CN117690988B - A weather-resistant low-water-transmitting photovoltaic backsheet and preparation method thereof - Google Patents

Abstract

The invention provides a weather-proof low-water light-transmitting photovoltaic backboard and a preparation method thereof, and belongs to the technical field of photovoltaics; the modified fluorine film layer comprises the following components in percentage by mass: 73% -77% of PVDF, 8.5% -10.5% of modified multi-wall carbon nano-tubes, 6% -7.2% of toughening agents, 6.6% -7.8% of silicon-containing modified polyurethane, 0.5% -0.8% of antioxidants and 0.5% -0.8% of lubricants; the preparation method of the modified multi-wall carbon nano tube comprises the following steps: a1, putting the multi-wall carbon nano tube into strong acid, heating to 85-100 ℃, and keeping for 1-3 hours to obtain an acid-washed carbon nano tube; a2, placing the acid-washed carbon nano tube into water, carrying out ultrasonic treatment for 30 minutes, carrying out centrifugal separation, and washing the water to be neutral to obtain a neutral carbon nano tube; and A3, putting the neutral carbon nano tube into a polyethyleneimine water solution, oscillating for 24 hours in a constant-temperature water bath, washing with water, and drying to obtain the nano-tube. The photovoltaic backboard prepared by the invention has excellent illumination weather resistance, low water permeability and excellent mechanical property.

Description

A weather-resistant low-water-transmitting photovoltaic backsheet and preparation method thereof

Technical Field

The present invention belongs to the field of photovoltaic technology, and in particular relates to a weather-resistant low-water-permeable photovoltaic backboard and a preparation method thereof.

Background technique

The photovoltaic backsheet is located on the back of the solar panel and is one of the key components of the photovoltaic module. It plays a role in protecting the cells and supporting the overall structure. It also has important functions such as blocking air, blocking water vapor, and blocking ultraviolet rays. The photovoltaic backsheet is a multi-layer structure, such as a three-layer structure (PVDF/PET/PVDF), in which the outer protective layer PVDF film has good resistance to environmental erosion.

PVDF (polyvinylidene fluoride) is a fluorinated polymer. Fluorinated polymers refer to polymers in which all or part of the hydrogen atoms connected to the C-C bonds in the polymer are replaced by fluorine atoms. Since fluorine atoms have low polarizability, strong negative charge and small van der Waals radius, compared with other conventional polymers, fluoropolymers containing C-F groups often have many excellent properties. For example, they have very high chemical resistance, barrier properties, high temperature resistance and good electrical properties, and do not absorb moisture, have a very low friction coefficient, and have good weather resistance. In addition, its properties can be improved by blending other materials or grafting materials of different molecular weights on the surface of the membrane. For example, blending PVDF with polysulfone (PSF), polyacrylonitrile (PAN), polyvinyl alcohol (PVA) and other materials can effectively improve the antioxidant properties and weather resistance of PVDF membranes.

The Chinese invention patent with the announcement number CN113912885B discloses a low-temperature resistant PVDF film for photovoltaic backplane and its preparation method; the PVDF film prepared with PVDF, polymethyl methacrylate, magnetic toughening agent, titanium dioxide, antioxidant and ultraviolet absorber as raw materials has good weather resistance, high barrier properties, low water permeability, low temperature resistance, excellent mechanical properties in a severe cold environment of -40°C, and no cracking. However, titanium dioxide as a filler has an average particle size between 0.2-0.3μm, which has a poor effect on filling the gaps between the molecules of PVDF and polymethyl methacrylate blend materials, resulting in more water permeation paths and higher water permeability of the PVDF film; and titanium dioxide particles have poor shielding effects on ultraviolet and infrared rays, resulting in poor light weather resistance of the PVDF film; the compatibility and interface bonding strength of titanium dioxide particles with PVDF and polymethyl methacrylate blend materials are insufficient, which also leads to poor mechanical properties of the PVDF film.

Summary of the invention

In order to solve the problems existing in the background technology, the present invention provides a weather-resistant and low-water-permeability photovoltaic backboard and a preparation method thereof, so as to obtain a photovoltaic backboard with excellent light weather resistance, low water permeability and excellent mechanical properties.

In order to achieve the above-mentioned object, in a first aspect, the present invention provides a weather-resistant low-water-transmitting photovoltaic backsheet, comprising an EVOH layer, a first adhesive layer, a PET layer, a second adhesive layer and a modified fluorine film layer arranged in sequence;

The modified fluorine film layer comprises the following raw material components by mass percentage: PVDF 73%-77%, modified multi-walled carbon nanotubes 8.5%-10.5%, toughening agent 6%-7.2%, silicon-modified polyurethane 6.6%-7.8%, antioxidant 0.5%-0.8% and lubricant 0.5%-0.8%;

The preparation method of the modified multi-walled carbon nanotubes is as follows:

A1. Put the multi-walled carbon nanotubes into a strong acid, heat to 85-100°C, and keep it for 1-3 hours to obtain acid-washed carbon nanotubes;

A2, putting the acid-washed carbon nanotubes obtained in A1 into deionized water, ultrasonically treating them in an ultrasonic cleaning machine for 30 minutes, then centrifuging them in a centrifuge, and repeatedly washing them with deionized water until they are neutral, to obtain neutral carbon nanotubes;

A3. The neutral carbon nanotubes obtained in A2 are placed in a polyethyleneimine aqueous solution, shaken in a constant temperature water bath for 24 hours, then washed with deionized water and dried to obtain modified multi-walled carbon nanotubes.

Furthermore, in A1, the strong acid is a mixed acid prepared by mixing 98% by mass sulfuric acid and 68% by mass nitric acid in a mass ratio of 3:1.

Furthermore, in A3, the concentration of the polyethyleneimine aqueous solution is 50%.

Furthermore, the preparation method of the silicon-modified polyurethane is as follows:

B1. Mix isophorone diisocyanate and hydroxy-terminated polybutadiene acrylonitrile at n(NCO)/n(HTBN)=1.6, add 0.5wt% dibutyltin dilaurate, add aminosilicone oil at n(aminosilicone oil)/n(HTBN)=0.06, heat to 78°C under dry nitrogen protection, and react for 2 h;

B2. Add chain extender methyl propylene glycol according to n (chain extender) / n (HTBN) = 0.05, maintain the temperature at 78 ° C for 0.5 h, then slowly raise the temperature to 90 ° C to complete the reaction, and cool to room temperature to obtain silicon-modified polyurethane.

Furthermore, the toughening agent includes a styrene toughening agent or a polyolefin toughening agent.

Furthermore, the antioxidant includes butylated hydroxyanisole and/or 2,6-di-tert-butyl-p-cresol.

Furthermore, the lubricant includes an alcohol lubricant or a silicone lubricant.

Furthermore, the preparation method of the modified fluorine film layer is as follows: take PVDF, modified multi-walled carbon nanotubes, toughening agent, silicon-modified polyurethane, antioxidant and lubricant, mix them in a high-speed mixer, add ultrasound, melt extrude through a twin-screw, cool and granulate, and obtain the constituent materials of the modified fluorine film layer.

Furthermore, the first adhesive layer and the second adhesive layer are both maleic anhydride grafted polyethylene.

In a second aspect, the present invention provides a method for preparing a weather-resistant, low-water-permeable photovoltaic backboard, which is used to prepare the above-mentioned weather-resistant, low-water-permeable photovoltaic backboard, comprising the following steps: preparing a photovoltaic backboard through a co-extrusion process of the constituent materials of an EVOH layer, a first adhesive layer, a PET layer, a second adhesive layer and a modified fluorine film layer.

This application has the following beneficial effects:

EVOH is a high barrier material that not only exhibits excellent processing properties, but also exhibits excellent blocking effects on gases and solvents, and has good strength, elastic modulus and tortuosity. PET is a polyester thermoplastic polymer, and its mechanical properties and chemical stability mainly come from its molecular structure. PVDF itself has excellent weather resistance, wear resistance and high temperature resistance. The three are compounded with adhesives to form a multi-layer photovoltaic backsheet, which can give full play to the advantages of each material.

Among them, the modified fluorine film layer is prepared with PVDF, and the raw material components include modified multi-walled carbon nanotubes and silicon-containing modified polyurethane. The modified multi-walled carbon nanotubes are prepared by strong acid washing and polyethyleneimine modification of multi-walled carbon nanotubes. Strong acid washing changes the surface properties of multi-walled carbon nanotubes, improves their compatibility with hot-melt polymers, and increases their dispersibility in the polymer matrix; multi-walled carbon nanotubes themselves have extremely high surface energy, and excessive amounts are prone to agglomeration, and may even promote excessive generation or uneven distribution of β-phase crystals of PVDF, and modification with polyethyleneimine can offset this promotion effect; both are conducive to the modified multi-walled carbon nanotubes to better fill the gaps between material molecules, reduce the permeation path, and thus effectively reduce the water vapor permeability of the material; and, experiments have shown that the synergy between the two is better than ordinary superposition;

At the same time, after being treated with strong acid, the surface of multi-walled carbon nanotubes may also be endowed with active groups such as carboxyl and hydroxyl groups, which can directly improve the interfacial bonding force with the polymer matrix, thereby enhancing the tensile strength; while the β-crystals formed by the regular arrangement of molecular chains may lead to a decrease in the mechanical properties (tensile strength) of the material, and the offsetting effect brought about by the modification of polyethyleneimine can offset the downward trend of mechanical properties and enhance the mechanical properties in disguise; and, experiments have shown that the synergy between the two is better than ordinary superposition;

Polyurethane has a strong polarity and can firmly bond with most materials, thereby enhancing its ability to prevent moisture penetration; after polyurethane is modified with silicon, silicon-containing segments with low surface energy are introduced into the polyurethane molecular chain, which can enhance hydrophobicity and reduce water vapor permeability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a weather-resistant, low-water-permeable photovoltaic backsheet according to the present invention;

1. EVOH layer; 2. first adhesive layer; 3. PET layer; 4. second adhesive layer; 5. modified fluorine film layer.

Detailed ways

The present application is further described in detail below with reference to the embodiments.

Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

Example 1

This embodiment provides a weather-resistant, low-water-permeable photovoltaic backsheet, comprising an EVOH layer 1, a first adhesive layer 2, a PET layer 3, a second adhesive layer 4, and a modified fluorine film layer 5 arranged in sequence. The constituent material of the EVOH layer 1 is EVOH, the constituent material of the PET layer 3 is PET slices, and the constituent materials of the first adhesive layer 2 and the second adhesive layer 4 are both maleic anhydride grafted polyethylene.

The modified fluorine film layer 5 includes the following raw material components by mass percentage: 73% PVDF, 10.4% modified multi-walled carbon nanotubes, 7.2% toughening agent, 7.8% silicon-containing modified polyurethane, 0.8% antioxidant and 0.8% lubricant.

Among them, the toughening agent adopts styrene toughening agent SEBS.

The antioxidant is prepared by mixing butylated hydroxyanisole and 2,6-di-tert-butyl-p-cresol in a mass ratio of 1:1.2.

The lubricant used is a silicone lubricant.

The preparation method of modified multi-walled carbon nanotubes is as follows:

A1. Put the multi-walled carbon nanotubes into a strong acid, the mass ratio of the multi-walled carbon nanotubes to the strong acid is 1:3; the strong acid is a mixed acid, which is prepared by mixing 98% sulfuric acid (mass fraction) and 68% nitric acid (mass fraction) in a mass ratio of 3:1; heat to 90°C and keep for 2 hours to obtain acid-washed carbon nanotubes.

A2, putting the acid-washed carbon nanotubes obtained in A1 into deionized water, ultrasonically treating them in an ultrasonic cleaning machine for 30 minutes, then centrifuging them in a centrifuge, and repeatedly washing them with deionized water until they are neutral, to obtain neutral carbon nanotubes;

A3. The neutral carbon nanotubes obtained in A2 are placed in a 50% (mass fraction) polyethyleneimine aqueous solution, shaken in a constant temperature water bath (30°C) for 24 hours, then washed with deionized water to remove unreacted polyethyleneimine, and finally dried in a vacuum drying oven to obtain modified multi-walled carbon nanotubes.

The preparation method of silicon-modified polyurethane is as follows:

B1. Mix isophorone diisocyanate and hydroxy-terminated polybutadiene acrylonitrile at n(NCO)/n(HTBN)=1.6, add 0.5wt% dibutyltin dilaurate, add aminosilicone oil at n(aminosilicone oil)/n(HTBN)=0.06, heat to 78°C under dry nitrogen protection, and react for 2 h;

B2. Add chain extender methyl propylene glycol according to n (chain extender) / n (HTBN) = 0.05, maintain the temperature at 78 ° C for 0.5 h, then slowly raise the temperature to 90 ° C to complete the reaction, and cool to room temperature to obtain silicon-modified polyurethane.

The preparation method of the modified fluorine film layer is as follows: take PVDF, modified multi-walled carbon nanotubes, toughening agent, silicon-modified polyurethane, antioxidant and lubricant, mix them in a high-speed mixer, add ultrasound (in the specific implementation, it is necessary to connect the ultrasonic equipment with the high-speed mixer; specifically, install an ultrasonic generator on the high-speed mixer, and link the ultrasonic generator with the control system of the high-speed mixer. When the high-speed mixer is turned on, the ultrasonic generator will also start at the same time), melt extrude through a twin-screw, cool and granulate to obtain the constituent materials of the modified fluorine film layer; continue to cast film to obtain the modified fluorine film layer.

The preparation method of the weather-resistant low-water-permeable photovoltaic backsheet comprises the following steps: preparing the photovoltaic backsheet by co-extrusion process of the constituent materials of EVOH, maleic anhydride grafted polyethylene, PET slices, maleic anhydride grafted polyethylene and modified fluorine film layer. The photovoltaic backsheet has a five-layer structure, which is sequentially an EVOH layer with a thickness of 40 μm, a first bonding layer with a thickness of 30 μm, a PET layer with a thickness of 250 μm, a second bonding layer with a thickness of 30 μm and a modified fluorine film layer with a thickness of 20 μm.

When in use, it is used to prepare photovoltaic modules, which include battery cells, packaging films and weather-resistant low-water-permeable photovoltaic back panels. The EVOH layer of the weather-resistant low-water-permeable photovoltaic back panel is in contact and bonded with the packaging film.

Example 2

The difference between this embodiment and embodiment 1 is that the modified fluorine film layer includes the following raw material components by mass percentage: PVDF 74%, modified multi-walled carbon nanotubes 10%, toughening agent 7%, silicon-modified polyurethane 7.6%, antioxidant 0.6% and lubricant 0.8%.

Example 3

The only difference between this embodiment and embodiment 1 is that the modified fluorine film layer includes the following raw material components by mass percentage: PVDF 75%, modified multi-walled carbon nanotubes 10%, toughening agent 6.8%, silicon-containing modified polyurethane 7%, antioxidant 0.6% and lubricant 0.6%.

Example 4

The difference between this embodiment and embodiment 1 is that the modified fluorine film layer includes the following raw material components by mass percentage: PVDF 76%, modified multi-walled carbon nanotubes 9%, toughening agent 7%, silicon-containing modified polyurethane 6.8%, antioxidant 0.7% and lubricant 0.5%.

Example 5

The only difference between this embodiment and embodiment 1 is that the modified fluorine film layer includes the following raw material components by mass percentage: PVDF 77%, modified multi-walled carbon nanotubes 8.5%, toughening agent 6.2%, silicon-containing modified polyurethane 7.2%, antioxidant 0.5% and lubricant 0.6%.

Example 6

The only difference between this embodiment and embodiment 1 is that the toughening agent adopts polyolefin toughening agent EPDM.

Example 7

The only difference between this embodiment and embodiment 1 is that butylated hydroxyanisole is used as an antioxidant.

Example 8

The only difference between this embodiment and embodiment 1 is that 2,6-di-tert-butyl-p-cresol is used as the antioxidant.

Example 9

The difference between this embodiment and embodiment 1 is that in the preparation of the modified multi-walled carbon nanotubes, sulfuric acid with a concentration (mass fraction) of 98% is used as a strong acid.

Example 10

The difference between this embodiment and embodiment 1 is that in the preparation of the modified multi-walled carbon nanotubes, the strong acid used is nitric acid with a concentration (mass fraction) of 68%.

Comparative Example 1

The only difference between this comparative example and Example 3 is that the lubricant is deleted from the raw material components of the modified fluorine film layer.

Specifically, the modified fluorine film layer includes the following raw material components by mass percentage: 75.6% PVDF, 10% modified multi-walled carbon nanotubes, 6.8% toughening agent, 7% silicon-containing modified polyurethane and 0.6% antioxidant.

Comparative Example 2

The only difference between this comparative example and Example 3 is that the toughening agent is deleted from the raw material components of the modified fluorine film layer.

Specifically, the modified fluorine film layer includes the following raw material components by mass percentage: 81.8% PVDF, 10% modified multi-walled carbon nanotubes, 7% silicon-containing modified polyurethane, 0.6% antioxidant and 0.6% lubricant.

Comparative Example 3

The difference between this comparative example and Example 3 is that the modified multi-walled carbon nanotubes are prepared by washing the multi-walled carbon nanotubes with a strong acid.

Specifically, the preparation method of the modified multi-walled carbon nanotubes is as follows:

A1. Put the multi-walled carbon nanotubes into a strong acid, the mass ratio of the multi-walled carbon nanotubes to the strong acid is 1:3; the strong acid is a mixed acid, which is prepared by mixing 98% sulfuric acid (mass fraction) and 68% nitric acid (mass fraction) in a mass ratio of 3:1; heat to 90°C and keep for 2 hours to obtain acid-washed carbon nanotubes.

A2. The acid-washed carbon nanotubes obtained in A1 are placed in deionized water, ultrasonically treated in an ultrasonic cleaner for 30 minutes, then centrifuged and separated in a centrifuge, and repeatedly washed with deionized water until neutral, and finally dried in a vacuum drying oven to obtain modified multi-walled carbon nanotubes.

Comparative Example 4

The difference between this comparative example and Example 3 is that the modified multi-walled carbon nanotubes are prepared by reacting multi-walled carbon nanotubes with a 50% polyethyleneimine aqueous solution.

Specifically, the preparation method of the modified multi-walled carbon nanotubes is as follows:

The multi-walled carbon nanotubes were placed in a 50% (mass fraction) polyethyleneimine aqueous solution, shaken in a constant temperature water bath (30°C) for 24 hours, then washed with deionized water to remove unreacted polyethyleneimine, and finally dried in a vacuum drying oven to obtain modified multi-walled carbon nanotubes.

Comparative Example 5

The difference between this comparative example and Example 3 is that among the raw material components of the modified fluorine film layer, the multi-walled carbon nanotubes are not modified.

Specifically, the modified fluorine film layer includes the following raw material components by mass percentage: PVDF 75%, multi-walled carbon nanotubes 10%, toughening agent 6.8%, silicon-modified polyurethane 7%, antioxidant 0.6% and lubricant 0.6%.

Comparative Example 6

The only difference between this comparative example and Example 3 is that among the raw material components of the modified fluorine film layer, the polyurethane is not modified.

Specifically, the modified fluorine film layer includes the following raw material components by mass percentage: PVDF 75%, modified multi-walled carbon nanotubes 10%, toughening agent 6.8%, polyurethane 7%, antioxidant 0.6% and lubricant 0.6%.

Comparative Example 7

The difference between this comparative example and Example 3 is that among the raw material components of the modified fluorine film layer, the multi-walled carbon nanotubes are not modified and the polyurethane is not modified.

Specifically, the modified fluorine film layer includes the following raw material components by mass percentage: 75% PVDF, 10% multi-walled carbon nanotubes, 6.8% toughening agent, 7% polyurethane, 0.6% antioxidant and 0.6% lubricant.

Comparative Example 8

The difference between this comparative example and Example 3 is that the modified multi-walled carbon nanotubes are replaced by modified single-walled carbon nanotubes.

Specifically, the preparation method of the modified single-walled carbon nanotubes is as follows:

A1. Put the single-walled carbon nanotubes into a strong acid, the mass ratio of the single-walled carbon nanotubes to the strong acid is 1:3; the strong acid is a mixed acid, which is prepared by mixing 98% sulfuric acid (mass fraction) and 68% nitric acid (mass fraction) in a mass ratio of 3:1; heat to 90°C and keep for 2 hours to obtain acid-washed carbon nanotubes.

A2, putting the acid-washed carbon nanotubes obtained in A1 into deionized water, ultrasonically treating them in an ultrasonic cleaning machine for 30 minutes, then centrifuging them in a centrifuge, and repeatedly washing them with deionized water until they are neutral, to obtain neutral carbon nanotubes;

A3. The neutral carbon nanotubes obtained in A2 are placed in a 50% (mass fraction) polyethyleneimine aqueous solution, shaken in a constant temperature water bath (30°C) for 24 hours, then washed with deionized water to remove unreacted polyethyleneimine, and finally dried in a vacuum drying oven to obtain modified single-walled carbon nanotubes.

Comparative Example 9

The difference between this comparative example and Example 3 is that the modified multi-walled carbon nanotubes are replaced with titanium dioxide, specifically R-996 rutile titanium dioxide.

Comparative Example 10

The difference between this comparative example and Example 3 is that the modified multi-walled carbon nanotubes are deleted from the raw material components of the modified fluorine film layer.

Specifically, the modified fluorine film layer includes the following raw material components by mass percentage: 85% PVDF, 6.8% toughening agent, 7% silicon-containing modified polyurethane, 0.6% antioxidant and 0.6% lubricant.

Comparative Example 11

The only difference between this comparative example and Example 3 is that the silicon-containing modified polyurethane is deleted from the raw material components of the modified fluorine film layer.

Specifically, the modified fluorine film layer includes the following raw material components by mass percentage: 82% PVDF, 10% modified multi-walled carbon nanotubes, 6.8% toughening agent, 0.6% antioxidant and 0.6% lubricant.

Comparative Example 12

The difference between this comparative example and Example 3 is that the modified multi-walled carbon nanotubes and silicon-containing modified polyurethane are deleted from the raw material components of the modified fluorine film layer.

Specifically, the modified fluorine film layer includes the following raw material components by mass percentage: PVDF 92%, toughening agent 6.8%, antioxidant 0.6% and lubricant 0.6%.

Comparative Example 13

The only difference between this comparative example and Example 3 is that the fluorine film layer is not modified and its raw material component is a single PVDF.

Specifically, a weather-resistant, low-water-transmitting photovoltaic back sheet comprises an EVOH layer, a first adhesive layer, a PET layer, a second adhesive layer and a fluorine film layer which are arranged in sequence.

The preparation method of the fluorine film layer is as follows: PVDF is placed in a high-speed mixer, and ultrasound is applied (in specific implementation, the ultrasonic device needs to be connected to the high-speed mixer; specifically, an ultrasonic generator is installed on the high-speed mixer, and the ultrasonic generator is linked to the control system of the high-speed mixer. When the high-speed mixer is turned on, the ultrasonic generator will also start at the same time), and the constituent materials of the fluorine film layer are obtained by twin-screw melt extrusion, cooling and granulation; and the film is continued to be cast to obtain the fluorine film layer.

The preparation method of the weather-resistant low-water-permeable photovoltaic backsheet comprises the following steps: preparing the photovoltaic backsheet by co-extrusion process of the constituent materials of EVOH, maleic anhydride grafted polyethylene, PET slices, maleic anhydride grafted polyethylene and fluorine film layer. The photovoltaic backsheet has a five-layer structure, which is, in sequence, an EVOH layer with a thickness of 40 μm, a first bonding layer with a thickness of 30 μm, a PET layer with a thickness of 250 μm, a second bonding layer with a thickness of 30 μm and a fluorine film layer with a thickness of 20 μm.

Comparative Example 14

The difference between this comparative example and Example 3 is that no ultrasound is applied during the preparation of the constituent materials of the modified fluorine film layer.

Specifically, the preparation method of the modified fluorine film layer is as follows: take PVDF, modified multi-walled carbon nanotubes, toughening agent, silicon-modified polyurethane, antioxidant and lubricant, mix them in a high-speed mixer, melt extrude them through a twin-screw, cool and granulate to obtain the constituent materials of the modified fluorine film layer; continue to cast the film to obtain the modified fluorine film layer.

Comparative Example 15

The difference between this comparative example and Example 3 is that: a weather-resistant, low-water-permeable photovoltaic backsheet includes a three-layer structure of an EVOH layer, an adhesive layer and a modified fluorine film layer arranged in sequence.

Comparative Example 16

The only difference between this comparative example and Example 3 is: a weather-resistant, low-water-permeable photovoltaic backsheet, comprising a three-layer structure of a PET layer, an adhesive layer and a modified fluorine film layer arranged in sequence.

Test Example 1

Test objects: Examples 1-10 and Comparative Examples 1-16.

Test basis: CQC3308-2013.

Test items: See Table 1:

Test results: See Table 2:

Result analysis: From Examples 1-10 combined with the data in Table 2, it can be seen that the various indicators (heat shrinkage, water vapor permeability, tensile strength and elongation at break) of the weather-resistant and low-water-permeable photovoltaic backsheet prepared by the present invention meet the standards and have excellent performance; among them, Example 3 is the best example.

It can be seen from Example 3, Comparative Examples 8-10 and Comparative Examples 11-14 combined with the data in Table 2 that in the preparation of the modified fluorine film layer, the participation of modified multi-walled carbon nanotubes is beneficial to reducing the thermal shrinkage of the modified fluorine film layer; and replacing multi-walled carbon nanotubes with single-walled carbon nanotubes, or directly replacing modified multi-walled carbon nanotubes with titanium dioxide, are not conducive to reducing the thermal shrinkage; the operation method of adding ultrasound is also beneficial to reducing the thermal shrinkage, which may be because the external ultrasound is conducive to the dispersion of modified multi-walled carbon nanotubes in the film-forming material, thereby playing an auxiliary effect.

It can be seen from Example 3 and Comparative Examples 3-14 combined with the data in Table 2 that the two treatment methods of strong acid washing and polyethyleneimine modification of multi-walled carbon nanotubes to obtain modified multi-walled carbon nanotubes for the preparation of modified fluorine film layers can effectively reduce the water vapor permeability of the final photovoltaic backplane, and the two treatment methods work synergistically, and the effect is better than the ordinary superposition of the two. At the same time, the participation of silicon-containing modified polyurethane can also produce the effect of reducing the water vapor permeability, and in this regard, there is also a certain synergistic effect between the silicon-containing modified polyurethane and the modified multi-walled carbon nanotubes.

It can be seen from Example 3, Comparative Examples 3-5, Comparative Examples 7-10 and Comparative Examples 12-14 and combined with the data in Table 2 that the two treatment methods of strong acid washing and polyethyleneimine modification of multi-walled carbon nanotubes to obtain modified multi-walled carbon nanotubes for participating in the preparation of the modified fluorine film layer can effectively enhance the mechanical properties (tensile strength) of the final photovoltaic backplane, and the two treatment methods work synergistically, and the effect is better than the ordinary superposition of the two.

It can be seen from Example 3, Comparative Examples 6-7 and Comparative Examples 11-14 combined with the data in Table 2 that the participation of silicon-modified polyurethane can improve the elongation at break of the modified fluorine film layer, thereby improving the elongation at break of the final photovoltaic backsheet.

Test Example 2

Test objects: Example 3, Comparative Examples 3-5, 9 and 10.

Test basis: Irradiate the photovoltaic back panel with 300kWh ultraviolet light and measure the yellowing Δb before and after ultraviolet light irradiation; Δb is measured according to the methods of GB/T3979-2008 and GB/T7921-2008.

Test item: light weather resistance.

Test results: See Table 3:

Result analysis: From Example 3, Comparative Examples 3-5, 9 and 10 combined with the data in Table 3, it can be seen that the participation of multi-walled carbon nanotubes as raw materials is conducive to improving the light weatherability of the photovoltaic backplane; strong acid washing and polyethyleneimine water modification of multi-walled carbon nanotubes can enhance the improvement effect. This may be because nanoparticles (multi-walled carbon nanotubes) can effectively and long-term shield ultraviolet rays, thereby improving light weatherability; and the treatment methods of strong acid washing and polyethyleneimine water modification can change the surface properties and surface energy of multi-walled carbon nanotubes, making it difficult to migrate in the material, and can also adsorb and prevent the migration of organic molecules, thereby enhancing the improvement effect.

It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims (9)

1. The weather-resistant low-water light-transmitting photovoltaic backboard is characterized by comprising an EVOH layer (1), a first bonding layer (2), a PET layer (3), a second bonding layer (4) and a modified fluorine film layer (5) which are sequentially arranged;

the modified fluorine film layer (5) comprises the following raw material components in percentage by mass: 73% -77% of PVDF, 8.5% -10.5% of modified multi-wall carbon nano-tubes, 6% -7.2% of toughening agents, 6.6% -7.8% of silicon-containing modified polyurethane, 0.5% -0.8% of antioxidants and 0.5% -0.8% of lubricants;

The preparation method of the modified multi-wall carbon nano tube comprises the following steps:

A1, putting the multi-wall carbon nano tube into strong acid, heating to 85-100 ℃, and keeping for 1-3 hours to obtain an acid-washed carbon nano tube;

A2, putting the acid-washed carbon nano tube obtained in the step A1 into deionized water, performing ultrasonic treatment in an ultrasonic cleaner for 30 minutes, then performing centrifugal separation by using a centrifugal machine, and repeatedly washing with the deionized water to be neutral to obtain a neutral carbon nano tube;

A3, putting the neutral carbon nano tube obtained in the step A2 into a polyethyleneimine water solution, oscillating for 24 hours in a constant-temperature water bath, then washing with deionized water, and drying to obtain the modified multi-wall carbon nano tube;

the preparation method of the silicon-containing modified polyurethane comprises the following steps:

b1, mixing isophorone diisocyanate and hydroxyl-terminated polybutadiene acrylonitrile according to N (NCO)/n (HTBN) =1.6, adding 0.5wt% of dibutyltin dilaurate, adding amino silicone oil according to n (amino silicone oil)/n (HTBN) =0.06, heating to 78 ℃ under the protection of dry nitrogen, and reacting for 2 hours;

and B2, adding a chain extender methyl propylene glycol according to n (chain extender)/n (HTBN) =0.05, keeping the temperature at 78 ℃ for reaction for 0.5h, slowly heating to 90 ℃ to complete the reaction, and cooling to room temperature to obtain the silicon-containing modified polyurethane.

2. The weather-resistant low-water light-transmitting photovoltaic back sheet according to claim 1, wherein in A1, the strong acid adopts mixed acid, and the strong acid is prepared from 98% sulfuric acid and 68% nitric acid according to a mass ratio of 3:1, and mixing.

3. The weatherable low water light transmitting photovoltaic backsheet according to claim 1, wherein in A3, the mass fraction of the aqueous polyethyleneimine solution is 50%.

4. The weatherable low water light transmitting photovoltaic backsheet of claim 1, wherein the toughening agent comprises a styrenic toughening agent or a polyolefin toughening agent.

5. The weatherable low water light transmitting photovoltaic backsheet of claim 1, wherein the antioxidant comprises butyl hydroxyanisole and/or 2, 6-di-tert-butyl-p-cresol.

6. The weatherable low water light transmitting photovoltaic backsheet of claim 1, wherein the lubricant comprises an alcohol lubricant or a silicone based lubricant.

7. The weatherable low water light transmission photovoltaic backsheet according to any one of claims 1 to 6, wherein the modified fluorine film layer is prepared by the following method: PVDF, modified multi-wall carbon nano tube, toughening agent, silicon-containing modified polyurethane, antioxidant and lubricant are taken, mixed in a high-speed mixer, added with ultrasound, and subjected to double-screw melt extrusion, cooled and granulated to obtain the modified fluorine film layer constituent material.

8. The weatherable low water light transmitting photovoltaic backsheet of claim 1, wherein the first tie layer and the second tie layer are both maleic anhydride grafted polyethylene.

9. A method for preparing a weatherable low water transmission photovoltaic backsheet according to any one of claims 1 to 8, comprising the steps of: and (3) carrying out coextrusion on the constituent materials of the EVOH layer, the first bonding layer, the PET layer, the second bonding layer and the modified fluorine film layer to obtain the photovoltaic backboard.