CN106046681B - A kind of flax fiber element base phosphorus expanding fire retardant and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of phosphorus-containing intumescent flame retardants, and discloses a flax cellulose-based phosphorus-based intumescent flame retardant, a preparation method and application thereof. The flame retardant comprises 2 to 10 parts by weight of a carbon source, 1 to 10 parts by weight of an acid source and 1 to 10 parts by weight of a gas source; the carbon source is carboxylated flax fiber with a high carboxyl content, which comprises the following steps Preparation method: Soak flax fiber in water, add H ₂ O ₂ and catalyst, stir and react to obtain carboxyl flax fiber with high carboxyl content. The present invention also provides an epoxy resin composite material based on the above flame retardant. The flame retardant of the invention uses carboxylated flax cellulose with high carboxyl content as a carbon source, has a char formation rate of 20-27.2%, and releases less combustible gas through thermal decomposition. The obtained epoxy resin composite material has a limiting oxygen index of more than 29, a vertical combustion rating of V-0, a reduction in total combustion heat release of more than 60%, and has the advantages of low water absorption and high mechanical properties.

Description

A flax cellulose-based phosphorus-based intumescent flame retardant and its preparation method and application

technical field

The invention belongs to the technical field of phosphorus-containing intumescent flame retardants, and in particular relates to a flax cellulose-based phosphorus-based intumescent flame retardant and a preparation method and application thereof.

Background technique

Cellulose is the most widely distributed and most abundant polysaccharide in nature, accounting for more than 50% of the carbon content in the plant kingdom. As a kind of cellulose derivative, carboxylated flax fiber has the characteristics of good biocompatibility, biodegradability, environmental friendliness and non-toxicity, and has been widely used in many industries. The preparation of carboxylated flax fiber by hydrogen peroxide (H ₂ O ₂ ) has attracted much attention due to its advantages of greenness, environmental protection and high purity. After cellulose is oxidized, its performance is greatly improved compared with natural cellulose. For example, Chinese patent application CN104017090A discloses a method for preparing carboxycellulose by using hydrogen peroxide, its carbonyl content is as high as 10.4%, and the adsorption of lead ions is more than 10 times higher than that of pure fiber.

Epoxy resin has many excellent properties, such as corrosion resistance, electrical insulation, mechanical properties, bondability, and better processing than other thermosetting resins. Therefore, whether in high-tech or general-purpose technology, whether in national defense or civilian industry, or even in daily life, traces of epoxy resin and its secondary processed products can be seen. Epoxy resin is a very important kind of thermosetting resin, but its flame retardancy is poor and its oxygen index is low (about 19.8). The flammability of epoxy resin and the disadvantages of continuous spontaneous combustion after leaving the fire are easy to cause fires, which limit its application. Halogenated flame retardants have become the mainstream of the market due to their low dosage, high flame retardant efficiency and wide application range. ) issues have received widespread attention. The European Union promulgated the "Restriction of Hazardous Substances Directive" (RoHS) in February 2003, and the "Restriction of the Use of Certain Hazardous Substances Directive in Electrical and Electronic Equipment" (RoHS Directive for short) began to be implemented on July 1, 2006. The list of hazardous substances that have been implemented in batches and substances of concern for environmental management in the near future. The use of polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBOEs) and formaldehyde is prohibited in electrical and electronic equipment. The use of halogenated flame retardants has been hit hard.

Therefore, it is imminent to develop a new type of flame retardant epoxy resin to replace the existing halogen flame retardant epoxy resin. Therefore, new intumescent flame retardants have attracted much attention due to their advantages of low toxicity, smoke suppression and simple preparation. The polymer added with intumescent flame retardant decomposes during combustion to produce non-combustible gas to isolate oxygen and take away a large amount of heat, and forms a layer of charcoal layer on the surface of the material to isolate heat and oxygen. Intumescent flame retardants mainly have three major components: carbon source, acid source and gas source. With the in-depth research on intumescent flame retardant in the last century, typical carbon sources such as pentaerythritol can no longer meet the needs of large-scale production due to its high price, so starch with a wide range of sources, green and pollution-free, has become the most common char-forming agent. For example, Li Bin and others studied the effect of starch replacing pentaerythritol on polyethylene intumescent flame retardant system (Li Bin, Zhang Xiucheng, Sun Caiying. Effect of starch on thermal degradation and flame retardancy of polyethylene intumescent flame retardant system[J]. Polymer Materials Science and Engineering.2000(02)). In daily use, starch is easy to absorb water and migrate out of the material, resulting in the inability to form enough char layers, which further affects the flame retardant effect. However, among the intumescent flame-retardant carbon sources, flax fiber, which is also a polysaccharide, is rarely mentioned. Compared with starch, flax fiber, which is also a natural macromolecular polysaccharide, has better water resistance and structural stability.

In order to prepare carboxylated cellulose, Zhang Shenghong et al. used NaOH solution to modify natural cellulose to improve its oxidizing ability, and used the TEMPO-NaOCl-NaBr system as an oxidant to selectively convert the primary hydroxyl group of the carboxyl flax fiber glucosyl ring into a carboxyl group. A cellulose-based heavy metal adsorption material prepared by the technology can be placed in the regulating tank of the biological aerated filter to pretreat heavy metal ions such as Cu ²⁺ and Cd ²⁺ (Zhang Shenghong, Chen Jihua, Organic aerated deep purification of biological aerated filter Wastewater Research, 2006). The method adopted by the patent whose publication number is CN1O201899A is to use viscose fiber filament fabric as the starting material, and use an organic oxidation solvent system to oxidize the viscose fiber filament fabric. After the oxidation reaction is completed, it is washed and dried to make carboxyl flax Fiber hemostatic product, the carboxyl content of the product can reach 15-24%, and the organic oxidation solvent used is cyclohexane or methylcyclohexane. U.S. Patent No. 6,627,749B1 discloses a method of oxidizing cellulose with a mixed solution of sodium nitrite, phosphoric acid, and nitric acid to prepare carboxylated flax fibers with a carboxyl content lower than 24.5%, which can be used in the fields of medicine, chemical industry, and medical polymers. U.S. Patent US6120554-A discloses a kind of adopting alkyl quaternary ammonium salt as catalyst, taking hydrogen peroxide as oxidant carboxyl flax fiber, thereby prepares carboxy flax fiber, but oxidation degree is low, oxidation efficiency is poor, and preparation process needs relatively It is difficult to be widely used under high temperature. Japanese Patent No. 2011057749A reported the use of polar oxidants to oxidize the hydroxyl groups on cellulose C6 into aldehyde groups and carboxyl groups, wherein the carboxyl group content in the obtained carboxylated flax fibers was 0.6-2.2 mmol/g. German patent DE102010034782 reports a method for preparing cellulose with an oxidation degree of 5-50%. The method uses an oxidizing agent such as sodium hypochlorite for oxidation treatment at a reaction temperature of 20-160°C.

So far, there have been reports on the preparation of carboxycellulose at home and abroad, but the preparation process is complicated and the conditions are harsh, and it must be prepared in a strongly acidic or alkaline medium. The selected oxidizing agent is not only destructive to cellulose itself, but also has by-products left over, which has a certain impact on the environment. The present invention uses hydrogen peroxide, an environmentally friendly oxidant, to prepare carboxy flax fibers with a carboxyl content of up to 40% through designed reaction conditions, and use it as a new type of intumescent flame retardant carbon source, coated with melamine microcapsules The composition formed by ammonium polyphosphate realizes the expansion of flame retardant epoxy resin at a lower content, and has the advantages of high flame retardant grade, high mechanical properties and low water absorption.

Contents of the invention

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a flax cellulose-based phosphorus-based intumescent flame retardant. The present invention uses carboxyl flax fiber with high carboxyl content as the material, and ammonium polyphosphate coated with melamine microcapsules to form an intumescent flame retardant, and utilizes its high char formation and low flammable gas release to reduce the content of the flame retardant , to improve the flame retardant properties, used in epoxy resin flame retardant.

Another object of the present invention is to provide a method for preparing the flax cellulose-based phosphorus-based intumescent flame retardant.

Another object of the present invention is to provide an epoxy resin composite material based on the flax cellulose-based phosphorus-based intumescent flame retardant.

Another object of the present invention is to provide the application of the flax cellulose-based phosphorus-based intumescent flame retardant in resin and rubber, especially the application in epoxy resin flame retardancy.

The object of the present invention is achieved through the following solutions:

A flax cellulose-based phosphorus-based intumescent flame retardant, comprising 2 to 10 parts by weight of a carbon source, 1 to 10 parts by weight of an acid source and 1 to 10 parts by weight of a gas source;

The carbon source is carboxy flax fiber with high carboxyl content, which is prepared by the following steps: soak flax fiber in water, add H ₂ O ₂ and a catalyst, stir and react to obtain carboxy flax fiber with high carboxyl content.

The mass ratio of the used flax fiber to H ₂ O ₂ is preferably 20:10˜20:80.

The conditions of the stirring reaction are preferably stirring and reacting at 20-50° C. for 0.5-72 hours.

The amount of the catalyst used is just a catalytic amount, preferably 0.02-2% of the flax fiber mass.

Described catalyst can be ferric sulfate, copper sulfate, cobalt sulfate, manganese sulfate, zinc sulfate, zinc chloride, cobalt chloride, cuprous chloride, ferrous chloride, ferric chloride, cupric chloride, zinc bromide , cobalt bromide, ferrous bromide, iron bromide and copper bromide at least one. The catalyst is preferably dissolved in water before use to prepare a solution with a concentration of 0.1 mol/L.

The flax fiber is preferably soaked in water for 1-5 hours, and then added with H ₂ O ₂ and a catalyst for reaction. The amount of water used is preferably twice or more the mass of flax fiber.

After the stirring reaction, a purified product is preferably obtained by separation, washing and drying. The washing is preferably to use water to rinse the separated solid to neutrality. The drying is preferably performed at 50° C. to 85° C. for 4 to 12 hours.

Described acid source and gas source are preferably melamine-coated ammonium polyphosphate (MFAPP), and its preparation method can refer to literature (Yang L, Cheng W L, Zhou J, et al.Polym Degradation Stab,2014,105(1) :150-159.) to get.

The total amount of the acid source and the gas source is preferably 3-10 parts by weight.

In order to better realize the present invention, the flax cellulose-based phosphorus-based intumescent flame retardant includes 2 to 10 parts by weight of carbon source, and 3 to 10 parts by weight of ammonium polyphosphate coated with melamine;

The carbon source is carboxy flax fiber with high carboxyl content, which is prepared by the following steps: soak flax fiber in water, add H ₂ O ₂ and a catalyst, stir and react to obtain carboxy flax fiber with high carboxyl content.

The carbon source of the flame retardant of the present invention is carboxyl flax cellulose with high carboxyl content, compared with traditional carbon forming agents such as pentaerythritol, pure starch and pure flax fiber, it has high char formation rate and releases methanol during combustion. It has the advantages of less flammable gas and high water resistance. Its carboxyl content is 10-40%. When the thermal decomposition temperature is 600°C in the air atmosphere, the char formation rate is 20-27.2%. The thermal decomposition releases methanol and other flammable gases. The ratio is 50-95%.

The present invention also provides a preparation method of the flax cellulose-based phosphorus-based intumescent flame retardant, by adding 2-10 parts by weight of carbon source, 1-10 parts by weight of acid source and Source mixes are prepared.

The present invention also provides an epoxy resin composite material based on the flax cellulose-based phosphorus-based intumescent flame retardant, comprising 100 parts by mass of epoxy resin, 20-60 parts by mass of curing agent, 5-20 parts by mass of the flax Cellulose-based phosphorus-based intumescent flame retardant. It is obtained by mixing and stirring the combination uniformly.

The curing agent used can be the conventional curing agent used in this field, preferably 33 parts by mass.

The above components are mixed and stirred evenly, put into the mold, cured, demoulded, and the epoxy resin composite material is obtained.

The epoxy resin composite material prepared above has excellent flame retardancy, its limiting oxygen index exceeds 29, its vertical combustion rating is V-0, and its total heat release in combustion decreases by more than 60% compared with pure epoxy resin. Among them, the epoxy resin composite material prepared by using carboxylated flax cellulose with a high carboxyl content of 32.2% as a carbon source has outstanding and excellent flame retardant effect.

In the present invention, carboxylated flax cellulose with high carboxyl content is used as a carbon source, and the melamine-coated ammonium polyphosphate exerts a synergistic effect and can be used as a flame retardant in resins and rubbers, especially in epoxy resin flame retardants. It is used in epoxy resin intumescent flame retardant, relying on its high char formation and high flame retardancy, so that the epoxy resin has good flame retardant performance under the condition of low flame retardant additive amount, thus Promote the application of carboxylated flax fiber in the field of intumescent flame retardant.

Mechanism of the present invention is:

The invention prepares flax cellulose with high carboxyl content and uses it as a novel carbon source to play a synergistic effect with ammonium polyphosphate to obtain an intumescent flame retardant. The carboxyl group content of this new type of carbon source is 10-40%, the amount of char formation exceeds 27.2%, the amount of flammable gases such as methanol is greatly reduced during the combustion process, and the carbon layer obtained by expansion has a uniform and dense structure and a high expansion rate, which is slightly different from melamine. The flame retardant formed by capsule-coated ammonium polyphosphate has the characteristics of excellent expansion and high flame retardant efficiency. Based on 100 parts by mass of epoxy resin (the amount of curing agent is 21 parts), when the amount of ammonium polyphosphate coated with melamine microcapsules in the intumescent flame retardant used is 3 to 10 parts by mass, the amount of carbon source is 2～10 parts by mass, the limiting oxygen index of the obtained epoxy resin composite material exceeds 29, the vertical combustion grade is V-0, the maximum value of the total heat release of combustion decreases by more than 60%, and has low water absorption (water absorption within 24 hours less than 4%), high mechanical properties (tensile strength and notched impact strength are not lower than 85% and 130% of pure epoxy resin, respectively), and its comprehensive performance is far superior to the common carbon source pentaerythritol and pure starch. It has wide application value.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) Compared with the existing technology, the carbon source of the flame retardant of the present invention, the carboxyl flax fiber of high carboxyl content, has the high char formation rate, and the char layer structure is dense and uniform, and the combustible gas that combustion produces is few, synergistic retardation It has high combustion efficiency and can be used as a new type of carbon source for intumescent flame retardants.

(2) The inventive use of high carboxyl flax fiber as a new type of char-forming agent in the intumescent flame retardant has achieved remarkable results and greatly broadened the application range of flax fiber and its derivatives.

(3) Through comparison, it was found that carboxy-flax cellulose with high carboxyl content and ammonium polyphosphate exerted a synergistic effect and was used in the intumescent flame retardant of epoxy resin to obtain a high degree of expansion, a dense carbon layer structure, and a good flame retardant effect. Intumescent flame retardant.

Description of drawings

Fig. 1 is the infrared spectrogram of the carboxyl flax cellulose prepared by embodiment 1, 2 and 4. Wherein, curve a is pure flax fiber, curve b is OLF12.6 prepared in Example 1, curve c is OLF27.4 prepared in Example 2, and curve d is OLF34.5 prepared in Example 4.

Fig. 2 is the carbon nuclear magnetic resonance spectrogram of the carboxy flax cellulose prepared in embodiment 1, 2 and 4. Wherein, curve a is pure flax fiber, curve b is OLF12.6 prepared in Example 1, curve c is OLF27.4 prepared in Example 2, and curve d is OLF34.5 prepared in Example 4.

Fig. 3 is the thermogravimetric analysis spectrogram of the carboxyl flax cellulose prepared in embodiment 1, 2 and 4. Wherein, curve a is pure flax fiber, curve b is OLF12.6 prepared in Example 1, curve c is OLF27.4 prepared in Example 2, and curve d is OLF34.5 prepared in Example 4.

Fig. 4 is the thermogravimetric infrared spectrogram of carboxy-flax cellulose prepared in Examples 1, 2 and 4. Wherein, curve a is pure flax fiber, curve b is OLF12.6 prepared in Example 1, curve c is OLF27.4 prepared in Example 2, and curve d is OLF34.5 prepared in Example 4.

Fig. 5 is average heat release rate (A), total heat release (B) and total smoke density spectrum (C) in the cone calorimetry test of example 5, 6 and 7, wherein, curve a is pure epoxy Resin, curve b is comparative example 2, curve c is comparative example 1, curve d is embodiment 5, curve e is embodiment 6, and curve f is embodiment 7.

Fig. 6 is the appearance of the charcoal layer of the sample after the cone calorimetry combustion test of Examples 5, 6 and 7.

Detailed ways

The present invention will be further described in detail below with reference to the examples and drawings, but the implementation of the present invention is not limited thereto.

The experimental methods in the following examples that do not specify specific conditions are generally in accordance with conventional conditions, such as the conditions in "Beilstein Organic Chemistry Handbook" (Chemical Industry Press, 1996), or in accordance with the conditions suggested by the manufacturer. Ratios and percentages are by weight unless otherwise indicated.

Unless otherwise defined or stated, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described can be applied to the method of the present invention.

All reagents used in the following examples can be purchased from commercial sources.

Comparative example 1

27.5g of epoxy resin curing agent (D230) and 82.5g of bisphenol A epoxy resin (DGEBA) were placed in a plastic beaker, stirred and mixed for 10min; the mixture was placed in a vacuum oven at 40°C for 1 hour; then 4.11g Melamine-coated ammonium polyphosphate (MFAPP) and 5.48g pentaerythritol (PER) were stirred and mixed for 5 minutes, then stirred at 2000 rpm for 3 minutes using a high-speed mixer until a uniform and stable mixture was formed; poured into a polytetrafluoroethylene mold and placed in vacuum drying Curing in the box, the curing condition is 55°C for 45 minutes, then the temperature is raised to 85°C for 90 minutes, and the mold is demoulded to obtain a composite material sample.

Comparative example 2

27.5g of epoxy resin curing agent (D230) and 82.5g of bisphenol A epoxy resin (DGEBA) were placed in a plastic beaker, stirred and mixed for 10min; the mixture was placed in a vacuum oven at 40°C for 1 hour; then 4.11g Melamine-coated ammonium polyphosphate (MFAPP) and 5.48g flax fiber were stirred and mixed for 5 minutes, and then stirred at 2000rpm for 3 minutes using a high-speed mixer until a uniform and stable mixture was formed; poured into a polytetrafluoroethylene mold and placed in a vacuum oven Medium curing, the curing condition is 55°C for 45 minutes, then the temperature is raised to 85°C for 90 minutes, and the mold is demoulded to obtain a composite material sample.

Example 1

Immerse 100 parts of flax fibers in 1500 parts of distilled water, drop ₂ parts of pre-configured 0.1mol/L CuSO solution, slowly add 24.6 parts of hydrogen peroxide (H ₂ O ₂ content 30%) solution, place at 30 ℃ constant temperature stirring reaction for 72 hours, suction filtration and distilled water to wash the carboxy flax fiber, put it in a drying oven at 80 ℃ and dry for 12 hours. After taking it out, it was pulverized with a high-speed mixer for 6 minutes to obtain a solid product. The carboxyl content was measured to be about 12.6% by titration method, and the marked sample was OLF12.6.

Example 2

Immerse 100 parts of flax fibers in 1500 parts of distilled water, drop 3 parts of pre-configured 0.05mol/L _FeCl solution, slowly add 48.6 parts of hydrogen peroxide (H ₂ O ₂ content 30%) solution, place at 35 ℃ constant temperature stirring reaction for 60 hours, suction filtration and distilled water to wash the carboxy flax fiber, put it in a drying oven at 85 ℃ and dry for 12 hours. After taking out, the fiber was pulverized with a high-speed mixer for 6 minutes to obtain a solid product. The carboxyl content was measured to be about 27.4% by titration method, and the marked sample was OLF27.4.

Example 3

Soak 100 parts of flax fibers in 1500 parts of distilled water, drop 3 parts of pre-configured 0.05mol/L CoCl solution _, slowly add 50.9 parts of hydrogen peroxide (H ₂ O ₂ content 30%) solution, place at 40 ℃ constant temperature stirring reaction for 70 hours, will be suction filtered and washed with distilled water carboxy flax fiber, put into 85 ℃ drying oven to dry for 12 hours. After taking it out, the fiber was pulverized with a high-speed mixer for 6 minutes to obtain a solid product. The carboxyl content was measured to be about 28.4% by titration method, and the marked sample was OLF28.4.

Example 4

Immerse 100 parts of flax fibers in 1500 parts of distilled water, drop 3 parts of pre-configured 0.05mol/L _NiCl solution, slowly add 92.2 parts of hydrogen peroxide (H ₂ O ₂ content 30%) solution, place at 40 ℃ constant temperature stirring reaction for 70 hours, suction filtration and distilled water to wash the carboxy flax fiber, put it in a drying oven at 85 ℃ for 12 hours. After taking it out, the fiber was pulverized with a high-speed mixer for 6 minutes to obtain a solid product. The carboxyl content was measured to be about 34.5% by titration method, and the marked sample was OLF34.5.

Carboxylated flax fibers prepared in Examples 1-4 were analyzed by infrared, nuclear magnetic resonance, thermogravimetric, and thermogravimetric infrared, and the results are shown in Figs. 1-4. It can be seen from Figure 1 that compared with flax, OLF has a new strong absorption peak at 1735cm ^-1 , which is attributed to the C=O stretching vibration peak. With the increase of carboxyl content, the intensity of the absorption peak at 1735cm ^-1 Increase. At the same time, at 1640cm ^-1 corresponding to the absorption vibration peak of the flax fiber adsorbed water hydroxyl group, its intensity decreased obviously. The results of infrared spectrum showed that the flax fiber was oxidized by H ₂ O ₂ and the product was carboxylated flax fiber. As can be seen from Figure 2, 61ppm is attributed to the characteristic absorption peak of C6 of the side chain of the glucose ring, 74ppm, 73ppm, and 71ppm are respectively assigned to the characteristic absorption peaks of C3, C2 and C5 of the glucose skeleton, and 101ppm is the characteristic absorption peak of C1. Compared with the NLF curve, the curves OLF12.6, OLF27.4 and OLF34.5 have a new characteristic absorption peak at 173ppm, which belongs to the response peak after the hydroxyl group on C6 is oxidized to carboxyl group. , the intensity of the response peak gradually increases. From Figure 2, it can be confirmed that the primary hydroxyl group of C6 is selectively oxidized to carboxyl group, and the curve has no new absorption peak at 220-230ppm, so it is judged that the hydroxyl group at positions C2 and C3 does not oxidize during the reaction process. reaction. Figure 3 shows that as the content of carboxyl groups increases, the amount of carbon residue from thermal decomposition of OLF gradually increases. In an intumescent flame retardant system, increasing the carbonization rate can reduce the amount of flammable volatile products that escape into the combustion zone and play a role in heat insulation. The role of oxygen barrier reduces the flammability of materials under the carbon layer; as can be seen from Figure 4, the presence of carboxyl groups can play a role in catalyzing the formation of glucose units into carbon. At the same time, the presence of carboxyl groups makes OLF produce less carbon-containing elements during the combustion process. As the content of carboxyl groups increases, the catalytic char formation effect is more obvious, the release of carbon-containing gas is less, and more carbon elements are retained in the condensed phase, so that the char formation rate of OLF gradually increases. Therefore, the OLF of the present invention can be used as a novel carbon source.

Example 5

27.5g of epoxy resin curing agent (D230) and 82.5g of bisphenol A epoxy resin (DGEBA) were placed in a plastic beaker, stirred and mixed for 10min; the mixture was placed in a vacuum oven at 40°C for 1 hour; then 4.11g The ammonium polyphosphate (MFAPP) coated with melamine and the carboxyl flax fiber (OLF12.6) prepared by 5.48g embodiment 1 were stirred and mixed for 5min, then utilized a high-speed stirrer, and stirred for 3min at 2000rpm until a uniform and stable mixture was formed; Place in a tetrafluoroethylene mold and cure in a vacuum drying oven. The curing condition is 55°C for 45 minutes, then raise the temperature to 85°C for 90 minutes, and demould to obtain a composite material sample.

Example 6

27.5g of epoxy resin curing agent (D230) and 82.5g of bisphenol A epoxy resin (DGEBA) were placed in a plastic beaker, stirred and mixed for 10min; the mixture was placed in a vacuum oven at 40°C for 1 hour; then 4.11g The ammonium polyphosphate (MFAPP) coated with melamine and the carboxyl flax fiber (OLF27.4) prepared by 5.48g embodiment 2 were stirred and mixed for 5min, then utilized a high-speed stirrer, and stirred for 3min at 2000rpm until a uniform and stable mixture was formed; Place in a tetrafluoroethylene mold and cure in a vacuum drying oven. The curing condition is 55°C for 45 minutes, then raise the temperature to 85°C for 90 minutes, and demould to obtain a composite material sample.

Example 7

27.5g of epoxy resin curing agent (D230) and 82.5g of bisphenol A epoxy resin (DGEBA) were placed in a plastic beaker, stirred and mixed for 10min; the mixture was placed in a vacuum oven at 40°C for 1 hour; then 4.11g The ammonium polyphosphate (MFAPP) coated with melamine and the carboxyl flax fiber (OLF34.5) prepared by 5.48g embodiment 4 were stirred and mixed for 5min, then utilized a high-speed stirrer, and stirred for 3min at 2000rpm until a uniform and stable mixture was formed; Place in a tetrafluoroethylene mold and cure in a vacuum drying oven. The curing condition is 55°C for 45 minutes, then raise the temperature to 85°C for 90 minutes, and demould to obtain a composite material sample.

Various performance indicators of the epoxy resin composite materials prepared in Examples 5-7 were tested, and the results are shown in Table 1 and Table 2, and Fig. 5 and Fig. 6 . Among them, Table 1 shows the flame retardant properties of intumescent flame retardant epoxy resins prepared with different carbon sources, and Table 2 shows the cone calorimetry parameters of intumescent flame retardant epoxy resins prepared with pure EP and different carbon sources.

It can be seen from Table 1 that the carbon source is PER, NLF, OLF (amount of 5 parts) on the flame retardancy of MFAPP/EP. Under the same addition amount (MFAPP dosage is 3.75 parts), when PER is used as a carbon source, The LOI of EP is only 24.5%, and there is no flame retardant grade, and the flame retardant effect is the worst. This is because the char formation rate of PER is only 0.9%, which cannot form an effective intumescent char layer and play a flame retardant effect. When 5% OLF was added as carbon source, the flame retardancy of EP gradually improved with the increase of carboxyl content, and the flame retardancy of MFAPP/EP with OLF27.4 as carbon source was the best. With the increase of carboxyl content, the thermal stability of OLF decreases, and the carbonization temperature drops to match the initial decomposition temperature of MFAPP; and the amount of residual carbon gradually increases, and the flammable gas released by combustion gradually decreases, thus improving the flame retardancy of EP performance. However, because the carbonization temperature of OLF34.4 decreased too much, before the decomposition of MFAPP, it had been decomposed into charcoal in advance, and finally the porous charcoal layer could not be formed, and the flame retardant performance of EP was reduced. The flame retardant effect of using OLF27.4 as a carbon source is obviously better than that of pure flax fiber, mainly because OLF27.4 is more likely to form carbon during combustion to form a porous carbon layer structure, which can reduce the amount of flammable volatile products that escape into the combustion zone, and at the same time A smaller amount of combustibles released by combustion, etc.

Table 1 Flame retardant properties of intumescent flame retardant epoxy resins prepared with different carbon sources

Table 2 Cone calorimetry parameters of intumescent flame retardant epoxy resins prepared from pure EP and different carbon sources

It can be seen from the cone calorimetry diagram in Figure 5 that the heat release rate (PHRR) of pure epoxy resin is 1247.3kW/m ² , the total heat release (THR) is 49.8MJ/m ² , and the smoke density (TSP) is 26.7m ² /kg, indicating that epoxy resin is a flammable material. When different flame retardants (MFAPP/PER, MFAPP/NLF and MFAPP/OLF) are introduced, the PHRR and THR of epoxy resin can be reduced. value. Among them, MFAPP/OLF27.4 decreased the most, PHRR decreased to 553.5kW/m ² , and THR decreased to 19.4MJ/m ² . At the same time, the addition of MFAPP/OLF27.4 to epoxy resin greatly reduces the total smoke emission (TSP) of the material. This is because OLF27.4 and MFAPP have a better synergistic flame retardant effect. A relatively continuous and dense carbon layer can be formed in the medium, thereby hindering the transfer of heat, flammable gas and oxygen to the interior of the substrate, and playing a good barrier role, thereby achieving a better flame retardant effect. This inference can be confirmed by the picture shown in Figure 6, that is, when the carbon source is carboxylated flax fiber, the char formation rate after combustion is higher (the maximum value exceeds 41%), which is convenient for covering the gas released by the decomposition of MFAPP, making the system The expansion rate is better, and the effect of heat and oxygen insulation is more sufficient, so the flame retardant effect is better.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (5)

1. a kind of flax fiber element base phosphorus expanding fire retardant, it is characterised in that：Charcoal source including 2~10 parts by weight, 3~10 The ammonium polyphosphate of the melamine cladding of parts by weight；

The charcoal source is the carboxyl flax fiber of high-carboxyl-content, is prepared by method comprising the following steps：By flax In fiber soaking water, H is added₂O₂And catalyst, it is stirred to react, obtains the carboxyl flax fiber of high-carboxyl-content；

Flax fiber and H used₂O₂Mass ratio be 100:24.6~100:92.2；The condition being stirred to react is 30~40 60~72h is stirred to react at DEG C；

The catalyst is copper sulphate, iron chloride, cobalt chloride or nickel chloride；

The carboxyl-content of the carboxyl flax fiber of the high-carboxyl-content is 12.6~34.5%.

2. a kind of preparation method of flax fiber element base phosphorus expanding fire retardant described in claim 1, it is characterised in that logical It crosses and is mixed with to obtain by the ammonium polyphosphate of the melamine cladding of the charcoal source of 2~10 parts by weight, 3~10 parts by weight.

3. a kind of epoxy resin composite material based on flax fiber element base phosphorus expanding fire retardant described in claim 1, It is characterized by comprising 100 mass parts epoxy resin, 20~60 mass parts curing agent, 5~20 mass parts are described in claim 1 Flax fiber element base phosphorus expanding fire retardant.

4. the preparation method of the epoxy resin composite material described in claim 3, it is characterised in that the component to be mixed Uniformly, it is added in mold, cures, demoulding obtains epoxy resin composite material.

5. application of the flax fiber element base phosphorus expanding fire retardant described in claim 1 in resin, rubber.