ABS Flame Retardant Compound Methods And Flame Retardant Selection

ABS Flame Retardant Compound Methods and Flame Retardant Selection

ABS resin is a thermoplastic polymer between general-purpose plastics and engineering plastics, which is a copolymerization of three monomers: acrylonitrile (A), butadiene (B) and styrene (S).

ABS resin has impact resistance, heat resistance, low temperature resistance, chemical resistance, easy processing and molding and surface gloss and other properties, is now widely used in automotive, electronics, electrical appliances, textiles, appliances and building materials and other fields, so the flame retardant requirements of ABS is also increasingly high.

Next, let's take stock of the importance of ABS flame retardant modification, the main methods and applicable types of flame retardants.

The Importance of ABS Flame Retardant Modification

With the wide application of polymers in modern life and various industries, people have higher and higher requirements for flame retardancy and other properties of materials. China's requirements for flame retardant polymer materials are also becoming more and more urgent.

Like most polymer materials, ABS is a flammable material (its oxygen index isonly 22%), burns fast when it catches fire and produces a lot of smoke, so the flame retardancy of ABS is an important scientific research topic.

The use of ABS alone when the flame retardant is poor, in practical applications to add flame retardants to improve its flame retardant effect, and add flame retardants will reduce the physical and mechanical properties of ABS, especially the impact performance of the product has decreased significantly, and usually the price of flame retardant is 2-3 times the price of ABS, so that the cost of the product to increase.

The flame retardant used by most domestic manufacturers is decabromodiphenyl ether (DEBDE), which has a high bromine content, excellent thermal stability, small additive amount and good flame retardant effect.

However, with the application of modern high-tech, the traditional flame retardant has been far from meeting the market requirements for its performance, the future of the new flame retardant will be non-halogen, high efficiency, low smoke, low toxicity, multi-functional composite flame retardant.

The main methods of ABS flame retardant modification

1. Change the components of ABS copolymer, such as adding transbutylene succinateor tribromostyrene as the fourth monomer and styrene, butadiene, acrylonitrile co-polymerization, to obtain four-component flame retardant copolymer. This method has good flame retardant durability, but it needs to be added in the process of ABS polymerization, and its process is complicated and high cost, so it is less used.

2. Mixing high flame retardant resin (such as PVC, CPE, etc.). This method needs to add a large number of high flame retardant resin to be effective, which will greatly affect the inherent properties of ABS.

3. Adding inorganic flame retardants (such as Al(OH)3, Mg(OH)2, MoO3, etc.). The flame retardants used in this method need to be added in large quantities (usually more than 60 parts) in order to have a significant flame retardant effect, which will lead to a significant decline in the mechanical properties and processing properties of the polymer, the loss of value.

4. Add organic flame retardants (such as halogen compounds, phosphorus flame retardants, etc.). The method of flame retardant additive, although less, flame retardant effect is good, but there are poor weather resistance, expensive, black smoke when burning.

At present, most of the latter three additive flame retardant methods to prepare a better performance of the low smoke flame retardant ABS system.

Classification of ABS flame retardants

1. Halogen flame retardants

Brominated flame retardants

Halogenated flame retardants mainly refer to brominated flame retardants. Brominated flame retardants are divided into the following categories.

I. PBDEs: PBDEs include octabromodiphenyl ether (octaBDE) and decabromodiphenyl ether (decaBDE), etc. This kind of flame retardant has high efficiency and low dosage, and the products have good mechanical properties and moderate price. However, these flame retardants do not comply with the RoHS ban, are non-environmentally friendly products, and are now banned.

II. Decabromodiphenyl ethane (DBDPE): Due to the presence of non-free bromine, it does not belong to the category of polybrominated diphenyl ethers, and does not produce polybrominated biphenyls and polybrominated diphenyl ethers when burned, and other substances prohibited by the RoHS ban.

Its cost is comparable to decabromodiphenyl ether, and safety assessment shows that DBDPE is a low-toxicity, non-irritating flame retardant, negative for many in vivo genetic genes, and low repeat dose toxicity, so it can be used in place of PBDEs as a flame retardant for ABS.

In addition, antimony flame retardant is an important flame retardant synergist, can be used alone or composite use, especially in conjunction with halogenated flame retardants can greatly improve the effectiveness of halogenated flame retardants, halogenated flame retardant is an indispensable synergist. The main varieties are Sb₂O₃, Sb₂O₅ and sodium antimonate (NaSbO₃-1/4H₂O) and so on.

III. Brominated epoxy resin: Brominated epoxy resin refers to the epoxy resin synthesized from tetrabromobisphenol A. It has excellent melt flowability, high flame retardant efficiency, excellent thermal stability and light stability, and good physical and mechanical properties, which is an ideal flame retardant for ABS.

Chlorinated polyethylene (CPE) flame retardant

CPE has the appearance of white powder, non-toxic, soluble in aromatic hydrocarbons and halogenated hydrocarbons, insoluble in aliphatic hydrocarbons, decomposes above 170℃, releasing hydrogen chloride gas.

Because CPE molecular structure does not contain unsaturated double bonds and access to chlorine groups, and chlorine atoms are distributed along the polyethylene chain randomly, so it has a stable chemical structure, excellent heat aging resistance, cold resistance, weathering resistance, chemical resistance, ozone resistance and electrical insulation.

As an elastomeric polymer, CPE has good compatibility with many kinds of polymers and can be used as a modifier for ABS, PVC, PP, PE, PS, etc. At the same time, CPE contains halogens.

Meanwhile, because CPE contains halogens, it is flame retardant and can be used as the second flame retardant, and the price of CPE is lower than that of ABS, so CPE is an ideal choice for the modification of flame retardant ABS.

Synergistic flame retardant effect of CPE and Sb₂O₃: adding CPE to the material of ABS and composite flame retardant DBDPE/Sb₂O₃, the oxygen index of the composite material will increase, and the rate of heat release, effective heat of combustion, and the rate of mass loss will be reduced, which indicates that CPE has a flame retardant effect, and can be used as a second flame retardant.

After adding CPE, the impact strength of the composites was greatly improved, indicating the synergistic effect between CPE and Sb₂O₃. In addition, after adding CPE/Sb₂O₃, the rate of smoke generation of the composite material can be significantly reduced, indicating that CPE/Sb₂O₃ also has a very good smoke suppression effect for ABS.

2. Halogen-free flame retardants

Aluminum hydroxide and magnesium hydroxide: Aluminum hydroxide and magnesium hydroxide are two common inorganic filler-type flame retardants, which are characterized by non-halogen, non-toxic, smoke suppression, and inexpensive.

The flame retardant mechanism is basically the same, are cohesive phase flame retardant mechanism (i.e., high temperature aluminum hydroxide on the surface of the ABS to form a cohesive phase, isolated from the air, to prevent heat transfer, reduce the amount of flammable gas release: magnesium hydroxide / ABS composite material combustion, the surface of the formation of a dense charcoal layer.

The formation of the charcoal layer can block the combustion heat to the unburned part of the feedback and decomposition products to the flame area of the diffusion of combustion, play the role of heat insulation, insulation, can effectively reduce the rate of heat release of the material, to slow down the combustion of the material) and cooling mechanism (i.e., flame retardant undergoes heat-absorbing dehydration, phase change, decomposition or other heat-absorbing reactions, reduce the temperature of the polymer surface and combustion area, to prevent thermal degradation, and thus reduce the amount of flammable gas volatilization, and ultimately destroy the combustion gas.

However, the dosage added alone is large, and the mechanical properties of the resin are greatly changed, so these two flame retardants are generally not commonly used as the main flame retardant.

Coated red phosphorus: Coated red phosphorus contains only the flame retardant element phosphorus, and its flame retardant efficiency is higher than other phosphorus-containing flame retardants. Its flame retardant mechanism is based on cohesive phase flame retardant, that is, at high temperature, the coated red phosphorus forms a cohesive phase on the surface of ABS, which isolates the air, prevents the heat transfer, and reduces the amount of flammable gas release, so as to achieve the flame retardant purpose.

However, the effect of flame retardancy of ABS using coated red phosphorus alone is not obvious, and better flame retardancy can be obtained by using it with other synergists. It is found that when the amount of coated red phosphorus is 9%, the amount of aluminum hydroxide is 20%, the mechanical and flame retardant properties can be obtained are more desirable synergistic environmental protection flame retardant ABS.

Phosphorus and nitrogen composite flame retardant: nitrogen-containing flame retardants are mainly used in the decomposition process to form nitrogen and other non-combustible gases, dilute and dilute flammable gases or cover the surface of the material and flame retardant. The common ones are melamine, melamine cyanurate (MCA), melamine pyrophosphate and so on.

Phosphorus, nitrogen as the main component of the expansion type flame retardant to become ABS halogen-free flame retardant, when the phosphorus compounds to join the nitrogen can be formed after the phosphorus - nitrogen flame retardant, due to nitrogen compounds heat release N₂, CO₂, NH₃, H₂O and other gases, these non-combustible gases to block the supply of oxygen, to achieve the purpose of the flame retardant enhancement and synergistic effect.

Development trend of ABS flame retardants

Throughout the research and development and development of flame retardants in recent years, it can be seen that the development trend is.

1. Environmental protection and low toxicity. Halogen flame retardants will still be the main varieties of flame retardants, but because of the combustion of this type of flame retardant will generate toxic and corrosive substances, and therefore the demand for halogen-free flame retardants and environmentally friendly flame retardants will grow.

2. Efficient, multi-functional. The development of efficient, multi-functional flame retardants, not only to reduce the impact of flame retardants on the physical and mechanical properties of the substrate, and at the same time for the reduction of pollution, reduce costs will be beneficial.

3. Nano and microencapsulation. With the continuous development of nano and microencapsulation technology, the surface modification of inorganic flame retardants and ultrafine is the direction of development. Due to the poor flame retardant effect of inorganic flame retardants, the addition of large quantities, must be improved using new technologies, such as ultrafine, surface modification, macromolecular bonding.

4. Application of compounding technology. Some products use phosphorus elements to replace the original halogen, through volume expansion to achieve the effect of flame retardant. When the product is added to the composite material, the flame retardant in it will foam and cross-link, and form a stable carbonized layer on the surface of the material.

The carbonized layer can block heat, reduce the entry of oxygen, prevent the dripping of molten polymer, reduce the concentration of smoke and the emission of organic matter, and play a good role in protecting the material. And the masterbatch has good high temperature stability, easy processing, and good coloring performance.

Conclusion

After discussing the importance of ABS flame retardant modification, the main methods and the types of flame retardants applicable, we have to mention the outstanding contribution of YINSU in this field. The ABS flame retardant product lines launched by YINSU flame retardant company, including red phosphorus flame retardant ABS-P-20M, antimony bromide masterbatch for ABS YS-BRT, and composite antimony flame retardant T series, are all based on the design concept of environmental protection, high efficiency, and multi-functionality. These products not only meet the high standard of flame retardant performance required by the market for ABS materials, but also take into account cost-effectiveness and environmental friendliness.

With the rapid development of home appliance industry and automobile industry, the consumption of ABS resin in China is growing rapidly, and the environmental protection and flame retardancy of ABS also put forward higher requirements, and the development of new flame retardant with excellent performance is not only an important topic in the research of flame retardant materials, but also the direction of the development of ABS.