Preparation and use method of polydopamine-coated red phosphorus microcapsule flame retardant
Technical Field
The invention belongs to the technical field of flame retardants, and particularly relates to a preparation method and a use method of a polydopamine-coated red phosphorus microcapsule flame retardant.
Background
With the rapid development of economy in China, high polymer materials are used all over the world, and thermosetting resin is applied to various industries. Unsaturated polyurethane resins are preferred by many because of their high functionality as thermosets. The unsaturated polyurethane resin has good physical and chemical properties after being cured, the bonding strength and flexibility are well shown on the surfaces of metal and nonmetal materials, the hardness is high, the dielectric property is excellent, the set shrinkage rate is small, the size of a product is stable, the product is stable to alkali and most of solvents, and the unsaturated polyurethane resin can resist chemical corrosion, so that the unsaturated polyurethane resin is widely applied to national defense and other industrial production. However, the polymer belongs to heat-sensitive substances, and the inflammability is one of the main defects of the polymer, so that the hazard of fire is greatly increased, and the application of the polymer is limited. In order to prevent and reduce the fire loss, it is very effective to use flame retardant materials for daily life and production materials. The use of fire retardant materials allows better conditions to be created to effectively extinguish incipient fires and minimize fire losses. Therefore, increasing the flame retardancy of unsaturated resins is receiving attention from more and more researchers.
The conventional flame retardants have the disadvantage that only substances which cannot be burnt are required, and halogen-based flame retardants or flame-retardant mixtures comprising a combination of halogen-containing flame retardants are the first to be considered for use in the materials. The halogen flame retardant has a great advantage of good flame retardant effect, but has the following disadvantages: the first is that it releases a large amount of smoke when burned, and the second is that the hydrogen halide gas released is very corrosive. The inorganic flame retardant is excellent in thermal stability, can suppress the generation of smoke well, is extremely reduced in the amount of harmful gas in endothermic decomposition, and is low in cost. However, when it is added into a flame-retardant system, the addition amount is large, the effect of compatibility with organic substances is not good, the mechanical property of the product is also seriously influenced, and therefore, the use amount of the inorganic flame retardant is gradually reduced.
The Red Phosphorus (RP) flame retardant is a flame retardant represented by red phosphorus, is purplish red or slightly brown amorphous powder, is an organic halogen-free flame retardant, has the characteristics of excellent thermal stability, nonvolatility, no generation of corrosive gas, good flame retardant effect, good electrical insulation and the like, and has the advantages of no toxicity risk, small addition amount, insolubility, high melting point and the like in the use process. But the weaknesses are that the processing property of red phosphorus is poor, the compatibility with resin is not good, and the mechanical property of the processed and manufactured material is poor.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method and a use method of a polydopamine-coated red phosphorus microcapsule flame retardant.
The invention is realized by the following technical scheme.
A preparation method of a polydopamine-coated red phosphorus microcapsule flame retardant comprises the following operation steps:
(1) mixing a disodium hydrogen phosphate solution and a sodium dihydrogen phosphate solution, and adjusting the pH value to 8-9 by using any one of a sodium hydroxide solution or a potassium hydroxide solution to prepare a buffer solution;
(2) adding 5-9 parts by weight of red phosphorus flame retardant, 0.3-0.6 part by weight of dopamine and 0.5-1.0 part by weight of rare earth oleate into 1000 parts by weight of buffer solution, magnetically stirring and reacting at 20-40 ℃ for 25-35min, and performing vacuum filtration to obtain a layer of red phosphorus coated with polydopamine;
(3) replacing the red phosphorus flame retardant in the step (2) with one layer of polydopamine-coated red phosphorus, repeating the step (2) to obtain two layers of polydopamine-coated red phosphorus, replacing the two layers of polydopamine-coated red phosphorus with the red phosphorus flame retardant in the step (2), repeating the step (2) to obtain three layers of polydopamine-coated red phosphorus, drying and grinding the red phosphorus, and then sieving the red phosphorus with a 200-mesh sieve to obtain the polydopamine-coated red phosphorus microcapsule flame retardant;
the oleic acid rare earth is prepared by the following method: adding 20-28 parts by weight of ytterbium chloride and 13-16 parts by weight of samarium chloride into 160-200 parts by weight of water, then continuously adding 40-50 parts by weight of sodium oleate, heating the mixture to 60-70 ℃, preserving heat, continuously stirring for 3-4 hours, pouring out an upper water layer, washing the precipitate with deionized water, and evaporating to remove water to obtain rare earth oleate.
Specifically, in the step (1), the concentration of the disodium hydrogen phosphate solution and the concentration of the sodium dihydrogen phosphate solution are both 0.1mol/L, and the concentration of the sodium hydroxide solution or the potassium hydroxide solution is both 0.5 mol/L.
Specifically, in the step (2), the rotation speed of the magnetic stirring is 250-300 r/min.
Specifically, in the step (3), the drying temperature is 75-80 ℃, and the drying time is 2-3 hours.
The invention also provides a use method of the polydopamine-coated red phosphorus microcapsule flame retardant, which comprises the following steps: adding 8-12 parts by weight of polydopamine-coated red phosphorus microcapsule flame retardant into 80-90 parts by weight of unsaturated polyurethane resin, carrying out ultrasonic treatment for 3-5min, sequentially adding 2-4 parts of curing agent and 2-4 parts of accelerator, fully stirring, and carrying out curing treatment for 2-3 days to obtain the flame-retardant resin.
Specifically, the acid value of the unsaturated polyurethane resin was 28mgKOH/g, and the solid content was 28%.
Specifically, the curing agent is any one of vinyl triamine, diaminocyclohexane and ethylenediamine, and the accelerator is any one of dibutyltin dilaurate and stannous octoate.
According to the technical scheme, the beneficial effects of the invention are as follows:
the preparation method of the polydopamine-coated red phosphorus microcapsule flame retardant provided by the invention is simple to operate and low in cost, the polydopamine is used for coating the red phosphorus flame retardant by three layers, so that the water resistance of the red phosphorus flame retardant can be effectively improved, the compatibility between the polydopamine and a polymer is improved, various mechanical properties of flame-retardant resin are further ensured, and the polydopamine and the red phosphorus flame retardant can generate phosphorus-nitrogen synergistic flame retardance, so that the flame retardance and the thermal stability are more excellent. The oleic acid rare earth provided by the invention can effectively promote dopamine polymerization to generate polydopamine nanoparticles, can also improve the adsorption effect of the polydopamine nanoparticles on a red phosphorus flame retardant, ensures the density of a polydopamine coating layer of the red phosphorus flame retardant, and further improves various mechanical properties and flame retardant properties of flame retardant resin.
Drawings
FIG. 1 is a thermogravimetric plot of UPR-0, UPR-RP and UPR-MRP, wherein UPR-0 is an unsaturated polyurethane resin to which no flame retardant is added, UPR-RP is an unsaturated polyurethane resin to which unmodified red phosphorus is added, and UPR-MRP is an unsaturated polyurethane resin to which polydopamine-coated tertiary red phosphorus is added.
FIG. 2 is a scanning electron micrograph of the surface morphology of the UPR-0 tensile fracture surface.
FIG. 3 is a scanning electron micrograph of the surface morphology of the UPR-RP tensile fracture surface.
FIG. 4 is a scanning electron micrograph of the surface morphology of the UPR-MRP tensile fracture surface.
Detailed Description
The principles and features of this invention are described in connection with the drawings and the detailed description of the invention, which are set forth below as examples to illustrate the invention and not to limit the scope of the invention. The pharmaceutical products used in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods used by those skilled in the art without further specification.
Example 1
A preparation method of a polydopamine-coated red phosphorus microcapsule flame retardant comprises the following operation steps:
(1) mixing equal volume of 0.1mol/L disodium hydrogen phosphate solution and 0.1mol/L sodium dihydrogen phosphate solution, and adjusting pH value to 8 with 0.5mol/L sodium hydroxide solution to obtain buffer solution;
(2) adding 5 parts by weight of red phosphorus flame retardant, 0.3 part by weight of dopamine and 0.5 part by weight of rare earth oleate into 950 parts by weight of buffer solution, magnetically stirring and reacting at the temperature of 20 ℃ at the rotating speed of 250r/min for 25min, and performing vacuum filtration to obtain a layer of polydopamine-coated red phosphorus;
(3) replacing one layer of polydopamine-coated red phosphorus with the red phosphorus flame retardant in the step (2), repeating the step (2) to obtain two layers of polydopamine-coated red phosphorus, replacing the two layers of polydopamine-coated red phosphorus with the red phosphorus flame retardant in the step (2), repeating the step (2) to obtain three layers of polydopamine-coated red phosphorus, drying the polydopamine-coated red phosphorus at 75 ℃ for 2 hours, grinding the polydopamine-coated red phosphorus, and sieving the ground polydopamine-coated red phosphorus with a 200-mesh sieve to obtain a polydopamine-coated red phosphorus microcapsule flame retardant;
the oleic acid rare earth is prepared by the following method: adding 20 parts by weight of ytterbium chloride and 13 parts by weight of samarium chloride into 160 parts by weight of water, then continuously adding 40 parts by weight of sodium oleate into the mixture, heating the mixture to 60 ℃, preserving heat, continuously stirring for 3 hours, pouring out an upper water layer, washing precipitates by using deionized water, and evaporating to remove water to obtain the rare earth oleate.
The embodiment also provides a use method of the polydopamine-coated red phosphorus microcapsule flame retardant, which comprises the following steps: adding 8 parts by weight of polydopamine-coated red phosphorus microcapsule flame retardant into 80 parts by weight of unsaturated polyurethane resin, carrying out ultrasonic treatment for 3min, sequentially adding 2 parts by weight of vinyl triamine and 2 parts by weight of dibutyltin dilaurate, fully stirring, and carrying out curing treatment for 2 days to obtain the flame-retardant resin, wherein the acid value of the used unsaturated polyurethane resin is 28mgKOH/g, and the solid content is 28%.
Example 2
A preparation method of a polydopamine-coated red phosphorus microcapsule flame retardant comprises the following operation steps:
(1) mixing equal volume of 0.1mol/L disodium hydrogen phosphate solution and 0.1mol/L sodium dihydrogen phosphate solution, and adjusting pH value to 8.5 with 0.5mol/L sodium hydroxide solution to obtain buffer solution;
(2) adding 7 parts by weight of red phosphorus flame retardant, 0.5 part by weight of dopamine and 0.8 part by weight of rare earth oleate into 980 parts by weight of buffer solution, magnetically stirring at the temperature of 30 ℃ and at the rotating speed of 280r/min for reaction for 30min, and carrying out vacuum filtration to obtain a layer of polydopamine-coated red phosphorus;
(3) replacing one layer of polydopamine-coated red phosphorus with the red phosphorus flame retardant in the step (2), repeating the step (2) to obtain two layers of polydopamine-coated red phosphorus, replacing the two layers of polydopamine-coated red phosphorus with the red phosphorus flame retardant in the step (2), repeating the step (2) to obtain three layers of polydopamine-coated red phosphorus, drying the polydopamine-coated red phosphorus at 78 ℃ for 2.5 hours, grinding the polydopamine-coated red phosphorus, and sieving the polydopamine-coated red phosphorus with a 200-mesh sieve to obtain the polydopamine-coated red phosphorus microcapsule flame retardant;
the oleic acid rare earth is prepared by the following method: adding 24 parts by weight of ytterbium chloride and 15 parts by weight of samarium chloride into 180 parts by weight of water, then continuously adding 45 parts by weight of sodium oleate, heating the mixture to 65 ℃, preserving heat, continuously stirring for 3.5 hours, pouring out an upper water layer, washing the precipitate with deionized water, and evaporating to remove water to obtain the rare earth oleate.
The embodiment also provides a use method of the polydopamine-coated red phosphorus microcapsule flame retardant, which comprises the following steps: adding 10 parts by weight of polydopamine-coated red phosphorus microcapsule flame retardant into 85 parts by weight of unsaturated polyurethane resin, carrying out ultrasonic treatment for 4min, sequentially adding 3 parts of diaminocyclohexane and 3 parts of stannous octoate, fully stirring, and carrying out curing treatment for 2 days to obtain the flame-retardant resin, wherein the acid value of the used unsaturated polyurethane resin is 28mgKOH/g, and the solid content is 28%.
Example 3
A preparation method of a polydopamine-coated red phosphorus microcapsule flame retardant comprises the following operation steps:
(1) mixing equal volume of 0.1mol/L disodium hydrogen phosphate solution and 0.1mol/L sodium dihydrogen phosphate solution, and adjusting pH to 9 with 0.5mol/L sodium hydroxide solution to obtain buffer solution;
(2) adding 9 parts by weight of red phosphorus flame retardant, 0.6 part by weight of dopamine and 1.0 part by weight of rare earth oleate into 1000 parts by weight of buffer solution, magnetically stirring and reacting at 40 ℃ at a rotating speed of 300r/min for 35min, and performing vacuum filtration to obtain a layer of polydopamine-coated red phosphorus;
(3) replacing one layer of polydopamine-coated red phosphorus with the red phosphorus flame retardant in the step (2), repeating the step (2) to obtain two layers of polydopamine-coated red phosphorus, replacing the two layers of polydopamine-coated red phosphorus with the red phosphorus flame retardant in the step (2), repeating the step (2) to obtain three layers of polydopamine-coated red phosphorus, drying the polydopamine-coated red phosphorus at 80 ℃ for 3 hours, grinding the polydopamine-coated red phosphorus, and sieving the ground polydopamine-coated red phosphorus with a 200-mesh sieve to obtain a polydopamine-coated red phosphorus microcapsule flame retardant;
the oleic acid rare earth is prepared by the following method: adding 28 parts by weight of ytterbium chloride and 16 parts by weight of samarium chloride into 200 parts by weight of water, then continuously adding 50 parts by weight of sodium oleate into the mixture, heating the mixture to 70 ℃, preserving heat, continuously stirring for 4 hours, pouring out an upper water layer, washing precipitates by using deionized water, and evaporating to remove water to obtain the rare earth oleate.
The embodiment also provides a use method of the polydopamine-coated red phosphorus microcapsule flame retardant, which comprises the following steps: adding 12 parts by weight of polydopamine-coated red phosphorus microcapsule flame retardant into 90 parts by weight of unsaturated polyurethane resin, carrying out ultrasonic treatment for 5min, sequentially adding 4 parts by weight of ethylenediamine and 4 parts by weight of stannous octoate, fully stirring, and carrying out curing treatment for 3 days to obtain the flame-retardant resin, wherein the acid value of the used unsaturated polyurethane resin is 28mgKOH/g, and the solid content is 28%.
Comparative example 1
The rare earth oleate is not added in the step (2), and the rest of the operation steps are completely the same as those in the embodiment 1.
Sample testing method:
1. oxygen index test
The oxygen index (10I) is the minimum value required for the material to undergo flamed combustion under a predetermined condition in the presence of a mixed gas of oxygen and nitrogen to support combustion. A high oxygen index indicates that the material is not readily combustible and is a nonflammable material, while a low oxygen index indicates that the material is readily combustible and is a flammable or combustible material, generally speaking, the flammable material has an oxygen index of less than 22, the flammable material has an oxygen index in the range of 22 to 27, and the nonflammable material has an oxygen index of greater than 27. The oxygen index determinator used in the experiment is implemented by executing the GB-T2406-1993 standard, and a sample is made into 15cm multiplied by 1cm multiplied by 3 cm;
TABLE 1 flame retardant resin oxygen index test study
Item
|
Oxygen index%
|
Example 1
|
30.8
|
Comparative example 1
|
29.1
|
Example 2
|
30.9
|
Example 3
|
31.0
|
Without addition of MRP
|
23
|
RP flame retardants were untreated
|
28.3
|
Coating with polydopamine 1 time
|
29.2
|
Poly dopamine coating 2 times
|
29.5
|
Polydopamine coating 4 times
|
29.3 |
As can be seen from Table 1, the flame retardant effect of polydopamine-coated red phosphorus (MRP) on unsaturated resin is better, the main reason is that the polydopamine serving as a wall material contains flame retardant element nitrogen and can generate good flame retardant synergistic effect with phosphorus serving as a core material through surface modified Red Phosphorus (RP), so that the flame retardant effect on unsaturated resin is further improved, meanwhile, the polydopamine can be coated more excellently and has stronger flame retardant effect through the addition of rare earth oleate, and the result of coating RP for 3 times is found to be best through the measurement of oxygen index by coating for different times, because phosphorus-nitrogen synergy has the best element ratio, when RP is coated for 3 times, a carbon layer formed during combustion is most compact, so that the flame retardant effect is achieved, and coating is carried out for 4 times, although the adhesion capability is enhanced, the phosphorus content in MRP is also reduced, the flame retarding ability is lowered.
2. Tensile test
The universal testing machine is also called a universal tensile testing machine, the specification of a mechanical property testing sample strip is 15cm multiplied by 1cm multiplied by 3cm, according to the execution standard GB/T1040.2-2006, a sample of the poly-dopamine iron coated red phosphorus flame retardant is made into a sample according to the standard GB/T1040.2-2006, the sample is subjected to a tensile test by using the universal testing machine to research the tensile strength and the breaking elongation after coating, and the mechanical property of the material is relatively better compared with that of the flame retardant formula. The specification of a mechanical property test sample strip is 15cm multiplied by 1cm multiplied by 30 mm;
TABLE 2 tensile Property results for flame retardant resins
The unsaturated polyurethane added with MRP has relatively improved tensile property, the tensile strength is improved compared with the unsaturated polyurethane directly added with BR, and the tensile elastic modulus is increased, because the compatibility of RP and unsaturated resin is improved after polydopamine coating, and the mechanical property is improved.
3. Thermogravimetric experiments
The conditions required by the experiment are that inert gas nitrogen is used as protective gas and tap water is used as coolant, the pressure difference of the protective gas is about 0.1Mpa to 0.15Mpa, the gas flow is controlled at 30ml/min, the mass of the sample is 5 mg to 10mg, and the temperature is raised to about 650 ℃. In order to obtain the activation energy better, the heating rates are respectively 5 ℃/min, 10 ℃/min, 15 ℃/min and 20 ℃/min. Before the thermogravimetric experiment, a sample is firstly kept still on a microcomputer balance for a period of time, and the experiment is started after the balance is stable.
As shown in the attached figure 1, the thermal stability of UPR-0, UPR-RP and UPR-MRP is enhanced in sequence, so that polydopamine serving as a mussel-like material is firmly adhered to the surface of a flame retardant, the mussel-like material serving as a wall material and the flame retardant serving as a core material maximally maintain the original characteristics of the flame retardant, and a carbon source is added.
4. Scanning electron microscope test
The method comprises the steps of firstly carrying out a cone calorimetric experiment and a tensile experiment on UPR-0, UPR-RP and UPR-MRP in the experiment, then collecting burnt residual ash and a tensile sample, then preparing a special sample for a scanning electron microscope, then plating a metal layer on the surface of a sample material, using an SBC-12 type ion sputtering instrument, respectively scanning the surface and a tensile fracture surface of the material residual ash after amplifying 50 times, 500 times and 1000 times under the experiment condition of 26kv under the vacuum condition according to the working principle of the scanning electron microscope, and selecting a clear and visible relatively uniform area for imaging.
As can be seen from the attached figures 2-4, compared with the fracture surface of the UPR-MRP, the UPR-RP fracture surface has more particles, and a large gap exists between the RP and the base material, so that the compatibility of the modified RP is obviously greatly improved, the gap between the additive and the base material is reduced, the influence of the addition of the flame retardant on the mechanical property of the base material is reduced, and the reason why the mechanical property of the red phosphorus modified by the polydopamine is obviously improved can be well explained.