High-transparency polyphenylene sulfide film with rigid-tough balance performance and manufacturing method and application of high-transparency polyphenylene sulfide film

Abstract

The invention discloses a high-transparency polyphenylene sulfide film with rigidity-toughness balance performance and a manufacturing method and application thereof, and belongs to the technical field of film manufacturing. The high-transparency polyphenylene sulfide film with the rigid-tough balance performance comprises a polyphenylene sulfide base material which is formed by sequentially carrying out uniaxial stretching and hot-pressing annealing forming on a polyphenylene sulfide original sheet. The polyphenylene sulfide base material has the following characteristics that (a) the crystallinity is larger than or equal to 46.0%; (b) the grain orientation degree is greater than or equal to 0.979; (c) the mechanical strength is greater than or equal to 276.5 MPa; (b) the elongation at break is greater than or equal to 44.3%; and (e) the light transmittance is greater than 82.7%. A densified molecular chain network is formed in the polyphenylene sulfide film, the stress transmission and dissipation capacity can be enhanced, reinforcing and toughening of the polyphenylene sulfide film are synchronously achieved, and the formed polyphenylene sulfide film has the good rigid-tough balance characteristic; the light scattering effect of a polyphenylene sulfide molecular chain can be greatly reduced, and the optical transparency of the formed polyphenylene sulfide film is effectively improved.

Description

Technical Field

[0001] This application belongs to the field of thin film manufacturing technology, specifically a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness, its manufacturing method, and its application. Background Technology

[0002] Polyphenylene sulfide (PPS) possesses high mechanical strength, high temperature resistance, chemical corrosion resistance, and low density, making it a promising candidate for next-generation lightweight specialty materials in the aerospace field, potentially driving the transformation of materials towards lightweight and high performance. However, PPS films generally suffer from low optical transparency and an imbalance between stiffness and toughness, making them unsuitable for applications requiring light transmission and resistance to complex stresses. Therefore, the development of highly transparent PPS films with a balanced stiffness and toughness holds immense market potential.

[0003] Currently, toughening modification in related fields can be achieved through the following technical routes: 1) introducing plasticizers / elastomers for composite toughening, but the toughening effect is limited and easily leads to a decrease in mechanical strength; 2) although tensile annealing technology can simultaneously improve the strength and toughness of materials, the excessively fast crystallization rate of PPS easily causes uneven crystal growth and poor film uniformity during film formation, making it difficult to achieve large-scale production. In addition, for the key manufacturing technology of high-performance PPS films, there are currently no PPS film products in China that combine a balance of rigidity and toughness, high transparency, and processing feasibility.

[0004] Therefore, developing a PPS film that combines high transparency with a balance of rigidity and toughness is crucial for filling domestic technological gaps and meeting the material needs of high-end fields. Summary of the Invention

[0005] This application effectively solves the technical problem that existing toughening modification strategies are unable to manufacture high-performance PPS films with both high optical transparency and a balance of rigidity and toughness by disclosing a highly transparent polyphenylene sulfide film with a rigidity-toughness balance.

[0006] To achieve the above objectives, the technical solution provided in this application is as follows:

[0007] The first aspect of this application provides a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness, comprising a polyphenylene sulfide substrate formed sequentially by uniaxial stretching and hot pressing annealing, wherein the polyphenylene sulfide substrate has the following characteristics:

[0008] (a) Crystallinity ≥ 46.0%; (b) Grain orientation ≥ 0.979;

[0009] (c) Mechanical strength ≥ 276.5 MPa; (b) Elongation at break ≥ 44.3%;

[0010] (e) Transmittance > 82.7%.

[0011] According to the disclosure of the first aspect, the polyphenylene sulfide substrate has the following characteristics:

[0012] (a) Crystallinity is 46.0–51.8%; (b) Grain orientation is 0.986–0.989;

[0013] (c) Mechanical strength is 276.5 MPa to 383.8 MPa;

[0014] (b) Elongation at break was 44.3%–55.9%; and,

[0015] (e) Light transmittance > 82.7%.

[0016] According to the disclosure of the first aspect, the uniaxial stretching temperature is 100°C and the stretching ratio is 8.0.

[0017] According to the disclosure of the first aspect, the hot pressing annealing pressure is 3 MPa, the temperature is 140~230℃, and the time is 15 min.

[0018] According to the disclosure of the first aspect, the thickness of the polyphenylene sulfide substrate is 0.1 mm to 0.2 mm.

[0019] The second aspect of this application also discloses a method for manufacturing a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness as described in this application, which includes the following steps:

[0020] Polyphenylene sulfide resin is melt-extruded by a single screw extruder and then cooled to obtain polyphenylene sulfide raw sheet material;

[0021] After the polyphenylene sulfide sheet is uniaxially stretched and cooled, an initial polyphenylene sulfide film is obtained.

[0022] The initial polyphenylene sulfide film is subjected to hot pressing annealing to obtain the highly transparent polyphenylene sulfide film with a balance of rigidity and toughness.

[0023] According to the disclosure of the second aspect, the melt index of the polyphenylene sulfide resin is 20~200 g / 10 min.

[0024] According to the disclosure of the second aspect, the extrusion temperature of the single-screw melt extrusion is 280~350℃, and the screw speed is 20~100r / min.

[0025] According to the disclosure of the second aspect, the thickness of the original polyphenylene sulfide sheet is 0.9 mm to 1 mm, and the grain orientation degree is 0.011.

[0026] The third aspect of this application also discloses the application of the highly transparent polyphenylene sulfide film with a balance of rigidity and toughness described in this application in the fields of flexible electronics, biomedicine, smart wearables, and aerospace.

[0027] Compared with the prior art, the advantages or beneficial effects of this application include at least:

[0028] This application employs a combined treatment process of uniaxial stretching and hot-pressing annealing on the original polyphenylene sulfide (PPS) sheet. This synergistically induces the orientation and crystallization of PPS molecular chains, significantly improving the perfection of the oriented crystal structure. This not only constructs a dense molecular chain network but also simultaneously enhances the toughness and rigidity of the PPS film, resulting in a well-balanced rigidity and toughness. Furthermore, it effectively improves the optical transparency of the formed PPS film. In addition, this application features a simple manufacturing process, high production efficiency, and stable and easily achievable production conditions, making it suitable for large-scale industrial production. Test results from examples show that the PPS film of this application exhibits a mechanical strength ≥276.5 MPa, an elongation at break ≥44.3%, and a light transmittance >82.7%, demonstrating excellent rigidity-toughness balance and optical transparency. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The WAXD two-dimensional images of PPS films formed by different uniaxial stretching ratios (100°C) and hot pressing temperatures provided in this application;

[0031] Figure 2 This paper illustrates the variation of the internal grain size of the PPS film provided in this application with uniaxial stretching-annealing combined treatment.

[0032] Figure 3 This paper illustrates the change in the internal crystal orientation of the PPS film provided in this application with uniaxial stretching-annealing combined treatment.

[0033] Figure 4 DSC curves obtained by uniaxial stretching at different magnifications for this application;

[0034] Figure 5 The DSC curves provided for this application after uniaxial tensile (100°C)-hot pressing annealing combined treatment;

[0035] Figure 6 Crystallinity analysis diagrams of the initial PPS films formed under different uniaxial stretching ratios (100°C) provided in this application;

[0036] Figure 7Crystallinity analysis diagram of the PPS film formed by uniaxial stretching-hot pressing annealing provided in this application;

[0037] Figure 8 The change in the amorphous molecular chain orientation of the PPS raw sheet provided in this application with uniaxial stretching (100°C) treatment;

[0038] Figure 9 The curve of change of the initial PPS film after uniaxial stretching (100℃-DR8.0) provided in this application with hot pressing annealing treatment;

[0039] Figure 10 The optical transparency of the initial PPS films formed at different uniaxial stretching ratios (100°C) provided in this application;

[0040] Figure 11 The optical transparency of the PPS film formed by uniaxial stretching-hot pressing annealing combined treatment provided in this application;

[0041] Figure 12 Digital photographs of the initial PPS film samples formed by uniaxial stretching treatment at 100℃-DR0 and 100℃-DR8.0 respectively, provided for this application;

[0042] Figure 13 Digital photographs of PPS film samples formed by combined treatment of uniaxial stretching (100℃-DR0)-hot pressing annealing (200℃) and uniaxial stretching (100℃-DR8.0)-hot pressing annealing (200℃), respectively, provided for this application;

[0043] Figure 14 The storage modulus of the PPS film formed by different treatments provided in this application varies with temperature.

[0044] Figure 15 The heat resistance temperature provided in this application is the temperature of the material after being molded through different treatments. Detailed Implementation

[0045] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort are within the scope of protection of this application.

[0046] In the following description of this application, the term "and / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. Here, A and B can be singular or plural; the symbol " / " means "or".

[0047] In the following description of this application, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions mean any combination of such items, including any combination of single or multiple items. For example, "at least one of A, B or C" or "at least one of A, B and C" can mean any one of A, B, and C, or A+B, or A+C, or B+C, or A+B+C, where A, B, and C can be single or multiple.

[0048] In the following description of this application, the order of the sequence numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be specifically determined by its function and internal logic, and does not constitute any limitation on the execution process of this embodiment.

[0049] In the following description of this application, the numerical range should be understood to also specifically disclose each intermediate value between the upper and lower limits of the range. Any intermediate value within a stated range, as well as any other stated value or each smaller range between intermediate values ​​within a stated range, are also included in this embodiment, and the upper and lower limits of the smaller ranges may be independently included or excluded from the range.

[0050] Unless otherwise stated, the technical / scientific terms used in this application have the meanings commonly understood by one of ordinary skill in the art. While this application describes only preferred materials and methods, similar or equivalent methods and materials may be used in specific embodiments or test cases. All references to this application are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this application shall prevail.

[0051] To address the problem that existing toughening modification strategies struggle to form high-performance PPS films with both high transparency and a balance of rigidity and toughness, the first aspect of this application provides a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness, comprising a polyphenylene sulfide substrate formed sequentially by uniaxial stretching and hot-pressing annealing, wherein the polyphenylene sulfide substrate possesses the following characteristics:

[0052] (a) Crystallinity ≥ 46.0%; (b) Grain orientation ≥ 0.979;

[0053] (c) Mechanical strength ≥ 276.5 MPa; (b) Elongation at break ≥ 44.3%;

[0054] (e) Transmittance > 82.7%.

[0055] This application embodiment involves a combination of uniaxial stretching and hot-pressing annealing sequentially on the raw polyphenylene sulfide (PPS) sheet. Through the synergistic effect of these two steps, the PPS molecular chains are efficiently oriented and crystallized, while the integrity of the oriented nanocrystal structure is significantly improved. On one hand, this constructs a dense molecular chain network, achieving a synergistic enhancement of the PPS film's reinforcement and toughness, endowing the molded PPS film with excellent rigidity-toughness balance properties. On the other hand, the highly refined oriented nanocrystal structure significantly reduces the light scattering effect of the molecular chains, substantially optimizing the optical transparency of the molded PPS film. Furthermore, this application features a simple process flow, high production efficiency, and stable and easily controllable production conditions, making it fully adaptable to the needs of large-scale industrial production.

[0056] In possible disclosed examples, the polyphenylene sulfide substrate preferably has the following characteristics:

[0057] (a) Crystallinity is 46.0–51.8%; (b) Grain orientation is 0.986–0.989;

[0058] (c) Mechanical strength is 276.5 MPa to 383.8 MPa;

[0059] (b) Elongation at break was 44.3%–55.9%; and,

[0060] (e) Light transmittance > 82.7%.

[0061] In possible public examples, the uniaxial stretching temperature is preferably 100°C, and the stretching ratio is preferably 8.0. Specifically, in this application embodiment, by subjecting the original polyphenylene sulfide sheet to uniaxial stretching at a temperature of 100°C and a stretching ratio of 8.0, the orientation and crystallization of the polyphenylene sulfide molecular chains can be efficiently induced, effectively improving the rigidity-toughness balance and optical transparency of the formed film.

[0062] In possible public examples, the hot-press annealing pressure is preferably 3 MPa, the temperature is preferably 140~230℃, and the time is preferably 15 min. Specifically, in this embodiment, by subjecting the initial polyphenylene sulfide (PPS) film after uniaxial stretching to hot-press annealing at a pressure of 3 MPa and a temperature of 140~230℃ for 15 min, the orientation degree of the PPS molecular chains is significantly improved, thereby synergistically constructing a dense molecular chain network. This simultaneously achieves reinforcement and toughening of the PPS film, endowing the molded film with excellent rigidity-toughness balance properties. Furthermore, it perfects the oriented crystal structure, thereby significantly reducing the light scattering effect of the molecular chains and thus significantly optimizing the optical transparency of the molded film.

[0063] In possible public examples, the thickness of the polyphenylene sulfide substrate is preferably 0.1 mm to 0.2 mm. A substrate with a thickness of 0.1 mm to 0.2 mm possesses a better balance of rigidity and toughness, exhibiting good adaptability to subsequent processing, while also allowing the film to maintain better optical transparency, meeting the needs of applications with high light transmittance requirements.

[0064] In a second aspect, embodiments of this application also provide a method for manufacturing a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness as described above, comprising the following steps:

[0065] Polyphenylene sulfide resin is melt-extruded by a single screw extruder and then cooled to obtain polyphenylene sulfide raw sheet material;

[0066] After the polyphenylene sulfide sheet is uniaxially stretched and cooled, an initial polyphenylene sulfide film is obtained.

[0067] The initial polyphenylene sulfide film is subjected to hot pressing annealing to obtain the highly transparent polyphenylene sulfide film with a balance of rigidity and toughness.

[0068] It should be noted that this application does not impose any special limitations on the equipment used for single-screw melt extrusion and uniaxial stretching, as long as it can meet the requirements of the process. For example, in the embodiments of this application, a torque single-screw extruder is used for melt extrusion, wherein the polyphenylene sulfide resin is melted and extruded through a slit die to form a shaped polyphenylene sulfide sheet; at the same time, this application controls the stretching ratio by changing the speed difference of the stretching rollers of the stretching device.

[0069] In possible disclosed examples, the melt index (MI) of the polyphenylene sulfide resin is 20~200 g / 10 min, preferably 50~150 g / 10 min, and more preferably 50 g / 10 min. In this application, by controlling the melt index of polyphenylene sulfide resin to be 20~200 g / 10 min, it can ensure that the polyphenylene sulfide resin has good plasticization uniformity and sheet formability during the extrusion stage, and also provide a suitable viscosity window for the "forced orientation" of subsequent uniaxial stretching and the "crystallization perfection" of hot pressing annealing, which helps to ensure process stability and product qualification rate during mass production. The preferred melt index (MI) is 50~150 g / 10 min, which can not only build a dense and stable molecular chain network, improve the mechanical load-bearing capacity of the crystal structure (enhancement), but also alleviate brittleness through the synergistic effect of oriented crystals and amorphous regions (toughening), which helps to achieve excellent rigidity and toughness balance characteristics. In particular, when the melt index (MI) is 50 g / 10 min, the molecular chain rigidity and orientation stability are stronger, the crystallization perfection is further improved, and the scattering loss of light at the crystal interface and disordered regions of molecular chains can be minimized, which helps to optimize the transmittance and haze index of the film.

[0070] In possible public examples, the extrusion temperature of the single-screw melt extrusion is preferably 280~350℃, and the screw speed is preferably 20~100 r / min. The extrusion temperature of 280~350℃ allows the polyphenylene sulfide molecular chains to be in a "flowable and oxidizable" state, ensuring the orderly arrangement of oriented molecular chains and the formation of a more complete oriented nanocrystalline structure without oxidation during subsequent hot-pressing annealing. The speed range of 20~100 r / min achieves a balance between "moderate shearing and reasonable residence time," breaking up molecular chain entanglement through the shearing action of the screw edges to promote uniform resin plasticization, while avoiding structural defects caused by excessive shear heat or improper residence time, ensuring consistent performance across all areas of the sheet. The synergy of both factors helps improve the mechanical properties and transparency of the molded film.

[0071] In possible public examples, the thickness of the polyphenylene sulfide (PPS) raw sheet is preferably 0.9 mm to 1 mm, and the grain orientation degree is preferably 0.011. Specifically, by controlling the thickness of the raw sheet to 0.9 mm to 1 mm and the grain orientation degree to 0.011, this application provides a structurally compatible substrate for the subsequent "fully oriented" uniaxial stretching and "perfectly crystallized" hot-pressing annealing, while also ensuring process stability and the uniformity of the formed film's performance.

[0072] Thirdly, embodiments of this application also provide applications of the highly transparent polyphenylene sulfide (PPS) film with a balanced stiffness and toughness as described in this application, specifically in the fields of flexible electronics, biomedicine, smart wearables, and aerospace. Since the PPS film described in this application possesses excellent stiffness-toughness balance and optical transparency, its application in these fields can effectively promote the transformation of materials towards lightweight and high-performance materials.

[0073] The technical solution of this application will be further described below with reference to specific embodiments.

[0074] Example 1

[0075] This embodiment provides a method for manufacturing a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness, the steps of which include:

[0076] S1: After fully dehumidifying the polyphenylene sulfide resin particles with a melt index of 50g / 10min, they are added to a torque single screw extruder and successively melted at 300℃~320℃, extruded through a slit die, and air-cooled to obtain low-crystallinity polyphenylene sulfide raw sheet.

[0077] S2: The original polyphenylene sulfide sheet is fed into a stretching device with a roller temperature of 100°C, a stretching ratio of 8.0, and a stretching roller speed of 0.5m / min for stretching treatment. After annealing and cooling by annealing rollers, an initial polyphenylene sulfide film is obtained.

[0078] S3: The initial polyphenylene sulfide film is placed in a hot press at a pressure of 3 MPa and a temperature of 230°C for annealing for 15 minutes, and then naturally cooled for 5 minutes to obtain a highly transparent polyphenylene sulfide film PPS-RFB1 with a balance of rigidity and toughness.

[0079] Example 2

[0080] This embodiment provides a method for manufacturing a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness, the steps of which include:

[0081] S1: After fully dehumidifying the polyphenylene sulfide resin particles with a melt index of 50g / 10min, they are added to a torque single screw extruder and successively melted at 300℃~320℃, extruded through a slit die, and air-cooled to obtain low-crystallinity polyphenylene sulfide raw sheet.

[0082] S2: The original polyphenylene sulfide sheet is fed into a stretching device with a roller temperature of 100°C, a stretching ratio of 8.0, and a stretching roller speed of 0.5m / min for stretching treatment. After annealing and cooling by annealing rollers, an initial polyphenylene sulfide film is obtained.

[0083] S3: The initial polyphenylene sulfide film is placed in a hot press at a pressure of 3 MPa and a temperature of 200°C for annealing for 15 minutes, and then naturally cooled for 5 minutes to obtain a highly transparent polyphenylene sulfide film PPS-RFB2 with a balance of rigidity and toughness.

[0084] Example 3

[0085] This embodiment provides a method for manufacturing a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness, the steps of which include:

[0086] S1: After fully dehumidifying the polyphenylene sulfide resin particles with a melt index of 50g / 10min, they are added to a torque single screw extruder and successively melted at 300℃~320℃, extruded through a slit die, and air-cooled to obtain low-crystallinity polyphenylene sulfide raw sheet.

[0087] S2: The original polyphenylene sulfide sheet is fed into a stretching device with a roller temperature of 100°C, a stretching ratio of 8.0, and a stretching roller speed of 0.5m / min for stretching treatment. After annealing and cooling by annealing rollers, an initial polyphenylene sulfide film is obtained.

[0088] S3: The initial polyphenylene sulfide film is placed in a hot press at a pressure of 3 MPa and a temperature of 170°C for annealing for 15 minutes, and then naturally cooled for 5 minutes to obtain a highly transparent polyphenylene sulfide film PPS-RFB3 with a balance of rigidity and toughness.

[0089] Example 4

[0090] This embodiment provides a method for manufacturing a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness, the steps of which include:

[0091] S1: After fully dehumidifying the polyphenylene sulfide resin particles with a melt index of 50g / 10min, they are added to a torque single screw extruder and successively melted at 300℃~320℃, extruded through a slit die, and air-cooled to obtain low-crystallinity polyphenylene sulfide raw sheet.

[0092] S2: The original polyphenylene sulfide sheet is fed into a stretching device with a roller temperature of 100°C, a stretching ratio of 8.0, and a stretching roller speed of 0.5m / min for stretching treatment. After annealing and cooling by annealing rollers, an initial polyphenylene sulfide film is obtained.

[0093] S3: The initial polyphenylene sulfide film is placed in a hot press at a pressure of 3 MPa and a temperature of 140°C for annealing for 15 minutes, and then naturally cooled for 5 minutes to obtain a highly transparent polyphenylene sulfide film PPS-RFB4 with a balance of rigidity and toughness.

[0094] To illustrate the technical effects of the manufacturing method of this application, this application first investigated the effects of stretching temperature and stretching ratio on the initial properties of polyphenylene sulfide film, as shown in Table 1 below.

[0095] Table 1: Mechanical properties of the initial film formed at different stretching temperatures and stretching ratios

[0096]

[0097] As shown in Table 1, although biaxial stretching at 100℃-4×4 can significantly improve the elongation at break of the film, the tensile strength decreases considerably. Uniaxial stretching in Scheme 8 yielded the initial film with the highest increase in tensile strength, and the elongation at break also increased significantly. Although Scheme 5 yielded the initial film with the highest increase in elongation at break, the tensile strength of the film decreased more significantly compared to the uniaxial stretching in Scheme 6. Therefore, the uniaxial stretching schemes of Scheme 6 (100℃-DR4.0) and Scheme 8 (100℃-DR8.0) were selected for hot pressing treatment, as detailed in Table 2 below.

[0098] Table 2: Mechanical properties of films formed at different hot-pressing temperatures

[0099]

[0100] As shown in Table 2, when the initial film formed by uniaxial stretching at 100℃-DR4.0 undergoes hot pressing, although the elongation at break increases significantly, the tensile strength does not improve significantly. However, when the initial film formed by uniaxial stretching at 100℃-DR8.0 undergoes hot pressing, both the tensile strength and elongation at break increase significantly. Therefore, the preferred uniaxial stretching method for the polyphenylene sulfide (PPS) sheet in this application is 100℃-DR8.0. Furthermore, within the hot pressing temperature range of 110~260℃, both the tensile strength and elongation at break of the initial film show a trend of first increasing and then decreasing with increasing temperature. Considering all factors, the preferred hot pressing temperature range is 140~230℃ to ensure that the tensile strength of the PPS film is ≥276.5MPa and the elongation at break is ≥44.3%.

[0101] To clarify the effect of stretching ratio on the properties of the molded film, this application also performed hot pressing treatment on the uniaxial stretching scheme of Scheme 10 (100℃-DR0), as shown in Table 3 below.

[0102] Table 3: Mechanical properties of films formed at different hot-pressing temperatures

[0103]

[0104] As shown in Table 3, when the initial film formed by uniaxial stretching at 100℃-DR0 is subjected to hot pressing, the elongation at break of the film increases significantly, while the tensile strength decreases significantly. This indicates that when the polyphenylene sulfide raw sheet is subjected to a combination of uniaxial stretching and hot pressing annealing under the aforementioned conditions, the uniaxial stretching and hot pressing annealing can work synergistically to effectively achieve simultaneous reinforcement and toughening of the polyphenylene sulfide film through the synergistic effect of the two-step process, giving the formed film excellent rigidity-toughness balance characteristics.

[0105] In summary, when the original polyphenylene sulfide (PPS) sheet is subjected to a combination of uniaxial stretching and hot-pressing annealing, this application can efficiently induce the orientation and crystallization of PPS molecular chains, significantly improve the integrity of the oriented nanocrystal structure, and construct a dense molecular chain network. This helps to enhance the transmission and dissipation of stress, resulting in a simultaneous improvement in the mechanical strength and toughness of the PPS film, and endowing the molded PPS film with excellent rigidity-toughness balance characteristics.

[0106] To further clarify the technical solution of this application, the following characterization tests are also provided.

[0107] 1. Wide-angle X-ray diffraction (WAXD) characterization

[0108] This application used wide-angle X-ray diffraction (WAXD) to test the internal crystal lattice information of PPS films subjected to different uniaxial stretching ratios (100℃) and hot-pressing temperatures. The results are as follows: Figure 1 As shown. Among them, Figure 1 The WAXD two-dimensional images of PPS films formed by different uniaxial stretching ratios (100℃) and hot pressing temperatures.

[0109] according to Figure 1 It can be seen that as the uniaxial stretching ratio gradually increases, the isotropic rings gradually transform into anisotropic arcs or even bright spots, indicating that oriented crystals are generated inside the initial PPS film formed by uniaxial stretching. At the same time, after the initial PPS film is hot-pressed and annealed, the orientation signal inside the PPS film is further enhanced, proving that the hot-pressing and annealing process is beneficial to the thickening of oriented lamellar crystals.

[0110] 2. Grain size characterization of PPS films

[0111] This application analyzes the grain size and crystal orientation of the (111 / 200) crystal plane of PPS thin film, and the results are as follows: Figures 2 to 3 As shown. Among them, Figure 2 The variation of PPS film internal grain size with uniaxial stretching-annealing combined treatment (casting refers to the original PPS sheet); Figure 3 This shows the change in the internal crystal orientation of PPS films with uniaxial stretching-annealing combined treatment.

[0112] according to Figure 2 It can be seen that the grain size of the original PPS sheet first increases slightly and then gradually decreases during uniaxial stretching, while the grain size gradually increases again during hot pressing and annealing.

[0113] according to Figure 3 It is known that the stretching process is beneficial to crystal orientation growth. In particular, the crystal orientation degree reached 0.354 after uniaxial stretching treatment at 100℃-DR8.0. After annealing treatment, the crystal orientation degree was found to be greatly improved and basically stabilized above 0.979. This indicates that the present application has successfully constructed highly oriented nanocrystals inside the molded PPS film by performing a combined treatment of uniaxial stretching and hot pressing annealing on low crystallinity polyphenylene sulfide raw sheet.

[0114] 3. Characterization of the crystallization properties of molded PPS films

[0115] This application performed DSC analysis on the PPS film, and the results were as follows: Figures 4 to 5 As shown. Among them, Figure 4 The DSC curves are obtained after uniaxial stretching at different magnifications. Figure 5 The DSC curves are those obtained after uniaxial tensile (100℃) and hot-press annealing combined treatment.

[0116] according to Figure 4 It can be seen that the uniaxial stretching process causes the cold crystallization peak to shift to a lower temperature and gradually disappear, and the melting point to shift to a higher temperature, proving that uniaxial stretching at 100℃ can induce the crystallization behavior of polyphenylene sulfide.

[0117] according to Figure 5 It can be seen that after uniaxial stretching (100℃) and hot pressing annealing, the crystallinity is further improved, forming a PPS film with high crystallinity content.

[0118] 4. Crystallinity test

[0119] This application quantitatively analyzes the crystallinity of initial PPS films formed under different uniaxial stretching ratios (100℃) and PPS films formed after uniaxial stretching-hot pressing annealing. The results are as follows: Figures 6 to 7 As shown. Among them, Figure 6 Crystallinity analysis diagram of initial PPS films formed under different uniaxial stretching ratios (100℃); Figure 7 This is a crystallinity analysis diagram of a PPS film formed by uniaxial stretching-hot pressing annealing.

[0120] according to Figure 6 It can be seen that the crystallinity of PPS raw sheets increases when subjected to uniaxial stretching treatment at different stretching ratios. In particular, when subjected to uniaxial stretching treatment at 100℃-DR8.0, the crystallinity increases from 14.3% to 44.6%.

[0121] according to Figure 7 It is known that when the raw PPS sheet undergoes uniaxial stretching-hot pressing annealing treatment, the crystallinity of the formed PPS film is further improved. In particular, after the combined treatment of uniaxial stretching (100℃-DR8.0)-hot pressing annealing, the crystallinity can be increased to a maximum of 52.0%.

[0122] 4. Orientation degree of amorphous molecular chains in PPS films

[0123] This application also characterized the changes in the amorphous molecular chain orientation of the molded PPS film with uniaxial stretching (100℃) and uniaxial stretching (100℃)-annealing combined treatment by polarized Raman spectroscopy. The results are as follows: Figures 6 to 7 As shown. Among them, Figure 8 The change in the amorphous molecular chain orientation of PPS raw sheets with uniaxial stretching (100℃) treatment; Figure 9 The curves show the changes of the initial PPS film after uniaxial stretching with hot pressing and annealing treatment.

[0124] according to Figure 8It can be seen that the amorphous molecular chain orientation degree of the PPS raw sheet increased from 0.029 to 0.782 during uniaxial stretching at 100℃.

[0125] according to Figure 9 It can be seen that the initial PPS film formed by uniaxial stretching underwent significant changes during hot pressing and annealing, especially at 200℃ where the molecular chain orientation was the greatest. This may be because low-temperature annealing cannot perfect the crystal, and the molecular chain relaxes under the action of the thermal field. Although high temperature can perfect the crystal, the thermal motion of the molecular chain is too intense, and relaxation also occurs.

[0126] 5. Optical transparency of PPS film

[0127] This application tested the optical transparency of initial PPS films formed by uniaxial stretching at different stretch ratios (100°C) and PPS films formed by a combination of uniaxial stretching and hot pressing annealing. The results are as follows: Figures 10 to 11 As shown. Among them, Figure 10 Optical transparency of initial PPS films formed under different uniaxial stretching ratios; Figure 11 The optical transparency of PPS films formed by uniaxial stretching-hot pressing annealing combined treatment.

[0128] according to Figure 10 It can be seen that the transparency of the original PPS sheet is 80.1%, and the optical transparency of the film has a slow upward trend as the uniaxial stretching ratio increases. When the uniaxial stretching ratio is 8.0, the maximum transparency of 84.2% is reached.

[0129] according to Figure 11 It can be seen that the initial PPS film can maintain good transparency after being treated at different annealing temperatures, while the transparency of the original PPS sheet first decreases and then increases with the annealing temperature, which is related to the fact that its internal crystals are first perfected and then partially melted.

[0130] To more intuitively observe the changes in transparency between annealed samples, this application presents digital photographs of initial PPS film samples formed by uniaxial stretching at 100℃-DR0 and 100℃-DR8.0, as well as PPS film samples formed by combined uniaxial stretching (100℃-DR0 / 100℃-DR8.0) and hot pressing annealing (200℃). The results are shown below. Figures 12 to 13 As shown. Among them, Figure 12 Digital photographs of initial PPS film samples formed by uniaxial stretching at 100℃-DR0 and 100℃-DR8.0, respectively. Figure 13Digital photographs of PPS film samples formed by a combination of uniaxial stretching (100℃-DR0)-hot pressing annealing (200℃) and uniaxial stretching (100℃-DR8.0)-hot pressing annealing (200℃).

[0131] according to Figures 12 to 13 It can be seen that the transparency of PPS film formed by the combined treatment of uniaxial stretching (100℃-DR0)-hot pressing annealing (200℃) is significantly reduced, and it appears white and opaque. However, the PPS film formed by the combined treatment of uniaxial stretching (100℃-DR8.0)-hot pressing annealing (200℃) still maintains good transparency. This may be because the highly oriented nanocrystals suppress the relaxation of amorphous molecular chains at high temperatures, and their smaller size reduces the light scattering effect of polyphenylene sulfide molecular chains.

[0132] 6. Heat resistance test

[0133] The heat resistance of the PPS film manufactured in this application was tested, and the results were as follows: Figures 14 to 15 As shown. Among them, Figure 14 The storage modulus of PPS films formed after different treatments varies with temperature. Figure 15 The heat resistance temperature is determined by the different treatment processes used to form the product.

[0134] according to Figure 14 It can be seen that the PPS film formed by the combined treatment of uniaxial stretching (100℃-DR8.0) and hot pressing annealing (200℃) has the largest initial storage modulus, which may be due to its perfect crystal structure. At the same time, it can be found that the temperature at which the storage modulus begins to decrease during the heating process is the highest, indicating that the sample has high heat resistance.

[0135] according to Figure 15 It can be seen that when the raw PPS sheet undergoes uniaxial stretching (100℃-DR0), the initial heat resistance temperature of the PPS film is 91.8℃. After a combined hot-pressing annealing treatment at 200℃, the heat resistance temperature of the PPS film increases to 93.8%, an increase of only 2.18%. However, when the raw PPS sheet undergoes uniaxial stretching (100℃-DR8.0), the initial heat resistance temperature of the PPS film is 96.4℃. After a combined hot-pressing annealing treatment at 200℃, the heat resistance temperature of the PPS film increases to 119.5%, an increase of 23.96%. This demonstrates that this application also possesses superior and advanced characteristics in improving the heat resistance of the sample.

[0136] The various embodiments in this application are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0137] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A highly transparent polyphenylene sulfide film with a balanced rigidity and toughness, characterized in that, The polyphenylene sulfide substrate comprises a polyphenylene sulfide raw sheet formed by sequential uniaxial stretching and hot-press annealing, the polyphenylene sulfide substrate having the following characteristics: (a) Crystallinity ≥ 46.0%; (b) Grain orientation ≥ 0.979; (c) Mechanical strength ≥ 276.5 MPa; (b) Elongation at break ≥ 44.3%; (e) Transmittance > 82.7%.

2. The high-transparency polyphenylene sulfide film according to claim 1, characterized in that, The polyphenylene sulfide substrate has the following characteristics: (a) Crystallinity is 46.0–51.8%; (b) Grain orientation is 0.986–0.989; (c) Mechanical strength is 276.5 MPa to 383.8 MPa; (b) Elongation at break: 44.3%–55.9%; and, (e) Light transmittance > 82.7%.

3. The high-transparency polyphenylene sulfide film according to claim 2, characterized in that, The uniaxial stretching temperature is 100℃, and the stretching ratio is 8.

0.

4. The highly transparent polyphenylene sulfide film according to claim 3, characterized in that, The hot pressing annealing is performed at a pressure of 3 MPa, a temperature of 140~230℃, and a time of 15 min.

5. The high-transparency polyphenylene sulfide film according to claim 1, characterized in that, The thickness of the polyphenylene sulfide substrate is 0.1 mm to 0.2 mm.

6. A method for manufacturing a highly transparent polyphenylene sulfide film with a balance of rigidity and toughness as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Polyphenylene sulfide resin is melt-extruded by a single screw extruder and then cooled to obtain polyphenylene sulfide raw sheet material; After the polyphenylene sulfide sheet is uniaxially stretched and cooled, an initial polyphenylene sulfide film is obtained. The initial polyphenylene sulfide film is subjected to hot pressing annealing to obtain the highly transparent polyphenylene sulfide film with a balance of rigidity and toughness.

7. The manufacturing method according to claim 5, characterized in that, The melt index of the polyphenylene sulfide resin is 20~200g / 10min.

8. The manufacturing method according to claim 5, characterized in that, The extrusion temperature of the single-screw melt extrusion is 280~350℃, and the screw speed is 20~100r / min.

9. The manufacturing method according to claim 5, characterized in that, The thickness of the original polyphenylene sulfide sheet is 0.9 mm to 1 mm, and the grain orientation degree is 0.

011.

10. The highly transparent polyphenylene sulfide film with a balance of rigidity and toughness as described in any one of claims 1 to 3 is used in the fields of flexible electronics, biomedicine, smart wearables, and aerospace.

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