High-temperature-resistant geothermal film and preparation method thereof

Abstract

The application relates to the technical field of PET geothermal film, and discloses a high-temperature-resistant geothermal film and a preparation method thereof. Polyethylene terephthalate, carboxyl polyetherimide and modified graphene are blended, extruded and blow molded to obtain the high-temperature-resistant geothermal film. The carboxyl polyetherimide contains benzyl benzoate structural units similar to PET, and the two form an alloy-like system with good compatibility. The modified graphene has good dispersibility and excellent compatibility with PET, and contains more carboxyl groups, which form hydrogen bonds and other interactions with the carboxyl groups in the side chains of the carboxyl polyetherimide, so that the graphene can be uniformly dispersed in the composite system of PET and the carboxyl polyetherimide, and better reinforcing effect is achieved, and the tensile strength and elongation at break of the PET composite geothermal film are significantly improved. The geothermal film has high retention rates of the tensile strength and the elongation at break after high-temperature thermal aging, and has good high-temperature resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of PET geothermal films, in particular to a high-temperature resistant geothermal film and a preparation method thereof. Background Art

[0002] Geothermal membranes are widely used in floor heating systems. Primarily made from polyesters such as polyethylene terephthalate (PET), their widespread use has led to higher demands for mechanical strength, toughness, high-temperature resistance, waterproofness, and tensile strength. PET can be combined with materials such as nylon, polyethylene, polyimide, and polycarbonate to create high-performance alloys. Polyetherimide (PEI) offers increased toughness, high mechanical strength, and excellent high-temperature resistance, making it a widely used material.

[0003] As a high-performance nanomaterial, graphene has important applications in polymer materials such as plastics and fibers. Surface modification of graphene to improve dispersibility and enhance interfacial compatibility with substrates has become a research hotspot. Patent CN116814174B discloses a composite PET protective film and its preparation method. Using polyethylene terephthalate, polyimide resin, epoxy acrylate, nano-aluminum oxide, graphene, molecular sieves, and compatibilizers as raw materials, the resulting PET main layer and PET protective film material have advantages such as flexibility and high conformability. However, this patent does not improve the PET film's tensile properties or high-temperature resistance, hindering its practical application in geothermal films and other applications. Summary of the Invention

[0004] (1) Technical problems to be solved: The present invention provides a PET geothermal film with high thermal conductivity, high temperature resistance and excellent mechanical properties.

[0005] (2) Technical solution: A high-temperature resistant geothermal film, comprising 100 parts by weight of polyethylene terephthalate, 10-25 parts by weight of carboxyl polyetherimide, and 0.5-3 parts by weight of modified graphene.

[0006] Preferably, the preparation method of the high-temperature resistant geothermal film is: polyethylene terephthalate, carboxyl polyetherimide, and modified graphene are added to a mixer and mixed, and then extruded in a twin-screw extruder at a temperature of 270-300°C and a screw speed of 100-150r / min; pelletized, and blow-molded in a film blowing machine to obtain a high-temperature resistant geothermal film.

[0007] Preferably, the present invention may further comprise low-density polyethylene and a toughening agent ethylene-methyl acrylate-glycidyl methacrylate blend.

[0008] Preferably, the preparation method of carboxyl polyetherimide is:

[0009] Pyridine, 2,2-dihydroxymethylpropionic acid, and trimellitic anhydride chloride in a molar ratio of (2.2-2.6):1:(2-2.2) are added to tetrahydrofuran at 0-5°C, stirred, reacted at 20-25°C for 8-12 hours, and distilled under reduced pressure. The product is recrystallized from dichloromethane to obtain propionic acid bis(hydroxymethyl trimellitic anhydride ester).

[0010] The reaction formula is:

[0011]

[0012] Add dianhydride monomer, propionic bis(hydroxymethyl trimellitic anhydride), and 4,4'-diaminodiphenyl ether in a molar ratio of (50-80):(20-50):100 to N,N-dimethylformamide, react at 20-30°C for 12-18 hours, pour the solution onto the surface of a glass mold, heat-treat in an oven at 100-280°C for 7-8 hours, cool, shear, and crush to obtain carboxyl polyetherimide. The reaction formula is:

[0013]

[0014] Preferably, the dianhydride monomer is pyromellitic anhydride or 4,4'-biphenyl ether dianhydride.

[0015] The preparation method of modified graphene is as follows: add graphene oxide to N,N-dimethylformamide, ultrasonically disperse, then add phthalic anhydride in a mass ratio of 1:(12-20), heat to 80-90°C, react for 3-5 hours, filter, wash with ethanol, and dry to obtain modified graphene. The reaction formula is:

[0016]

[0017] (III) Technical Effect: The present invention produces a high-temperature resistant geothermal film by extruding a blend of polyethylene terephthalate, carboxyl polyetherimide, and modified graphene and then blow-molding the mixture. Carboxyl polyetherimide contains benzoate structural units similar to those of PET, significantly improving their polarity and interfacial compatibility, forming a highly compatible alloy-like system that improves the tensile properties of the PET composite geothermal film.

[0018] The modified graphene of the present invention has better dispersibility and excellent compatibility with PET. At the same time, the modified graphene contains more carboxyl groups, which form hydrogen bonds and other interactions with the carboxyl groups of the carboxyl polyetherimide side chains, so that the graphene and the carboxyl polyetherimide also have good interface bonding strength, so that the graphene can be evenly dispersed in the composite system of PET and carboxyl polyetherimide, playing a better reinforcing role, and significantly improving the tensile strength and elongation at break of the PET composite geothermal film.

[0019] The PET composite geothermal film of the present invention has high retention rates of tensile strength and elongation at break after high-temperature thermal aging, and exhibits better high-temperature resistance. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] Example 1

[0022] (1) Add 11 mmol of pyridine, 5 mmol of 2,2-dihydroxymethylpropionic acid, and 11 mmol of trimellitic anhydride chloride to 20 mL of tetrahydrofuran at 5°C, stir, and react at 20°C for 12 hours. Distill under reduced pressure, and recrystallize the product from dichloromethane to obtain propionic acid bis(hydroxymethyl trimellitic anhydride ester).

[0023] (2) Add 8 mmol of 4,4'-biphenyl ether dianhydride, 2 mmol of propionic acid bis(hydroxymethyl trimellitic anhydride), and 10 mmol of 4,4'-diaminodiphenyl ether to 20 mL of N,N-dimethylformamide, and react at 25°C for 18 hours. Pour the solution on the surface of a glass mold and heat-treat it in an oven at 100°C for 1 hour, 160°C for 2 hours, 220°C for 1.5 hours, 250°C for 1.5 hours, and 280°C for 1 hour. Cool it, shear it, and crush it to obtain carboxyl polyetherimide.

[0024] (3) 0.5 g of graphene oxide was added to 120 mL of N,N-dimethylformamide and ultrasonically dispersed. Then, 6 g of phthalic anhydride was added and the mixture was heated to 90 °C and reacted for 3 h. The mixture was filtered, washed with ethanol, and dried to obtain modified graphene.

[0025] (4) 1 kg of polyethylene terephthalate, 100 g of carboxyl polyetherimide, and 5 g of modified graphene were added to a mixer and mixed, and then extruded in a twin-screw extruder with the temperatures of sections 1-4 being 270°C, 290°C, 300°C, and 295°C, and the screw speed being 150 r / min; pelletized, and blown into shape in a film blowing machine with a blow-up ratio of 3.0 and a tensile pulling rate of 6 m / min to obtain a high-temperature resistant geothermal film.

[0026] Example 2

[0027] (1) Add 13 mmol of pyridine, 5 mmol of 2,2-dihydroxymethylpropionic acid, and 10 mmol of trimellitic anhydride chloride to 20 mL of tetrahydrofuran at 0°C, stir, and react at 25°C for 8 hours. Distill under reduced pressure, and recrystallize the product from dichloromethane to obtain propionic acid bis(hydroxymethyl trimellitic anhydride ester).

[0028] (2) Add 6.5 mmol of 4,4'-biphenyl ether dianhydride, 3.5 mmol of propionic acid bis(hydroxymethyl trimellitic anhydride), and 10 mmol of 4,4'-diaminodiphenyl ether to 25 mL of N,N-dimethylformamide, and react at 30°C for 12 hours. Pour the solution on the surface of a glass mold and heat-treat it in an oven at 100°C for 1 hour, 150°C for 2 hours, 200°C for 2 hours, 240°C for 2 hours, and 280°C for 1 hour. Cool it, shear it, and crush it to obtain carboxyl polyetherimide.

[0029] (3) 0.5 g of graphene oxide was added to 150 mL of N,N-dimethylformamide and ultrasonically dispersed. Then, 8 g of phthalic anhydride was added and the mixture was heated to 80 °C and reacted for 4 h. The mixture was filtered, washed with ethanol, and dried to obtain modified graphene.

[0030] (4) 1 kg of polyethylene terephthalate, 180 g of carboxyl polyetherimide, and 17 g of modified graphene were added to a mixer and mixed, and then extruded in a twin-screw extruder with the temperatures of sections 1-4 being 270°C, 290°C, 300°C, and 295°C, and the screw speed being 100 r / min; pelletized, and blown into shape in a film blowing machine with a blow-up ratio of 3.0 and a tensile traction rate of 6 m / min to obtain a high-temperature resistant geothermal film.

[0031] Example 3

[0032] (1) To 20 mL of N,N-dimethylformamide, 5 mmol of pyromellitic anhydride, 5 mmol of propionic acid bis(hydroxymethyl trimellitic anhydride ester) (prepared according to the method of Example 1), and 10 mmol of 4,4'-diaminodiphenyl ether were added, and the mixture was reacted at 20°C for 18 h. The solution was poured on the surface of a glass mold and heat-treated in an oven at 100°C for 1 h, 150°C for 2 h, 200°C for 2 h, 240°C for 2 h, and 280°C for 1 h. The mixture was cooled, sheared, and crushed to obtain carboxyl polyetherimide.

[0033] (2) 0.5 g of graphene oxide was added to 150 mL of N,N-dimethylformamide and ultrasonically dispersed. Then, 10 g of phthalic anhydride was added and the mixture was heated to 80 °C and reacted for 5 h. The mixture was filtered, washed with ethanol, and dried to obtain modified graphene.

[0034] (3) 1 kg of polyethylene terephthalate, 250 g of carboxyl polyetherimide, and 30 g of modified graphene were added to a mixer and mixed, and then extruded in a twin-screw extruder with the temperatures of sections 1-4 being 270°C, 290°C, 300°C, and 295°C, and the screw speed being 150 r / min; pelletized, and blown into shape in a film blowing machine with a blow-up ratio of 3.0 and a tensile pulling rate of 6 m / min to obtain a high-temperature resistant geothermal film.

[0035] Comparative Example 1

[0036] (1) 1 kg of polyethylene terephthalate was extruded in a twin-screw extruder with the temperatures of sections 1-4 being 270°C, 290°C, 300°C, and 295°C, and the screw speed being 150 r / min; pelletized, and blown into a film in a film blowing machine with a blow-up ratio of 3.0 and a tensile pulling rate of 6 m / min to obtain a high-temperature resistant geothermal film.

[0037] Comparative Example 2

[0038] (1) 1 kg of polyethylene terephthalate and 100 g of carboxyl polyetherimide (prepared according to the method of Example 1) were added to a mixer and mixed, and then extruded in a twin-screw extruder with the temperatures of sections 1-4 being 270°C, 290°C, 300°C, and 295°C and the screw speed being 150 r / min; pelletized, and blown into shape in a film blowing machine with a blow-up ratio of 3.0 and a tensile pulling rate of 6 m / min to obtain a high-temperature resistant geothermal film.

[0039] Comparative Example 3

[0040] (1) 1 kg of polyethylene terephthalate and 5 g of modified graphene (prepared according to the method of Example 1) were added to a mixer and mixed, and then extruded in a twin-screw extruder with the temperatures of sections 1-4 being 270°C, 290°C, 300°C, and 295°C, and the screw speed being 150 r / min; pelletized, and blown into shape in a film blowing machine with a blow-up ratio of 3.0 and a tensile pulling rate of 6 m / min to obtain a high-temperature resistant geothermal film.

[0041] Comparative Example 4

[0042] (1) 1 kg of polyethylene terephthalate, 100 g of carboxyl polyetherimide (prepared according to the method of Example 1), and 5 g of graphene oxide were added to a mixer and mixed, and then extruded in a twin-screw extruder with the temperatures of sections 1-4 being 270°C, 290°C, 300°C, and 295°C, and the screw speed being 150 r / min; pelletized, and blown into shape in a film blowing machine with a blow-up ratio of 3.0 and a tensile pulling rate of 6 m / min to obtain a high-temperature resistant geothermal film.

[0043] Comparative Example 5

[0044] (1) Add 10 mmol of 4,4'-biphenyl ether dianhydride and 10 mmol of 4,4'-diaminodiphenyl ether to 20 mL of N,N-dimethylformamide, react at 25°C for 18 h, pour the solution on the surface of a glass mold, and heat-treat in an oven at 100°C for 1 h, 160°C for 2 h, 220°C for 1.5 h, 250°C for 1.5 h, and 280°C for 1 h. Cool, shear, and crush to obtain polyetherimide.

[0045] (2) 1 kg of polyethylene terephthalate, 100 g of polyetherimide, and 5 g of modified graphene (prepared according to the method of Example 1) were added to a mixer and mixed, and then extruded in a twin-screw extruder with the temperatures of sections 1-4 being 270°C, 290°C, 300°C, and 295°C, and the screw speed being 150 r / min; pelletized, and blown into shape in a film blowing machine with a blow-up ratio of 3.0 and a tensile traction rate of 6 m / min to obtain a high-temperature resistant geothermal film.

[0046] Comparative Example 6

[0047] (1) Add 8 mmol of 4,4'-biphenyl ether dianhydride and 2 mmol of ethylene glycol ditrimellitate anhydride (structural formula: CAS registration number 1732-96-3), 10 mmol 4,4'-diaminodiphenyl ether, react at 25°C for 18 h, pour the solution on the surface of a glass mold, and heat-treat in an oven at 100°C for 1 h, 160°C for 2 h, 220°C for 1.5 h, 250°C for 1.5 h, and 280°C for 1 h, followed by cooling, shearing and crushing to obtain polyetherimide.

[0048] (2) 1 kg of polyethylene terephthalate, 100 g of polyetherimide, and 5 g of modified graphene (prepared according to the method of Example 1) were added to a mixer and mixed, and then extruded in a twin-screw extruder with the temperatures of sections 1-4 being 270°C, 290°C, 300°C, and 295°C, and the screw speed being 150 r / min; pelletized, and blown into shape in a film blowing machine with a blow-up ratio of 3.0 and a tensile traction rate of 6 m / min to obtain a high-temperature resistant geothermal film.

[0049] The tensile properties of geothermal film were tested according to the method of GB / T1040.3-2006. The geothermal film was placed in a blast dryer, heat aged at 90°C for 72 hours, cooled to room temperature for 12 hours, and then the tensile properties were tested.

[0050] Table 1 Tensile strength test

[0051]

[0052]

[0053] Table 2 Elongation at break test

[0054]

[0055] After testing, the high temperature resistant geothermal film of embodiment 1-3 has higher tensile strength, elongation at break.Mainly because in polyethylene terephthalate PET, carboxyl polyetherimide and modified graphene are added, carboxyl polyetherimide contains the benzoate structural unit similar to PET, significantly improve polarity and interfacial compatibility between the two, form the class alloy system of good compatibility, be conducive to improving the tensile property of PET composite geothermal film, simultaneously modified graphene dispersibility becomes better, with the compatibility of PET excellent, simultaneously modified graphene contains a large amount of carboxyl, forms the interactions such as hydrogen bond with the carboxyl of carboxyl polyetherimide side chain, make graphene and carboxyl polyetherimide also have good interfacial bonding force, make graphene can be uniformly dispersed in the composite system of PET and carboxyl polyetherimide, play better reinforcement, significantly improve the tensile strength and elongation at break of PET composite geothermal film.And through high temperature thermal aging, the tensile strength of geothermal film and the retention rate of elongation at break are high, show better high temperature resistance.

[0056] In Comparative Example 1, carboxyl polyetherimide and modified graphene were not added, and the tensile properties of the geothermal film were low. After high-temperature thermal aging, the tensile strength and elongation at break decreased significantly, the retention rate was low, and the high-temperature resistance was poor.

[0057] Compared with Example 1, Comparative Example 2 did not add modified graphene, and Comparative Example 3 did not add carboxyl polyetherimide, resulting in lower tensile strength and elongation at break of the PET geothermal film.

[0058] Comparative Example 4 added unmodified graphene oxide, which is easy to agglomerate and has poor compatibility with PET. At the same time, the surface carboxyl content is low, and the hydrogen bonding force with the carboxyl group of the carboxyl polyetherimide side chain is low, resulting in the dispersion of graphene oxide in the composite system of PET and carboxyl polyetherimide being lower than that in Example 1, the reinforcing effect of graphene is not good, and the tensile strength and elongation at break of the geothermal film are lower than those in Example 1.

[0059] Comparative Example 5 does not add propionic acid bis (hydroxymethyl trimellitic anhydride ester), and the prepared polyetherimide does not contain benzoate structural units or carboxyl groups. It has poor polarity and interfacial compatibility with PET, and the interfacial bonding force between it and the modified graphene is also low, resulting in low tensile strength and elongation at break of the PET composite film.

[0060] Comparative Example 6 adds ethylene glycol bis(trimellitic anhydride), and the prepared polyetherimide contains a benzoate structural unit similar to PET, which significantly improves the polarity and interfacial compatibility between the two, forming an alloy-like system with good compatibility, which is beneficial to improving the tensile properties of the PET composite geothermal film. However, it does not contain carboxyl groups, and the interfacial bonding force between it and the modified graphene is also low, resulting in the tensile strength and elongation at break of the PET composite film being lower than those in Example 1.

[0061] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A high temperature resistant geothermal film, characterized in that: The high-temperature resistant geothermal film comprises 100 parts by weight of polyethylene terephthalate, 10-25 parts by weight of carboxyl polyetherimide, and 0.5-3 parts by weight of modified graphene; The preparation method of the carboxyl polyetherimide comprises: adding dianhydride monomer, propionic acid bis (hydroxymethyl trimellitic anhydride ester), and 4,4'-diaminodiphenyl ether to N,N-dimethylformamide, pouring the solution on the surface of a mold after the reaction, performing heat treatment, cooling, shearing and crushing to obtain the carboxyl polyetherimide; The molar ratio of the dianhydride monomer, propionic bis(hydroxymethyl trimellitic anhydride ester), and 4,4'-diaminodiphenyl ether is (50-80):(20-50):100; The modified graphene preparation method comprises: adding graphene oxide to N,N-dimethylformamide, ultrasonically dispersing, then adding phthalic anhydride, heating to 80-90° C., reacting for 3-5 hours, filtering, washing, and drying to obtain the modified graphene; The preparation method of the propionic acid bis(hydroxymethyl trimellitic anhydride ester) comprises: adding pyridine, 2,2-dihydroxymethylpropionic acid, and trimellitic anhydride chloride to tetrahydrofuran at 0-5° C., stirring, reacting at 20-25° C. for 8-12 hours, performing reduced pressure distillation, and recrystallizing to obtain the propionic acid bis(hydroxymethyl trimellitic anhydride ester).

2. The high temperature resistant geothermal film according to claim 1, characterized in that: In the preparation method of the carboxyl polyetherimide, the reaction is carried out at 20-30° C. for 12-18 hours; and the heat treatment is carried out at 100-280° C. for 7-8 hours.

3. The high temperature resistant geothermal film according to claim 1, characterized in that: The dianhydride monomer is pyromellitic anhydride or 4,4'-biphenyl ether dianhydride.

4. The high temperature resistant geothermal film according to claim 1, characterized in that: The molar ratio of pyridine, 2,2-dihydroxymethylpropionic acid and trimellitic anhydride chloride is (2.2-2.6):1:(2-2.2).

5. The high temperature resistant geothermal film according to claim 1, characterized in that: The mass ratio of the graphene oxide to phthalic anhydride is 1:(12-20).

6. A method for preparing a high temperature resistant geothermal film according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: adding polyethylene terephthalate, carboxyl polyetherimide and modified graphene into a mixer and mixing them; then extruding them in a twin-screw extruder at a temperature of 270-300° C. and a screw speed of 100-150 r / min; pelletizing the obtained materials and blow molding them in a film blowing machine to obtain a high-temperature resistant geothermal film.

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