General Plastics Flame Retardant Technology & Application Techniques

General Plastics Flame Retardant Technology & Application Techniques

General-purpose plastics have a wide range of applications, mainly polypropylene (PP), polyethylene (PE), polystyrene (PS) and polyvinyl chloride (PVC), etc., which are used in a large number of industries such as packaging, automotive, sundries, electronic devices and electrics, tubing, and wires and cables.

As flame retardant safety involves all aspects of the place, polymers at high temperatures particularly flammable, while burning will release a large number of toxic gases, the ecological environment and people's lives, health are causing great harm, so the flame retardant safety of polymer materials is a very urgent need to solve the problem.

As a material person, in-depth research on flame retardant mechanism and the development and application of new flame retardant materials are of great significance to the development of society and the people's livelihood.

1.General Plastic Combustion Characteristics and Recognition

Polypropylene

Polypropylene (PP) is made of propylene polymerization (homopolymer PP), or propylene and a small amount of ethylene copolymerization (copolymer PP). Regular structure, high crystallinity, melting point of about 167 ℃, low density, is the lightest general-purpose plastics, with excellent surface rigidity and bending fatigue resistance, is currently used in a large number of home appliance shells, automotive interior and exterior decoration, as well as electronic and electrical components and other products.

PP combustion characteristics: highly flammable, oxygen index of about 17%, high calorific value of combustion, fast, CH-components are not easy to become charcoal, combustion will melt and drip, the upper end of the flame was yellow and the lower end was blue, basically no black smoke, accompanied by a faint smell of burning petroleum, away from the fire can continue to burn, the combustion residue for the black colloidal material.

Polyethylene

Polyethylene (PE) by the polymerization of ethylene, a typical crystalline polymer, according to the degree of crystallinity can be divided into LDPE, HDPE and a small amount of a-olefin copolymer (LLDPE). With excellent low temperature resistance (the lowest can reach -70 ℃ below), good chemical stability, good electrical insulation properties, easy to process. Now widely used in plastic packaging bags, agricultural film and hollow blow molding injection molding products.

PE combustion characteristics: highly flammable, oxygen index of 17% or so, cracking at high temperatures, fast combustion, the same CH-structure difficult to become charcoal, combustion will melt and drip, the upper end of the flame was yellow and the lower end was blue, basically no black smoke, accompanied by the characteristic paraffin burning odor, can continue to burn after leaving the fire, there is a black residue.

Polystyrene

Polystyrene (PS) is a two-phase system polymerized from butadiene and styrene, usually containing 5-15% polybutadiene content, relatively low cost ABS, higher strength, better rigidity, good dimensional stability. Mainly used in consumer packaging materials, household appliances shell and other injection molded parts.

PS combustion characteristics: high calorific value, burning intensely, near the fire sharp contraction, difficult to become charcoal, combustion surface softening, blistering, the flame was orange-yellow, there is a thick black smoke was charcoal ash flying, smoke density is greater, there is the odor of styrene monomer, away from the fire to continue to burn, there is a black residue.

Polyvinyl chloride

Polyvinyl chloride (PVC) is a synthetic polymer produced by free radical polymerization of vinyl chloride monomer. Its chemical structure consists of repeating vinyl chloride units, each containing one carbon atom, two hydrogen atoms, and one chlorine atom.

This structure gives PVC unique physical and chemical properties that allow it to excel in a wide variety of applications. It has good mechanical properties and chemical stability, is resistant to a wide range of chemicals, and has a certain degree of flame retardancy of its own. The oxygen index of pure PVC reaches 45%, but due to the processing of a large number of plasticizers added to increase the flammability.

These characteristics make PVC widely used in many fields such as construction, packaging, wire and cable insulation, artificial leather and so on.

PVC combustion characteristics: As PVC itself is self-extinguishing, there is a certain charcoal ability, its combustion will be soft, the flame is yellow at the upper end of the lower end of the green, there is black smoke, there is a stimulating odor of hydrogen chloride, away from the fire will extinguish, there is a black residue.

2.General plastics flame retardant application techniques

Halogen flame retardants: currently one of the world's largest production of flame retardants, although due to environmental issues and high smoke density, currently still accounts for the dominant position of flame retardants in plastic materials, mainly because of its high flame retardant efficiency, more varieties of halogen flame retardants, applicability is very wide, so the scope of application is still wide, which bromine flame retardant is the halogen flame retardant is one of the most important and most effective.

Typical brominated flame retardants include decabromodiphenyl ether, decabromodiphenylethane, tetrabromobisphenol A, bromotriazine, brominated epoxy resins and brominated styrene.

Non-halogenated flame retardants: Due to environmental reasons, non-halogenated flame retardants are now vigorously promoted and applied. The main non-halogenated flame retardants include inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide, phosphorus flame retardants (red phosphorus, diethyl aluminum hypophosphite, inorganic aluminum hypophosphite and phosphoric acid ester, etc.), phosphorus and nitrogen flame retardants (ammonium polyphosphate, melamine polyphosphate, etc.) and nitrogen flame retardants (melamine, melamine cyanuronate, etc.).

By adding these single flame retardants or compound flame retardants to plastics, flame retardant modified materials with different flame retardant levels and requirements can be achieved.

Applications of Polypropylene Flame Retardants

Flame retardant PP - UL standard V2 grade, the solution selection is as follows:

- Octabromo ether (or octabromo sulfide) system: add antimony trioxide synergistic flame retardant, the total additive amount of 6~8%, up to the off-fire extinguishing, but there is dripping, the mechanical properties of the material to maintain a fair.

- Phosphorus nitrogen bromine system: homopolymerization PP add 1~2%, copolymerization PP add 4~6%, up to the fire extinguished, but there is dripping and skimming cotton combustion, the mechanical properties of the material and pure PP is almost the same.

Flame retardant PP -- UL standard V0 level, the solution options are as follows:

- Bromine antimony system (DBDPE + Sb2O3): the total addition of about 25%, up to UL-94 V0 level, but due to the addition of more, the material cost is high, and mechanical properties have an impact on the need to add compatibilizers and toughening agents to adjust the mechanical properties, you can also add some talc and other filler to reduce costs.

- IFR halogen-free system: phosphorus and nitrogen expansion type flame retardant system, add 25-30%, up to UL 94 V0 level, due to the addition of more, the same mechanical properties have a greater impact, need to add suitable toughening agent and other additives to enhance the performance of the material.

- Inorganic magnesium hydroxide (MDH) system: flame retardant PP can also be added by adding a large number of inorganic flame retardants to achieve higher flame retardant requirements, such as magnesium hydroxide and aluminum hydroxide, but the amount of additives need to reach more than 50-60% to have a satisfactory flame retardant effect and the oxygen index requirements, and therefore the impact on the mechanical properties of the material is also very large. It can also be used by compounding with other flame retardants to reduce the amount of inorganic flame retardants added, thus reducing the impact on the mechanical properties of the material.

PP Flame Retardant Comparison

Application of polyethylene flame retardant

Polyethylene flame retardant solution selection:

- Red phosphorus (RP) flame retardant system: PE flame retardant is the most efficient flame retardant is generally used red phosphorus system, due to safety requirements, are generally used modified coated red phosphorus masterbatch as a flame retardant, the addition of about 15% can be achieved UL94 standard 1.6mm V0 level.

- Bromine antimony (DBDPE/Sb2O3) flame retardant system: the total additive amount of about 25%, up to UL-94 standard 1.6mm V0 level, can add a small amount of mineral filler, high flame retardant efficiency, you can add toughening agent to reduce the impact of the impact strength of the impact of the strength of the better retention.

- IFR halogen-free system: PE system can not be used with APP-containing system, the flame retardant properties have an impact on the use of phosphorus and nitrogen compounding flame retardant with a total addition of 25~26%, can reach UL94 standard 1.6mm V0 level. The system generally can not add mineral filler, the flame retardant effect will be greater.

- Inorganic Magnesium Hydroxide (MDH) and Aluminum Hydroxide (ATH) system: generally are used to add a large number of MDH or ATH (more than 60%), you can achieve an oxygen index of 30 or more, low smoke density of flame retardant low smoke halogen-free material, can also be compounded with Red Phosphorus (RP) or IFR to get a higher flame retardant effect.

PE Flame Retardant Comparison

Polystyrene flame retardant application

Flame retardant solution selection:

- Bromine-antimony system: Generally the ratio of bromine-antimony is 3:1, there are more bromine flame retardants suitable for polystyrene, each with different advantages and disadvantages, and generally can meet the requirements of flame retardancy, so it is necessary to select the flame retardant system according to the characteristics of the products.

PS Halogen Flame Retardant Comparison

- IFR/expandable graphite system: The layer structure of expandable graphite can form a special type of intercalation compound. Some research shows that expandable graphite and phosphorus and nitrogen flame retardants can achieve better flame retardant effect when used in combination.

- IFR+PPO system: IFR and polyphenylene ether are chosen as the composite flame retardant system for compounding flame retardant PS, which can effectively improve the flame retardant performance of PS. PPO has very good charcoal formation performance and has good synergistic flame retardant effect with IFR. However, due to the poor UV resistance of PPO, the mobility is relatively low, making the application of products have limited occasions.

- Inorganic magnesium hydroxide flame retardant system: by adding a large amount of magnesium hydroxide inorganic flame retardant, can achieve flame retardant effect, can also be compounded with red phosphorus flame retardant, to get higher flame retardant materials. However, due to the addition of large amounts of magnesium hydroxide, the toughness of the material has an impact on the need for toughening and compatibility modification in order to get the desired mechanical properties.

Here is the content of the image presented in an English table format:

PS Halogen-free Flame Retardant Comparison

Application of polyvinyl chloride flame retardant

Flame retardant selection solution:

- Metal oxide synergistic flame retardant: As PVC itself is high in chlorine, usually by adding a certain amount of CPE and metal oxides to PVC, a higher flame retardant performance can be achieved. In all kinds of metal oxides, to improve the oxygen index ability, generally zinc stannate > Sb2O3 > ammonium octamolybdate > zinc borate.

- Inorganic aluminum hydroxide and magnesium hydroxide systems:

Magnesium hydroxide and aluminum hydroxide can significantly reduce the amount of smoke and improve the flame retardant properties of PVC, and at the same time can reduce the filling amount of flame retardants. Inorganic mineral flame retardants have a greater impact on the physical and mechanical properties of rigid PVC materials, flame retardant properties, smoke reduction properties.

After testing and verification of the author found that the use of hard gypsum powder as a filler enhancer than calcium carbonate filler material oxygen index is significantly better, and gypsum powder compared to calcium carbonate, its environmental performance is more superior, and magnesium hydroxide, metal oxides flame retardant synergistic compounding, you can get a higher oxygen index of the flame retardant environmentally friendly materials.

- Adopting flame retardant plasticizer TCPP or tetrabromophthalic anhydride ester (B45-Z) to replace part of the combustible plasticizer can greatly improve the oxygen index. Since B45-Z itself is a bromine-containing compound with a large specific gravity, it will increase the hardness and specific gravity of the material, and the cost is higher, while TCPP is cheaper, but the flame retardant effect is not as good as that of B45-Z.

Here is the content of the image presented in an English table format:

PVC Flame Retardant Comparison

Conclusion

In the research of flame retardant technology for general-purpose plastics, YINSU Flame Retardant Company has responded positively to the market demand and has developed a series of specialized and dedicated flame retardants. These flame retardants not only have highly effective flame retardant properties, but also can significantly reduce the cost of flame retardancy at low addition levels.

YINSU Flame Retardant understands the differences in flame retardant properties between different materials and offers tailor-made flame retardant solutions for a wide range of materials such as polypropylene, polyethylene, polystyrene and polyvinyl chloride. Whether it is a standard application or a special need, YINSU Flame Retardant can provide individualized flame retardant solutions based on the specific requirements of the customer to ensure that the safety standards and performance needs of each type of product are met. This flexible and customized service not only enhances the market competitiveness of the products, but also provides customers with more choices and guarantees.