products, PTFE pure powder is more often chosen to be added.

(4) In the future, as people's awareness of safety increases, environmental regulations tighten, and in response to the EU requirements for the use of halogen-free flame retardants in electronic display products and China's 5G, new energy vehicles and other rapid development, China's flame retardant engineering plastics, especially PC / ABS and flame-retardant PC production will be faster growth, thus pulling the demand for organic non-halogenated phosphorus flame retardant and antidropping agent at a faster rate of growth. growth.

(5) China is the world's main producer of halogen-free phosphorus flame retardants, the world's new production capacity in the future mainly from domestic. Coated PTFE anti-drip agent industrial production, need to balance the anti-drip effect and product surface gloss, has a high technical threshold. Early due to the lack of domestic production and higher prices, coupled with the market for downstream products, surface gloss is not too high requirements, the market share is small; in 2003, the domestic industrial production, its price gradually decreased, domestic users began to turn to coated products, while the market for 3C products for the enhancement of surface gloss requirements, so that PTFE powder can not meet the customer's requirements, the demand for coated products Significantly increased.

The article provides a comprehensive look at the basics of flame retardants, including evaluation, rating and testing of various materials. It is worth noting that YINSU Flame Retardant also has a wide range of flame retardants for different materials such as Red Phosphorus FRP-950, FRP-750, Antimony Composite T3 and Antimony Bromide Replacement T-30, which play a vital role in improving fire safety.