Polyurethane composite material for aviation drawing die and preparation method of polyurethane composite material

Abstract

The invention discloses a polyurethane composite material for an aviation drawing mold and a preparation method thereof. The method comprises the following steps: firstly, carrying out vacuum drying on isocyanate and polyether polyol to remove moisture and bubbles, then adding a filler into the dried polyether polyol, uniformly stirring, then adding a curing agent isocyanate, uniformly stirring, and pouring the mixture into a mold for curing. The stretch-forming die prepared by the method disclosed by the invention not only improves the mechanical properties such as bending strength, impact strength and hardness, but also is simple to operate, low in mixed material viscosity, capable of being cured at room temperature, environment-friendly and easy to realize industrial production.

Description

Technical Field

[0001] The present invention disclosure relates to the technical field of the preparation of stretch forming die materials, and particularly relates to a polyurethane composite material for aviation stretch forming dies and a preparation method thereof. Background Art

[0002] The aircraft fuselage skin is used to maintain the theoretical shape of the aircraft, enabling the aircraft to have good aerodynamic characteristics and being the main load-bearing component of the aircraft. The forming methods of the aircraft metal material skin include stretching, flanging, roll bending, and drop pressing. As the main forming method of the aircraft metal material skin, stretching forming usually relies on the movement of a stretch forming machine to achieve the lifting of the workbench and the stretching and wrapping movement of the clamps at both ends of the sheet metal, so that the sheet metal adheres to the die and obtains the required skin part shape. The factor affecting stretching forming is the frictional resistance, which prevents the relative movement of the material and the die. Therefore, it is required that the surface of the stretch forming die can be as smooth as possible to reduce the frictional force. And as the stretch forming die, it has to bear the pressure applied by the stretch forming machine during use. Therefore, the stretch forming die needs to have a certain hardness and strength to prevent deformation during use.

[0003] With the continuous improvement of the performance index requirements of modern aircraft, the shapes of skin parts are becoming increasingly complex, the dimensional accuracy of the outer shape and the surface requirements are getting higher and higher, and the requirements for stretch forming dies are also getting higher and higher. Stretch forming dies play a key role in the manufacture of aircraft skins, enabling the aircraft skin materials to form characteristics of large curvature and smoothness, meeting the application requirements of the aircraft, and improving the aircraft quality. With the research and development requirements of the large-scale aircraft models, traditional dies are either several tons in weight, and have high manufacturing costs and long production cycles. Therefore, the structural form and die performance of stretch forming dies are also constantly innovating. The optimization of stretch forming die materials is of great significance for improving the performance of aircraft skins, reducing costs, improving production efficiency and quality, and enhancing the environmental adaptability and safety of aircraft. In summary, it has very important practical significance to provide a new type of material for aviation stretch forming dies. Summary of the Invention

[0004] In view of this, the present invention disclosure provides a polyurethane composite material for aviation stretch forming dies and a preparation method thereof to improve the disadvantages of the traditional polyurethane stretch forming die materials, such as poor heat resistance, easy aging, and low hardness.

[0005] On the one hand, the present invention provides a preparation method of a polyurethane composite material for aviation stretch forming dies, including:

[0006] Step 1: Using polyether polyol as the main material and isocyanate as the curing agent, the isocyanate and polyether polyol are respectively subjected to water removal and degassing treatment;

[0007] Step 2: Conducting drying treatment on the filler;

[0008] Step 3: Add the dried filler into the polyether polyol after water removal and degassing treatment, and stir and mix to degas to obtain a prepolymer;

[0009] Step 4: Add the degassed isocyanate into the prepolymer, stir evenly to obtain a mixed material;

[0010] Step 5: Pour the mixed material into a mold for curing. After curing, perform cutting treatment according to the design requirements.

[0011] Preferably, the process conditions for the water removal and degassing treatment of the isocyanate and polyether polyol respectively in Step 1 are: drying temperature is 90 - 100 °C, drying time is 0.5 - 1 h, and vacuum degree is 1 - 3 mbar.

[0012] Preferably, the process conditions for the drying treatment of the filler in Step 2 are: drying temperature is 100 - 120 °C, drying time is 6 - 8 h.

[0013] Preferably, the filler in Step 2 is one or a mixture of aluminum hydroxide and alumina.

[0014] Preferably, by weight, in Step 3, the polyether polyol is 0.87 - 1.02 parts, the filler is 0.87 - 2.54 parts, and in Step 4, the isocyanate is 0.87 - 1.02 parts

[0015] Preferably, in Step 3, the process parameters for stirring and mixing are: stirring time is 20 - 30 min, and stirring power is 2000 - 2200 W.

[0016] Preferably, in Step 4, the stirring time is 8 - 10 min, and the stirring power is 2000 - 2200 W.

[0017] Preferably, in Step 4, the process for pouring the mixed material into a mold for curing is: temperature is 20 - 30 °C, and time is 5 - 6 h.

[0018] Preferably, in Step 4, before applying the mold, heat and dry the mold to remove surface moisture, and then cool it to room temperature and evenly apply a layer of mold release agent on its surface.

[0019] The present invention also provides a polyurethane composite material for aviation stretch forming die prepared by the preparation method, including: by weight: 0.87 - 1.02 parts of polyether polyol, 0.87 - 2.54 parts of filler, and 0.87 - 1.02 parts of isocyanate; wherein the filler is: one or a mixture of aluminum hydroxide and alumina.

[0020] The polyurethane composite material for aviation stretch forming die provided by the present invention uses ether polyol (-OH) as the main material and isocyanate (-NCO) as the curing agent. By mixing the filler with the polyurethane, the disadvantages of traditional polyurethane materials for stretch forming die, such as poor heat resistance, easy aging, and low hardness, are improved. In addition, by adding the filler, the mechanical properties of the stretch forming die are more excellent.

[0021] Using the method of the present invention to prepare the stretch forming die not only improves its mechanical properties such as tensile strength, impact strength, and hardness, but also has the advantages of simple operation, low mixing viscosity, room temperature curing, environmental friendliness, and easy industrial production.

[0022] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the disclosure of the present invention. Detailed implementation manners

[0023] The following further explains the present invention in combination with specific implementation manners, but does not limit the protection scope of the present invention.

[0024] The preparation method of the polyurethane composite material for aviation stretch forming die provided by this implementation manner is as follows: First, the main material isocyanate and polyether polyol are vacuum dried to remove moisture and bubbles. Then, the filler is added to the dried polyether polyol and stirred evenly, and then the curing agent isocyanate is added and stirred evenly. The mixture is poured into the mold for curing.

[0025] Specifically, it includes the following steps:

[0026] Step 1: Using isocyanate as the curing agent and polyether polyol as the main material, the isocyanate and polyether polyol are respectively subjected to water removal and degassing treatment;

[0027] Preferably, the main material isocyanate and polyether polyol are placed in a vacuum oven for water removal and degassing treatment; the drying temperature is 90 - 100 °C, the drying time is 0.5 - 1 h, and the vacuum degree is 1 - 3 mbar.

[0028] Step 2: The filler is dried;

[0029] Preferably, the filler is placed in an oven, heated and dried to remove moisture. The drying temperature is 100 - 120 °C, and the drying time is 6 - 8 h.

[0030] Step 3: The dried filler is added to the polyether polyol after water removal and degassing treatment, and stirred and mixed for degassing to obtain a prepolymer; the filler is one or a mixture of aluminum hydroxide and alumina;

[0031] Preferably, after the filler is cooled to room temperature, the filler and polyether polyol are placed in a vacuum mixer for stirring;

[0032] Step 4: Add the isocyanate after water removal and degassing to the prepolymer, and stir evenly to obtain a mixed material; the stirring time is 30 min, and the stirring power is 2000 - 2200 W; by weight, the polyether polyol is 0.87 - 1.02 parts, the filler is 0.87 - 2.54 parts, and the isocyanate is 0.87 - 1.02 parts. The stirring time is 10 min, and the stirring power is 2000 - 2200 W.

[0033] Step 5: Pour the mixed material into a mold for curing. After curing, perform cutting treatment according to the design requirements. Preferably, the curing process is: the temperature is 20 - 30 °C, and the time is 5 - 6 h.

[0034] Preferably, before using the mold, the treatment process is: place the mold in an oven for heating and drying to remove surface moisture, and after cooling to room temperature, evenly apply a layer of mold release agent.

[0035] In this application, the polyurethane formed by the isocyanate and the polyether polyol. The added filler aluminum hydroxide forms hydrogen bonds with the -NCO groups in the polyurethane, enhancing the interfacial bonding. At the same time, the filler improves the flexural strength of the overall composite material through rigid reinforcement and stress dispersion.

[0036] The polyurethane of the polyether polyol type in this application has low hardness and poor temperature resistance, and cannot meet the usage conditions of an aviation stretch die. This embodiment combines the use of aluminum hydroxide or alumina fillers to improve the physical, chemical, and functional properties of the polyurethane resin material. By reasonably selecting and compounding the two components in the filler, the comprehensive properties of the resulting polyurethane can be synergistically optimized. In addition, during the curing process of the polyurethane resin, there are high requirements for reaction control, environmental sensitivity, and process parameter accuracy. The polyurethane resin obtained by the present invention can achieve rapid curing at room temperature.

[0037] When applying the above composite material, the filler aluminum hydroxide in the components plays a role through endothermic decomposition and gas-phase-solid-phase flame retardancy. It can decompose into alumina and water at about 200 °C, and can reduce the surface temperature of the material at high temperatures. The generated water vapor can dilute oxygen and combustible gases, and the generated alumina can achieve the purpose of isolating heat and oxygen. The filler alumina provides a heat conduction path and mechanical support. Alumina has a high thermal conductivity (30 W / (m·K)) and can form a heat network to accelerate heat diffusion. Alumina is a rigid particle that can improve hardness and wear resistance; the combined use of aluminum hydroxide and alumina can form a dual-effect network of flame retardancy and heat conduction.

[0038] Polyurethane is a polymer between rubber and plastic, which has a series of excellent physical properties such as high strength, high toughness, wear resistance, oil resistance, chemical resistance, good weather resistance, excellent low-temperature performance, and good processing performance. The design and manufacture of skin stretch forming dies are one of the key technologies in aviation process equipment. The molecular weight of polyurethane has a wide span, and its performance is closely related to the molecular weight. Specifically, as the molecular weight increases, polyurethane exhibits more excellent mechanical properties, and at the same time, its chemical corrosion resistance and weather resistance are also significantly enhanced. The composite material used for the aircraft skin in this invention is polyurethane, and compared with epoxy resin, the synthesis steps of polyurethane are simpler and the preparation time required is less.

[0039] The polyurethane composite material for aviation stretch forming dies obtained through the above steps of this implementation scheme can be cured at room temperature, with a short curing time, a fast curing rate, and a low heat release, avoiding the formation of a hollow foaming structure inside due to curing heat release, and having good processing technology;

[0040] The polyurethane composite material of this invention has a low density and is light in weight, which is convenient for use, transportation, storage, and preservation; it also has ultra-high hardness, high toughness, relatively high stiffness, excellent impact resistance, resistance to high and low temperatures, and dimensional stability, etc., overcoming the problems of excessive rigidity and excessive mass of traditional skin stretch forming dies, resulting in increased costs and difficulties in transportation and installation.

[0041] The following further explains the present invention with specific embodiments, but it does not limit the protection scope of the present invention.

[0042] Example 1:

[0043] (1) Molding die treatment: Place the die in an oven and heat it to 100 °C, dry it for 2 h to remove surface moisture, and after cooling to room temperature, evenly apply a layer of mold release agent.

[0044] (2) Perform water removal and degassing treatment on isocyanate and polyether polyol, and dry the filler. Place isocyanate and polyether polyol in a vacuum oven for drying, with a temperature of 90 °C, a time of 0.5 h, and a vacuum degree of 1 mbar. Place the filler aluminum hydroxide in a forced-air oven at a temperature of 100 °C and a drying time of 6 h.

[0045] (3) Stir and mix the filler and polyether polyol and degas to obtain a prepolymer. Mix the polyether polyol cooled to room temperature with aluminum hydroxide. Among them, the polyether polyol is 1 part and the filler is 1 part. Place it in a vacuum stirring tank for stirring, with a stirring time of 30 min and a stirring power of 2000 - 2200 W. Obtain a prepolymer.

[0046] (4) Add isocyanate to the prepolymer and stir. Among them, the isocyanate is 1.02 parts. The stirring time is 10 min and the stirring power is 2000 - 2200 W.

[0047] Pour the well - stirred mixture into a mold for curing. The curing process is: temperature is 25°C and time is 5 h.

[0048] Example 2

[0049] (1) Molding mold treatment. Place the mold in an oven and heat it to 100°C, dry for 2 h to remove surface moisture. After cooling to room temperature, evenly apply a layer of mold release agent.

[0050] (2) Carry out dehydration and degassing treatment on isocyanate and polyether polyol, and dry the filler. Place isocyanate and polyether polyol in a vacuum oven for drying, with a temperature of 100°C, a time of 0.5 h, and a vacuum degree of 2 mbar. Place the filler aluminum hydroxide in a forced - air oven at a temperature of 110°C and a drying time of 6 h.

[0051] (3) Stir and mix the filler with polyether polyol and degas to obtain a prepolymer. Mix the polyether polyol cooled to room temperature with aluminum hydroxide. Among them, the polyether polyol is 1 part and the filler is 1.5 parts. Place it in a vacuum stirring tank for stirring, with a stirring time of 30 min and a stirring power of 2000 - 2200 W. Obtain the prepolymer.

[0052] (4) Add isocyanate to the prepolymer and stir. Among them, the isocyanate is 1.02 parts. The stirring time is 10 min and the stirring power is 2000 - 2200 W.

[0053] (5) Pour the well - stirred mixture into a mold for curing. The curing process is: temperature is 25°C and time is 5 h.

[0054] Example 3

[0055] (1) Molding mold treatment. Place the mold in an oven and heat it to 120°C, dry for 3 h to remove surface moisture. After cooling to room temperature, evenly apply a layer of mold release agent.

[0056] (2) Carry out dehydration and degassing treatment on isocyanate and polyether polyol, and dry the filler. Place isocyanate and polyether polyol in a vacuum oven for drying, with a temperature of 100°C, a time of 1 h, and a vacuum degree of 3 mbar. Place the filler aluminum hydroxide in a forced - air oven at a temperature of 120°C and a drying time of 8 h.

[0057] (3) Stir and mix the filler with polyether polyol and degas to obtain a prepolymer. Mix the polyether polyol cooled to room temperature with aluminum hydroxide. Among them, the polyether polyol is 1 part and the filler is 2 parts. Place it in a vacuum stirring tank for stirring, with a stirring time of 30 min and a stirring power of 2000 - 2200 W. Obtain the prepolymer.

[0058] (4) Add isocyanate to the prepolymer based on stirring. The amount of isocyanate is 1.02 parts. The stirring time is 10 min and the stirring power is 2000 - 2200 W.

[0059] (5) Pour the uniformly stirred mixture into a mold for curing. The curing process is as follows: the temperature is 25 °C and the time is 6 h.

[0060] Example 4

[0061] (1) Treat the molding die. Place the die in an oven and heat it to 100 °C, dry for 2 h to remove surface moisture, and after cooling to room temperature, evenly apply a layer of mold release agent.

[0062] (2) Conduct dehydration and degassing treatment on the isocyanate and polyether polyol, and dry the filler. Place the isocyanate and polyether polyol in a vacuum oven for drying, with a temperature of 90 °C, a time of 0.5 h, and a vacuum degree of 1 mbar. Place the filler alumina in a forced-air oven at a temperature of 100 °C and a drying time of 6 h.

[0063] (3) Stir and mix the filler and polyether polyol and degas to obtain a prepolymer. Mix the polyether polyol cooled to room temperature with alumina. Among them, the polyether polyol is 1 part and the filler is 1 part. Place it in a vacuum stirring tank for stirring. The stirring time is 30 min and the stirring power is 2000 - 2200 W. Obtain a prepolymer.

[0064] (4) Add isocyanate to the prepolymer based on stirring. The amount of isocyanate is 1.02 parts. The stirring time is 10 min and the stirring power is 2000 - 2200 W.

[0065] (5) Pour the uniformly stirred mixture into a mold for curing. The curing process is as follows: the temperature is 25 °C and the time is 5 h.

[0066] Example 5

[0067] (1) Treat the molding die. Place the die in an oven and heat it to 100 °C, dry for 2 h to remove surface moisture, and after cooling to room temperature, evenly apply a layer of mold release agent.

[0068] (2) Conduct dehydration and degassing treatment on the isocyanate and polyether polyol, and dry the filler. Place the main material isocyanate and polyether polyol in a vacuum oven for drying, with a temperature of 100 °C, a time of 0.5 h, and a vacuum degree of 2 mbar. Place the filler alumina in a forced-air oven at a temperature of 110 °C and a drying time of 6 h.

[0069] (3) Stir and mix the filler with the polyether polyol and degas to obtain a prepolymer. Mix the polyether polyol cooled to room temperature with alumina. Among them, the polyether polyol is 1 part and the filler is 1.5 parts. Place it in a vacuum stirring tank for stirring. The stirring time is 30 min and the stirring power is 2000 - 2200 W. Obtain the prepolymer.

[0070] (4) Add isocyanate to the prepolymer and stir. Among them, the isocyanate is 1.02 parts. The stirring time is 10 min and the stirring power is 2000 - 2200 W.

[0071] (5) Pour the uniformly stirred mixture into a mold for curing. The curing process is: the temperature is 25 °C and the time is 5 h.

[0072] Comparative Example 1

[0073] (1) Process the molding die. Place the die in an oven and heat it to 100 °C for 2 h to remove surface moisture. After cooling to room temperature, evenly apply a layer of mold release agent.

[0074] (2) Conduct water removal and degassing treatment on the main materials of isocyanate and polyether polyol. Place the main materials of isocyanate and polyether polyol in a vacuum oven for drying. The temperature is 90 °C, the time is 0.5 h, and the vacuum degree is 1 mbar.

[0075] (3) Stir and mix the isocyanate with the polyether polyol and degas to obtain a prepolymer. Mix the isocyanate cooled to room temperature with the polyether polyol. Among them, the polyether polyol is 1 part and the isocyanate is 1.02 parts.

[0076] The stirring time is 10 min and the stirring power is 2000 - 2200 W.

[0077] (4) Pour the uniformly stirred mixture into a mold for curing. The curing process is: the temperature is 25 °C,

[0078] The time is 5 h.

[0079] In Comparative Example 1, without adding filler, the polyurethane molecule lacks a rigid structure to resist deformation, there is no filler stress network, and the load cannot be effectively dispersed, which results in lower flexural strength and hardness of the polyurethane resin.

[0080] Comparative Example 2:

[0081] Different from Example 3, the addition order of the reactants is different. In this Comparative Example 2, the degassed isocyanate, polyether polyol, and filler are stirred and mixed together according to the weight ratio to obtain a mixture. After pouring the obtained mixture into a mold and curing at room temperature, the tensile strength, flexural strength, and other indexes of the obtained composite material are extremely low and cannot be applied;

[0082] The reason is that the reaction between isocyanate and polyether polyol is rapid, and the filler has not been evenly mixed yet,

[0083] which affects the properties of the resulting composite material.

[0084] Comparative Example 3:

[0085] Different from Example 3, the addition order of the reactants is different. In this Comparative Example 2, the isocyanate after dehydration and degassing is first stirred and mixed with the filler, and the resulting mixture is then stirred and mixed with polyether polyol to obtain a blended material. After pouring the obtained blended material into a mold and curing it at room temperature, the tensile strength, flexural strength and other indicators of the resulting composite material are extremely low and cannot be applied;

[0086] The reason is that even though the dried aluminum hydroxide may still adsorb trace amounts of water. If it is first mixed with isocyanate, water will react with -NCO preferentially, causing the isocyanate to react with water to form carbamic acid, which further decomposes into amine and carbon dioxide, resulting in an increase in the porosity of the cured material. The consumption of -NCO groups leads to insufficient crosslinking during the subsequent reaction with polyether polyol, and the mechanical properties decline.

[0087] Comparative Example 4:

[0088] Different from Example 3, the addition ratio of the reactants is different. The addition ratio of the filler is 3 parts, polyether polyol is 1 part, and isocyanate is 1.02 parts. After testing the obtained material, it is found that its tensile strength is extremely low and it cannot be applied to a drawing die. The reason is that excessive filler leads to serious interfacial defects and restricted molecular chain movement, resulting in a significant decrease in tensile strength.

[0089] The mechanical properties of the material obtained by the present invention were measured, including: three-point bending test, tensile property test, compression property, and hardness test. The national standards relied on are: GB / T 9341-2008, GB / T 1040.2-2006, GB\T1041-2008, GB\T 2411-2008.

[0090] The test results of the materials obtained in the above Examples 1-5 and Comparative Example 1 are shown in the following table:

[0091]

[0092]

[0093] Other embodiments of the present invention will be readily apparent to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following the general principles of the invention and including known common general knowledge or conventional technical means in the technical field not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are pointed out by the following claims.

[0094] It should be understood that the present invention is not limited to what has been described above and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A method for preparing a polyurethane composite material for an aviation drawing die, characterized in that: include: Step 1: using polyether polyol as the main material and isocyanate as the curing agent, respectively subjecting them to dehydration and degassing treatment; Step 2: Drying the filler; Step 3: adding the dried filler to the dehydrated and degassed polyether polyol, stirring, mixing and degassing to obtain a prepolymer; Step 4: adding the dehydrated and degassed isocyanate to the prepolymer, stirring evenly to obtain a mixture; Step 5: Pour the mixture into the mold for curing. After curing, cut it according to the design requirements.

2. The method for preparing the polyurethane composite material for aviation drawing mold according to claim 1, characterized in that: The process conditions for dehydrating and degassing the isocyanate and the polyether polyol in step 1 are as follows: a drying temperature of 90-100° C., a drying time of 0.5-1 h, and a vacuum degree of 1-3 mbar.

3. The method for preparing the polyurethane composite material for aviation drawing mold according to claim 1, characterized in that: The process conditions for the filler drying treatment in step 2 are: drying temperature is 100-120° C., and drying time is 6-8 hours.

4. The method for preparing the urethane composite material for an aviation drawing die according to claim 1, characterized in that: The filler in step 2 is one or a mixture of aluminum hydroxide and aluminum oxide.

5. The method for preparing the polyurethane composite material for aviation drawing mold according to claim 1, characterized in that: In terms of weight parts, in step 3, the polyether polyol is 0.87-1.02 parts, the filler is 0.87-2.54 parts, and in step 4, the isocyanate is 0.87-1.02 parts.

6. The method for preparing the polyurethane composite material for aviation drawing mold according to claim 1, characterized in that: In step 3, the process parameters of stirring and mixing are: stirring time 20-30min, stirring power 2000-2200W.

7. The method for preparing the polyurethane composite material for aviation drawing mold according to claim 1, characterized in that: In step 4, the stirring time is 8-10 minutes, and the stirring power is 2000-2200W.

8. The method for preparing the polyurethane composite material for aviation drawing mold according to claim 1, characterized in that: In step 4, the mixed material is poured into a mold for curing at a temperature of 20-30° C. for 5-6 hours.

9. The method for preparing the polyurethane composite material for aviation drawing mold according to claim 1, characterized in that: In step 4, before using the mold, the mold is heated and dried to remove surface moisture, and then a layer of release agent is evenly applied to its surface after cooling to room temperature.

10. The polyurethane composite material for aviation drawing molds prepared by the preparation method according to any one of claims 1 to 9, characterized in that: include: Calculated by weight: 0.87-1.02 parts of polyether polyol, 0.87-2.54 parts of filler, 0.87-1.02 parts of isocyanate; wherein the filler is: one or a mixture of aluminum hydroxide and aluminum oxide.

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