A multilayer composite polyester-based film structure with high weather resistance

Abstract

The application provides a multilayer composite polyester-based film structure with high weather resistance, belongs to the technical field of composite polyester-based films, and comprises, which are arranged in sequence, a surface ultraviolet resistant layer (1-3 mu m), a weather resistance reinforcing layer (5-8 mu m), a polyethylene terephthalate base material layer (25-50 mu m), a bonding layer (2-5 mu m) and a high barrier inner layer (10-15 mu m). The surface ultraviolet resistant layer, the weather resistance reinforcing layer, the PET base material layer, the bonding layer and the high barrier inner layer are constructed through nano modification, cross-linking reinforcement, irradiation grafting and other technologies to form a five-layer composite structure. The five-layer synergistic system not only significantly improves the weather resistance, mechanical strength and barrier property, but also meets diversified application requirements through modular inner layer design, and provides a high-performance, long-life and environment-friendly film material solution for high-end packaging, new energy, electronic packaging and other fields.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite polyester-based film, in particular to a multi-layer composite polyester-based film structure with high weather resistance. BACKGROUND

[0002] Polyester-based film has become a core material in the fields of packaging, electronics, new energy, etc. due to its excellent mechanical strength, transparency and cost-effectiveness. In the field of photovoltaic backsheet, the traditional structure usually uses fluorine-containing materials as the weather-resistant layer combined with PET substrate to form a composite film. Although it can provide basic ultraviolet blocking and moisture resistance, it still faces obvious limitations in extreme environments. In the field of high-end packaging, polyester-based film mainly realizes high barrier performance through polyvinylidene chloride (PVDC) coating layer, but its alkali resistance is insufficient and it is easily degraded in alkaline environment, resulting in a sharp decline in barrier performance. In the field of new energy batteries, PET-based film is used as a composite current collector material, which is plated with aluminum / copper on the surface to act as a safety "fuse" for the battery. When the battery temperature abnormally rises, the base film melts to cut off the current path and prevent fire.

[0003] At present, the traditional PET-based film is prone to molecular chain rupture under long-term stress or in a humid heat environment, resulting in a decline in mechanical properties. The existing weather-resistant reinforcing layer relies on a single modification method and cannot resist multiple environmental stresses. The ultraviolet shielding layer usually relies on titanium dioxide or zinc oxide nanoparticles, but their content exceeding 5wt% can cause agglomeration, resulting in a decrease in film transmittance of more than 20%. The moisture-proof layer is mostly modified with epoxy resin polyurethane, but when the content of epoxy resin exceeds 15%, the flexibility of the coating layer deteriorates and the elongation at break decreases to less than 5%. The high-barrier inner layer material has the defects of poor solvent universality and unsustainable function.

[0004] In view of the above problems, the application provides a multi-layer composite polyester-based film structure with high weather resistance, which adopts a five-layer composite structure design and realizes the improvement of weather resistance, barrier property and mechanical stability through the synergistic effect of each functional layer. SUMMARY

[0005] The application aims to solve the above problems of the existing technology and provides a multi-layer composite polyester-based film structure with high weather resistance.

[0006] The object of the application can be achieved by the following technical solutions:

[0007] A multi-layer composite polyester-based film structure with high weather resistance, comprising:

[0008] An ultraviolet-resistant surface layer (1-3 microns) blocks ultraviolet radiation and prolongs the service life of the film;

[0009] Weathering reinforced layer (5-8 μm), to improve mechanical stability and environmental stress resistance;

[0010] Polyethylene terephthalate substrate layer (25-50 μm), the PET substrate layer provides core mechanical support;

[0011] Adhesion layer (2-5 μm), to ensure high-strength bonding between layers;

[0012] High-barrier inner layer (10-15 μm), to block water and oxygen permeation and protect the contents.

[0013] The five-layer composite structure realizes functional layering and synergy, so that the film product has weather resistance, mechanical strength, and barrier properties.

[0014] Preferably, the surface layer is a hydrotalcite-modified polyethylene terephthalate composite material;

[0015] The hydrotalcite content is 5-8 wt%, and the particle size is ≤100 nm.

[0016] Preferably, the surface of the hydrotalcite in the hydrotalcite-modified polyethylene terephthalate composite material is modified with silane coupling agent KH550. The hydrotalcite can efficiently scatter or absorb ultraviolet rays, improving the UV shielding rate. KH550 silane modification enhances the compatibility of the hydrotalcite-PET interface, inhibits nanoparticle agglomeration, improves dispersibility and light transmittance, and enhances the durability of the anti-ultraviolet property through a double-path mechanism.

[0017] Preferably, the weathering reinforced layer is a modified polyurethane layer, which includes a polyether polyurethane prepolymer, epoxy resin E-51, and a penetrating agent.

[0018] The epoxy resin E-51 accounts for 10-15% of the mass of the polyether polyurethane prepolymer. The crosslinking of the epoxy resin E-51 and the polyurethane prepolymer improves rigidity and chemical corrosion resistance. The use of a specific sulfonate penetrating agent optimizes the wettability of the coating, enhances the compactness, blocks the penetration of corrosive media, and significantly improves the stability in humid and acidic or alkaline environments.

[0019] Preferably, the surface of the polyethylene terephthalate substrate layer is irradiation grafted and modified. The grafted substance is reduced graphene oxide (RGO), the grafting density is 0.5-1.2 wt%, and the grafting method is cobalt source gamma ray irradiation with a dose of 20-30 kGy. The grafting is used to improve the strength, thermal stability, and barrier property of the substrate. Before irradiation, the substrate layer is immersed in an RGO dispersion liquid containing 0.5 wt% of p-styrenesulfonic acid. The p-styrenesulfonic acid promotes the grafting reaction, enhances the RGO-PET interface bonding force, and inhibits shedding, thereby ensuring that the strength retention rate is ≥90% under high temperature and high humidity.

[0020] Preferably, the adhesive layer is an isocyanate modified polyurethane adhesive, wherein the isocyanate is toluene diisocyanate, accounting for 0.8-1.5wt% of the total mass of the isocyanate modified polyurethane adhesive, balancing the crosslinking degree and flexibility, and the peel strength after curing is ≥10N / inch, ensuring that the interlayer does not delaminate under high stress environment.

[0021] Preferably, the high-barrier inner layer is one of a polyvinylidene chloride coating layer, a Mo-Co co-doped Ni(OH)2 nanosheet / polycarbonate composite layer, or a PVA / modified sericite composite layer, achieving high barrier through multiple paths to adapt to different application scenarios;

[0022] Preferably, the polyvinylidene chloride coating layer has a thickness of 10-15μm and an oxygen transmission rate (OTR) ≤5cc / m²·day.

[0023] Preferably, the Mo-Co co-doped Ni(OH)2 nanosheet / polycarbonate composite layer has a MoCo-Ni(OH)2 content of 8-12wt%, and a nanosheet diameter ≤200nm, constructing a tortuous barrier path through nanosheets to synergistically improve barrier properties.

[0024] Preferably, the composite film passes the ultraviolet aging test (QUV500h) with a yellowing index Δb ≤1.5, passes the alkaline solution immersion test (5% NaOH, 72h) with a mass loss rate ≤3%, and has a tensile strength retention rate ≥95% under high temperature and high humidity conditions (85℃ / 85%RH, 1000h).

[0025] Preferably, the PVA / modified sericite composite layer has a modified sericite content of 0.4-0.8wt% for enhancing barrier properties and mechanical properties.

[0026] Compared with the prior art, the multilayer composite polyester-based film structure with high weather resistance has the following beneficial effects:

[0027] 1. The multilayer composite polyester-based film structure with high weather resistance provided by the present application has a five-layer composite structure design of a surface layer of ultraviolet-resistant layer, weather-resistant reinforced layer, PET substrate layer, adhesive layer, and high-barrier inner layer, each layer has a clear function and synergizes with each other, breaks through the performance limitations of traditional single-layer films, and achieves a balance between weather resistance, mechanical strength, and barrier properties.

[0028] 2. The multilayer composite polyester-based film structure with high weather resistance provided by the present application uses KH550 silane coupling agent modified hydrotalcite nanoparticles to modify PET in the surface layer, uses a double-path enhancement of ultraviolet resistance through efficient scattering / absorption of ultraviolet rays by nanoparticles and interface compatibility optimization, significantly improves the UV shielding rate and inhibits yellowing.

[0029] 3, The multilayer composite polyester-based film structure with high weather resistance provided by the application has a weather resistance reinforcing layer which is crosslinked by epoxy resin E-51 (10-15 wt%) and polyurethane prepolymer, combines with a sulfonate penetrant to optimize the compactness of the coating, and simultaneously improves rigidity, chemical corrosion resistance and hygrothermal stability, and breaks through the performance singleness of traditional polyurethane layers.

[0030] 4, The multilayer composite polyester-based film structure with high weather resistance provided by the application has a PET substrate layer which is irradiated by cobalt source gamma rays to graft reduced graphene oxide, and combines with p-styrene sulfonic acid to promote the grafting reaction, thereby significantly improving the strength, thermal stability and high-temperature and high-humidity strength retention rate of the substrate.

[0031] 5, The multilayer composite polyester-based film structure with high weather resistance provided by the application adopts toluene diisocyanate modified polyurethane adhesive to balance the crosslinking degree and flexibility, realizes a peeling strength of ≥10 N / inch, solves the interlayer delamination problem of the multilayer composite film, and guarantees the structural stability under high stress environment.

[0032] 6, The multilayer composite polyester-based film structure with high weather resistance provided by the application provides three optional schemes for a high-barrier inner layer, and adapts to different application scene requirements through a nano-barrier path, a metal hydroxide synergistic barrier or a composite material reinforcement mechanism.

[0033] In summary, the multilayer composite polyester-based film structure with high weather resistance provided by the application has a five-layer composite structure of an ultraviolet-resistant surface layer, a weather resistance reinforcing layer, a PET substrate layer, an adhesive layer and a high-barrier inner layer, which is constructed through nano modification, crosslinking reinforcement, irradiation grafting and other technologies. The five-layer synergistic system not only significantly improves the weather resistance, mechanical strength and barrier performance, but also meets the diversified application requirements through modular inner layer design, and provides a high-performance, long-life and environmentally friendly film material solution for high-end packaging, new energy, electronic packaging and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure One The multilayer composite polyester-based film structure in embodiment one is shown in the figure. DETAILED DESCRIPTION

[0035] The following is a further description of the technical solutions of the application in conjunction with the drawings, but the application is not limited to these embodiments. Embodiment one:

[0037] A multilayer composite polyester-based film structure with high weather resistance, comprising, in sequence:

[0038] Surface anti-ultraviolet layer (1-3 μm), which blocks ultraviolet radiation through an ultrathin anti-ultraviolet layer (1-3 μm) to prolong the service life of the film, uses a hydrotalcite-modified polyethylene terephthalate composite material, the content of hydrotalcite is 5-8 wt%, and the particle size is ≤100 nm, wherein the surface of the hydrotalcite in the hydrotalcite-modified polyethylene terephthalate composite material is modified by silane coupling agent KH550, the hydrotalcite can efficiently scatter or absorb ultraviolet rays to improve the UV shielding rate, KH550 silane modification enhances the interfacial compatibility of hydrotalcite-PET, inhibits the agglomeration of nanoparticles, and improves the dispersibility and light transmittance, thereby strengthening the anti-ultraviolet durability through two paths.

[0039] Weathering reinforcement layer (5-8 μm), which uses a modified polyurethane layer including a polyether type polyurethane prepolymer, epoxy resin E-51, and a penetrating agent, wherein the content of the epoxy resin E-51 in the polyether type polyurethane prepolymer is 10-15%, the crosslinking of the epoxy resin E-51 and the polyurethane prepolymer improves rigidity and chemical corrosion resistance, a specific sulfonate penetrating agent is used to optimize the wettability of the coating, enhance the compactness, block the penetration of corrosive media, significantly improve the stability in humid heat or acid-base environments, and improve mechanical stability and environmental stress resistance.

[0040] Polyethylene terephthalate substrate layer (25-50 μm), which provides core mechanical support, the surface of the polyethylene terephthalate substrate layer is modified by irradiation grafting, the grafted substance is reduced graphene oxide (RGO), the grafting density is 0.5-1.2 wt%, and the grafting method is cobalt source gamma ray irradiation with a dose of 20-30 kGy, which is used to improve the strength, thermal stability, and barrier property of the substrate, before irradiation, the substrate layer is immersed in an RGO dispersion liquid containing 0.5 wt% of p-styrenesulfonic acid, p-styrenesulfonic acid promotes the grafting reaction and enhances the interfacial bonding force of RGO-PET, thereby inhibiting shedding and ensuring that the strength retention rate is ≥90% under high temperature and high humidity.

[0041] Adhesive layer (2-5 μm), which uses an isocyanate-modified polyurethane adhesive, wherein the isocyanate is toluene diisocyanate, which accounts for 0.8-1.5 wt% of the total mass of the isocyanate-modified polyurethane adhesive, and the balance of crosslinking degree and flexibility, the peel strength after curing is ≥10 N / inch, which ensures that the layers do not delaminate under high stress environment and ensures high strength bonding between the layers.

[0042] High-barrier inner layer (10-15 μm), which blocks water and oxygen penetration to protect the contents, uses one of a polyvinylidene chloride coating layer, a Mo-Co co-doped Ni(OH)2 nanosheet / polycarbonate composite layer, or a PVA / modified sericite composite layer, and realizes high barrier through multiple paths to adapt to different application scenarios.

[0043] The polyvinylidene chloride coating layer has a thickness of 10-15 μm and an oxygen transmission rate (OTR) ≤5 cc / m2·day.

[0044] The Mo-Co co-doped Ni(OH)2nanosheet / polycarbonate composite layer has a MoCo-Ni(OH)2content of 8-12 wt%, and the nanosheet diameter is ≤200 nm, and the nanosheet is used to construct a tortuous barrier path to synergistically improve the barrier property.

[0045] The PVA / modified sericite composite layer has a modified sericite content of 0.4-0.8 wt%, and is used to enhance the barrier property and mechanical property.

[0046] The five-layer composite structure realizes functional layering synergy, and the film product has weather resistance, mechanical strength and barrier property.

[0047] The composite film passes the ultraviolet aging test (QUV 500h), has a yellowing index Δb ≤1.5, passes the alkaline solution immersion test (5% NaOH, 72h), has a mass loss rate ≤3%, and has a tensile strength retention rate ≥95% under high temperature and high humidity conditions (85℃ / 85%RH, 1000h). Specific embodiment two:

[0049] Specific embodiment two is a performance detection of the PVA / modified sericite coating layer mentioned in specific embodiment one, and analyzes the influence of the mass fraction of the modified sericite on the performance of the composite material. The content of specific embodiment two is as follows:

[0050] The mica is modified by a silane coupling agent modification method. The modifier is γ-glycidoxypropyltrimethoxysilane (KH550). First, the mica is pretreated. The natural sericite is activated by calcination at 800℃ for 1 hour, acidified with 5 mol / L nitric acid (95℃, 5h), and sodiumized with a saturated NaCl solution. The sodiumized mica is dispersed in deionized water, and ultrasonic treatment is performed for 2-6 hours to form a 1g / mL suspension. The suspension is diluted in ethanol, and KH550 is added (water:KH550:ethanol=1:1:15). Reflux stirring is performed at 80℃ for 5-8 hours. Washing and drying are performed three times, and the modified sericite modified with KH550 is obtained by drying at 80℃ for 24 hours.

[0051] Preparation of PVA / modified sericite coating, first raw material preparation, polyvinyl alcohol is dissolved in hot water, 10-15wt% solution. Modified sericite suspension is added to the PVA solution, sericite accounts for 0.4, 0.5, 0.6, 0.7, 0.8wt%. Add crosslinking agent glutaraldehyde (GA) (5% of PVA mass), 60℃ stirring to promote the formation of PVA-OH and GA-CHO acetal bond. Add 16wt% stearic acid, its carboxyl group is esterified with PVA, then ethanol ultrasonic cleaning, preparation of different components of modified PVA emulsion, preparation of PET coating composite film, test performance.

[0052] Coating water resistance analysis

[0053] Solubility test: the coating is cast on a glass plate into a film, cut into 20x20mm film samples, after drying, using an electronic balance to weigh its mass and record as m1, then the sample is placed in 23°C deionized water for 24 hours, after taking out and drying and weighing record as m2, each test is repeated 3 times to take the average value, according to the formula to calculate the solubility of the coating to evaluate the water resistance:

[0054] Solubility = m2 / m1x100%;

[0055] Wherein: m1 is the dry weight before soaking, m2 is the dry weight after soaking.

[0056] When the coating water absorption and solubility is high, it will absorb water in the environment and dissolve and swell, resulting in the destruction of the coating gas barrier, the lower the coating water absorption and solubility in water, the better the water resistance of the coating, the better the environmental stability, when the water absorption and solubility is low, the coating has better gas barrier performance under high humidity conditions. From table 1 data can be obtained, when the sericite content is 0.6wt%, the solubility is the lowest (3.1%), which indicates that the crosslinking degree of PVA molecular chain is the highest at this time, which can effectively inhibit the polymer dissolution. Specific embodiment three:

[0058] Specific embodiment three is the performance test of PVA / modified sericite coating mentioned in specific embodiment one, to analyze the influence of mass fraction of modified sericite on the performance of composite material, specific embodiment three content as follows:

[0059] Mica was modified by silane coupling agent modification method, and the modifier was γ-glycidoxypropyltrimethoxysilane (KH550). First, the mica was pretreated. The natural sericite was calcined at 800°C for 1 hour to activate, then acidized with 5 mol / L nitric acid (95°C, 5h), and sodiumized with saturated NaCl solution. The sodiumized mica was dispersed in deionized water, and ultrasonic treatment was performed for 2-6 hours to form a 1 g / mL suspension. The suspension was diluted in ethanol, and KH550 was added (water:KH550:ethanol=1:1:15), and reflux stirring was performed at 80°C for 5-8 hours. After washing and drying for 3 times, the modified sericite mica modified by KH550 was obtained by drying at 80°C for 24 hours.

[0060] PVA / modified sericite mica coating was prepared. First, the raw materials were prepared. Polyvinyl alcohol was dissolved in hot water to prepare a 10-15wt% solution. The modified sericite mica suspension was added to the PVA solution, and the content of sericite mica was 0.4, 0.5, 0.6, 0.7, and 0.8wt%, respectively. Glutaraldehyde (GA) was added as a crosslinking agent (5% of the mass of PVA), and stirring was performed at 60°C to promote the formation of acetal bonds between the -OH of PVA and the -CHO of GA. 16wt% stearic acid was added, and the carboxyl group thereof was esterified with PVA. Then, ethanol ultrasonic cleaning was performed to prepare modified PVA emulsions with different components, and PET coating composite films were prepared for performance testing.

[0061] Water resistance analysis of coating

[0062] Water absorption test: According to the standard GB / T1034-2008 "Determination of water absorption of plastics", the coating was cast on a glass plate to form a film, and the film sample was cut into 20×20mm. The initial dry mass m1 was measured. After immersing the sample in 23°C deionized water for 24 hours, the surface water was quickly absorbed with filter paper, and the mass m2 was recorded. Each test was repeated 3 times to take the average value, and the water absorption was calculated according to the formula to represent the water resistance:

[0063] Water absorption = m 2- m2-m1 / m1×100%;

[0064] Wherein: m1 is the mass before water absorption, and m2 is the mass after water absorption.

[0065] According to the data in Table 1, when the content is <0.6wt%, the mica filling is insufficient, and the PVA crosslinking network has hydrophilic micropores (water absorption >25%). When the content is >0.6wt%, the mica agglomerates, which easily produces interface defects, leading to the penetration of water molecules along the edge of the agglomerates, thereby causing the water absorption to rise again. Excessive mica hinders the crosslinking of PVA-GA. When the content of sericite mica is 0.6wt%, the water absorption is the lowest (18.3%), at which time the hydrophobic groups of stearic acid cover the hydroxyl groups of PVA, and the mica sheet layer blocks the penetration path of water molecules. In summary, the content of sericite mica is determined to be 0.6wt%.

[0066] Table 1 Water resistance test table

[0067] . Specific embodiment four:

[0069] Specific embodiment four is a lateral performance comparison of the coating mentioned in specific embodiments two and three, the mica is modified by silane coupling agent modification method, the modifier uses γ-glycidoxypropyltrimethoxysilane (KH550), first the mica pretreatment, natural sericite is activated by calcining at 800°C for 1 hour, then acidified with 5 mol / L nitric acid (95°C, 5h), and sodiumized with saturated NaCl solution. The sodiumized mica is dispersed in deionized water, and ultrasonic for 2-6 hours to form a 1g / mL suspension. Dilute the suspension in ethanol, add KH550 (water: KH550: ethanol = 1: 1: 15), reflux and stir at 80°C for 5-8 hours. Wash and dry 3 times, and dry at 80°C for 24 hours to obtain KH550 modified modified sericite.

[0070] Prepare PVA / modified sericite coating, first prepare the raw materials, dissolve polyvinyl alcohol in hot water to make a 10-15wt% solution. Add the modified sericite suspension to the PVA solution, and the sericite accounts for 0.6wt%. Add the crosslinking agent glutaraldehyde (GA) (5% of the mass of PVA), and stir at 60°C to promote the formation of acetal bonds between the -OH of PVA and the -CHO of GA. Add 16wt% stearic acid, which is esterified with the carboxyl group of PVA, then perform ethanol ultrasonic cleaning to prepare a modified PVA emulsion with different components, prepare a PET coating composite film, and test the performance.

[0071] The results are as follows:

[0072] Table 2 Water resistance lateral comparison

[0073] ;

[0074] Conclusion: The solubility of modified mica is reduced by 68%, and the water absorption rate is reduced by 75% (compared with pure PVA), and compared with the unmodified mica coating, the solubility is reduced by 68%, and the water absorption rate is reduced by 54%. Specific embodiment five:

[0076] Specific embodiment five is a mechanical property test of the PVA / modified sericite coating mentioned in specific embodiment one, to determine the hardness and adhesion of the coating. The specific embodiment five is as follows:

[0077] The sample was prepared according to the steps described in the specific embodiment three, and then the adhesion test was carried out. The composite coating was coated on the PET film substrate and dried to form a film. According to GB / T9286-1998, five cuts were made on the horizontal and vertical directions of the coated PET film coating surface to form a 4x4 1x1 cm rectangle. After the 3M grid test transparent tape was adhered, it was quickly torn open, and the coating damage was observed to determine the grade.

[0078] Pencil hardness test: The coating hardness was determined according to GB / T6739-1996 using BGD505 combined pencil hardness tester. The PET film with coating was placed horizontally on the test bench, and the installed pencil hardness tester was placed at 45° to the coating surface. Starting from the hardest pencil, push it at a speed of 5-10 cm / min for 10 cm to observe whether the coating surface is scratched. Each pencil of hardness is drawn 5 times, and if 2 out of 5 times can scratch the sample, a softer pencil number is selected until at most 1 out of 5 times can scratch the sample. The corresponding number of this pencil is the pencil hardness of the coating being tested.

[0079] Table 3 Coating hardness and adhesion

[0080] ;

[0081] As shown in the table, the addition of sericite significantly improves the coating hardness. The pure PVA soft amorphous structure (hardness B) is easy to be pressed into the pencil, while the addition of unmodified mica physically fills the hardness to HB. However, the mica-matrix interface is weak, and the silane coupling agent forms a -Si-O-C- covalent bond between mica / PVA, and the hardness jumps to 3H, which improves the coating hardness by 5 grades, significantly enhancing the coating hardness.

[0082] As can be seen from the data in the table, the adhesion of the PVA coating is poor, while the adhesion of the coating added with mica is improved, which is mainly due to the large surface energy of mica, which makes the bonding force between the coating and the substrate stronger. In summary, the adhesion of the coating to the PET substrate is good, and the hardness of the coating is also relatively high due to the addition of mica. Specific embodiment six:

[0084] Specific embodiment six is a mechanical property test of the multi-layer composite polyester film mentioned in specific embodiment one, to explore the tensile strength, elongation at break and peel strength of the composite film. The content of specific embodiment six is as follows:

[0085] Test method: According to GB / T1040.3-2006 "Determination of tensile properties of plastics Part 3: test conditions for films and sheets", electronic tensile testing machine was used for testing.

[0086] Sample preparation: cut into long strip (type 2 sample), width 15mm, gauge length 50mm, thickness according to actual film thickness (total thickness about 43-80pm).

[0087] Test conditions: tensile speed 50mm / min, test ambient temperature 23±2℃, relative humidity 50±5%.

[0088] Conclusion: RGO grafting makes the modulus of the substrate increase by 50%, and the strength retention rate under high temperature and high humidity meets the standard.

[0089] Table 4 Tensile strength and modulus of composite film

[0090] ;

[0091] Peeling strength (interlayer adhesion) test method: according to GB / T2790-1995 "adhesive 180° peeling strength test method", using 180° peeling strength tester to test the performance of the adhesive layer.

[0092] Sample preparation: glue the composite film with rigid test plate, glue length 150mm, test after curing.

[0093] Test conditions: peeling speed 100±10mm / min, record the average peeling force.

[0094] Results: after optimizing the crosslinking degree of isocyanate modified polyurethane adhesive, the peeling strength is ≥12N / inch. Specific embodiment seven:

[0096] Specific embodiment seven is the detection of the ultraviolet resistance of the multi-layer composite polyester-based film mentioned in specific embodiment one, to determine the ultraviolet shielding rate and yellowing index of the composite film. The content of specific embodiment seven is as follows:

[0097] Ultraviolet shielding rate test method: using ultraviolet spectrophotometer method, measuring the transmittance in the wavelength range of 280-400nm, and calculating the shielding rate.

[0098] Sample preparation: cut into 50mm×50mm square samples and fix them on the test fixture.

[0099] Test equipment: ultraviolet-visible spectrophotometer (such as Shimadzu UV-3600).

[0100] Results: due to the high efficiency of scattering or absorbing ultraviolet light by hydrotalcite nanoparticles, the ultraviolet shielding rate of the composite film is ≥98%.

[0101] Yellowing index (Ab) test method: according to GB / T30669-2014 "textile color fastness test light fastness yellowing fastness", using ultraviolet aging test box for 500h irradiation.

[0102] Test condition: wavelength 340 nm, irradiation intensity 0.89 W / m2, black panel temperature 60°C.

[0103] Data calculation: Δb value was measured by color difference meter before and after irradiation.

[0104] Results: The surface ultraviolet resistant layer and the weather resistant reinforcing layer synergistically inhibited yellowing, and the Δb value of the composite film was ≤1.5. Specific embodiment eight:

[0106] Specific embodiment eight is the weather resistance detection of the multi-layer composite polyester-based film mentioned in specific embodiment one, to clarify the chemical corrosion resistance, hygrothermal stability and environmental stress cracking resistance of the composite film, and the content of specific embodiment eight is as follows:

[0107] Chemical corrosion resistance (alkaline solution immersion) detection method: immerse the sample completely in 5% NaOH solution, take it out after 72 h, clean and dry, and measure the mass loss rate.

[0108] Test condition: temperature 25±2°C, solution volume / sample area ratio ≥10 mL / cm2.

[0109] Data calculation: mass loss rate = (mass before immersion-mass after immersion) / mass before immersion × 100%.

[0110] Results: The modified polyurethane layer and the PVA / sere mica composite layer blocked the corrosion medium, and the final mass loss rate was ≤3%.

[0111] Hygrothermal stability (high temperature and high humidity conditions) detection method: according to GB / T 2423.3 "Environmental testing Part 2: test methods Test Cab: constant humidity test", expose under 85°C / 85% RH conditions for 1000 h.

[0112] Test equipment: constant temperature and humidity test chamber.

[0113] Data calculation: tensile strength retention rate = strength after hygrothermal treatment / initial strength × 100%.

[0114] Results: The thermal stability was improved by irradiation grafting RGO on the PET substrate layer, and the tensile strength retention rate was ≥95%.

[0115] Environmental stress cracking (ESC) detection method: use ASTM D1693 "Plastics environmental stress cracking resistance test method", cut a small notch on the surface of the sample, immerse in surfactant solution (such as 1% Igepal CO-630) after bending, and observe the crack generation time.

[0116] Test condition: temperature 50°C, bending stress 10 MPa.

[0117] Results: The modified polyurethane layer crosslinking structure inhibits crack propagation, and the environmental stress cracking resistance time is ≥500h.

[0118] Table 5 Composite film performance table

[0119] ;

[0120] Conclusion: The composite film through the synergistic effect of the five-layer structure, in the mechanical strength, anti-UV aging, chemical corrosion resistance and humidity stability, all show excellent performance, can meet the needs of high-end packaging, photovoltaic backplane and other harsh application scenarios.

[0121] The specific embodiments described herein are merely illustrative of the spirit of the present application. Those skilled in the art of the present application can make various modifications or supplements to the described specific embodiments or replace them with similar ways, but will not deviate from the spirit of the present application or exceed the scope defined by the appended claims.

Claims

1. A multilayer composite polyester-based film structure with high weather resistance, characterized in that, Including the following settings in sequence: The surface UV-resistant layer has a thickness of 1-3μm; Weather-resistant reinforcement layer, with a thickness of 5-8μm; Polyethylene terephthalate substrate layer, with a thickness of 25-50μm; Adhesive layer, with a thickness of 2-5μm; High-barrier inner layer, with a thickness of 10-15μm; The surface UV-resistant layer is a hydrotalcite-modified polyethylene terephthalate composite material; The hydrotalcite content is 5-8 wt%, and the particle size is ≤100 nm; The surface of the hydrotalcite-modified polyethylene terephthalate composite material is modified with silane coupling agent KH550. The weather-resistant reinforcing layer is a modified polyurethane layer, comprising a polyether-type polyurethane prepolymer, epoxy resin E-51, and a penetrant; The epoxy resin E-51 accounts for 10-15% of the mass of the polyether-type polyurethane prepolymer. The surface of the polyethylene terephthalate substrate layer is irradiated and grafted with reduced graphene oxide. The grafting material is reduced graphene oxide with a grafting density of 0.5-1.2 wt% and the grafting method is cobalt source gamma ray irradiation with a dose of 20-30 kGy. Before irradiation, the substrate layer is immersed in a reduced graphene oxide dispersion containing 0.5 wt% p-styrene sulfonic acid. The adhesive layer is an isocyanate-modified polyurethane adhesive, wherein the isocyanate is toluene diisocyanate, accounting for 0.8-1.5 wt% of the total mass of the isocyanate-modified polyurethane adhesive, and the peel strength after curing is ≥10 N / inch. The high-barrier inner layer is one of the following: polyvinylidene chloride coating layer, Mo-Co co-doped Ni(OH)2 nanosheet / polycarbonate composite layer, or PVA / modified sericite composite layer. The thickness of the polyvinylidene chloride coating layer is 10-15 μm, and the oxygen permeability is ≤5cc / m²·day. The content of Mo-Co co-doped Ni(OH)2 nanosheets in the Mo-Co co-doped Ni(OH)2 nanosheet / polycarbonate composite layer is 8-12wt%, and the nanosheet diameter is ≤200nm.

2. The multilayer composite polyester film structure with high weather resistance as described in claim 1, characterized in that, The modified sericite content in the PVA / modified sericite composite layer is 0.4-0.8 wt%.

Images