Fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material and preparation method thereof
1. A preparation method of a fiber reinforced flame retardant polyurethane foam wave-absorbing composite material comprises the following steps:
(1) surface treatment of the wave absorber:
treatment of the first absorbent: treating the first absorbent by using 30-50% nitric acid solution, wherein the first absorbent is a resistance absorbent;
and (3) treating a second wave absorbing agent: treating a second wave absorbing agent by using a 20-40% silane coupling agent solution, wherein the second wave absorbing agent is a magnetic loss absorbent;
(2) surface treatment of the reinforcing material:
treating a reinforcing material by using 20-40% nitric acid solution, wherein the reinforcing material is short fiber shreds;
(3) preparation of A component: uniformly mixing and stirring 100 parts of polyol, 5-20 parts of treated first wave absorber, 3-15 parts of treated second wave absorber, 4-8 parts of treated reinforcing material, 0.02-2.5 parts of catalyst, 5-10 parts of flame retardant and 0.1-4 parts of foaming agent to obtain a component A, wherein the parts are parts by weight;
(4) adding a component B: adding 20-50 parts of polyisocyanate serving as a component B into the component A prepared in the previous step;
(5) mixing and foaming: and pouring the mixed materials into a foaming mold preheated to 70-90 ℃, and foaming and curing for 2-4 hours at the temperature of 70-90 ℃ to obtain the fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material.
2. The preparation method of the fiber reinforced flame retardant polyurethane foam wave-absorbing composite material according to claim 1, which is characterized in that,
the first wave absorbing agent is treated by adding the first wave absorbing agent into 30-50% nitric acid solution, uniformly stirring, then placing the mixture into a drying oven at the temperature of 80-120 ℃, treating for 4-6 hours, then washing the mixture to be neutral by using distilled water, and drying the mixture for later use;
the second wave absorbing agent is treated by putting the second wave absorbing agent into a solid stirrer, adding 20-40% of silane coupling agent solution, stirring for 15-30 min at the rotating speed of 2000-4000 rpm, and then drying for 2-4 h in an oven at the temperature of 80-120 ℃;
the surface treatment of the reinforcing material is to add the reinforcing material into 20-40% nitric acid solution to be uniformly stirred, then put the mixture into a drying oven at 100 ℃ to be treated for 2-4 hours, then use distilled water to wash the mixture to be neutral, and dry the mixture for later use.
3. The preparation method of the fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material according to claim 1, wherein in the preparation step of the component A, 1-4 parts by weight of a chain extender, 0.1-2 parts by weight of a surfactant, 0.5-1.5 parts by weight of an antioxidant and 0.2-1 part by weight of a light stabilizer are further added.
4. A fiber reinforced flame retardant polyurethane foam wave-absorbing composite material is prepared by the following steps:
(1) surface treatment of the wave absorber:
treatment of the first absorbent: treating the first absorbent by using 30-50% nitric acid solution, wherein the first absorbent is a resistance absorbent;
and (3) treating a second wave absorbing agent: treating a second wave absorbing agent by using a 20-40% silane coupling agent solution, wherein the second wave absorbing agent is a magnetic loss absorbent;
(2) surface treatment of the reinforcing material:
treating a reinforcing material by using 20-40% nitric acid solution, wherein the reinforcing material is short fiber shreds;
(3) preparation of A component: uniformly mixing and stirring 100 parts of polyol, 5-20 parts of treated first wave absorber, 3-15 parts of treated second wave absorber, 4-8 parts of treated reinforcing material, 0.02-2.5 parts of catalyst, 5-10 parts of flame retardant and 0.1-4 parts of foaming agent to obtain a component A, wherein the parts are parts by weight;
(4) adding a component B: adding 20-50 parts of polyisocyanate serving as a component B into the component A prepared in the previous step;
(5) mixing and foaming: and pouring the mixed materials into a foaming mold preheated to 70-90 ℃, and foaming and curing for 2-4 hours at the temperature of 70-90 ℃ to obtain the fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material.
5. The fiber reinforced flame retardant polyurethane foam wave-absorbing composite material according to claim 4, wherein the first wave-absorbing agent is conductive carbon black or graphite, preferably superconducting carbon black or conductive graphite, and the second wave-absorbing agent is hydroxyl iron powder or carbon fiber powder, preferably nano hydroxyl iron powder.
6. The fiber reinforced flame retardant polyurethane foam wave absorbing composite material as claimed in claim 4, wherein the polyol is one or more of polyether polyol, polyester polyol, polyether ester polyol, polyolefin polyol, hydroxyl terminated polysiloxane, vegetable oil polyol, rosin polyester polyol, urethane polyol and polypropylene ester polyol;
the polyisocyanate is a mixture of diphenylmethane diisocyanate and carbodiimide-modified diphenylmethane diisocyanate;
the catalyst is one or more of triethylene diamine, tin isooctanoate and dibutyltin dilaurate;
the foaming agent is one or more of pentafluoropropane, pentafluorobutane, tetrafluoroethane, cyclopentane, dichloromethane and purified water;
the flame retardant is one or more of methyl dimethyl phosphate, ethyl diethyl phosphate, propyl dimethyl phosphate and triethyl phosphate;
the reinforcing material is one of carbon fiber short cut filament, glass fiber short cut filament and aramid fiber short cut filament.
7. The fiber reinforced flame retardant polyurethane foam wave absorbing composite material as claimed in claim 4, wherein the polyol has a relative molecular weight in the range of 2000-6000.
8. The fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material as claimed in claim 4, wherein the hydroxyl value ratio of the polyol to the polyisocyanate is 1: 1.05-1.20.
9. The fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material as claimed in claim 5, wherein the polyisocyanate contains 70-90% by weight of diphenylmethane diisocyanate, and 30-10% by weight of carbodiimide-modified diphenylmethane diisocyanate.
10. The fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material as claimed in claim 4, wherein in the step of preparing the component A, 1-4 parts by weight of a chain extender, 0.1-2 parts by weight of a surfactant, 0.5-1.5 parts by weight of an antioxidant and 0.2-1 part by weight of a light stabilizer are further added, wherein the chain extender is one or more of 1, 4-butanediol, ethylene glycol, propylene glycol and 1, 4-cyclohexanediol;
the surfactant is a polydimethylsiloxane,
the silane coupling agent is one of KH550 or KH 560;
the antioxidant is one or more of antioxidant 1010, antioxidant 1098 and antioxidant BHT;
the light stabilizer is one or more of light stabilizer 622, light stabilizer 770, and light stabilizer 944.
Background
With the development of the electronic industry and the wide use of electronic equipment, the pollution of electromagnetic waves is increasingly serious, so that the requirements on wave-absorbing materials and shielding materials are increasingly vigorous, and meanwhile, due to the hidden requirements on military equipment such as fighters, missiles, warships and the like in military affairs, the requirement on the materials capable of absorbing radar waves is increasingly urgent, so that the requirements of the wave-absorbing materials in practical application are urgent in both military and civil markets.
The wave-absorbing foam material is one of the wave-absorbing materials which is paid more attention, and the wave-absorbing foam composite material not only has good absorption effect on electromagnetic waves, but also has the advantages of low density, high strength, sound absorption, heat insulation and shock absorption. The heat-insulating and noise-reducing composite material is applied to civil facilities, can effectively improve the influence of electromagnetic waves on equipment, reduces the bearing of a main body of a building, and has the functions of heat insulation and noise reduction; the radar stealth agent is applied to military equipment such as airplanes, missiles, ships and warships, can effectively reduce the weight of the equipment, provides a radar stealth effect, improves the working environment of operators, and has a good application prospect.
The polyurethane foam has the characteristics of porosity, small relative density, temperature resistance, ageing resistance, organic solvent corrosion resistance, easiness in molding and processing and the like, and is widely applied to wave-absorbing materials. At present, flexible polyurethane foam is mainly cut into a preset shape, then a flame-retardant wave absorber solution is soaked in the polyurethane foam, and then the polyurethane foam is pasted and installed through an adhesive; or the polyurethane foam composite wave-absorbing material is prepared by means of spraying and the like. The existing related patents include CN 107936539A, CN 101519487A and the like, the polyurethane wave-absorbing materials prepared by the methods have the defects of complex manufacturing process, single function, narrow absorption broadband, low reflection loss absorption peak value, easy falling off of wave-absorbing auxiliary agents, flammability, poor mechanical property and the like.
Disclosure of Invention
Based on the technical problems in the background art, one of the purposes of the invention is to provide a preparation method of a fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material, which is simple to operate, low in cost and environment-friendly.
The second purpose of the invention is to provide the fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material prepared by the preparation method, which has excellent electromagnetic wave absorption capacity, wide absorption frequency band, and better flame-retardant property and mechanical property.
The above object of the present invention is achieved by the following technical solutions:
the invention provides a preparation method of a fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material, which is a salt spray-resistant chopped carbon fiber-hard polyurethane foam wave-absorbing material and comprises the following steps:
(1) surface treatment of the wave absorber:
treatment of the first absorbent: treating the first absorbent by using 30-50% nitric acid solution, wherein the first absorbent is a resistance absorbent;
and (3) treating a second wave absorbing agent: treating a second wave absorbing agent by using a 20-40% silane coupling agent solution, wherein the second wave absorbing agent is a magnetic loss absorbent;
(2) surface treatment of the reinforcing material:
treating a reinforcing material by using 20-40% nitric acid solution, wherein the reinforcing material is short fiber shreds;
(3) preparation of A component: uniformly mixing and stirring 100 parts of polyol, 5-20 parts of treated first wave absorber, 3-15 parts of treated second wave absorber, 4-8 parts of treated reinforcing material, 0.02-2.5 parts of catalyst, 5-10 parts of flame retardant and 0.1-4 parts of foaming agent to obtain a component A, wherein the parts are parts by weight;
(4) adding a component B: adding 20-50 parts of polyisocyanate serving as a component B into the component A prepared in the previous step;
(5) mixing and foaming: and pouring the mixed materials into a foaming mold preheated to 70-90 ℃, and foaming and curing for 2-4 hours at the temperature of 70-90 ℃ to obtain the fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material.
According to one embodiment of the invention, the first wave absorbing agent is treated by adding the first wave absorbing agent into 30-50% nitric acid solution, uniformly stirring, then placing the mixture into a drying oven at 80-120 ℃, treating for 4-6 hours, then washing the mixture to be neutral by using distilled water, and drying for later use;
the second wave absorbing agent is treated by putting the second wave absorbing agent into a solid stirrer, adding 20-40% of silane coupling agent solution, stirring for 15-30 min at the rotating speed of 2000-4000 rpm, and then drying for 2-4 h in an oven at the temperature of 80-120 ℃;
the surface treatment of the reinforcing material is to add the reinforcing material into 20-40% nitric acid solution to be uniformly stirred, then put the mixture into a drying oven at 100 ℃ to be treated for 2-4 hours, then use distilled water to wash the mixture to be neutral, and dry the mixture for later use.
According to one embodiment of the invention, in the step of preparing the component A, 1-4 parts of chain extender, 0.1-2 parts of surfactant, 0.5-1.5 parts of antioxidant and 0.2-1 part of light stabilizer are also added, wherein the parts are parts by weight.
According to one embodiment of the invention, the invention provides a fiber reinforced flame retardant polyurethane foam wave-absorbing composite material, which is prepared by the method.
According to one embodiment of the invention, the first wave absorber is conductive carbon black or graphite, preferably superconducting carbon black or conductive graphite, and the second wave absorber is hydroxyl iron powder or carbon fiber powder, preferably nano hydroxyl iron powder;
the polyol is one or more of polyether polyol, polyester polyol, polyether ester polyol, polyolefin polyol, hydroxyl-terminated polysiloxane, vegetable oil polyol, rosin polyester polyol, urethane polyol and polypropylene ester polyol;
the polyisocyanate is a mixture of diphenylmethane diisocyanate and carbodiimide-modified diphenylmethane diisocyanate;
the catalyst is one or more of triethylene diamine, tin isooctanoate and dibutyltin dilaurate;
the foaming agent is one or more of pentafluoropropane, pentafluorobutane, tetrafluoroethane, cyclopentane, dichloromethane and purified water;
the flame retardant is one or more of methyl dimethyl phosphate, ethyl diethyl phosphate, propyl dimethyl phosphate and triethyl phosphate;
the reinforcing material is one of carbon fiber short cut filament, glass fiber short cut filament and aramid fiber short cut filament.
According to one embodiment of the present invention, the relative molecular weight of the polyol is in the range of 2000 to 6000, and the hydroxyl number ratio of the polyol to the polyisocyanate is 1:1.05 to 1.20.
According to one embodiment of the invention, the polyisocyanate has 70 to 90% by weight of diphenylmethane diisocyanate and 30 to 10% by weight of carbodiimide-modified diphenylmethane diisocyanate.
According to one embodiment of the invention, the chain extender is one or more of 1, 4-butanediol, ethylene glycol, propylene glycol, 1, 4-cyclohexanediol;
the surfactant is a polydimethylsiloxane,
the silane coupling agent is one of KH550 or KH 560;
the antioxidant is one or more of antioxidant 1010, antioxidant 1098 and antioxidant BHT;
the light stabilizer is one or more of light stabilizer 622, light stabilizer 770, and light stabilizer 944.
According to one embodiment of the invention, the flame-retardant polyurethane foam is characterized in that the flame-retardant property is an oxygen index of more than 24%.
The fiber reinforced flame retardant polyurethane foam wave-absorbing composite material and the preparation method thereof provided by the preferred embodiment of the invention have the beneficial effects that:
firstly, the wave absorbing agent and the reinforcing material are subjected to surface pretreatment, and then the polyol, the catalyst, the flame retardant, the foaming agent, the optional chain extender, the surfactant, the silane coupling agent, the antioxidant, the light stabilizer and the like are mixed and stirred uniformly; and then adding polyisocyanate, quickly stirring, uniformly stirring, and then carrying out mixing foaming and foaming curing processes. The process can effectively avoid the phenomenon that the wave absorbing agent and the fiber reinforced material are not uniformly mixed because polyether polyol reacts with isocyanate after being contacted.
By adding the fiber reinforced material, the fiber reinforced flame-retardant polyurethane foam wave-absorbing composite material has the characteristics of high strength, high modulus and the like.
By adding the antioxidant and the light stabilizer, the fiber reinforced flame-retardant polyurethane foam wave-absorbing composite material has excellent aging resistance.
Drawings
FIG. 1 is a fiber reinforced flame retardant polyurethane foam wave-absorbing composite material of example 1;
FIG. 2 is a graph showing the energy efficiency of the fiber reinforced flame retardant polyurethane foam wave-absorbing composite material in example 1 for absorbing electromagnetic waves with a frequency of 1-18 GHz.
Detailed Description
The invention provides a fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material which has the characteristics of strong wave-absorbing capacity, wide absorption spectrum, good flame-retardant property, good mechanical property and the like. The drugs/reagents used are all commercially available unless otherwise specified.
According to a preferred embodiment of the invention, the invention provides a preparation method of a fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material, wherein the composite material is a salt-fog-resistant chopped carbon fiber-rigid polyurethane foam wave-absorbing material, and the method comprises the following steps:
(1) surface treatment of the wave absorber:
treatment of the first absorbent: adding the first absorbent into a 30-50% nitric acid solution, uniformly stirring, then placing the mixture into an oven at 80-120 ℃ for treatment for 4-6 hours, and then washing the mixture with distilled water until the mixture is neutral and dried for later use; and (3) treating a second wave absorbing agent: putting the second wave absorbing agent into a solid stirrer, adding 20-40% of silane coupling agent solution, stirring for 15-30 min at the rotating speed of 2000-4000 rpm, and drying for 2-4 hours in an oven at the temperature of 80-120 ℃;
(2) surface treatment of the reinforcing material: adding the reinforcing material into a 20-40% nitric acid solution, uniformly stirring, then placing the mixture into a drying oven at 100 ℃ for treatment for 2-4 hours, and then washing the mixture with distilled water until the mixture is neutral and dried for later use;
(3) preparation of A component: uniformly mixing and stirring 100 parts of polyol, 5-20 parts of treated first wave absorber, 3-15 parts of treated second wave absorber, 4-8 parts of treated reinforcing material (short fiber), 0.02-2.5 parts of catalyst, 5-10 parts of flame retardant, 0.1-4 parts of foaming agent, 1-4 parts of optionally used chain extender, 0.1-2 parts of surfactant, 0.5-1.5 parts of antioxidant and 0.2-1% of light stabilizer to obtain a component A, wherein the component A is in parts by weight;
(4) adding a component B: adding 20-50 parts of polyisocyanate serving as a component B into the prepared component A and quickly stirring;
(5) mixing and foaming: and pouring the mixed materials into a foaming mold preheated to 70-90 ℃, preferably 80 ℃, closing the mold, and foaming and curing for 2-4 hours at the temperature of 70-90 ℃, preferably 80 ℃ to obtain the fiber reinforced flame retardant polyurethane foam wave-absorbing composite material.
Preferred polyols are one or more of polyether polyols, polyester polyols, polyetherester polyols, polymer polyols, polyolefin polyols, hydroxyl terminated polysiloxanes, vegetable oil polyols, rosin polyester polyols, urethane polyols and polyacrylate polyols.
According to one embodiment of the present invention, the preferred first wave absorbing agent of the present invention is a resistive type absorbing agent, preferably conductive carbon black or graphite, more preferably the conductive carbon black is superconducting carbon black, more preferably the graphite is conductive graphite, and the second wave absorbing agent is a magnetic loss absorbing agent, preferably hydroxyl iron powder or carbon fiber powder, more preferably the hydroxyl iron powder is nano hydroxyl iron powder. The wave absorbing agent is characterized in that conductive carbon black, graphite, hydroxyl iron powder, carbon fiber powder and the like mixed in the flame-retardant polyurethane foam have an electromagnetic loss function.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The embodiment provides a fiber-reinforced flame-retardant polyurethane wave-absorbing foam composite material which has the characteristics of strong wave-absorbing capacity, wide absorption frequency band, flame-retardant property, good mechanical property and the like.
The specific preparation process of the fiber reinforced flame-retardant polyurethane wave-absorbing foam composite material comprises the following steps:
1. surface treatment of the wave absorber: adding the superconducting carbon black into a 30% nitric acid solution, uniformly stirring, then placing the mixture into a drying oven at 100 ℃ for treatment for 4 hours, and then washing the mixture to be neutral and drying the mixture for later use by using distilled water.
Putting hydroxyl iron powder into a solid stirrer, adding 20% KH550 solution serving as a silane coupling agent, stirring for 30min at the rotating speed of 3000 revolutions per minute, and drying in an oven at 120 ℃ for 2 hours.
2. Surface treatment of the reinforcing material: adding the carbon fiber chopped strands used as the reinforcing materials into a 20% nitric acid solution, uniformly stirring, then placing the mixture into a drying oven at 100 ℃ for treatment for 4 hours, and then washing the mixture with distilled water until the mixture is neutral and dried for later use.
3. Preparation of A component: weighing 100 parts of polyether polyol (with a relative molecular weight of 3000), 0.01 part of triethylene diamine serving as a catalyst, 0.01 part of tin isooctanoate, 2 parts of 1, 4-butanediol serving as a chain extender, 4 parts of dimethyl methyl phosphate serving as a flame retardant, 6 parts of triethyl phosphate, 2 parts of polydimethylsiloxane serving as a surfactant, 1 part of purified water, 10 parts of treated superconducting carbon black, 8 parts of treated hydroxyl iron powder, 6 parts of treated carbon fiber chopped strand, 1 part of antioxidant BHT and 1 part of light stabilizer 622, mixing and stirring uniformly, wherein the parts are parts by weight.
4. Adding a component B: 36 parts of polyisocyanate (the weight ratio of the diphenylmethane diisocyanate in the polyisocyanate is 70%, and the weight ratio of the carbodiimide-modified diphenylmethane diisocyanate in the polyisocyanate is 30%) is added into the prepared component A, and the mixture is rapidly stirred.
5. Mixing and foaming: and pouring the mixed materials into a foaming mold which is preheated to 80 ℃, closing the mold, and foaming and curing at the temperature of 80 ℃ for 2 hours to obtain the fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material.
The volume resistivity of the fiber reinforced flame-retardant polyurethane wave-absorbing foam composite material obtained in the embodiment is 438 omega cm, and the density is 340kg/m3And the thickness is 20 mm.
Fig. 1 is a composite material of the fiber reinforced flame retardant polyurethane wave-absorbing foam of the embodiment.
The radar wave absorption performance of the composite material in the embodiment is tested by adopting an arch method specified in GJB 2038A-2011 radar wave absorbing material reflectivity test method, FIG. 2 is an energy efficiency absorption curve diagram of the composite material in the embodiment for radar waves with the frequency of 1-18 GHz, the graph shows that the average values of the absorption attenuation of the electromagnetic wave reflectivity at 1-2 GHz, 2-4 GHz, 4-8 GHz and 8-18 GHz are respectively 2dB, 14dB, 12dB and 9dB, and the corresponding absorption peak value can reach-32.5 dB when the absorption bandwidth is 4 GHz. The resistance type loss wave-absorbing material layer has a good absorption loss effect on the electromagnetic wave band of 4-18 GHz, and also has a certain electromagnetic wave absorption loss effect on the low-frequency electromagnetic wave band of 1-4 GHz.
The flame retardant property of the composite material of the embodiment was tested by the oxygen index method specified in GB/T2406 "Plastic burning Properties test methods", and the oxygen index was 27.3%.
Example 2
The embodiment provides a fiber-reinforced flame-retardant polyurethane wave-absorbing foam composite material which has the characteristics of strong wave-absorbing capacity, wide absorption frequency band, flame-retardant property, good mechanical property and the like.
The specific preparation process of the fiber reinforced flame-retardant polyurethane wave-absorbing foam composite material comprises the following steps:
1. surface treatment of the wave absorber: adding the conductive graphite into 35% nitric acid solution, stirring uniformly, then placing the mixture into a drying oven at 100 ℃ for treatment for 4 hours, and then washing the mixture to be neutral and drying the mixture for later use by using distilled water.
Putting hydroxyl iron powder into a solid stirrer, adding 20% KH550 solution serving as a silane coupling agent, stirring for 30min at the rotating speed of 3000 revolutions per minute, and drying in an oven at 120 ℃ for 2 hours.
2. Surface treatment of the reinforcing material: adding the glass fiber chopped strands used as the reinforcing materials into a 25% nitric acid solution, uniformly stirring, then placing the mixture into a drying oven at 100 ℃ for treatment for 4 hours, and then washing the mixture to be neutral and drying the mixture for later use by using distilled water.
3. Preparation of A component: weighing 100 parts of polyether polyol (with a relative molecular weight of 3000), 0.01 part of triethylene diamine serving as a catalyst, 0.02 part of dibutyltin dilaurate, 1 part of ethylene glycol serving as a chain extender, 1 part of propylene glycol, 4 parts of diethyl ethylphosphate serving as a flame retardant, 6 parts of dimethyl propyl phosphate, 2 parts of polydimethylsiloxane serving as a surfactant, 1 part of cyclopentane serving as a foaming agent, 12 parts of treated conductive graphite, 7 parts of treated hydroxyl iron powder, 5 parts of treated glass fiber chopped strands, 1 part of antioxidant 1098 and 1 part of light stabilizer 944, mixing and stirring uniformly, wherein the parts are parts by weight.
4. Adding a component B: 42 parts of polyisocyanate (the weight ratio of the diphenylmethane diisocyanate in the polyisocyanate is 70%, and the weight ratio of the carbodiimide-modified diphenylmethane diisocyanate in the polyisocyanate is 30%) is added into the prepared component A, and the mixture is rapidly stirred.
5. Mixing and foaming: and pouring the mixed materials into a foaming mold which is preheated to 90 ℃, closing the mold, and foaming and curing at the temperature of 90 ℃ for 2 hours to obtain the fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material.
The volume resistivity of the fiber reinforced flame-retardant polyurethane wave-absorbing foam composite material obtained in the embodiment in the test is 965 omega-cm, and the density is540kg/m3And the thickness is 20 mm.
The radar wave absorption performance of the composite material is tested by adopting an arch method specified in GJB 2038A-2011 radar absorbing material reflectivity test method, the average values of absorption and attenuation of electromagnetic wave reflectivity of 1-2 GHz, 2-4 GHz, 4-8 GHz and 8-18 GHz are respectively 1dB, 9dB, 8dB and 7dB, and the corresponding absorption peak value can reach-18.9 dB when the absorption bandwidth is 4 GHz. The resistance type loss wave-absorbing material layer has a good absorption loss effect on the electromagnetic wave band of 4-18 GHz, and also has a certain electromagnetic wave absorption loss effect on the low-frequency electromagnetic wave band of 1-4 GHz.
The flame retardant property of the composite material of the embodiment was tested by the oxygen index method specified in GB/T2406 "Plastic burning Properties test methods", and the oxygen index was 24.8%.
Example 3
The embodiment provides a fiber-reinforced flame-retardant polyurethane wave-absorbing foam composite material which has the characteristics of strong wave-absorbing capacity, wide absorption frequency band, flame-retardant property, good mechanical property and the like.
The specific preparation process of the fiber reinforced flame-retardant polyurethane wave-absorbing foam composite material comprises the following steps:
1. surface treatment of the wave absorber: adding the superconducting carbon black into 35% nitric acid solution, stirring uniformly, then placing the mixture into a drying oven at 100 ℃ for treatment for 4 hours, and then washing the mixture to be neutral and drying the mixture for later use by using distilled water.
Putting hydroxyl iron powder into a solid stirrer, adding 20% KH550 solution serving as a silane coupling agent, stirring for 30min at the rotating speed of 3000 revolutions per minute, and drying in an oven at 120 ℃ for 2 hours.
2. Surface treatment of the reinforcing material: adding the glass fiber chopped strands used as the reinforcing materials into a 25% nitric acid solution, uniformly stirring, then placing the mixture into a drying oven at 100 ℃ for treatment for 4 hours, and then washing the mixture to be neutral and drying the mixture for later use by using distilled water.
3. Preparation of A component: 100 parts of polyether polyol (with a relative molecular weight of 3000), 0.01 part of triethylene diamine, 0.02 part of dibutyltin dilaurate, 1 part of ethylene glycol, 1 part of propylene glycol, 4 parts of ethyl diethyl phosphate, 6 parts of propyl dimethyl phosphate, 2 parts of polydimethylsiloxane, 1 part of cyclopentane, 12 parts of treated superconducting carbon black, 7 parts of treated hydroxyl iron powder, 5 parts of treated glass fiber chopped strand, 1 part of antioxidant 1098 and 1 part of light stabilizer 944 are weighed and mixed uniformly, wherein the parts are parts by weight.
4. Adding a component B: 42 parts of polyisocyanate (the weight ratio of the diphenylmethane diisocyanate in the polyisocyanate is 70%, and the weight ratio of the carbodiimide-modified diphenylmethane diisocyanate in the polyisocyanate is 30%) is added into the prepared component A, and the mixture is rapidly stirred.
5. Mixing and foaming: and pouring the mixed materials into a foaming mold which is preheated to 75 ℃, closing the mold, and foaming and curing for 2 hours at the temperature of 75 ℃ to obtain the fiber-reinforced flame-retardant polyurethane foam wave-absorbing composite material.
In the embodiment, the volume resistivity of the fiber reinforced flame-retardant polyurethane wave-absorbing foam composite material is 965 omega-cm, and the density is 540kg/m3And the thickness is 20 mm.
The radar wave absorption performance of the composite material is tested by adopting an arch method specified in GJB 2038A-2011 radar absorbing material reflectivity test method, the average values of absorption and attenuation of electromagnetic wave reflectivity of 1-2 GHz, 2-4 GHz, 4-8 GHz and 8-18 GHz are respectively 2dB, 11dB, 9dB and 7dB, and the corresponding absorption peak value can reach-21.9 dB when the absorption bandwidth is 4 GHz. The resistance type loss wave-absorbing material layer has a good absorption loss effect on the electromagnetic wave band of 4-18 GHz, and also has a certain electromagnetic wave absorption loss effect on the low-frequency electromagnetic wave band of 1-4 GHz.
The flame retardant property of the composite material of the present example was tested by the oxygen index method specified in GB/T2406 "test method for Plastic Combustion Properties", which oxygen index was 25.8%.
The examples described above are only a few embodiments of the invention and are not intended to represent all embodiments which can be practiced. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
