An energy-saving PET car roof and its production process

Abstract

This application relates to the technical field of automotive ceiling production, and specifically discloses an energy-saving PET automotive ceiling and its production process. An energy-saving PET automotive ceiling and its production process include a fabric layer, an adhesive film, a fiberglass surface felt layer, a modified PET foam layer, a fiberglass surface felt layer, an adhesive film, and a non-woven fabric layer connected in sequence. The modified PET foam layer comprises raw materials in the following parts by weight: 45-60 parts of polyester, 2.95-5.61 parts of a reinforcing agent, and the reinforcing agent includes nanocrystalline cellulose whiskers, modified carbon nanotubes, and modified glass fibers; in addition, the preparation method of this application has the advantage of reducing energy waste in the production process of PET automotive ceilings.

Description

Technical Field

[0001] This application relates to the technical field of automotive ceiling production, and more specifically, it relates to an energy-saving PET automotive ceiling and its production process. Background Art

[0002] With the increasing requirements of the automotive industry for lightweight and environmental protection performance, various new materials and technologies have emerged continuously. Among them, foam materials made of high-performance plastics such as polyester (PET) have received extensive attention due to their excellent heat insulation and sound insulation properties. In the application of automotive interior parts, the ceiling, as an important component, the choice of its material directly affects the overall comfort and fuel economy of the vehicle. Traditionally, PU foam has dominated in automotive ceilings due to its good cushioning and processing flexibility. However, in recent years, with the growing demand for sustainable production and energy consumption reduction, PET foam, as a potential alternative, is gradually entering the market view.

[0003] PET foam can be produced by continuous extrusion. However, after the formed PET foam material is cooled after forming, it needs to be compounded with other layer structures such as adhesive films and felt layers. During the compounding process, each layer also needs to be heated, which makes the whole process require repeated heating and cooling, increasing energy consumption and at the same time reducing the overall production efficiency. Summary of the Invention

[0004] In order to reduce energy waste in the production process of PET automotive ceilings, this application provides an energy-saving PET automotive ceiling and its production process.

[0005] In a first aspect, this application provides an energy-saving PET automotive ceiling, adopting the following technical solution:

[0006] An energy-saving PET automotive ceiling includes a fabric layer, an adhesive film, a fiberglass surface felt layer, a modified PET foam layer, a fiberglass surface felt layer, an adhesive film, and a non-woven fabric layer connected in sequence. The modified PET foam layer comprises the following raw materials in parts by weight: 45 - 60 parts of polyester, 2.95 - 5.61 parts of reinforcing agents, and the reinforcing agents include nanocrystalline cellulose whiskers, modified carbon nanotubes, and modified glass fibers.

[0007] By adopting the above technical solution, the modified PET foam layer is prepared by mixing polyester with a reinforcing agent and foaming, so that the obtained modified PET foam layer has a smaller density, realizing lightweight. The reinforcing agent formed by the composite of nanocellulose whiskers, modified carbon nanotubes and modified glass fibers can improve the strength of the modified PET foam layer, and at the same time can provide crystallization points for PET foaming, which is beneficial to the growth and stability of the foaming structure, improving the pore uniformity and density of the modified PET foam layer. The modified PET foam layer is obtained by using a continuous foaming device. A glass fiber surface felt layer and an adhesive film are covered on both sides of the modified PET foam layer, and the temperature of the modified PET foam layer after the foaming process can be used to heat the adhesive film to complete the composite of each layer, and at the same time achieve continuous production, without repeated heating-cooling cycles, saving energy and improving production efficiency. The top adhesive film is covered by a reusable release layer, and the bonding process of the fabric layer is completed after cooling, effectively realizing the protection of the top adhesive film and the protection of the fabric layer.

[0008] Preferably, the mass ratio of nanocellulose whiskers, modified carbon nanotubes and modified glass fibers in the reinforcing agent is (4.65 - 4.81):(0.54 - 0.59):(1.25 - 1.48).

[0009] By adopting the above technical solution, the nanocellulose whiskers are mixed with the modified carbon nanotubes. The modified carbon nanotubes can be carried on the nanocellulose whiskers and dispersed together, which is beneficial to improving the dispersibility of the modified carbon nanotubes. At the same time, each raw material in the reinforcing agent is fibrous, and they can be intertwined and overlapped with each other to form a relatively complex microscopic network structure with the polyester foam, thus effectively improving the mechanical properties of the modified PET foam layer.

[0010] Preferably, the preparation method of the modified carbon nanotubes includes the following steps: ultrasonically disperse the carbon nanotubes in a mixed solution of ethanol and water, adjust the pH to 9 - 10 with ammonia water, add tetraethoxysilane, after reacting for 15 - 16 h, centrifuge, separate, wash, and then ultrasonically disperse again in a mixed solution of ethanol and water, and freeze-dry to obtain the modified carbon nanotubes.

[0011] By adopting the above technical solution, silica is deposited on the surface of the carbon nanotubes. Silica can effectively improve the dispersibility of the carbon nanotubes, and at the same time can improve the bonding degree between the modified carbon nanotubes and the polyester foam and the strength of the modified carbon nanotubes, which is beneficial to the mixing and overlapping between the modified carbon nanotubes and the nanocellulose whiskers and the modified glass fibers, thus effectively improving the impact resistance of the modified PET foam layer.

[0012] Preferably, the modified carbon nanotubes also undergo the following treatment: heat the modified carbon nanotubes to 150 °C, preheat for 2 h, and then introduce vaporized hexamethyldisilazane and react for 45 - 50 min.

[0013] By adopting the above technical solution, the vaporized hexamethyldisilazane can modify the silica deposited on the surface of the modified carbon nanotubes, effectively reducing the content of silanol groups and improving its hydrophobicity, thereby further improving the dispersibility of the modified carbon nanotubes.

[0014] Preferably, the addition amount of the hexamethyldisilazane is 10.25 - 13.59 wt% of the modified carbon nanotubes.

[0015] By adopting the above technical solution, the addition amount of the hexamethyldisilazane is controlled, thereby effectively regulating the content of silanol groups on the surface of the modified carbon nanotubes. If the addition amount is too small, it is easy to increase the content of silanol groups, and if the addition amount increases, it is easy to cause waste.

[0016] Preferably, the preparation method of the modified glass fiber includes the following steps: mixing a polydimethylsiloxane prepolymer, nano-silica and a curing agent, dispersing them in toluene to obtain a mixed solution, immersing the glass fiber in the mixed solution, taking it out after soaking for 3 - 5 min, air-drying naturally, and drying at 120 °C for 2 h.

[0017] By adopting the above technical solution, after the glass fiber is treated with the mixed solution, the surface is coated with polydimethylsiloxane, and at the same time, nano-silica is introduced, increasing the surface roughness of the glass fiber. Polydimethylsiloxane has good fiber adhesion, can effectively improve the bonding degree between the modified glass fiber and the polyester foam, and can also improve the connection strength between the modified glass fiber, nano-cellulose whiskers and modified carbon nanotubes, improving the enhancement effect of the impact resistance performance of the automotive ceiling.

[0018] Preferably, the mass ratio of the polydimethylsiloxane to the nano-silica is (1.52 - 1.68):(0.98 - 1.05).

[0019] By adopting the above technical solution, the addition amount of the nano-silica is controlled, increasing the surface roughness of the modified glass fiber while retaining more pores, which is beneficial to the combination with the polyester foam and also provides more growth sites for the foaming process of the PET foaming layer.

[0020] In the second aspect, the present application provides a production process for an energy-saving PET automotive ceiling, adopting the following technical solution:

[0021] A production process of an energy-saving PET car roof, comprising the following steps: After mixing polyester and a reinforcing agent, extruding and pelletizing, foaming through a supercritical carbon dioxide continuous extrusion foaming device, attaching a fiberglass surface felt layer and an adhesive film on both sides of the extruded modified PET foam layer, pasting non-woven fabric on one side, and having a release layer on the other side. After cooling together, peeling off the release layer and pasting a fabric layer to obtain the energy-saving PET car roof.

[0022] By adopting the above technical solution, the modified PET foam layer is continuously produced. Utilizing the temperature during the foaming process, the adhesive film and the fiberglass surface felt layer are attached, and the adhesive film is heated to complete the composite process, reducing the number of heating-cooling cycles and making full use of thermal energy.

[0023] In summary, the present application has the following beneficial effects:

[0024] 1. Since the modified PET foam layer in the present application is prepared by mixing and foaming polyester and a reinforcing agent, the obtained modified PET foam layer has a smaller density, achieving lightweight. And the reinforcing agent formed by the composite of nanocellulose whiskers, modified carbon nanotubes and modified glass fibers can improve the strength of the modified PET foam layer, and at the same time can provide crystallization points for PET foaming, facilitating the growth and stability of the foaming structure, improving the pore uniformity and compactness of the modified PET foam layer. The modified PET foam layer is obtained by using a continuous foaming device. Covering the adhesive film and the fiberglass surface felt layer on both sides of the modified PET foam layer can utilize the waste heat after the foaming process to heat the adhesive film, complete the composite between layers, and at the same time achieve continuous production, without repeated heating-cooling cycles, saving energy and improving production efficiency.

[0025] 2. In the present application, nanocellulose whiskers are mixed with modified carbon nanotubes. The modified carbon nanotubes can be carried on the nanocellulose whiskers and dispersed together, which is beneficial to improving the dispersibility of the modified carbon nanotubes. At the same time, each raw material in the reinforcing agent is fibrous, and they can be intertwined and overlapped with each other to form a relatively complex microscopic network structure with the polyester foam, thereby effectively improving the mechanical properties of the modified PET foam layer.

[0026] 3. In the present application, silica is deposited on the surface of the carbon nanotubes. Silica can effectively improve the dispersibility of the carbon nanotubes, and at the same time can improve the bonding degree between the carbon nanotubes and the polyester foam and the strength of the carbon nanotubes, facilitating the mixing and overlapping between the modified carbon nanotubes, nanocellulose whiskers and modified glass fibers, thereby effectively improving the impact resistance of the modified PET foam layer. Specific embodiments

[0027] The following further details the present application in conjunction with embodiments.

[0028] Preparation Examples 1 - 7 of Modified Carbon Nanotubes

[0029] Preparation Example 1

[0030] A method for preparing modified carbon nanotubes, comprising the following steps: ultrasonically disperse 0.49 g of carbon nanotubes in a mixed solution of 350 mL of ethanol and 50 mL of water, adjust the pH to 9 using ammonia water, add 1 mL of tetraethoxysilane, after reacting for 16 h, centrifuge, separate, wash, then ultrasonically disperse again in a mixed solution of 75 mL of ethanol and 5 mL of water, and freeze-dry to obtain modified carbon nanotubes.

[0031] Preparation Example 2

[0032] A method for preparing modified carbon nanotubes, comprising the following steps: ultrasonically disperse 0.57 g of carbon nanotubes in a mixed solution of 400 mL of ethanol and 55 mL of water, adjust the pH to 10 using ammonia water, add 1.5 mL of tetraethoxysilane, after reacting for 15 h, centrifuge, separate, wash, then ultrasonically disperse again in a mixed solution of 70 mL of ethanol and 3 mL of water, and freeze-dry to obtain modified carbon nanotubes.

[0033] Preparation Example 3

[0034] A method for preparing modified carbon nanotubes, comprising the following steps: ultrasonically disperse 0.52 g of carbon nanotubes in a mixed solution of 400 mL of ethanol and 60 mL of water, adjust the pH to 9 using ammonia water, add 1.2 mL of tetraethoxysilane, after reacting for 15 h, centrifuge, separate, wash, then ultrasonically disperse again in a mixed solution of 75 mL of ethanol and 4 mL of water, and freeze-dry to obtain modified carbon nanotubes.

[0035] Preparation Example 4

[0036] The difference between Preparation Example 4 and Preparation Example 1 is that in Preparation Example 4, the modified carbon nanotubes are further treated as follows: heat the modified carbon nanotubes to 150 °C, preheat for 2 h, then introduce vaporized hexamethyldisilazane and react for 45 min, and the addition amount of hexamethyldisilazane is 10.25 wt% of the modified carbon nanotubes.

[0037] Preparation Example 5

[0038] The difference between Preparation Example 5 and Preparation Example 1 is that in Preparation Example 5, the modified carbon nanotubes are further treated as follows: heat the modified carbon nanotubes to 150 °C, preheat for 2 h, then introduce vaporized hexamethyldisilazane and react for 50 min, and the addition amount of hexamethyldisilazane is 13.59 wt% of the modified carbon nanotubes.

[0039] Preparation Example 6

[0040] The difference between Preparation Example 6 and Preparation Example 4 is that in Preparation Example 6, the addition amount of hexamethyldisilazane is 5.95 wt% of the modified carbon nanotubes.

[0041] Preparation Example 7

[0042] The difference between Preparation Example 7 and Preparation Example 4 is that in Preparation Example 7, the addition amount of hexamethyldisilazane is 18.68 wt% of the modified carbon nanotubes.

[0043] Preparation Examples 8 - 12 of Modified Glass Fibers

[0044] Preparation Example 8

[0045] The preparation method of modified glass fibers includes the following steps: After mixing polydimethylsiloxane prepolymer, nano - silica and a curing agent, the mass ratio of polydimethylsiloxane to nano - silica is 1.52:0.98, the addition amount of the curing agent is 10 wt% of polydimethylsiloxane, dispersed in toluene to obtain a mixed solution, the mass fraction of polydimethylsiloxane prepolymer in the mixed solution is 2%, immerse the glass fibers in the mixed solution, take them out after soaking for 3 min, air - dry naturally, and then dry at 120 °C for 2 h.

[0046] Preparation Example 9

[0047] The preparation method of modified glass fibers includes the following steps: After mixing polydimethylsiloxane prepolymer, nano - silica and a curing agent, the mass ratio of polydimethylsiloxane to nano - silica is 1.68:1.05, the addition amount of the curing agent is 10 wt% of polydimethylsiloxane, dispersed in toluene to obtain a mixed solution, the mass fraction of polydimethylsiloxane prepolymer in the mixed solution is 2%, immerse the glass fibers in the mixed solution, take them out after soaking for 5 min, air - dry naturally, and then dry at 120 °C for 2 h.

[0048] Preparation Example 10

[0049] The preparation method of modified glass fibers includes the following steps: After mixing polydimethylsiloxane prepolymer, nano - silica and a curing agent, the mass ratio of polydimethylsiloxane to nano - silica is 1.62:1.02, the addition amount of the curing agent is 10 wt% of polydimethylsiloxane, dispersed in toluene to obtain a mixed solution, the mass fraction of polydimethylsiloxane prepolymer in the mixed solution is 2%, immerse the glass fibers in the mixed solution, take them out after soaking for 4 min, air - dry naturally, and then dry at 120 °C for 2 h.

[0050] Preparation Example 11

[0051] The difference between Preparation Example 11 and Preparation Example 8 is that in Preparation Example 11, the mass ratio of polydimethylsiloxane to nano - silica is 1.52:0.65.

[0052] Preparation Example 12

[0053] The difference between Preparation Example 12 and Preparation Example 8 is that in Preparation Example 12, the mass ratio of polydimethylsiloxane to nano-silica is 1.52:1.95. Examples

[0054] Example 1

[0055] An energy-saving PET car ceiling, comprising a fabric layer, an adhesive film, a fiberglass surface felt layer, a modified PET foam layer, a fiberglass surface felt layer, an adhesive film and a non-woven fabric layer connected in sequence. The adhesive film is a modified PE film purchased from Shanghai Hansi Industry Co., Ltd. The non-woven fabric is a spunlace non-woven fabric. The modified PET foam layer comprises the following raw materials in parts by weight: 45 kg of polyester, 2.95 kg of reinforcing agent. The reinforcing agent includes nano-cellulose whiskers, modified carbon nanotubes and modified glass fibers. The mass ratio of nano-cellulose whiskers, modified carbon nanotubes and modified glass fibers in the reinforcing agent is 4.65:0.54:1.25. The modified carbon nanotubes are the modified carbon nanotubes prepared in Preparation Example 1, and the modified glass fibers are the modified glass fibers prepared in Preparation Example 8.

[0056] The production process of the above energy-saving PET car ceiling comprises the following steps: mixing polyester and a reinforcing agent, extruding and pelletizing, foaming through a supercritical carbon dioxide continuous extrusion foaming device, attaching a fiberglass surface felt layer and an adhesive film on both sides of the extruded modified PET foam layer, pasting a non-woven fabric layer on one side, attaching a release layer on the other side, cooling together, peeling off the release layer, and pasting the fabric layer to obtain the energy-saving PET car ceiling.

[0057] Example 2

[0058] An energy-saving PET car ceiling, comprising a fabric layer, an adhesive film, a fiberglass surface felt layer, a modified PET foam layer, a fiberglass surface felt layer, an adhesive film and a non-woven fabric layer connected in sequence. The adhesive film is a modified PP film purchased from Shanghai Hansi Industry Co., Ltd. The non-woven fabric is a spunbond non-woven fabric. The modified PET foam layer comprises the following raw materials in parts by weight: 60 kg of polyester, 5.61 kg of reinforcing agent. The reinforcing agent includes nano-cellulose whiskers, modified carbon nanotubes and modified glass fibers. The mass ratio of nano-cellulose whiskers, modified carbon nanotubes and modified glass fibers in the reinforcing agent is 4.81:0.59:1.48. The modified carbon nanotubes are the modified carbon nanotubes prepared in Preparation Example 2, and the modified glass fibers are the modified glass fibers prepared in Preparation Example 9.

[0059] The production process of the above energy-saving PET automotive roof lining includes the following steps: Mix polyester and a reinforcing agent, then extrude and pelletize. Foam through a supercritical carbon dioxide continuous extrusion foaming device. Attach a fiberglass surface felt layer and an adhesive film on both sides of the extruded modified PET foam layer, paste a non-woven fabric layer on one side, and have a release layer on the other side. After cooling together, peel off the release layer and paste the fabric layer to obtain the energy-saving PET automotive roof lining.

[0060] Example 3

[0061] An energy-saving PET automotive roof lining includes a fabric layer, an adhesive film, a fiberglass surface felt layer, a modified PET foam layer, a fiberglass surface felt layer, an adhesive film, and a non-woven fabric layer connected in sequence. The adhesive film is a copolymer PA film purchased from Tianyang New Materials Shanghai Technology Co., Ltd. The non-woven fabric is a spunbonded hot-rolled fabric. The modified PET foam layer includes the following raw materials in parts by weight: 55 kg of polyester and 4.25 kg of a reinforcing agent. The reinforcing agent includes nanocrystalline cellulose whiskers, modified carbon nanotubes, and modified glass fibers. The mass ratio of nanocrystalline cellulose whiskers, modified carbon nanotubes, and modified glass fibers in the reinforcing agent is 4.72:0.56:1.38. The modified carbon nanotubes are the modified carbon nanotubes prepared in Preparation Example 3, and the modified glass fibers are the modified glass fibers prepared in Preparation Example 10.

[0062] The production process of the above energy-saving PET automotive roof lining includes the following steps: Mix polyester and a reinforcing agent, then extrude and pelletize. Foam through a supercritical carbon dioxide continuous extrusion foaming device. Attach a fiberglass surface felt layer and an adhesive film on both sides of the extruded modified PET foam layer, paste a non-woven fabric layer on one side, and have a release layer on the other side. After cooling together, peel off the release layer and paste the fabric layer to obtain the energy-saving PET automotive roof lining.

[0063] Example 4

[0064] The difference between Example 4 and Example 1 is that in Example 4, the mass ratio of nanocrystalline cellulose whiskers, modified carbon nanotubes, and modified glass fibers in the reinforcing agent is 4.65:1.52:0.58.

[0065] Example 5

[0066] The difference between Example 5 and Example 1 is that in Example 5, the mass ratio of nanocrystalline cellulose whiskers, modified carbon nanotubes, and modified glass fibers in the reinforcing agent is 4.65:0.25:2.68.

[0067] Example 6

[0068] The difference between Example 6 and Example 1 is that in Example 6, the modified carbon nanotubes are the modified carbon nanotubes prepared in Preparation Example 4.

[0069] Example 7

[0070] Example 7 is different from Example 1 in that in Example 7, the modified carbon nanotubes selected are the modified carbon nanotubes prepared in Preparation Example 5.

[0071] Example 8

[0072] Example 8 is different from Example 1 in that in Example 8, the modified carbon nanotubes selected are the modified carbon nanotubes prepared in Preparation Example 6.

[0073] Example 9

[0074] Example 9 is different from Example 1 in that in Example 9, the modified carbon nanotubes selected are the modified carbon nanotubes prepared in Preparation Example 7.

[0075] Example 10

[0076] Example 10 is different from Example 1 in that in Example 10, the modified glass fiber selected is the modified glass fiber prepared in Preparation Example 11.

[0077] Example 11

[0078] Example 11 is different from Example 1 in that in Example 11, the modified glass fiber selected is the modified glass fiber prepared in Preparation Example 12. Comparative Example

[0079] Comparative Example 1

[0080] Comparative Example 1 is different from Example 1 in that in Comparative Example 1, no reinforcing agent is added to the modified PET foam layer.

[0081] Comparative Example 2

[0082] Comparative Example 2 is different from Example 1 in that in Comparative Example 2, an equal amount of nanocrystalline cellulose whiskers is used to replace the reinforcing agent.

[0083] Comparative Example 3

[0084] Comparative Example 3 is different from Example 1 in that in Comparative Example 3, an equal amount of modified carbon nanotubes is used to replace the reinforcing agent.

[0085] Comparative Example 4

[0086] Comparative Example 4 is different from Example 1 in that in Comparative Example 4, an equal amount of modified glass fiber is used to replace the reinforcing agent.

[0087] Performance detection test

[0088] Automobile headliners are prepared according to the raw materials and production processes of Examples 1-11 and Comparative Examples 1-4, and the impact resistance of the automobile headliners is tested using a stamping testing machine, and the results are recorded in Table 1.

[0089] Table 1 Performance Test of Automobile Roof

[0090]

[0091] It can be seen from Examples 1-3 and Table 1 that the automobile roofs prepared in Examples 1-3 have good impact resistance. In the automobile roofs of Examples 1-3, a continuously extruded modified PET foam layer is used as the core layer, which is coated with an adhesive film and a glass fiber surface felt layer to form an automobile roof by compounding. The modified PET foam layer can effectively realize the lightweight of the automobile roof. At the same time, an enhancer is added to the modified PET foam layer. Nano cellulose whiskers, modified carbon nanotubes and modified glass fibers are all fibrous. They are intertwined and overlapped with each other, which can provide crystallization points for PET foaming, facilitate the progress of PET foaming, and improve the pore uniformity and compactness of the modified PET foam layer. The enhancer can form a complex network structure with the polyester foam, thereby effectively improving the impact resistance of the modified PET foam layer and further improving the impact resistance of the automobile roof.

[0092] Silica is deposited on the surface of carbon nanotubes for the modified carbon nanotubes. Silica can effectively improve the dispersibility of carbon nanotubes and improve the bonding degree between the modified carbon nanotubes and the polyester foam, which is conducive to the mixing and overlapping between the modified carbon nanotubes, nano cellulose whiskers and modified glass fibers. The modified glass fibers are coated with polydimethylsiloxane on the surface of the glass fibers, and nano silica is introduced at the same time, which increases the surface roughness of the glass fibers. Polydimethylsiloxane has good fiber adhesion, which can effectively improve the bonding strength between the modified glass fibers and the polyester foam, and at the same time improve the connection strength between the enhancers, which is beneficial to improving the enhancement effect of the enhancer on the impact resistance of the automobile roof.

[0093] Compared with Examples 1-3, the impact resistance of the automobile roofs prepared in Examples 4-5 and Comparative Examples 1-4 decreased. In Examples 4-5, the mass ratio of nano cellulose whiskers, modified carbon nanotubes and modified glass fibers in the enhancer was changed. In Comparative Example 1, no enhancer was added. In Comparative Example 2, only nano cellulose whiskers were added. In Comparative Example 3, only modified carbon nanotubes were added. In Comparative Example 4, only modified glass fibers were added. Compared with Examples 1-3, the impact resistance of the automobile roofs in Comparative Examples 2-4 decreased, indicating that there is a synergistic effect among nano cellulose whiskers, modified carbon nanotubes and modified glass fibers. The enhancer formed by compounding the three according to a certain mass ratio can effectively improve the impact resistance of the modified PET foam layer. When the composition and mass ratio change, the synergistic effect among nano cellulose whiskers, modified carbon nanotubes and modified glass fibers weakens, and the enhancement effect of the enhancer on the modified PET foam layer decreases.

[0094] Compared with Examples 1-3, the impact resistance of the automotive ceiling produced in Examples 6-7 is improved. When the modified carbon nanotubes used in Examples 6-7 are prepared, vaporized hexamethyldisilazane is used to modify the modified carbon nanotubes. Nano-silica is deposited on the surface of the carbon nanotubes, which can effectively improve the bonding degree between the modified carbon nanotubes and the polyester foam and the strength of the modified carbon nanotubes. The modification treatment with vaporized hexamethyldisilazane can reduce the silanol groups on the surface of the modified carbon nanotubes and improve their hydrophobicity, thereby further improving the dispersibility and bonding property of the modified carbon nanotubes.

[0095] Compared with Examples 6-7, the impact resistance of the automotive ceiling produced in Example 8 decreases, and the impact resistance of the automotive ceiling produced in Example 9 does not change significantly. When the modified carbon nanotubes used in Examples 8-9 are prepared, the addition amount of hexamethyldisilazane is reduced in Example 8, resulting in an increase in the content of silanol groups on the surface of the modified carbon nanotubes in Example 8, a decrease in hydrophobicity, and a weakening of dispersibility. In Example 9, the addition amount of hexamethyldisilazane is increased, and the performance of the produced automotive ceiling does not change significantly, indicating that the dosage of hexamethyldisilazane is excessive and there is waste.

[0096] Compared with Examples 1-3, the impact resistance of the automotive ceiling produced in Examples 10-11 decreases. When the modified glass fibers used in Examples 10-11 are prepared, the mass ratio of polydimethylsiloxane to nano-silica is changed, and the addition amount of nano-silica is controlled, resulting in an increase in the surface roughness of the modified glass fibers. When the addition amount of nano-silica decreases, the roughness decreases, and the bonding property between the modified glass fibers and the polyester foam decreases. When the addition amount of nano-silica increases, the pores of the polyester foam are easily blocked, reducing its impact resistance.

[0097] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. An energy-saving PET car roof, characterized in that: It includes a fabric layer, an adhesive film, a glass fiber surface felt layer, a modified PET foam layer, a glass fiber surface felt layer, an adhesive film and a non-woven fabric layer connected in sequence. The modified PET foam layer comprises raw materials in the following weight parts: 45-60 parts of polyester, 2.95-5.61 parts of a reinforcing agent. The reinforcing agent includes nanocrystalline cellulose whiskers, modified carbon nanotubes and modified glass fibers. The mass ratio of nanocrystalline cellulose whiskers, modified carbon nanotubes and modified glass fibers in the reinforcing agent is (4.65-4.81):(0.54-0.59):(1.25-1.48). The preparation method of the modified carbon nanotubes includes the following steps: ultrasonically disperse the carbon nanotubes in a mixed solution of ethanol and water, adjust the pH to 9-10 with ammonia water, add tetraethoxysilane, after reacting for 15-16 h, centrifuge, separate, wash, then ultrasonically disperse again in a mixed solution of ethanol and water, and freeze-dry to obtain the modified carbon nanotubes. The preparation method of the modified glass fibers includes the following steps: mix a polydimethylsiloxane prepolymer, nano-silica and a curing agent, disperse them in toluene to obtain a mixed solution, immerse the glass fibers in the mixed solution, take them out after soaking for 3-5 min, air-dry naturally, and air-dry at 120 °C for 2 h.

2. The energy-saving PET car roof according to claim 1, characterized in that: The modified carbon nanotubes also undergo the following treatment: heat the modified carbon nanotubes to 150 °C, preheat for 2 h, and then introduce vaporized hexamethyldisilazane and react for 45-50 min.

3. The energy-saving PET car roof according to claim 2, characterized in that: The addition amount of the hexamethyldisilazane is 10.25-13.59 wt% of the modified carbon nanotubes.

4. An energy-saving PET car roof according to claim 1, characterized in that: The mass ratio of the polydimethylsiloxane to the nano-silica is (1.52-1.68):(0.98-1.05).

5. The production process of an energy-saving PET car roof as described in any one of claims 1-4, characterized in that: It includes the following steps: Mix the polyester and the reinforcing agent, extrude and pelletize, foam via a supercritical carbon dioxide continuous extrusion foaming device, attach a glass fiber surface felt layer and an adhesive film on both sides of the extruded modified PET foam layer, paste a non-woven fabric layer on one side, and have a release layer on the other side. After cooling together, peel off the release layer and paste the fabric layer to obtain an energy-saving PET car roof lining.

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