Research Progress Of Flame Retardants In Flame Retardant Coatings

Research Progress Of Flame Retardants In Flame Retardant Coatings

Flame retardant coatings are functional materials that serve to decorate and protect the substrate when a fire occurs. Flame retardant coatings are generally composed of two parts: the base material and the flame retardant. The development of flame retardant coatings in recent years and the flame retardants applied to flame retardant coatings are introduced in detail. Flame retardants mainly include: halogen flame retardants, phosphorus and nitrogen flame retardants, intumescent flame retardants, biomass flame retardants and graphene flame retardants. In this paper, the application of flame retardant coatings in the field of epoxy resin, polyurethane and other fields is described, in addition to the application of new biomass flame retardant and graphene flame retardant is introduced, and the future development of flame retardant coatings and flame retardant is described.

Introduction

Flame retardant coatings can play the role of flame retardant is mainly due to the role of flame retardant coatings, in recent years, people have been committed to the development of different kinds of new flame retardants applied to coatings, so as to prepare the ideal flame retardant coatings. In this paper, the flame retardants in flame retardant coatings in recent years are described in detail.

Experiment

Flame retardants commonly used in flame retardant coatings

1.1 Traditional halogen flame retardants

The halogen flame retardants traditionally applied to flame retardant coatings are mainly chlorine-containing, bromine-containing flame retardants and derivatives. The advantages of this flame retardant are stable performance, low price and easy processing.

Traditional halogenated flame retardants are mainly decabromodiphenyl ether, chlorinated paraffin, brominated polystyrene, tetrabrominated flame retardant, flame retardant mechanism is mainly when a fire occurs, the generation of halogen radicals, resulting in HX, and then combining with a large number of material combustion releases HO-radicals, releasing H2O and X-. X-reacts with the material in the RH-reaction, and so on, so as to prevent the combustion of the chain reaction to prevent combustion to achieve the purpose of combustion, the specific process, as shown in the following table. The specific process is shown in Figure 1.

However, along with the improvement of people's quality of life, especially the increasingly strict health and environmental protection requirements, halogenated flame retardants in the combustion reaction will release dioxin and other toxic and harmful substances, resulting in secondary damage, so in recent years the halogenated flame retardants in many places has been restricted to use.

1.2 Phosphorus and nitrogen flame retardants

phosphorus flame retardants and nitrogen flame retardants are currently used more environmentally friendly flame retardants, in which the phosphorus flame retardants can generate a more stable carbon layer in the combustion process to prevent the transfer of heat, which in turn plays a flame retardant effect. The main phosphorus flame retardants are ammonium polyphosphate, phosphate flame retardants, organic phosphates, polymer phosphate flame retardants. Nitrogen-based flame retardants belong to a gas-phase flame retardant mechanism, the reaction process releases NO, NO₂ and other flame retardant gases, thereby diluting the oxygen concentration, and thus achieve the effect of flame retardant. Traditional nitrogen-based flame retardants mainly include melamine, melamine urate, melamine salt and other substances. In recent years, it is found that a single flame retardant with a single flame retardant mechanism is difficult to meet the flame retardant requirements of materials, and phosphorus and nitrogen composite flame retardants are more widely used in the field of polymer flame retardancy.

• YINSU's R&D team synthesized an epoxy curing agent by using epoxy resin and triethylenetetramine as raw materials, and then synthesized a cyclic trisphosphonitrile flame retardant by reacting hexachlorocyclic trisphosphonitrile and rhodamine acyl, and then prepared a flame-retardant epoxy coating by adding the flame retardant into epoxy coating, and it was found that the best flame-retardant effect was achieved when the amount of the nitrile flame retardant added reaches 10% with an oxygen index of 28%, and its vertical combustion rating reaches UL94 V- 0, and it also has good mechanical properties. The vertical combustion level reaches UL94 V- 0, and it also has better mechanical properties.

Polyurethane coatings have good adhesion, abrasion resistance, good chemical resistance and oil resistance and other excellent properties, polyurethane coatings are widely used in  wood, flooring, corrosion, electronics industry, pre-roll and other fields. However polyurethane coatings are as easy to burn as polyurethane. Flame retardant polyurethane coatings are a good solution to the problem that polyurethane is easy to burn, and flame retardant polyurethane coatings have better thermal stability, chemical stability, mechanical strength and adhesion. In order to expand the scope of application of polyurethane, many kinds of flame retardants have been developed and applied to polyurethane coatings in recent years.

• Our technicians synthesized a series of new phosphorus-containing and boron-containing flame retardants by esterification reaction using cyclic phosphate ester PEA and polyethylene glycol borate PEG-BA with different mass ratios as the raw materials, and added the phosphorus-containing flame retardants into polyurethane to prepare transparent fireproof coatings. The results of transparency analysis and fire test showed that the protective coatings had high transparency and could provide excellent fire resistance for wood. The introduction of PEG-BA was found to have good synergistic effect on reducing heat release and smoke density through the study of cone calorimeter and smoke density tester. The flame retardant has a good cohesive phase flame retardant mechanism, and the flame retardant coating forms a good char layer during the combustion process, which provides good protection for the wood. The synthesis route of polyethylene glycol borate is shown in Figure 2.

• Our technicians prepare aqueous acrylic flame retardant coatings from aqueous acrylic emulsions for wood fire retardancy. Ammonium polyphosphate (APP) and bleaching beads were used to co-efficiently retard the flame. The oxygen index and cone calorimeter experiments showed that the oxygen index of the flame-retardant coatings increased significantly to 28.7% when APP was added with bleaching beads. Compared with the flame retardant coatings without bleaching beads, the flame retardant effect was obvious. The heat release and smoke release of the prepared waterborne acrylic flame retardant coatings were significantly reduced, which can promote the charring of wood, and it is a better waterborne flame retardant coating applied to wood materials, which can effectively reduce the fire hazard of wood. Flame retardant waterborne polyurethane (WBPU) coatings were synthesized by reacting phosphorus-based polyester polyol and isophorone diisocyanate (IPDI) with different substance amount ratios, and it was found that the prepared WBPU coatings were environmentally friendly flame retardant coatings, and it was found that the waterborne flame retardant polyurethane coatings had a better flame retardant effect through oxygen index and vertical combustion experiments, and it was found that the WBPU coatings had a better flame retardant effect through TGA studies. The waterborne flame retardant polyurethane coatings have better thermal stability. The waterborne flame retardant coatings have good application value.

Results and Discussion

1.3 Expansion flame retardant

Expansion flame retardant is a kind of flame retardant integrating acid source, carbon source and gas source, which expands rapidly in the process of combustion, so as to achieve the effect of isolating oxygen and preventing heat transfer, and then achieve the purpose of flame retardant.

Expansion flame retardant is a relatively stable flame retardant, with a variety of flame retardant mechanism. In recent years, it has been applied more in flame retardant coatings, and intumescent flame retardant coatings account for about 10% of flame retardant coatings. A better intumescent carbon layer plays a better role in protecting the substrate of flame retardant coatings.

A series of new epoxy/PEPA phosphate (EPP) flame retardants were prepared by China University of Petroleum with polyphosphoric acid (PPA), pentaerythritol phosphate ester (PEPA), 1,4-butanediol diglycidyl ether (BDE) and bisphenol A epoxy resin E51 (EP). The EPPs were then incorporated into amino resins to prepare intumescent transparent fire retardant coatings. The flame retardant properties of the intumescent protective coatings were tested. The structural formula of the epoxy/PEPA phosphate (EPP) flame retardant is shown in Figure. 3.

• YINSU's R&D team prepared intumescent flame retardants from melamine phosphate and pentaerythritol, which were added to silicone-propylene emulsions and urea-formaldehyde resin matrix resins to prepare intumescent flame retardant coatings, respectively. The flame retardant effect of the flame retardant coatings was analyzed. It was found that the prepared intumescent flame-retardant coatings had a good flame retardant effect on wood with a good increase in oxygen index, and it was found that the flame-retardant coatings had a good thermal stability through TG studies. The prepared intumescent flame retardant was found to have better flame retardant effect by CONE and SEM studies. The prepared intumescent flame retardant is a better flame retardant for wood application.

• Intumescent flame retardants prepared from phenylphosphonic acid, neopentylglycol (NPG), and N,N-dimethylformamide were added to melamine formaldehyde resin (MF) to prepare transparent intumescent flame retardant coatings, and the transparent intumescent flame retardant coatings were coated onto plywood, and it was found that the flame retardant coatings had a better flame retardant effect.

When the additions of intumescent flame retardant and polyethylene glycol reached 40% and 5%, the oxygen index reached 27.4%. The transparent intumescent flame retardant coating has a good intumescent charcoal layer, which makes it have a better effect of protecting the substrate during combustion.

1.4 Biomass flame retardant

Biomass is a renewable resource, non-toxic, harmless, renewable and other advantages, biomass flame retardants have become a research hotspot in recent years, the use of renewable biomass resources to prepare a flame retardant used in people's daily life has a better application prospects.

YINSU prepared a flame retardant by using three kinds of substances, namely, poly(erythorbic acid amine), pentaerythritol and tea saponin, in which tea saponin was used as a gas source to prepare a composite tea saponin intumescent flame retardant by physical compounding technology, and then mixed with alkyd resin varnish to prepare an intumescent flame retardant coating. It is found that the intumescent flame retardant has a good flame retardant effect, in which the tea saponin plays a vital role. After adding the flame retardant, the intumescent flame retardant has better thermal stability and higher carbonization rate. When the flame retardant addition reached 50% of the solid content of the coating, the oxygen index of the coating was 34.2%, and the fire resistance time was 11.1 min with minimum mass loss.

1.5 Graphene flame retardant

Graphene is an emerging material composed of carbon atoms with a lamellar structure. Graphene can improve the anticorrosive properties of coatings, strengthen the waterproof penetration properties of materials, and at the same time has a better dense physical insulation layer, so graphene can improve the flame retardant properties of materials. Graphene can cross-link with resin to form a protective film, so that it can play a role in isolating heat and oxygen when burning. H2O and CO2 can be generated during combustion. In addition, graphene can also play a role in enhancing the carbon layer, which can further play a role in preventing the combustion reaction from proceeding.

• YINSU prepared polyurethane flame retardant coatings by compounding expandable graphite (EG) with oxidized treated graphite oxide with APP/magnesium hydroxide and APP/aluminum hydroxide [Al(OH)3], which were cured by casting. It was found that the composite flame retardant polyurethane coatings compounded with graphite oxide had better flame retardant effect. The oxygen index was improved and the heat release rate was reduced. The composite flame retardant has condensed phase and vapor phase flame retardant mechanism.

1.6 Other flame retardants

In recent years, many researchers have applied composite flame retardants to coatings, such as organosilicon flame retardants, organically modified montmorillonite flame retardants, inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide. By compound use, the flame retardant coatings have a better flame retardant effect.

• Our team, also prepares flame retardant epoxy resin coatings by modifying epoxy resin with organosilicon, and the flame retardant epoxy resin coatings have the best flame retardant effect when the curing agent is 10%, the content of organosilicon is 6%, the reaction temperature is 85℃, and the reaction time is 25min. Epoxy resin and silicone to form a graft copolymer. The prepared silicone modified flame retardant epoxy resin coating has the advantages of better thermal stability, better flame retardant effect and stronger adhesion.

• The technicians prepared terminal alkynyl-functionalized polyurethanes using 4,4'-dihydroxymethyl-1,4-heptadiyne functional monomer as chain extender, and then prepared aqueous polyurethane flame-retardant nanocomposites with azide-modified nano-montmorillonite, aluminum hydroxide, and magnesium hydroxide via Click reaction. It was found that the prepared flame-retardant aqueous polyurethane had a better flame retardant effect and the oxygen index was increased by 7% compared to the pure WPU. The ignition time was also extended, and the prepared composite flame retardant played a good flame retardant effect on the waterborne polyurethane flame retardant coatings.

Conclusion

With the rapid development of the world economy, people pay more and more attention to safety and fire prevention, flame retardant coatings will have a broad market prospect. In the field of construction, wood and steel are the two main materials that need flame retardant coatings. In the future market of flame retardant coatings, flame retardant coatings that are healthy and environmentally friendly, with strong adhesion, good stability, thin coating layer and good flame retardant effect will be favored by the market.

At the same time, flame retardant coatings should have multi-functionality, such as: waterproof, anti-corrosion, acid and alkali resistance, low smoke and low toxicity and other functions are also considered. With the increasingly stringent requirements of the world law, people's needs are getting higher and higher, environmental protection and efficient flame retardant and multifunctional flame retardant coatings will be more widely used in the field of application.

With the continuous advancement of flame retardant coating technology and the growing market demand for environmentally friendly and efficient flame retardant products, YINSU Flame Retardant Company has launched a series of innovative products based on its profound technical accumulation in the field of flame retardants. In addition to the traditional APP (ammonium polyphosphate) and antimony bromide flame retardants, YINSU has also developed highly efficient and high-temperature-resistant flame retardants such as MP (melamine phosphate) and PG-50 (red phosphorus paste), which not only have excellent flame retardant properties, but also maintain their stability at high temperatures, providing more environmentally friendly and highly efficient choices for the coating industry.

In addition, YINSU's T3 flame retardant, as a substitute for antimony trioxide, is not only comparable in performance, but also better in environmental protection and cost, and is fully applicable to coatings, bringing new changes to the coating flame retardant market YINSU is committed to providing customers with comprehensive flame retardant solutions to meet the ever-changing market demand, and to promote the development of flame-retardant coating industry in the direction of safer and more environmentally friendly. YINSU is committed to providing customers with comprehensive flame retardant solutions to meet the ever-changing market needs and to promote the development of flame retardant coating industry in the direction of safer and more environmentally friendly.