A flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage

Abstract

The present invention belongs to the technical field of composite materials, and relates to a flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage, wherein the flame-retardant unsaturated polyester resin-based fiber composite material is made of unsaturated polyester, liquid flame-retardant curing agent, initiator and basalt fiber cloth as raw materials, and the flow and penetration of the unsaturated polyester are utilized to realize the impregnation of the basalt fiber cloth, and the composite material with a certain resin / fiber ratio is solidified. The present invention introduces a bifunctional liquid flame-retardant curing agent containing P and N elements into the unsaturated polyester, effectively improving the flame retardancy and thermal stability of the flame-retardant unsaturated polyester resin-based fiber composite material, and the presence of two rigid benzene rings in the molecule increases the distance between the unsaturated polyester chain segments, thereby effectively reducing the volume shrinkage of the fiber composite material during curing, so that it has excellent mechanical properties; the curing volume shrinkage of the fiber composite material can reach 2.5-3.0%.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and in particular relates to a flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage. Background Art

[0002] At present, unsaturated polyester resin (UPR) is a kind of thermosetting resin with rapid development, wide application field and large number of products. It is a highly cross-linked polymer polymer prepared by polycondensation reaction of diols and unsaturated dibasic acids or anhydrides. Due to the advantages of good mechanical properties, strong processability and high cost performance, UPR is widely used in industries such as chemical corrosion protection, rail transportation, marine engineering, and electronic appliances. However, the high volume shrinkage rate and high flammability of UPR limit its further application in more fields. Therefore, it is urgent to develop a UPR and its composite material with excellent mechanical properties and flame retardant properties.

[0003] In the prior art, due to the poor compatibility between flame retardants and resin matrices, the addition of flame retardants will reduce the mechanical properties of the resin matrix. Basalt fiber has excellent mechanical properties and non-flammability. If flame retardant curing agent can be added to unsaturated polyester and combined with basalt fiber to form a fiber composite material, a flame retardant unsaturated polyester fiber composite material with low volume shrinkage, excellent mechanical properties and high flame retardancy can be developed. This is a new attempt and breakthrough, and also has broad application prospects. Summary of the invention

[0004] The purpose of the present invention is to provide a flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage, by mixing a PN type liquid flame retardant containing a benzene ring into the UPR and compounding it with basalt fiber to solve the problem of making the unsaturated polyester resin and its fiber composite material have high flame retardancy while reducing its curing volume shrinkage. The volume shrinkage of the flame-retardant unsaturated polyester resin and the flame-retardant unsaturated polyester fiber composite material reaches 2.5-3.0%.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage, wherein the volume shrinkage is 2.5-3.0%. The flame-retardant unsaturated polyester resin-based fiber composite material is made of unsaturated polyester, liquid flame-retardant curing agent, initiator and basalt fiber cloth as raw materials, and the basalt fiber cloth is impregnated by the flow and penetration of the unsaturated polyester, and is cured to form a composite material with a certain resin / fiber ratio; by mass fraction, the composite material comprises 29.4%-44.1% of unsaturated polyester, 8%-16% of liquid flame-retardant curing agent, 0.6%-1% of initiator, and 40%-60% of basalt fiber cloth;

[0007] The liquid flame retardant curing agent is a bifunctional liquid flame retardant curing agent containing P and N elements, and has two rigid benzene rings in the molecule, and contains both P and N flame retardant elements and unsaturated double bonds;

[0008] The flame-retardant unsaturated polyester-based basalt fiber composite material with low volume shrinkage is prepared according to the following steps:

[0009] A. Mix the initiator, liquid flame retardant curing agent and unsaturated polyester at 75°C, place in a vacuum oven for vacuum degassing for 5 minutes, and obtain an unsaturated polyester solution;

[0010] B. Fully impregnate the unsaturated polyester solution with the basalt fiber cloth by vacuum assisted molding;

[0011] C. The curing process of composite materials is: thermal curing at 80℃ for 1-1.5h, 100℃ for 1.5-2h, and 120℃ for 1-1.5h.

[0012] Furthermore, the unsaturated polyester is unsaturated polyester 196.

[0013] Furthermore, the initiator is benzoyl peroxide.

[0014] Furthermore, the liquid flame retardant curing agent is DH, which is prepared according to the following steps:

[0015] a. Add 500 mL of DCM, 0.2 mol of DOPO and 0.22 mol of Et3N into a flask in sequence and stir. After DOPO is completely dissolved, add 0.22 mol of HEAA into the flask;

[0016] b. Add 0.22 mol of CCl4 dropwise into the flask at 0°C and react at room temperature for 14 hours;

[0017] c. The product after the reaction was diluted with 600 mL of DCM, extracted with deionized water and saturated brine, and the organic layer obtained by extraction was dried over anhydrous magnesium sulfate and filtered. The organic layer after drying was distilled under reduced pressure to remove the solvent to obtain a light yellow liquid;

[0018] d. Use a mixture of ethyl acetate and petroleum ether as a developing agent to purify the product. The yellow liquid obtained after purification is the PN type liquid flame retardant containing a benzene ring.

[0019] Furthermore, the basalt fiber cloth is laid in multiple layers, and its surface weight is 300g / m 2 The number of layers is 6-8, and the thickness of the flame retardant unsaturated polyester resin fiber composite laminate is 1.96-2.04mm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention introduces a bifunctional liquid flame retardant curing agent containing P and N elements into unsaturated polyester, which can effectively improve the flame retardant performance and thermal stability of the flame retardant unsaturated polyester resin-based fiber composite material; P and N elements can play an excellent synergistic flame retardant effect in the gas phase and the condensed phase, so that it has excellent charring ability during combustion and can generate non-combustible gas and reduce smoke release; the introduction of the bifunctional liquid flame retardant curing agent containing P and N elements can make its mass retention rate at high temperature higher, thereby improving thermal stability;

[0022] 2. While improving the flame retardancy and thermal stability of the fiber composite material, the present invention can effectively reduce the volume shrinkage of the fiber composite material during curing due to the presence of two rigid benzene rings in the molecule, which increases the distance between the unsaturated polyester segments and enables it to have excellent mechanical properties.

[0023] 3. The volume shrinkage rate of the flame-retardant unsaturated polyester resin-based fiber composite material of the present invention can reach 2.5-3.0%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 These are TG and DTG curves of the flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage under nitrogen and air atmospheres. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0027] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0028] At present, the high volume shrinkage and high flammability of UPR limit its application in many fields. Based on this, the present invention pays attention to the relationship between volume shrinkage and mechanical properties, and prepares fiber composite materials by compounding basalt fibers with excellent mechanical properties and non-flammability with resin to improve the mechanical properties and flame retardant properties of the resin matrix. In addition, in order to further improve the mechanical properties and flame retardant properties of the resin matrix, the present invention mixes a reactive flame retardant into the resin matrix, and the reactive flame retardant curing agent of UPR can participate in the curing of UPR, so that it can effectively avoid the problem of poor compatibility between the flame retardant and the resin matrix. After the flame retardant is added to the resin, the viscosity is reduced, and vacuum-assisted molding can be performed.

[0029] The present invention provides a fiber composite material of flame-retardant unsaturated polyester resin with low volume shrinkage, which uses unsaturated polyester, liquid flame-retardant curing agent, initiator and basalt fiber cloth as raw materials, utilizes the flow and penetration of unsaturated polyester to impregnate basalt fiber cloth, and solidifies to form a composite material with a certain resin / fiber ratio. By mass fraction, it includes 29.4%-44.1% of unsaturated polyester, 8%-16% of liquid flame-retardant curing agent, 0.6%-1% of initiator, and 40%-60% of basalt fiber cloth.

[0030] The preparation process of the fiber composite material is as follows: first, the initiator, liquid flame retardant curing agent and unsaturated polyester are mixed at 75°C, and placed in a vacuum oven for vacuum degassing for 5 minutes to obtain an unsaturated polyester solution; then, the unsaturated polyester solution and basalt fiber cloth are fully impregnated by vacuum assisted molding; finally, the composite material curing process is: thermal curing at 80°C for 1-1.5h, 100°C for 1.5-2h, and 120°C for 1-1.5h.

[0031] Wherein, the unsaturated polyester is unsaturated polyester 196. The initiator is benzoyl peroxide.

[0032] The surface weight of the basalt fiber cloth is 300g / m2 The number of layers of basalt fiber cloth is 6-8, and the thickness of flame retardant unsaturated polyester fiber composite laminate is 1.96-2.04mm.

[0033] The liquid flame retardant curing agent is a flame retardant and curing dual-function liquid flame retardant curing agent DH containing P and N elements, and has two rigid benzene rings in the molecule, and contains both P and N flame retardant elements and unsaturated double bonds. It is prepared according to the following steps:

[0034] a. Add 500 mL of DCM, 0.2 mol of DOPO and 0.22 mol of Et3N into a flask in sequence and stir. After DOPO is completely dissolved, add 0.22 mol of HEAA into the flask;

[0035] b. Add 0.22 mol of CCl4 dropwise into the flask at 0°C and react at room temperature for 14 hours;

[0036] c. The product after the reaction was diluted with 600 mL of DCM, extracted with deionized water and saturated brine, and the organic layer obtained by extraction was dried over anhydrous magnesium sulfate and filtered. The organic layer after drying was distilled under reduced pressure to remove the solvent to obtain a light yellow liquid;

[0037] d. Use a mixture of ethyl acetate and petroleum ether as a developing agent to purify the product. The yellow liquid obtained after purification is the PN type liquid flame retardant containing a benzene ring.

[0038] The specific test process is:

[0039] 1. Mix the unsaturated polyester, flame retardant curing agent and initiator evenly under heating conditions, specifically in an oil bath pot at 75°C. After the flame retardant curing agent is completely dissolved in the resin, eliminate the bubbles in the solution to obtain a flame retardant unsaturated polyester solution;

[0040] 2. Cut the basalt fiber cloth to the required size, stack multiple layers of basalt fiber cloth on the stainless steel plate sprayed with release agent, stick double-sided butyl tape around the steel plate, cover with vacuum diversion release cloth, place diversion net and resin diversion switch valve on the resin side, place polyester adhesive felt and vacuum diversion switch valve on the vacuum side, and finally, use vacuum bag film to seal the entire device;

[0041] 3. Cut a section of vacuum diversion tube and extend it into the flame-retardant unsaturated polyester solution in step 1, and connect it to the resin diversion switch valve. Connect the vacuum pump to the vacuum diversion valve. After checking the air tightness of the device, turn on the vacuum pump to draw in the flame-retardant unsaturated polyester solution. After the resin completely infiltrates the basalt fiber cloth, close the resin diversion switch valve, and close the vacuum diversion valve after maintaining the pressure for a period of time;

[0042] 4. Place the vacuumed device on a heating plate and cure it according to the procedure. The curing process is: 80℃1-1.5h, 100℃1.5-2h, 120℃1-1.5h thermal curing.

[0043] The present invention mixes a reactive flame retardant into a resin matrix to participate in the curing of UPR. The PN type liquid flame retardant containing a benzene ring in the reactive flame retardant curing agent of UPR has an excellent effect on improving the mechanical properties and flame retardant properties of the resin matrix. The P and N elements synergistically flame retard the UPR in the gas phase and the condensed phase, and the rigid benzene ring structure is conducive to reducing the volume shrinkage during curing, thereby achieving the effect of simultaneously improving the mechanical properties and flame retardancy. The PN type liquid flame retardant containing a benzene ring is mixed into the UPR and compounded with basalt fiber to produce a flame-retardant unsaturated polyester fiber composite material with low volume shrinkage, excellent mechanical properties, and high flame retardancy.

[0044] In the present invention, the volume shrinkage rate of the flame-retardant unsaturated polyester fiber composite material is 2.5-3.0%.

[0045] Example 1

[0046] A flame-retardant unsaturated polyester fiber composite material with low volume shrinkage is prepared by vacuum-assisted molding process using basalt fiber cloth and flame-retardant unsaturated polyester solution as raw materials, wherein the mass fraction of basalt fiber cloth is 60%, the mass fraction of unsaturated polyester solution is 31.4%, the mass fraction of liquid flame-retardant curing agent is 8%, and the mass fraction of initiator is 0.6%.

[0047] Among them, the surface weight of basalt fiber cloth is 300g / m 2 The number of layers of basalt fiber cloth is 8, and the thickness of flame retardant unsaturated polyester fiber composite laminate is 2.01 mm.

[0048] The viscosity of the flame retardant unsaturated polyester solution is 54000 mPa·s, the liquid flame retardant curing agent is a bifunctional liquid flame retardant curing agent containing P and N elements, and the initiator is benzoyl peroxide.

[0049] The molding method of the fiber composite material is vacuum assisted molding, the curing process is: 80°C for 1.5h, 100°C for 1.5h, 120°C for 1h, and the molding pressure is normal pressure.

[0050] Example 2

[0051] A flame-retardant unsaturated polyester fiber composite material with low volume shrinkage is made of basalt fiber cloth and flame-retardant unsaturated polyester solution as raw materials and is produced by vacuum-assisted molding process. Among them, the mass fraction of basalt fiber cloth is 60%, the mass fraction of unsaturated polyester solution is 29.4%, the mass fraction of liquid flame-retardant curing agent is 10%, and the mass fraction of initiator is 0.6%;

[0052] Among them, the surface weight of basalt fiber cloth is 300g / m 2 , the number of layers of basalt fiber cloth is 8, and the thickness of the flame retardant unsaturated polyester fiber composite laminate is 2.03 mm;

[0053] The viscosity of the flame retardant unsaturated polyester solution is 47000 mPa·s, the liquid flame retardant curing agent is a bifunctional liquid flame retardant curing agent containing P and N elements, and the initiator is benzoyl peroxide.

[0054] The molding method of the fiber composite material is vacuum assisted molding, the curing process is: 80°C for 1h, 100°C for 1.5h, 120°C for 1.5h, and the molding pressure is normal pressure.

[0055] Example 3

[0056] A flame-retardant unsaturated polyester fiber composite material with low volume shrinkage is prepared by using basalt fiber cloth and flame-retardant unsaturated polyester solution as raw materials and adopting vacuum assisted molding process, wherein the mass fraction of basalt fiber cloth is 50%, the mass fraction of unsaturated polyester solution is 34.3%, the mass fraction of liquid flame-retardant curing agent is 15%, and the mass fraction of initiator is 0.7%.

[0057] Among them, the surface weight of basalt fiber cloth is 300g / m 2 The number of layers of basalt fiber cloth is 7, and the thickness of flame retardant unsaturated polyester fiber composite laminate is 1.96 mm.

[0058] The viscosity of the flame retardant unsaturated polyester solution is 40000 mPa·s, the liquid flame retardant curing agent is a bifunctional liquid flame retardant curing agent containing P and N elements, and the initiator is benzoyl peroxide.

[0059] The molding method of the fiber composite material is vacuum assisted molding, the curing process is: 80°C for 1h, 100°C for 2h, 120°C for 1h, and the molding pressure is normal pressure.

[0060] Example 4

[0061] A flame-retardant unsaturated polyester fiber composite material with low volume shrinkage is prepared by using basalt fiber cloth and flame-retardant unsaturated polyester solution as raw materials and adopting vacuum assisted molding process, wherein the mass fraction of basalt fiber cloth is 50%, the mass fraction of unsaturated polyester solution is 36.7%, the mass fraction of liquid flame retardant curing agent is 12.5%, and the mass fraction of initiator is 0.8%.

[0062] The surface weight of basalt fiber cloth is 300g / m 2 The number of layers of basalt fiber cloth is 7, and the thickness of flame retardant unsaturated polyester fiber composite laminate is 2.02 mm.

[0063] The viscosity of the flame retardant unsaturated polyester solution is 47000 mPa·s, the liquid flame retardant curing agent is a bifunctional liquid flame retardant curing agent containing P and N elements, and the initiator is benzoyl peroxide.

[0064] The molding method of the fiber composite material is vacuum assisted molding, the curing process is: 80°C for 1.5h, 100°C for 1.5h, 120°C for 1h, and the molding pressure is normal pressure.

[0065] Example 5

[0066] A flame-retardant unsaturated polyester fiber composite material with low volume shrinkage is prepared by vacuum-assisted molding process using basalt fiber cloth and flame-retardant unsaturated polyester solution as raw materials, wherein the mass fraction of basalt fiber cloth is 40%, the mass fraction of unsaturated polyester solution is 44.1%, the mass fraction of liquid flame-retardant curing agent is 15%, and the mass fraction of initiator is 0.9%.

[0067] The surface weight of basalt fiber cloth is 300g / m 2 ,The number of layers of basalt fiber cloth is 6, and the thickness of the flame retardant unsaturated polyester fiber composite laminate is 1.99 mm.

[0068] The viscosity of the flame retardant unsaturated polyester solution is 47000 mPa·s, the liquid flame retardant curing agent is a bifunctional liquid flame retardant curing agent containing P and N elements, and the initiator is benzoyl peroxide.

[0069] The molding method of the fiber composite material is vacuum assisted molding, the curing process is: 80°C for 1h, 100°C for 2h, 120°C for 1h, and the molding pressure is normal pressure.

[0070] Example 6

[0071] A flame-retardant unsaturated polyester fiber composite material with low volume shrinkage is made of basalt fiber cloth and flame-retardant unsaturated polyester solution as raw materials and is produced by vacuum-assisted molding process. Among them, the mass fraction of basalt fiber cloth is 40%, the mass fraction of unsaturated polyester solution is 43%, the mass fraction of liquid flame-retardant curing agent is 16%, and the mass fraction of initiator is 1%;

[0072] The surface weight of basalt fiber cloth is 300g / m 2 The number of layers of the basalt fiber cloth is 6, and the thickness of the flame-retardant unsaturated polyester fiber composite laminate is 2.00 mm.

[0073] The viscosity of the flame retardant unsaturated polyester solution is 54000 mPa·s, the liquid flame retardant curing agent is a bifunctional liquid flame retardant curing agent containing P and N elements, and the initiator is benzoyl peroxide.

[0074] The molding method of the fiber composite material is vacuum assisted molding, the curing process is: 80°C for 1h, 100°C for 1.5h, 120°C for 1.5h, and the molding pressure is normal pressure.

[0075] Example 7

[0076] A flame-retardant unsaturated polyester resin with low volume shrinkage, wherein the unsaturated polyester in the solution is 78.4%, the liquid flame-retardant curing agent is 20%, the initiator is 1.6%, and the viscosity is 54000mPa·s. The liquid flame-retardant curing agent is a bifunctional liquid flame-retardant curing agent containing P and N elements, and the initiator is benzoyl peroxide. The thermal curing process of the flame-retardant unsaturated polyester resin is: 80℃1.5h, 100℃1.5h, 120℃1h, and the molding pressure is normal pressure.

[0077] Example 8

[0078] A flame-retardant unsaturated polyester resin with low volume shrinkage, wherein the unsaturated polyester in the solution is 73.5%, the liquid flame-retardant curing agent is 25%, the initiator is 1.5%, and the viscosity is 47000mPa·s. The liquid flame-retardant curing agent is a bifunctional liquid flame-retardant curing agent containing P and N elements, and the initiator is benzoyl peroxide. The thermal curing process of the flame-retardant unsaturated polyester resin is: 80℃1h, 100℃2h, 120℃1h, and the molding pressure is normal pressure.

[0079] Example 9

[0080] A flame-retardant unsaturated polyester resin with low volume shrinkage, wherein the unsaturated polyester in the solution is 68.6% by mass, the liquid flame-retardant curing agent is 30% by mass, the initiator is 1.4% by mass, the viscosity is 40000 mPa·s, the liquid flame-retardant curing agent is a bifunctional liquid flame-retardant curing agent containing P and N elements, and the initiator is benzoyl peroxide. The thermal curing process of the flame-retardant unsaturated polyester resin is: 80℃1.5h, 100℃1.5h, 120℃1h, and the molding pressure is normal pressure.

[0081] Comparative Example 1

[0082] The flame retardant unsaturated polyester fiber composite material of this comparative example is made of basalt fiber cloth and flame retardant unsaturated polyester solution as raw materials and is prepared by vacuum assisted molding process, wherein the mass fraction of basalt fiber cloth is 50%, the mass fraction of unsaturated polyester solution is 43%, the mass fraction of liquid flame retardant curing agent is 16%, and the mass fraction of initiator is 1%.

[0083] Among them, the surface weight of basalt fiber cloth is 300g / m 2 The number of layers of basalt fiber cloth is 7, and the thickness of flame retardant unsaturated polyester fiber composite laminate is 2.01 mm.

[0084] The viscosity of the flame retardant unsaturated polyester solution is 30000 mPa·s, the liquid flame retardant is commercially available liquid flame retardant UND-06, and the initiator is benzoyl peroxide.

[0085] The molding method of the fiber composite material is vacuum assisted molding, the curing process is: 80°C for 1h, 100°C for 2h, 120°C for 1h, and the molding pressure is normal pressure.

[0086] Comparative Example 2

[0087] The flame-retardant unsaturated polyester fiber composite material of this comparative example is made of basalt fiber cloth and unsaturated polyester solution as raw materials and is prepared by vacuum-assisted molding process, wherein the mass fraction of basalt fiber cloth is 60%, the mass fraction of unsaturated polyester solution is 39.2%, and the mass fraction of initiator is 0.8%.

[0088] Among them, the surface weight of basalt fiber cloth is 300g / m 2 The number of layers of basalt fiber cloth is 8, and the thickness of flame retardant unsaturated polyester fiber composite laminate is 1.98 mm.

[0089] No flame retardant was added to the unsaturated polyester solution, the mass fraction of the initiator was 2%, the viscosity of the unsaturated polyester solution was 60000 mPa·s, and the initiator was benzoyl peroxide.

[0090] The molding method of the fiber composite material is vacuum assisted molding, the curing process is: 80°C for 1h, 100°C for 1.5h, 120°C for 1.5h, and the molding pressure is normal pressure.

[0091] Comparative Example 3

[0092] This comparative example is an unsaturated polyester resin without basalt fiber cloth, no flame retardant is added to the unsaturated polyester solution, the mass fraction of the unsaturated polyester solution is 98%, the mass fraction of the initiator is 2%, the viscosity of the unsaturated polyester solution is 60000mPa·s, and the initiator is benzoyl peroxide. The thermal curing process of the unsaturated polyester resin is: 80℃1h, 100℃2h, 120℃1h, and the molding pressure is normal pressure.

[0093] 1. Mechanical properties test of flame retardant unsaturated polyester fiber resin and its fiber composite materials

[0094] Mechanical property tests were conducted on each embodiment and comparative example, including tensile test, bending test, and Shore hardness test. The mechanical properties of each embodiment and comparative example are shown in Table 1. As can be seen from Table 1, the mechanical properties of Examples 7 to 9 and Examples 1 to 6 are better than those of the resin and fiber composite materials in the comparative example. This is because the dual-functional liquid flame retardant curing agent selected in each embodiment can participate in the curing of the unsaturated polyester resin. The commercially available flame retardant selected in Comparative Example 1 cannot participate in the curing of the resin, and the rigid benzene ring structure in the dual-functional liquid flame retardant curing agent can enhance the rigidity of the resin. Therefore, each embodiment has better mechanical properties than the corresponding comparative example. The fiber cloth layers of Examples 4 to 6 are relatively small, and their ability to disperse stress is relatively weak. Therefore, their tensile strength is not as good as that of Examples 1 to 3. In addition, since the bifunctional liquid flame retardant curing agent used in the embodiment has a larger molecular structure than the curing agent styrene in the unsaturated polyester, the presence of two rigid benzene rings in its molecule increases the distance between the unsaturated polyester segments, thereby effectively reducing the curing volume shrinkage of the resin and its composite material, which also ensures that the resin and fiber composite material have excellent mechanical properties. Comparing Examples 1 to 6 and Examples 7 to 9, it can be seen that the introduction of basalt fiber cloth greatly improves the tensile strength of the composite material. This is because when subjected to external stress, the basalt fiber bears and transmits most of the stress, thus giving the fiber composite material excellent mechanical properties.

[0095] Table 1 Mechanical properties of flame retardant unsaturated polyester resin and its fiber composites

[0096]

[0097]

[0098] 2. Flame retardant properties test of flame retardant unsaturated polyester fiber composites

[0099] Oxygen index (LOI) test was carried out on each embodiment and comparative example, and the test results are shown in Table 2; cone calorimetry test (CCT) was carried out on embodiment 9 and comparative example 3, and the parameters such as ignition time, peak heat release value, total heat release value, average effective heat of combustion, total smoke release value, and residual carbon rate are shown in Table 3. It can be seen from Table 2 that with the increase of the proportion of flame retardant curing agent in the resin, the LOI of unsaturated polyester resin and its fiber composite material is improved. It can be seen from Table 3 that in CCT, embodiment 9 with the addition of flame retardant curing agent has a shorter ignition time, lower total heat release and peak heat release, lower average effective heat of combustion and higher residual carbon rate. The embodiment introducing flame retardant curing agent has better flame retardant performance, which is due to the introduction of bifunctional liquid flame retardant curing agent containing P and N elements into unsaturated polyester, and P and N elements can play an excellent synergistic flame retardant effect in the gas phase and condensed phase when the composite material is burned. In the gas phase, the phosphorus-containing free radicals generated when the P-containing compound decomposes can capture highly active free radicals in the gas phase such as H·, OH· and react with them, playing a role in quenching the flame; while the N-containing compound will generate non-combustible gases such as N2 and NH3 when it decomposes, which plays a role in diluting the concentration of combustible gases, O2 and other gases. On the other hand, in the condensed phase, the phosphoric acid compound generated by the decomposition of the bifunctional liquid flame retardant curing agent containing P and N elements will catalyze and promote the formation of a phosphorus-containing carbon layer in the resin matrix, which can improve the mass retention rate of the resin and its fiber composite material and form a more dense and complete carbon layer, thereby inhibiting the transfer of gas phase products and heat. In addition, compared with Examples 1 to 6 and Examples 7 to 9, the introduction of basalt fiber cloth improves the flame retardant properties of unsaturated polyester resin, because basalt fiber itself is non-combustible and can transfer and disperse heat in the fiber composite material. In addition, the composition of basalt fiber contains a variety of metal oxides, which can promote carbonization. Therefore, the flame-retardant unsaturated polyester fiber composite material has better flame retardant properties than unsaturated polyester resin.

[0100] Table 2 Flame retardant properties of flame retardant unsaturated polyester and its fiber composites

[0101]

[0102] Table 3 Parameters of flame retardant unsaturated polyester in CCT

[0103]

[0104] 3. Thermal stability test of flame retardant unsaturated polyester fiber composites

[0105] Thermogravimetric tests were performed on Examples 1 to 3 and Comparative Example 2 under nitrogen and air atmospheres, and the TG and DTG curves thereof are shown in FIG. Figure 1 As shown in the figure, the T of each test item 5％ , T max The mass retention rates at 750°C and 750°C are shown in Table 4. Compared with Comparative Example 2 without adding a flame retardant curing agent, the T 5％ , T in nitrogen and air atmosphere max The mass retention rate at 750°C is lower and higher. This may be due to the preferential decomposition of the phosphorus-containing compounds in the dual-functional liquid flame retardant curing agent containing P and N elements to form phosphates and pyrophosphates. At the same time, the decomposition of UPR is catalyzed to form a denser and more complete carbon layer. In addition, the mass retention rate of each embodiment at 750°C exceeds 72%, indicating that the flame retardant unsaturated polyester fiber composite material prepared by the present invention has excellent thermal stability.

[0106] Table 4 Thermal stability of flame-retardant unsaturated polyester fiber composites in air and nitrogen atmosphere

[0107]

[0108] The flame-retardant unsaturated polyester resin and its fiber composite material provided by the present invention have excellent mechanical properties, flame-retardant properties and thermal stability, and their volume shrinkage is small; the bifunctional liquid flame-retardant curing agent containing P and N elements provided by the present invention can effectively improve the flame-retardant properties of the flame-retardant unsaturated polyester resin and its fiber composite material and can effectively reduce the curing volume shrinkage of the resin and fiber composite material.

[0109] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage, characterized in that: Its volume shrinkage rate is 2.5-3.0%. The flame-retardant unsaturated polyester resin-based fiber composite material is made of unsaturated polyester, liquid flame-retardant curing agent, initiator and basalt fiber cloth as raw materials, and utilizes the flow and penetration of unsaturated polyester to impregnate the basalt fiber cloth, and solidifies to form a composite material with a certain resin / fiber ratio; by mass fraction, it includes 29.4%-44.1% of unsaturated polyester, 8%-16% of liquid flame-retardant curing agent, 0.6%-1% of initiator, and 40%-60% of basalt fiber cloth; The liquid flame retardant curing agent is a bifunctional liquid flame retardant curing agent containing P and N elements, and has two rigid benzene rings in the molecule, and contains both P and N flame retardant elements and unsaturated double bonds; The flame-retardant unsaturated polyester-based basalt fiber composite material with low volume shrinkage is prepared according to the following steps: A. Mix the initiator, liquid flame retardant curing agent and unsaturated polyester at 75°C, place in a vacuum oven for vacuum degassing for 5 minutes, and obtain an unsaturated polyester solution; B. Fully impregnate the unsaturated polyester solution with the basalt fiber cloth by vacuum assisted molding; C. The curing process of composite materials is: thermal curing at 80℃ for 1-1.5h, 100℃ for 1.5-2h, and 120℃ for 1-1.5h.

2. The flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage according to claim 1, characterized in that: The unsaturated polyester is unsaturated polyester 196.

3. The flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage according to claim 1, characterized in that: The initiator is benzoyl peroxide.

4. The flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage according to claim 1, characterized in that: The liquid flame retardant curing agent is DH, which is prepared according to the following steps: a. Add 500 mL of DCM, 0.2 mol of DOPO and 0.22 mol of Et3N into a flask in sequence and stir. After DOPO is completely dissolved, add 0.22 mol of HEAA into the flask; b. Add 0.22 mol of CCl4 dropwise into the flask at 0°C and react at room temperature for 14 hours; c. The product after the reaction was diluted with 600 mL of DCM, extracted with deionized water and saturated brine, and the organic layer obtained by extraction was dried over anhydrous magnesium sulfate and filtered. The organic layer after drying was distilled under reduced pressure to remove the solvent to obtain a light yellow liquid; d. Use a mixture of ethyl acetate and petroleum ether as a developing agent to purify the product. The yellow liquid obtained after purification is the PN type liquid flame retardant containing a benzene ring.

5. The flame-retardant unsaturated polyester resin-based fiber composite material with low volume shrinkage according to claim 1, characterized in that: The basalt fiber cloth is laid in multiple layers, and its surface weight is 300g / m 2 The number of layers is 6-8, and the thickness of the flame retardant unsaturated polyester resin fiber composite laminate is 1.96-2.04mm.

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