RU2398798C1 - Glass-plastic honeycomb filler and preparation method thereof - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: honeycomb filler as a polymer matrix contains a cellular polyimide obtained via polymerisation of diethyl ether of benzophenone tetracarboxylic acid, diaminodiphenylmethane, ethyl ether of endic acid, furfuryl alcohol, maleic acid, as well as possibly triallylisocyanurate. Method of making glass-plastic honeycomb filler involves making a honeycomb packet from glass fabric, stretching it into a honeycomb block, impregnation with polyimide binder and solidification. The impregnated honeycomb blocks are dried in air for not less than 24 hours and hardened while heating stepwise at temperature between 180C and 310C. ^ EFFECT: improved environmental production conditions, longer life of the binder, lower hardening temperature, higher working temperature and strength of the honeycomb filler. ^ 3 cl, 6 ex, 7 tbl

Description

The invention relates to the construction of a honeycomb core and can be used in aircraft, shipbuilding, the automotive industry and others in three-layer structures (TSC), which are panels of various configurations, consisting of two thin skinings, between which there is a filler. The aggregates redistribute the loads to which the skin is subjected. Accordingly, aggregates must have high strength characteristics, ensuring the operability of three-layer structures and low density to ensure the minimum weight of the structure.

Various aggregates for TSC are known - honeycombs, corrugations, polystyrene, cotton wool, etc., but only honeycombs are able to provide maximum strength with minimum weight. Cellular fillers, both metallic and non-metallic, are manufactured on the basis of fiberglass, polymer films, cellulose and aramid papers. At the same time, cellular aggregates made from fiberglass fabrics impregnated with a binder based on phenol-formaldehyde resins have found particularly wide application in aircraft manufacturing. These are the frontal fairings of aircraft, floor panels, fuselage, wing and keel, wing mechanization units, etc.

Fiberglass honeycombs, selected as an analogue, made on the basis of various fiberglass impregnated with LBS-1 bakelite varnish, described in RF patent No. 2272712, op. 2006, IPC B32B 3/12, have high strength and operational characteristics. However, the temperature of their operation does not exceed 170 ° C.

It is known that in foreign industry honeycomb fillers made of fiberglass are used, impregnated with a binder on a polyimide basis (V.E. Bersudsky, V.N. Krysin, S.I. Lesnykh. "Manufacturing technology of cellular aviation structures." M .: Mechanical Engineering, 1975 city, p. 108). These aggregates can be used for a long time at temperatures up to 260 ° C and for a short time up to 350 ° C.

In the work "Steklosotoplast SSP-7P based on capillary fibers", Pavlov V.V. et al., collection "Aviation materials", issue 5. Honeycomb decorative panels for the interior of modern aircraft, VIAM, ONTI, M., 1977, pp. 11-17 describes a fiberglass honeycomb core containing a uniform hexagonal shape of cells made of T-24 (P) fiberglass impregnated with SP- polyimide binder 97, operable at temperatures up to 300 ° C - prototype.

The SP-97 polyimide binder is a solution of two imide-forming components in a mixture of an amide solvent (methylpyrrolidone) and ethanol (solvent ratio 1: 1, solution concentration 45-50%, solution density 1.0-1.2 g / cm ³ ): diethyl benzophenone tetracarboxylic acid ester (DEEBFTKK) and diamino-diphenylmethane (DADPM) at their stoichiometric ratio. The pot life of the binder SP-97 is no more than 2 months. According to the data indicated in the work: Startsev V.M., Tyukaev V.N., Ogarev V.A. Thermal polymerization of the polyimide binder SP-97 // Plastics, 1977, - No. 3; p. 9-10, during the interaction of the monomer components of SP-97 during heating at a relatively low temperature (200 ° C), the formation of polyamide ether occurs, which at temperatures up to 280-300 ° C turns into a linear polyimide. Linear polyimide has a sufficiently high strength, but low heat resistance (250 ° C). With further heating to 350 ° C, crosslinking of linear polyimide molecules occurs with the formation of a sparse cross-linked polyimide. Mesh polyimide has a higher heat resistance (up to 350 ° C), but low strength, because the crosslinking reaction proceeds according to the polycondensation mechanism with the release of a large number of low molecular weight products, which leads to the appearance of porosity in the crosslinked polyimide (up to 20 vol.%).

The disadvantages of the prototype include: the use of honeycomb for impregnation of a polyimide binder SP-97, which uses amide solvents with a high toxicological effect, a short pot life of the polyimide binder SP-97 (2 months), low heat resistance (250-280 ° C) impregnated them and uncured cells, a high curing temperature (350 ° C) and low strength impregnated with them and cured cells.

The book of V.E.Bersudsky et al. (See above) describes methods for producing cellular aggregates by stretching honeycomb packets obtained either from glued individual fiberglass cloths or from special bulk fiberglass.

In the case of the use of honeycomb packets glued from separate fiberglass webs, adhesive strips are applied in a certain way to the fiberglass roll. Fiberglass coated with adhesive strips is cut into blanks and assembled into honeycomb packets so that when the honeycomb is stretched into a honeycomb, cells of the correct hexagonal shape are formed. The glass blanks of the honeycomb package are glued in the process of pressing it at the curing temperature of the glue.

In the case of using bulk fiberglass on special machines, fiberglass is fabricated, which is a honeycomb of sheets of fiberglass, interconnected in a predetermined order by glass fibers, which, when stretched, allows you to get honeycomb blocks with cells of a given geometric shape.

In both cases, the obtained honeycomb packets are stretched into honeycomb so that the cells of the correct geometric shape (mainly hexagonal) are formed, after which the honeycomb is impregnated with a binder based on phenol-formaldehyde resins, cured and used for its intended purpose.

Fiberglass honeycombs obtained on the basis of LBS-1 bakelite varnish according to the patent of the Russian Federation 2272712 are made at low curing temperatures (up to 170 ° C), however, this method does not allow to obtain honeycombs with an operating temperature above 170 ° C - an analogue.

An article by V.V. Pavlov et al. (See above) describes a method for producing fiberglass plastic by the method of stretching honeycomb packets obtained from T-24 (P) fiberglass blanks glued with BF-2 glue. The honeycomb bag, stretched into a honeycomb, is impregnated with a SP-97 polyimide binder, and then cured. The obtained fiberglass plastics have low strength characteristics, but can be operated at temperatures up to 300 ° C - a prototype.

The objective of the invention is to improve the environmental conditions for the production of honeycomb aggregates by eliminating toxic amide solvents from the process, increase the pot life of the binder used to impregnate the honeycomb, reduce the curing temperature, and increase the operating temperature of the honeycomb aggregate (up to 400 ° C) and its strength.

The technical effect is achieved by the fact that the fiberglass honeycomb core contains a uniform hexagonal cell structure made of fiberglass impregnated with a polyimide binder, which is based on a mixture based on a mixture of imide-forming monomers containing benzophenone tetracarboxylic acid diethyl ether (DEEBFTKM), diaminodiphenylmethane, endic acid ester (EEEK) at a molar ratio of 1: 2: 2, as well as furyl alcohol (FS) with the addition of maleic acid (MK) as a solution spruce, forming during curing, net copolyimide (API composition) with the following ratio of components: DEEBFTKK from 22.0 to 23.0 wt.%, DADPM from 18.0 to 18.6 wt.%, EEEK from 19.0 to 20, 0 wt.%, FS from 37.0 to 39.4 wt.%, MK from 1.4 to 1.6 wt.% (1). Moreover, the composition based on imide-forming monomers may additionally contain trialisocyanurate (TAIC) in an amount of from 25 to 30 parts by weight. per 100 parts by weight composition (composition API-T).

In the method of manufacturing a fiberglass honeycomb core material, comprising making a honeycomb from a fiberglass fabric, stretching it into a honeycomb to obtain hexagonal cells, impregnating the stretched honeycomb with a polyimide binder and curing, according to the invention, roll or bulk fiberglass is used as the fiberglass, as the polyimide binder any of paragraphs 1 or 2, the impregnation of the honeycomb is carried out at room temperature in an impregnating bath by dipping. After keeping the honeycomb in an impregnating bath for at least 5 minutes, it is removed from the bath, the excess binder is drained from the walls of the honeycomb for at least 10 minutes, after which the impregnated honeycombs are dried in air for at least 24 hours, and curing is carried out by heating by step mode: heating to a temperature of 180 ° C at a speed of 4-6 ° C / min, holding at a temperature of 180 ° C for at least 1 hour, heating to a temperature of 280 ° C at a speed of 4-6 ° C / min, holding at a temperature 280 ° С for at least 2 hours, heating to a temperature of 310 ° С from speeds w 4-6 ° C / min, holding at 310 ° C for at least 2 hours.

The compositions of API and API-T are solutions of monomeric reagents in furyl alcohol, have good impregnating and wetting ability, the pot life of which at room temperature is at least 4 months. The characteristics of the solutions are presented in table 1.

Table 1 Binder Temperature ° C VZ-4 viscosity, s Density, g / cm ³ IPA twenty 155 1,188 40 40 1,168 60 19 1,160 API-T twenty 173 1,197 40 57 1,172 60 21 1,169

The honeycomb structure made of fiberglass impregnated at room temperature with an API or API-T binder is heat treated in a stepwise mode so that the binder located on the surface of the fiberglass undergoes all stages of the polymerization reaction: the formation of oligoamido acid and water removal, the formation of oligoimide and the removal of ethanol, the formation of three-dimensionally cross-linked copolyimide without isolation of low molecular weight products.

Since the formation of oligoimide from a mixture of three imide-forming monomers ends before the pyrolytic polymerization begins, the curing process, which proceeds via the polymerization mechanism, does not cause pore formation in the polymer matrix located on the surface of the walls of the cells of fiberglass honeycombs.

In the presence of maleic acid, furyl alcohol forms a furan oligomer (in the temperature range 100–160 ° С), a linear furan polymer (in the temperature range 140–200 ° С), and a net furan polymer by polymerization due to the opening of double bonds of the furan ring (in the temperature range 250-270 ° C). At the same time, the furan oligomer and the polymer, being in the molten state and acting as a plasticizer, facilitate the imidization reaction (by increasing the mobility of oligoamido acid and oligoimide molecules on the surface of the filler). The furan ring radicals formed at temperatures of 250-270 ° C initiate the opening of double bonds of the endic ring in the oligoimide; as a result of joint curing at temperatures up to 300 ° C, a network furanimide copolymer (copolyimide) is formed.

Thus, the use of API binders containing furyl alcohol capable of polymerizing simultaneously with imide-forming monomers allows: to exclude the use of a high-boiling amide (toxic) solvent and its removal before heat treatment of the honeycomb core; increase the viability of the binder to 4 months; reduce the curing temperature of the binder; increase strength by reducing pore formation at the final stage of obtaining a crosslinked polyimide; and increase the operating temperature of the honeycomb core.

The introduction of triallylisocyanurate (TAIC) into the IPA composition as a component capable of incorporating into the copolyimide structure upon curing due to the presence of double bonds in the TAIC leads to an increase in the mobility of oligoamido ether and oligoimide molecules (i.e., it performs the same way as furan oligomer and polymer, plasticizer functions at the stage of formation of oligoimide), and also plays the role of initiator of the curing reaction by opening its own double bonds, and, being integrated into the structure of the network copolyimide, reduces the structure tension ( falling as an "elasticizer"), increases the strength of the resulting copolyimide matrix in the honeycomb core.

Example 1

The manufacture of honeycombs from rolled fiberglass was carried out in a known manner (see V.E. Bersudsky, V.N. Krysin, S.I. Lesnykh. "The technology of manufacturing cellular aviation structures." M .: Mechanical Engineering, 1975, p. 108) why, on the fabric of the required brand of fiberglass in the longitudinal direction, adhesive strips of BF-2 glue were applied with a given width and pitch, providing hexagonal cells with a face size of 2.5; 3.5; 4.2; 8 and 10 mm. The resulting fiberglass was cut into blanks of the required size and stacked in a honeycomb. Glued adjacent sheets of fiberglass in a honeycomb in the process of pressing it at temperatures up to 170 ° C. We stretched the honeycomb packet into the honeycomb and fixed it in a special impregnating frame.

They were impregnated with honeycomb blocks made of electric insulating fiberglass E1 / 1-100 with a mesh size of 3.5 mm, an API binder in the following ratio of components: DEEBFTKK (TU 6-09-13-509-76) 22.6 wt.%, DADFM ( TU 6-14-415-76) 18.3 wt.%, DEEEK (TU 6-09-13-510-76) 19.5 wt.%, FS (MRTU 6-09-6508-70) 38.1 wt.%, MK (GOST 9803-61) 1.5 wt.%. The impregnation was carried out at room temperature by dipping the sotoblocks fixed in the framework in a bath filled with a binder. After keeping the honeycomb in the bath for 5 minutes, they were removed and the excess binder was drained from the walls of the honeycombs for 10 minutes. The impregnated honeycomb blocks were dried in air for 24 hours and heat treated in a stepwise mode:

180 ° C - 1 hour,

280 ° C - 2 hours,

310 ° C - 2 hours.

The heating rate between the steps is 4-6 ° C / min.

The properties of the obtained fiberglass honeycomb core were investigated. The tests were carried out on samples with a height of 10 mm, a diameter of 50 mm, cut from the obtained honeycomb. The density and compressive strength (OST 190150-74) were determined in the initial state, at a temperature of 400 ° C and at room temperature after exposure at 400 ° C for 1 hour.

The test results are presented in table 2.

table 2 Properties Indicators The size of the faces of the cells, mm 3,5 Density, kg / m ³ 73 ± 11 Tensile strength at compression at 20 ° С, MPa 2.2 ± 0.4 The compressive strength at 400 ° C (holding time 2 min), MPa 1.1 ± 0.3 The compressive strength at 400 ° C (exposure time 15 min), MPa 1.1 ± 0.3 The compressive strength at 20 ° C after exposure at 400 ° C for 1 hour, MPa 2.4 ± 0.4

As can be seen, the manufactured cellular aggregates are efficient at temperatures up to 400 ° C. In this case, the honeycomb samples have a fairly high stability at a test temperature of 400 ° C, and after holding at 400 ° C for 1 hour, their compressive strength even increases, probably due to additional crosslinking of the binder.

Example 2. Made fiberglass honeycomb aggregates, similarly to example 1, with the only difference being that for the impregnation of the honeycomb blocks an API binder was used in the following ratio of components:

Composition 1 DEEBFTKK - 22.0 wt.% DADPM - 18.0 wt.% DEEEK - 19.0 wt.% FS - 39.4 wt.% MK - 1.6 wt.% Composition 2 DEEBFTKK - 23.0 wt.% DADPM - 18.6 wt.% DEEEK - 20.0 wt.% FS - 37.0 wt.% MK - 1.4 wt.%

Analogously to example 1, we tested samples of the obtained glass-honeycomb. The test results are presented in table 3.

Table 3 Properties Indicators IPA Composition 1 Composition 2 Density, kg / m ³ 70 ± 10 75 ± 12 Tensile strength at compression at 20 ° С, MPa 2.1 ± 0.4 2.2 ± 0.5 Tensile strength at compression at 400 ° С, MPa 1.0 ± 0.2 1.1 ± 0.3 The compressive strength at 20 ° C, after exposure to 400 ° C for 1 hour, MPa 2.2 ± 0.5 2.3 ± 0.4

As you can see, a change in the composition of the binder API within the above ranges does not lead to a change in the properties of the obtained fiberglass.

Example 3. A fiberglass honeycomb core was prepared, similarly to Example 1, with the only difference being that an API binder was used to impregnate the honeycomb blocks, additionally containing TAIC (API-T binder) in the following ratio of components:

Composition 1 API - 100 wt.% TAIC - 27.5 wt.% Composition 2 API - 100 wt.% TAIC - 25.0 wt.% Composition 3 API - 100 wt.% TAIC - 30.0 wt.%

Analogously to example 1, tested samples of the obtained fiberglass. The test results are presented in table 4.

Table 4 Properties Indicators API-T Composition 1 Composition 2 Composition 3 Density, kg / m ³ 76 ± 8 75 ± 8 78 ± 10 Tensile strength at compression at 20 ° С, MPa 2.7 ± 0.3 2.7 ± 0.2 2.8 ± 0.3 The compressive strength at 400 ° C, MPa 1.3 ± 0.4 1.3 ± 0.5 1.4 ± 0.4 The compressive strength at 20 ° C, after exposure to 400 ° C for 1 hour, MPa 2.9 ± 0.4 2.9 ± 0.3 3.0 ± 0.4

As can be seen, the addition of TAIC to the composition of the polyimide binder IPA additionally allows to increase the strength characteristics of fiberglass in the initial state and does not lead to a decrease in its thermal stability.

Example 4. Fiberglass honeycomb core was prepared analogously to Example 1, with the only difference being that honeycomb cells with a cell face size of 2.5 were used to impregnate the API binder; 3.5; 4.2; 8.0 mm, obtained on the basis of various brands of fiberglass fabrics: E1 / 1-100. T-24 (P), E4-80, T-10.

Analogously to example 1, tested samples of the obtained fiberglass. The test results are presented in table 5.

Table 5 Properties Fiberglass brand E1 / 1-100 T-24 (P) E4-80 T-10 The size of the faces of the cells, mm 2.5 4.2 4.2 8 Density, kg / m ³ 100 ± 10 41 ± 5 44 ± 4 90 ± 5 Tensile strength at compression at 20 ° С, MPa 2.9 ± 0.3 1.3 ± 0.2 1.5 ± 0.3 2.8 ± 0.4 The compressive strength at 20 ° C after exposure at 400 ° C for 1 hour, MPa 3.1 ± 0.4 1.4 ± 0.2 1.6 ± 0.4 3.0 ± 0.3

For the obtained IPA-based fiberglass honeycomb aggregates with decreasing cell face sizes, an increase in density and compressive strength is observed. The use of thicker fiberglass (T-10) leads to an increase in density and compressive strength. Moreover, for all cells there is a high thermal stability at 400 ° C.

Example 5. Fiberglass honeycomb core was prepared analogously to Example 1, with the only difference being that honeycomb blocks obtained by stretching bulk cellular fiberglass OSST-10G-5, TU 1-596-256-87 were used to impregnate the API binder. For this, a blank of 150 mm length was cut from a bulk fiberglass roll and stretched in a special frame until a honeycomb block with hexagonal cells with a face size of 10 mm was formed, which was then impregnated with an API binder.

Analogously to example 1, tested samples of the obtained fiberglass. The test results are presented in table 6.

Table 6 Properties Indicators Density, kg / m ³ 48 ± 10 Tensile strength at compression at 20 ° С, MPa 2.3 ± 0.3 The compressive strength at 20 ° C after exposure at 400 ° C for 1 hour, MPa 2.4 ± 0.2

As you can see, the obtained fiberglass has high strength characteristics at low density.

Example 6. Received fiberglass honeycomb filler according to the method of the prototype, by impregnation with a binder SP-97, TU 2224-415-00209349-2000 cell blocks made analogously to example 1 of fiberglass T-24 (P) with hexagonal cells 3.5 mm in size. The honeycomb blocks impregnated with a binder SP-97 were dried in air for 24 hours and cured in step 1 and 2 mode:

mode 1 220 ° C - 1 hour 280 ° C - 1 hour mode 2 220 ° C - 1 hour 280 ° C - 1 hour 350 ° C - 1 hour

The rate of temperature rise between steps 4-6 ° C / min.

Analogously to example 1, tested samples of the obtained fiberglass. The test results are presented in table 7.

Table 7 Binder SP-97 Properties Curing Modes one 2 Density, kg / m ³ 60 ± 8 60 ± 8 The size of the faces of the cells, mm 3,5 3,5 Strength under compression, MPa: at 20 ° C 1.7 ± 0.2 1.3 ± 0.2 at 250 ° C 1.39 ± 0.3 - at 300 ° C 0.97 ± 0.2 - at 350 ° C 0.54 ± 0.1 1.16 ± 0.2

As can be seen, with a curing mode of 220 ° C - 1 hour and 280 ° C - 1 hour, that is, when the binder is in a linear polyimide state, fiberglass materials have a sufficiently high strength, but low thermal stability, and with a curing mode of 220 ° C - 1 hour, 280 ° C - 1 hour and 350 ° C - 1 hour, that is, when the binder is in the state of crosslinked polyimide, fiberglass reinforced plastics have low strength, but high thermal stability at 350 ° C.

Thus, according to the results presented in tables 2-6, it is shown that fiberglass honeycomb aggregates based on binders API and API-T have high strength and thermal stability at temperatures up to 400 ° C, exceeding the similar properties of fiberglass based on a binder SP-97 (table 7).

Claims (3)

1. Fiberglass honeycomb core containing a uniform structure of hexagonal cells made of fiberglass impregnated with a polyimide binder, characterized in that a composition based on a mixture of imide-forming monomers containing diethyl ether benzophenonetetracarboxylic acid, diaminodiphenylmethanoic acid, ethyl is used as a polyimide binder their molar ratio of 1: 2: 2, as well as furyl alcohol and maleic acid as a solvent, forming upon curing . Copolyimide first, with the following ratio of components, wt%:
benzophenone tetracarboxylic acid diethyl ester 22.0-23.0 diaminodiphenylmethane 18.0-18.6 endic acid ethyl ester 19.0-20.0 furyl alcohol 37.0-39.4 maleic acid 1.4-1.6 2. Fiberglass honeycomb core according to claim 1, characterized in that the composition based on imide-forming monomers additionally contains triallylisocyanurate in an amount of from 25 to 30 parts by weight per 100 parts by weight composition. 3. A method of manufacturing a fiberglass honeycomb aggregate, comprising obtaining a honeycomb from a fiberglass fabric, stretching it into a honeycomb to obtain hexagonal cells, impregnating the stretched honeycomb with a polyimide binder and curing, characterized in that a roll or bulk fiberglass is used as the fiberglass, as the polyimide binder the composition according to any one of claim 1 or 2, the impregnation of the honeycomb is carried out for a period of at least 5 minutes at room temperature in an impregnating bath by dipping , then it is removed from the bath, the excess binder is drained from the walls of the cells of the honeycomb for at least 10 minutes, after which the impregnated honeycombs are dried in air for at least 24 hours, and curing is carried out by heating in a stepwise mode: heating to a temperature of up to 180 ° C at a speed of 4 to 6 ° C / min, holding at a temperature of 180 ° C for at least 1 h, heating to a temperature of 280 ° C at a speed of 4 to 6 ° C / min, holding at a temperature of 280 ° C for at least 2 h , heating to a temperature of 310 ° C at a speed of 4 to 6 ° C / min, holding at a temperature of 310 ° C for at least 2 hours