In many occasions, the material is required to have flame retardancy. The more common occasions are electronic appliances, and the automotive industry also has
Flame Retardant requirements, but generally lower. Flame retardancy can be achieved by the addition of a flame retardant. Most
plastics are flammable. With the wide application of plastics in construction, furniture, transportation, aviation, aerospace, electrical appliances, etc., improving the flame retardancy of plastics has become an urgent issue.
Flame retardant: also known as flame retardant, fire retardant or fire retardant, a functional additive that imparts flame retardancy to flammable polymers; most of them are VA (phosphorus), VIIA (bromo, chlorine) and A compound of the IIIA (锑, aluminum) group element.
Molybdenum compounds, tin compounds and iron compounds, which have a smoke suppressing effect, are also in the category of flame retardants, and are mainly suitable for plastics having flame retardant requirements, delaying or preventing the burning of plastics, especially polymer plastics.
It makes its ignition time increase, ignites itself and is difficult to ignite.
Flame retardant principle
1) Endothermic effect
The heat released by any combustion in a short period of time is limited. If a part of the heat released by the fire source can be absorbed in a short time, the flame temperature will be lowered, radiated to the combustion surface and acted on the gasification. The heat of flammable molecules cleavage into free radicals is reduced, and the combustion reaction is suppressed to some extent.
Under high temperature conditions, the flame retardant undergoes a strong endothermic reaction, absorbs part of the heat released by combustion, reduces the temperature of the surface of the combustible material, effectively suppresses the formation of flammable gases, and prevents the spread of combustion. The flame retardant mechanism of Al(OH)3 flame retardant is to increase the heat capacity of the polymer to absorb more heat before reaching the thermal decomposition temperature, thereby improving its flame retardant performance. Such flame retardants fully exert the characteristics of a large amount of heat absorption when combined with water vapor, and improve their own flame retardant ability.
2) Coverage
After the flame retardant is added to the combustible material, the flame retardant can form a glass-like or stable foam coating layer at high temperature to isolate oxygen, and has the functions of heat insulation, oxygen barrier, and preventing the combustible gas from escaping outward, thereby achieving flame retardant. purpose.
For example, when the organic phosphorus-blocking flame retardant is heated, it can produce a crosslinked solid substance or a carbonized layer which is more stable in structure.
The formation of the carbonized layer on the one hand prevents the polymer from further pyrolysis, and on the other hand prevents the internal thermal decomposition products from entering the gas phase to participate in the combustion process.
3) inhibition of chain reaction
According to the chain reaction theory of combustion, it is the free radicals required to sustain combustion. The flame retardant acts on the gas phase combustion zone to capture free radicals in the combustion reaction, thereby preventing the flame from propagating, reducing the flame density in the combustion zone, and ultimately reducing the combustion reaction rate until termination.
For example, a halogen-containing flame retardant whose evaporation temperature and polymer decomposition temperature are the same or similar, when the polymer is thermally decomposed, the flame retardant is also volatilized at the same time. At this time, the halogen-containing flame retardant and the thermal decomposition product are simultaneously in the gas phase combustion zone, and the halogen can capture the radicals in the combustion reaction, thereby preventing the flame from being propagated, reducing the flame density in the combustion zone, and finally reducing the combustion reaction rate until the termination. .
4) Non-combustible gas suffocation
When the flame retardant is heated, the non-combustible gas is decomposed, and the concentration of the combustible gas which decomposes the combustible material is diluted to below the lower limit of combustion. At the same time, it also has a diluting effect on the oxygen concentration in the combustion zone, preventing the combustion from proceeding and achieving the flame retarding effect.
Plastic flame retardant grade
Flammability UL94 rating - the most widely used flammability performance standard for plastic materials. It is used to evaluate the ability of a material to extinguish after it has been ignited. There are various evaluation methods depending on the burning speed, the burning time, the drip resistance, and whether the beads are burned.
Plastic flame retardant grade: from HB, V-2, V-1, V-0, 5VB to 5VA step by step.
HB: The lowest flame retardant rating in the UL94 standard.
V-2, V-1, V-0, 5VB, 5VA flame retardant standard.
Colour PMMA Granule for Extrusion Super Cover
Pmma Impact Modifier resin is a new weather-resistance engineering plastics synthesized by acrylate. It has excellent impact strength and processability, super weather-resistance, good surface hardness and glossness,in addition has good optical performance. It is mainly used in co-extrusion with PVC / ABS / PS and also single extrusion.
ASA Copolymer for Extusion Super Cover
ASA resin is a ternary copolymer consisted of Acrylonitrile, Styrene and Acrylate. ASA copolymer integrates acrylates's high impact strength and excellent weather-resistance, chemical resistance and high hardness of acrylonitrile, good processability of styrene. It can be extruded single & coextruded over ABS and PVC. ASA is particularly used in outdoor applications that require long term color stability, excellent weather resistance.
Asa/Pmma Copolymer
Pmma Copolymer, ASA Copolymer, ASA Plastic Polymer
Shandong Novista Chemicals Co.,Ltd (Novista Group) , https://www.novistachem.com