CN113977841B - A kind of polyimide composite foam containing honeycomb core structure and preparation method thereof - Google Patents

Abstract

The invention discloses a polyimide composite foam containing a honeycomb core lattice structure and a preparation method thereof, wherein the preparation method comprises the following steps: s1, calculating the consumption of foaming slurry; according to the overall apparent density of the polyimide composite foam containing the honeycomb core lattice structure and the specification of a mould for preparing the polyimide foam honeycomb core lattice, designing the polyimide foam honeycomb core lattice with higher density and the polyimide composite foam containing the honeycomb core lattice structure with lower overall apparent density, and calculating the total consumption of foaming slurry and the consumption of foaming slurry for preparing the polyimide foam honeycomb core lattice, wherein the difference between the total consumption of foaming slurry and the consumption of foaming slurry for filling the honeycomb core lattice; s2, preparing foaming slurry; s3, preparing polyimide foam honeycomb core lattices by combining the S1-S2; s4, preparing polyimide composite foam containing the honeycomb core lattice structure by combining S1-S3. The invention realizes the effects of improving the flame retardant property, the safety and the mechanical property, simplifying the production process and reducing the production cost.

Description

A kind of polyimide composite foam containing honeycomb core structure and preparation method thereof

technical field

The invention relates to the technical field of flame-retardant materials, in particular to a polyimide composite foam with a honeycomb core structure and a preparation method thereof.

Background technique

One-step polyimide foam is a kind of polyimide foam prepared from acid anhydride and isocyanate as raw materials. Due to its imide ring structure and porous structure, the one-step polyimide foam has various outstanding physical and chemical properties such as sound absorption, heat insulation, radiation resistance, high and low temperature resistance, acid and alkali resistance, and is compatible with other types of polyimide foam. Compared with imine foam, its production process is relatively simple, the yield is higher and the price is lower, so it is widely used in high-end fields such as aerospace, automobiles, high-speed trains, and microelectronics.

Furthermore, when the flame retardancy and use safety requirements of heat-insulating and sound-absorbing foam materials are not strict, the price of fully imidized one-step polyimide foam is too high to be widely used in construction, storage, etc. In the field of technology, one-step polyimide foam shows unique technical advantages due to its strong formula adjustability and designability. The core is that the one-step polyimide foam formulation and foam molding preparation technology can reduce the proportion of acid anhydride or its derivatives to isocyanate by reducing the amount of acid anhydride or its derivatives that account for a high proportion of raw material costs. The reduction of the degree of imidization of the material can ultimately ensure the linear decrease of the material production cost, flame retardancy and safety of use, while still ensuring the foam molding of the foam, and obtaining a foam with good heat insulation and sound absorption effect. Therefore, the advantage of this preparation technology of one-step polyimide foam is conducive to the preparation and production of one-step polyimide foam with specific fire protection grade in different fields. While ensuring that the fire protection grade of the material is not seriously excessive, the price of the final product Compared with the fully imidized one-step polyimide foam, it has been effectively reduced, and the production capacity and application field of one-step polyimide foam have been greatly improved.

In order to further improve the market competitiveness of serialized one-step polyimide foam materials and other polymer-based heat-insulating and sound-absorbing foam materials, it is necessary to explore the method of anhydride or its derivatives without changing the preparation formula of serialized one-step polyimide foam materials. Under the conditions of the amount of material used and the degree of imidization, a new path to further improve its flame retardancy, safety in use and even mechanical properties has become the main direction for the development of serialized one-step polyimide foam materials. Based on the discovery of these new paths, the further adjustment of the one-step polyimide foam preparation formula that has met the requirements of a specific fire rating can be reversed, that is, the further reduction of the amount of anhydride or its derivatives, so as to further reduce the material cost. .

At the same time, one-step polyimide foam, as a lightweight functional material, exhibits problems such as easy tearing, easy fracture, and low strength at lower densities, and the current research on the mechanical properties of one-step polyimide foam The improvement is often solved by molding to increase the density, but it will cause a sharp increase in the amount of raw materials and manufacturing costs.

At present, domestic and foreign scientific research workers and related units mainly add various flame retardants to further improve the flame retardancy and safety of one-step polyimide foam.

In "A Halogen-Free Composite Flame-Retardant Polyimide Foam Material and Its Preparation Method" disclosed in the Chinese patent document CN107286343A, the inventor added graphite materials and phosphorus-based flame retardants to high-speed ball milling in a sealed ball mill steel tank. Graphene phosphoric acid or phosphorylated graphite flame retardant materials were prepared to improve the flame retardancy of one-step polyimide foam.

In the "one-step method for preparing high flame-retardant low-density polyimide foam" disclosed in Chinese patent document CN104497255A, the inventor significantly improved the one-step method of polyimide foam by adding hydrotalcite and liquid flame retardant at the same time. flame retardancy.

In "A Low-Cost Flame-Retardant Polyimide Thermal Insulation Foam and Its Preparation Method and Application" disclosed in Chinese patent document CN110922627A, the inventor improved the flame retardancy of the material by adding a self-synthesized reactive phosphorus-based flame retardant .

The above methods of adding flame retardants can effectively improve the flame retardancy and safety of one-step polyimide foam materials. However, the cost of most high-efficiency flame retardants is much higher than that of cheap pyromellitic anhydrides. Anhydride raw materials have become a new core cost element. At the same time, most high-efficiency flame retardants are liquids, which are easy to volatilize during the high-temperature curing process of one-step polyimide foam, which not only reduces its own flame retardant effect, but also is not conducive to environmental protection. It will cause internal agglomeration and seriously affect the mechanical properties of the material.

In "Effects of aramid honeycomb core on the flame retardance and mechanical property for isocyanate-based polyimide foams", the author realizes its flame retardancy by separating the space of the whole one-step polyimide foam with aramid honeycomb core lattice The effective improvement of the performance and the substantial improvement of the mechanical properties of the material. However, the cost of the aramid honeycomb core itself is higher than that of the one-step polyimide foam with a low degree of imidization, so it is not suitable for industrial production. Further, relevant researchers carried out research on the space separation of the whole one-step polyimide foam with aluminum honeycomb. Although its flame retardancy and safety in use have been improved, due to the thermal bridge effect of aluminum honeycomb, it has greatly lost Its heat insulation performance makes the thermal conductivity of one-step polyimide foam rise from about 0.04W/(m K) to about 0.5W/(m K), and the heat insulation or heat preservation function is reduced to about 10% of the original , which is extremely unfavorable to the application of the material.

Contents of the invention

In view of this, in order to solve the above-mentioned technical problems, the object of the present invention is to propose a polyimide composite foam containing a honeycomb core structure and a preparation method thereof, which can solve the problems of the flame-retardant properties of flame-retardant materials in the prior art and The technical problems of insufficient mechanical properties, complex production process and high production cost.

The technical solutions adopted are:

A kind of preparation method of the polyimide composite foam containing honeycomb core lattice structure of the present invention, comprises the following steps:

S1. Calculation of the amount of foaming slurry: According to the overall apparent density of the polyimide composite foam with the honeycomb core structure and the mold specifications for preparing the polyimide foam honeycomb core, design the polyimide foam honeycomb core The density is higher, and the overall apparent density of the polyimide composite foam containing the honeycomb core structure is low. To calculate the total amount of foaming slurry and the amount of foaming slurry used to prepare the polyimide foam honeycomb core, The difference between the two is the amount of foaming slurry used to fill the honeycomb cell;

S2. Preparation of foaming slurry: Weigh the polar solvent and aromatic dianhydride successively, add them to the reaction device connected to the reflux condenser, stir and raise the temperature of the system to 40-80°C, stop heating, then add fatty alcohol and Carry out esterification reaction of aromatic dianhydride to the end of the reaction; after cooling to room temperature, add foam stabilizer, surfactant, catalyst, and deionized water in sequence, and stir evenly to obtain a foaming base material; pour the foaming base material from the reaction device After entering the foaming slurry mixing container, immediately add polyisocyanate to the foaming base material, and after mechanical stirring, it is the foaming slurry;

S3. The preparation of polyimide foam honeycomb core grid: according to the foaming slurry consumption of the polyimide foam honeycomb core grid calculated in step S1 and the total foaming slurry prepared in step S2, the total foaming slurry prepared from step S2 After obtaining the calculated amount of foaming slurry used to prepare the polyimide foam honeycomb cell from the foaming slurry, pour the foaming slurry quickly and evenly into a steel mold with an upper opening and coated with a release agent At the bottom, use a steel plate with a circular evenly distributed steel hexagonal prism structure and coated with a release agent as the upper cover, quickly close the mold, tighten the screws, let it stand for 10-15 minutes, and then put the mold into an oven at a temperature of 160-240°C Inside, high-temperature curing for 2-3 hours, and polyimide foam honeycomb cells obtained after cooling and demoulding;

S4. the preparation of the polyimide composite foam that contains honeycomb core lattice structure: continue to use the steel mold that upper opening is used in step S3 and be coated with release agent, the foaming of filling honeycomb core lattice core lattice according to step S1 calculation Slurry consumption; After obtaining the calculated foaming slurry for filling the core material grid from the total foaming slurry prepared in step S2, the foaming slurry is quickly and evenly poured into its bottom, and then quickly Insert the polyimide foam honeycomb core grid prepared in step S3 into the mold, use the flat steel plate coated with the release agent as the upper cover, quickly close the mold, tighten the screws, let stand for 10-15min, and then put the mold into 160 In an oven at a temperature of -240°C, cure at a high temperature for 2-3 hours, and after cooling down and demolding, a polyimide composite foam with a honeycomb core structure is obtained.

Further, in step S2, by weight, 20-200 parts of aromatic dianhydride, 5-80 parts of fatty alcohol, 100-195 parts of isocyanate, 50-70 parts of polar solvent, 10-15 parts of foam stabilizer, the surface 10-15 parts of active agent, 5-10 parts of catalyst and 10-15 parts of deionized water.

Further, in step S2, the aromatic dianhydride includes 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4 , A mixture of one or more of 4'-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride.

Further, in step S2, the fatty alcohol includes a mixture of one or more of methanol, ethanol, propanol, and isopropanol.

Further, in step S2, the catalyst includes a mixture of one or more of triethanolamine, stannous octoate, dibutyltin dilaurate, and Dabco33-LV.

Further, in step S2, the isocyanate is polyphenylpolymethylene polyisocyanate with an NCO weight percentage of 30%-40%.

A polyimide composite foam containing a honeycomb core structure of the present invention is prepared by the preparation method described in any of the above schemes.

Further, the polyimide foam honeycomb cell has a wall thickness of 2-4mm.

Further, the diameter of the circumscribed circle of the polyimide foam honeycomb cell is 7.2-20.0 mm.

Compared with prior art, the beneficial effect of the present invention is:

The polyimide composite foam containing the honeycomb core structure prepared by the present invention can only be obtained by having The introduction of the high-density honeycomb core structure with the same composition can realize the macroscopic inhomogeneity and separation of local density, relying on the dense, self-supporting fire-proof and heat-insulating carbon layer formed by the high-density honeycomb core structure during the combustion process and the effect on the honeycomb core structure. The division of the flame when the low-density foam filled in the middle reduces the degree of flame aggregation, prevents air convection, and finally reduces the overall combustion degree, heat release behavior, and combustion smoke release behavior of the composite foam, and realizes its safe use. The further improvement of the property lays a technical foundation for the further reduction of the production cost of one-step polyimide foam with a specific fire protection grade, and improves the market competitiveness of one-step polyimide foam materials.

At the same time, relying on the special mechanical properties of the honeycomb structure to further improve the mechanical properties of the foam. Moreover, the invention has simple and convenient operation, low preparation requirements, and its products are convenient for industrialized production and wide application.

In summary, the present invention solves the problems of insufficient flame retardant and mechanical properties of flame retardant materials in the prior art, complicated production process and high production cost, and achieves local density by introducing a high-density honeycomb structure with the same composition. Under the macroscopic inhomogeneity and separation, the beneficial effects of improving flame retardancy, safety, mechanical properties, simplifying the production process and reducing the production cost are realized.

Description of drawings

FIG. 1 is a schematic structural view of a steel mold upper cover with annularly distributed hexagonal prisms used in Example 1 of the present invention.

Detailed ways

The present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present embodiment, as well as comparative examples and examples. Apparently, the described examples are only some, not all, examples of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Comparative example 1

Weigh 17.3 grams of N,N-dimethylformamide solution and 11.76 grams of 3,3',4,4'-benzophenone tetraacid dianhydride into the reaction device connected to the reflux condenser, stir and raise the temperature of the system After reaching 50°C, stop heating, then add 2.44 grams of methanol and 3,3',4,4'-benzophenonetetraacid dianhydride for esterification reaction, and obtain a transparent carboxylate solution after the reaction, wait for the above solution to cool After reaching room temperature, add 3.75 grams of polyethylene glycol 600, 3.75 grams of AK8805 surfactant, 2.4 grams of catalyst, 3.6 grams of deionized water, and stir evenly to obtain a foaming base material, which is poured into the foaming base material from the reaction device. After foaming slurry mixing container, add 45 grams of NCO weight fractions to be the polymethylene polyphenyl polyisocyanate of 31.5% at once in foaming base material, high-speed mechanical stirring obtains foaming slurry, foaming material The slurry is quickly and evenly poured into the bottom of the steel mold with a cavity size of 10cm*10cm*5cm on the upper opening and coated with a release agent. With a rectangular steel plate coated with a release agent as the upper cover, quickly tighten the screws to close the upper part of the experimental mold. mouth, closed the experimental mold, put it into an oven at 180°C after standing for 12 minutes, cured it at high temperature for 2 hours, cooled and demolded to obtain a one-step polyimide foam with a density of 94±2kg/ ^m3 .

The limiting oxygen index of the prepared one-step polyimide foam is 22.5%; the compressive strength is 364kPa; the thermal conductivity is 0.051W/(m·K); the peak value of combustion heat release is 183kW/m ² ; the total amount of combustion smoke is released 6.79m ² /m ² .

Comparative example 2

The difference between this comparative example and ^comparative example 1 is that the amount of all reagents or medicines is 20% of the weight of the corresponding reagents or medicines in the comparative example. imide foam.

The limiting oxygen index of the prepared one-step polyimide foam is 24.9%; the compressive strength is 290kPa; the thermal conductivity is 0.053W/(m·K); the peak value of combustion heat release is 214kW/m ² ; the total amount of combustion smoke is released 7.17m ² /m ² .

Comparative example 3

The difference between this comparative example and comparative example 1 is that the amount of 3,3',4,4'-benzophenonetetraacid dianhydride is 34.27 grams, and the amount of methanol added is 7.11 grams. After the reaction, the result is translucent Viscous carboxylate solution", all the other operations are the same as in Example 1 to obtain a density of 125 ± 2kg/m The ^one -step polyimide foam.

The limiting oxygen index of the prepared one-step polyimide foam is 22.2%; the compressive strength is 372kPa; the thermal conductivity is 0.049W/(m·K); the peak value of combustion heat release is 159kW/m ² ; the total amount of combustion smoke is released 5.41m ² /m ² .

Comparative example 4

The difference between this comparative example and comparative example 1 is that the amount of 3,3',4,4'-benzophenone tetraacid dianhydride is 56.78 grams, and the amount of methanol added is 11.38 grams. After the reaction, the obtained product is almost white The pasty carboxylate solution of ", all the other operations are identical with embodiment 1, obtain density about 147 ± 2kg/m ^The one-step polyimide foam of density.

The prepared one-step polyimide foam has a limiting oxygen index value of 30.7%; a compressive strength of 387kPa; a thermal conductivity of 0.047W/(m·K); a peak value of combustion heat release of 143kW/m ² ; a total combustion smoke emission 4.08m ² /m ² .

Example 1

Referring to the schematic diagram shown in Figure 1, the steel upper cover of the mold with annular distribution of hexagonal prisms is used to make the high-density polyimide foam honeycomb cell. The cavity size of the mold is 20cm*20cm*5cm. The length of the hexagonal prism inlaid on the steel upper cover of the mold is also 5cm, and the side length is 9.6mm (that is, the diameter of the circumscribed circle is 19.2mm). According to the design drawings, first inlay the first hexagonal prism in the center of the steel plate, and then inlay other hexagonal prisms in a uniform ring according to the drawing. The interval (gap) between two adjacent hexagonal prisms is 2mm, which is to ensure the final prepared honeycomb core. The grid wall thickness is 2mm. According to the drawings, after all the complete hexagonal prisms are inlaid, finally inlay the incomplete hexagonal prisms according to the drawings and the actual situation of the boundary.

In this embodiment, after the upper cover with the hexagonal prism is put into the mold, the ratio of the volume of the hexagonal prism to the remaining space in the mold is 39.9:10.2, that is, the volume of the low-density foam filled in the core lattice of the final composite foam and the honeycomb core Ratio of high-density foam volume.

In this example, a composite foam containing a honeycomb cell structure with the same density as Comparative Example 1 was prepared, that is, the overall apparent density of the composite foam was 94±2kg/m ³ . In view of the cavity volume of the mold used in this embodiment, that is, the overall apparent volume of the composite foam is 4 times that of Comparative Example 1, the total amount of reagents and chemicals used to prepare the foam foaming slurry of the honeycomb core grid and the core grid respectively is 4 times that of the corresponding reagents and chemicals in Comparative Example 1. In this embodiment, a high-density polyimide foam honeycomb cell with a foam density of 280 kg/m ³ is prepared, and the density of the low-density polyimide foam filled with the honeycomb cell is 46.4 kg/m ³ . According to above-mentioned data, further calculate the foaming slurry quality that is used to prepare high-density polyimide foam honeycomb lattice should be 2.43 times of the foaming slurry quality in comparative example 1, be used for filling the foaming slurry quality of honeycomb lattice The foam slurry quality should be 1.57 times of the foam slurry quality in Comparative Example 1.

According to the slurry preparation process in Comparative Example 1, and the above-mentioned calculated various material consumptions, the preparation is used to prepare the foaming slurry of high-density polyimide foam honeycomb core grid, and the foaming slurry is quickly and evenly poured Insert the bottom of the steel mold with an inner cavity size of 20cm*20cm*5cm with the upper opening and coated with a release agent, and then quickly apply the circular uniformly distributed steel hexagonal prism structure designed and manufactured in this embodiment and coated with a release agent. Quickly close the mold on the upper cover of the agent, tighten the screws, and let it stand for 15 minutes, then put the mold in an oven at a temperature of 180°C, and cure it at a high temperature for 2 hours. After cooling down and demoulding, the actual foam density is 277kg/ ^m3 Polyimide foam honeycomb grid, placed at room temperature for 1-2 days for later use. After the honeycomb cell is available, according to the slurry preparation process in Comparative Example 1, and the amount of various materials calculated above, the foaming slurry used to fill the honeycomb cell is prepared, and quickly and evenly poured into the inner cavity with a size of The bottom of the 20cm*20cm*5cm steel mold, and then quickly insert the polyimide foam honeycomb core prepared above into the mold, use the flat steel plate coated with the release agent as the upper cover, quickly close the mold, tighten the screws, and statically Set it aside for 15 minutes, then put the mold into an oven at 180°C, and cure it at high temperature for 2 hours. After cooling down and demoulding, a polyimide composite foam with a honeycomb core structure with an actual overall apparent density of 92.5kg/ ^m3 was obtained. .

The limiting oxygen index value of the prepared polyimide composite foam containing the honeycomb core structure is 28.4%; the compressive strength is 421kPa; the thermal conductivity is 0.040W/(m·K); the combustion heat release peak value is 67kW/m ² ; The total amount of combustion smoke released is 1.02m ² /m ² .

Example 2

This embodiment adopts the mold designed and made in Example 1. After the upper cover with hexagonal prism is put into the mold, the ratio of the volume of the hexagonal prism to the remaining space in the mold is still 39.9:10.2, that is, the final prepared composite foam The ratio of the volume of low density foam filled in the center cell to the volume of high density foam in the honeycomb cell.

In this example, a composite foam containing a honeycomb cell structure with the same density as Comparative Example 3 was prepared, that is, the overall apparent density of the composite foam was 125±1 kg/m ³ . In view of the cavity volume of the mold used in this embodiment, that is, the overall apparent volume of the composite foam is 4 times that of Comparative Example 3, the total amount of each reagent and chemicals used for preparing the foam foam slurry of the honeycomb core grid and the filled core grid respectively is 4 times that of the corresponding reagents and chemicals in Comparative Example 3. In this embodiment, a high-density polyimide foam honeycomb cell with a foam density of 400 kg/m ³ is prepared, and the density of the low-density polyimide foam filled with the honeycomb cell is 54.7 kg/m ³ . According to above-mentioned data, further calculate the foaming slurry quality that is used to prepare high-density polyimide foam honeycomb lattice should be 2.61 times of the foaming slurry quality in comparative example 3, be used for filling the foaming slurry quality of honeycomb lattice The foam slurry quality should be 1.39 times of the foam slurry quality in Comparative Example 3.

According to the slurry preparation process in Comparative Example 3, and the above-mentioned calculated various material consumptions, the preparation is used to prepare the foaming slurry of high-density polyimide foam honeycomb core lattice, pour the foaming slurry rapidly and evenly Insert the bottom of the steel mold with an inner cavity size of 20cm*20cm*5cm with the upper opening and coated with a release agent, and then quickly apply the circular uniformly distributed steel hexagonal prism structure designed and manufactured in this embodiment and coated with a release agent. Quickly close the mold on the upper cover of the agent, tighten the screws, and let it stand for 15 minutes, then put the mold in an oven at a temperature of 180°C, and cure it at a high temperature for 2 hours. After cooling down and demolding, the actual foam density is 394kg/ ^m3 Polyimide foam honeycomb grid, placed at room temperature for 1-2 days for later use. After the honeycomb cell is available, according to the slurry preparation process in Comparative Example 3, and the amount of various materials calculated above, the foaming slurry for filling the honeycomb cell is prepared, and poured quickly and evenly into the inner cavity with a size of The bottom of the 20cm*20cm*5cm steel mold, and then quickly insert the polyimide foam honeycomb core prepared above into the mold, use the flat steel plate coated with the release agent as the upper cover, quickly close the mold, tighten the screws, and statically Set it aside for 15 minutes, then put the mold into an oven at 180°C, and cure it at high temperature for 2 hours. After cooling down and demoulding, a polyimide composite foam with a honeycomb core structure with an actual overall apparent density of 123.8kg/ ^m3 was obtained. .

The limiting oxygen index value of the prepared polyimide composite foam containing the honeycomb core structure is 29.1%; the compressive strength is 464kPa; the thermal conductivity is 0.042W/(m·K); the combustion heat release peak value is 55kW/m ² ; The total combustion smoke emission is 0.93m ² /m ² .

Example 3

This embodiment adopts the mold designed and made in Example 1. After the upper cover with hexagonal prism is put into the mold, the ratio of the volume of the hexagonal prism to the remaining space in the mold is still 39.9:10.2, that is, the final prepared composite foam The ratio of the volume of low density foam filled in the center cell to the volume of high density foam in the honeycomb cell.

In this example, a composite foam with a honeycomb core structure having the same density as Comparative Example 4 was prepared, that is, the overall apparent density of the composite foam was 157±3kg/m ³ . In view of the cavity volume of the mold used in this embodiment, that is, the overall apparent volume of the composite foam is 4 times that of Comparative Example 4, the total amount of each reagent and chemicals used for preparing the foam foam slurry of the honeycomb core grid and the filled core grid respectively is 4 times of corresponding reagents and chemicals in comparative example 4. In this embodiment, a high-density polyimide foam honeycomb cell with a foam density of 450 kg/m ³ is prepared, and the density of the low-density polyimide foam filled with the honeycomb cell is 82.1 kg/m ³ . According to above-mentioned data, further calculate the foaming slurry quality that is used to prepare high-density polyimide foam honeycomb lattice should be 2.34 times of the foaming slurry quality in comparative example 4, be used for filling the foaming slurry quality of honeycomb lattice The foam slurry quality should be 1.66 times of the foam slurry quality in Comparative Example 4.

According to the slurry preparation process in Comparative Example 4, and the above-mentioned calculated various material consumptions, the preparation is used to prepare the foaming slurry of high-density polyimide foam honeycomb core lattice, pour the foaming slurry rapidly and evenly Insert the bottom of the steel mold with an inner cavity size of 20cm*20cm*5cm with the upper opening and coated with a release agent, and then quickly apply the circular uniformly distributed steel hexagonal prism structure designed and manufactured in this embodiment and coated with a release agent. Quickly close the mold on the upper cover of the agent, tighten the screws, and let it stand for 15 minutes, then put the mold in an oven at a temperature of 180°C, and cure it at a high temperature for 2 hours. After cooling down and demolding, the actual foam density is 441kg/ ^m3 Polyimide foam honeycomb grid, placed at room temperature for 1-2 days for later use. After the honeycomb cell is available, according to the preparation process of the slurry in Comparative Example 4 and the amount of various materials calculated above, the foaming slurry for filling the honeycomb cell is prepared, and quickly and evenly poured into the inner cavity with a size of The bottom of the 20cm*20cm*5cm steel mold, and then quickly insert the polyimide foam honeycomb core prepared above into the mold, use the flat steel plate coated with the release agent as the upper cover, quickly close the mold, tighten the screws, and statically Set it aside for 15 minutes, then put the mold into an oven at 180°C, and cure it at high temperature for 2 hours. After cooling down and demolding, a polyimide composite foam with a honeycomb core structure with an actual overall apparent density of 153.6kg/ ^m3 was obtained. .

The limiting oxygen index value of the prepared polyimide composite foam containing the honeycomb core structure is 31.1%; the compressive strength is 452kPa; the thermal conductivity is 0.039W/(m·K); the combustion heat release peak value is 51kW/m ² ; The total amount of combustion smoke released is 0.81m ² /m ² .

Example 4

This embodiment is consistent with the mold appearance size and inner cavity size used in Examples 1-3, that is, the mold inner cavity size is 20cm*20cm*5cm, which is used to prepare high-density polyimide foam honeycomb cells with annular distribution of hexagonal prisms. The length of the hexagonal prism inlaid on the mold steel upper cover is also 5cm, but the difference is that the side length of the hexagonal prism becomes 4.8mm (that is, the diameter of the circumscribed circle is 9.6mm). The interval (gap) between two adjacent hexagonal prisms is 2 mm, which means that the final prepared honeycomb cell has a wall thickness of 2 mm. Other manufacturing processes of the mold and the drawings referred to are consistent with the molds used in Examples 1-3.

In this embodiment, after the upper cover with the hexagonal prism is put into the mold, the ratio of the volume of the hexagonal prism to the remaining space in the mold is 10.0:5.4, that is, the volume of the low-density foam filled in the core cell of the final composite foam and the honeycomb core Ratio of high-density foam volume.

The preparation process and formula of the foam slurry used to prepare the foam material in this embodiment are the same as those in Embodiment 3.

In this example, a composite foam with a honeycomb core structure having the same density as Comparative Example 4 was prepared, that is, the overall apparent density of the composite foam was 157±3kg/m ³ . In view of the cavity volume of the mold used in this embodiment, that is, the overall apparent volume of the composite foam is 4 times that of Comparative Example 4, the total amount of each reagent and chemicals used for preparing the foam foam slurry of the honeycomb core grid and the filled core grid respectively is 4 times of corresponding reagents and chemicals in comparative example 4. In this embodiment, a high-density polyimide foam honeycomb cell with a foam density of 400 kg/m ³ is prepared, and the density of the low-density polyimide foam filled with the honeycomb cell is 25.8 kg/m ³ . According to above-mentioned data, further calculate the foaming slurry quality that is used to prepare high-density polyimide foam honeycomb lattice should be 3.57 times of the foaming slurry quality in comparative example 4, be used for filling the foaming slurry quality of honeycomb lattice The foam slurry quality should be 0.43 times of the foam slurry quality in Comparative Example 4.

Prepare high-density polyimide foam honeycomb core grid according to the process shown in embodiment 3, obtain actual foam density after the demoulding that is 395kg/m The polyimide foam honeycomb core grid of 395kg/ ^m3 , place 1-2 days standby under room temperature . After the honeycomb cell is available, the composite foam is prepared according to the process of Example 3. Finally, the polyimide composite foam containing the honeycomb core structure with an actual overall apparent density of 154.2kg/ ^m3 was obtained.

The limiting oxygen index value of the prepared polyimide composite foam containing the honeycomb core structure is 31.5%; the compressive strength is 437kPa; the thermal conductivity is 0.038W/(m·K); the combustion heat release peak value is 48kW/m ² ; The total combustion smoke emission is 0.77m ² /m ² .

The series of detailed descriptions listed above are only specific descriptions for feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiment or All changes should be included within the protection scope of the present invention.

Claims (10)

1. The preparation method of the polyimide composite foam containing the honeycomb core lattice structure is characterized by comprising the following steps of:

s1, calculating the consumption of foaming slurry: according to the overall apparent density of the polyimide composite foam containing the honeycomb core lattice structure and the specification of a mould for preparing the polyimide foam honeycomb core lattice, designing the polyimide foam honeycomb core lattice with higher density and the polyimide composite foam containing the honeycomb core lattice structure with lower overall apparent density, and calculating the total consumption of foaming slurry and the consumption of foaming slurry for preparing the polyimide foam honeycomb core lattice, wherein the difference between the total consumption of foaming slurry and the consumption of foaming slurry for filling the honeycomb core lattice;

s2, preparing foaming slurry: sequentially weighing polar solvent and aromatic dianhydride, adding into a reaction device connected with a reflux condenser, stirring, heating the system to 40-80 ℃, stopping heating, and then adding fatty alcohol and aromatic dianhydride for esterification reaction until the reaction is finished; cooling to room temperature, sequentially adding a foam stabilizer, a surfactant, a catalyst and deionized water, and uniformly stirring to obtain a foaming base material; pouring the foaming backing material into a foaming slurry mixing container from a reaction device, immediately adding polyisocyanate into the foaming backing material, and mechanically stirring uniformly to obtain foaming slurry;

s3, preparing polyimide foam honeycomb core lattices: according to the consumption of the foaming slurry of the polyimide foam honeycomb core lattice calculated in the step S1 and the total foaming slurry prepared in the step S2, obtaining the calculated amount of the foaming slurry used for preparing the polyimide foam honeycomb core lattice from the total foaming slurry prepared in the step S2, quickly and uniformly pouring the foaming slurry into the bottom of a steel mold with an upper opening and a release agent, taking a steel plate with a ring-shaped uniform distribution steel hexagonal prism structure and the release agent as an upper cover, quickly closing the mold, tightening screws, standing for 10-15min, then placing the mold into an oven with the temperature of 160-240 ℃, curing at high temperature for 2-3h, and cooling and demolding to obtain the polyimide foam honeycomb core lattice;

s4, preparing polyimide composite foam with a honeycomb core lattice structure: continuously using the steel mold with the upper opening and coated with the release agent used in the step S3, and calculating the consumption of the foaming slurry for filling the honeycomb core lattice according to the step S1; and (3) obtaining the calculated amount of foaming slurry for filling the core material cells from the total foaming slurry prepared in the step (S2), quickly and uniformly pouring the foaming slurry into the bottom of the core material cells, then quickly inserting the polyimide foam honeycomb core cells prepared in the step (S3) into a mold, taking a flat steel plate coated with a release agent as an upper cover, quickly closing the mold, screwing up screws, standing for 10-15min, then placing the mold into an oven at 160-240 ℃, curing at high temperature for 2-3h, and cooling and demolding to obtain the polyimide composite foam containing the honeycomb core cell structure.

2. The method for preparing a polyimide composite foam containing a honeycomb core cell structure according to claim 1, wherein in the step S2, 20-200 parts by weight of aromatic dianhydride, 5-80 parts by weight of fatty alcohol, 100-195 parts by weight of isocyanate, 50-70 parts by weight of polar solvent, 10-15 parts by weight of foam stabilizer, 10-15 parts by weight of surfactant, 5-10 parts by weight of catalyst and 10-15 parts by weight of deionized water are calculated.

3. The method for preparing a polyimide composite foam having a honeycomb cell structure according to claim 1, wherein the aromatic dianhydride comprises a mixture of one or more of 3,3', 4' -benzophenone tetracarboxylic dianhydride, 4' -oxydiphthalic anhydride, 3', 4' -biphenyl tetracarboxylic dianhydride and pyromellitic dianhydride in step S2.

4. The method for preparing a polyimide composite foam having a honeycomb cell structure according to claim 1, wherein in step S2, the aliphatic alcohol comprises a mixture of one or more of methanol, ethanol, propanol, and isopropanol.

5. The method for preparing a polyimide composite foam having a honeycomb cell structure according to claim 1, wherein the catalyst comprises a mixture of one or more of triethanolamine, stannous octoate, dibutyltin dilaurate, and Dabco33-LV in step S2.

6. The method for preparing a polyimide composite foam having a honeycomb core structure according to claim 1, wherein in the step S2, the isocyanate is polyphenyl polymethylene polyisocyanate having an NCO weight percentage of 30% to 40%.

7. A polyimide composite foam having a honeycomb cell structure, which is produced by the production method according to any one of claims 1 to 6.

8. The polyimide composite foam having a honeycomb cell structure according to claim 7, wherein the polyimide foam honeycomb cell has a wall thickness of 2 to 4mm.

9. The polyimide composite foam having a honeycomb cell structure according to claim 7, wherein the polyimide foam honeycomb cells have a circumscribed circle diameter of 7.2 to 20.0mm.

10. The polyimide composite foam having a honeycomb cell structure according to claim 7, wherein the polyimide foam honeycomb cell has a density of 250 to 470kg/m3; the polyimide composite foam containing the honeycomb core lattice structure has the overall apparent density of 90-160kg/m < 3 >.

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