A toughening method for naphthalene-biphenyl polyetherketone resin

Abstract

This invention discloses a toughening method for naphthalene-biphenyl polyetherketone resin, belonging to the field of composite material technology, comprising the following steps: vacuum drying of naphthalene-biphenyl polyetherketone resin, polyetherimide resin, and nano-silica; mixing nano-silica with polyetherimide resin to obtain a composite powder; feeding the composite powder and naphthalene-biphenyl polyetherketone resin into a twin-screw extruder for melt blending, wherein the temperatures of the first, second, and third zones and the die head of the twin-screw extruder increase in a stepped manner, and the twin-screw extruder outputs granulated blended material; using injection molding to prepare a hydrogen storage bottle liner from the blended material; this application, by introducing a polyetherimide toughening phase and utilizing nano-silica for interface control, constructs a ternary synergistic structure of naphthalene-biphenyl polyetherketone continuous phase-polyetherimide toughening phase-nano-silica interface layer, thereby improving the material's plastic deformation capacity and interfacial bonding capacity, achieving high toughness.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and specifically relates to a toughening method for naphthalene-biphenyl polyetherketone resin. Background Technology

[0002] With the rapid development of the hydrogen energy industry, high-pressure hydrogen storage technology has become an important research direction in the fields of fuel cell vehicles and hydrogen energy equipment. Among them, the 70MPa high-pressure Type IV hydrogen storage cylinder has become the mainstream development direction of on-board hydrogen storage systems due to its characteristics of light weight, high hydrogen storage efficiency, and excellent safety performance. Type IV hydrogen storage cylinders typically consist of a polymer inner liner and an outer carbon fiber reinforced winding layer. The polymer inner liner not only serves to isolate the hydrogen storage medium but also needs to ensure structural stability under long-term high-pressure cycling conditions; therefore, its performance directly affects the service life and safety of the hydrogen storage cylinder.

[0003] Currently, the main materials used for the inner liner of hydrogen storage cylinders are high-density polyethylene (HDPE), polyamide (PA), and some modified thermoplastic materials. However, these materials still have the following problems: (1) It has limited gas barrier properties and is prone to hydrogen permeation under high-pressure hydrogen environment; (2) Creep and fatigue failure are prone to occur under long-term high-pressure cycling conditions; (3) It has low high-temperature resistance and is difficult to adapt to complex service environments; (4) Insufficient dimensional stability and long-term reliability.

[0004] Polyetherketone (PPEK) resin, a high-performance aromatic engineering plastic, possesses excellent heat resistance, mechanical properties, chemical corrosion resistance, and gas barrier properties. Its molecular backbone contains rigid aromatic rings, ketone groups, and naphthalene-biphenyl structures, resulting in a tightly packed molecular chain, low free volume, and high glass transition temperature, making it a potential candidate for hydrogen storage. Compared to traditional polyethylene materials, PPEK exhibits higher modulus, lower gas permeability, and superior heat resistance, showing promising application prospects in high-pressure hydrogen storage cylinder liners, valve sealing components, and barrier layer materials.

[0005] However, due to the high rigidity of PPEK molecular chains, high glass transition temperature, and limited chain segment mobility, the material's plastic deformation capacity is insufficient. During high-pressure cyclic hydrogen charging and discharging, stress concentration is easily generated, leading to local cracking and brittle failure of the inner liner, thus limiting its further application in the field of hydrogen storage cylinder inner liners.

[0006] Existing toughening methods for high-performance polyketone resins mainly include rubber elastomer toughening and thermoplastic resin blending. However, traditional rubber systems have insufficient heat resistance and are difficult to apply to PPEK high-temperature processing systems. On the other hand, simple resin blending has problems such as insufficient interfacial compatibility and limited toughening efficiency. Summary of the Invention

[0007] To address the problems mentioned in the background art, the present invention provides a toughening method for naphthalene-biphenyl polyetherketone resin, which solves the problems of insufficient heat resistance of traditional rubber systems, making them unsuitable for high-temperature processing systems of PPEK; and the problems of insufficient interfacial compatibility and limited toughening efficiency of simple resin blending.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A toughening method for naphthalene-biphenyl polyetherketone resin includes the following steps: S1: Vacuum drying treatment of naphthalene-biphenyl polyetherketone resin, polyetherimide resin and nano silica; S2: Nano-silica is added to polyetherimide resin and mixed to obtain composite powder; S3: The composite powder and naphthalene-biphenyl polyetherketone resin are fed into a twin-screw extruder for melt blending. The temperature of the first, second, and third zones of the twin-screw extruder, as well as the die head, increases in a stepwise manner. The twin-screw extruder outputs the granulated blend. S4: Use injection molding process to prepare the inner liner of hydrogen storage cylinders from the blended materials.

[0009] The beneficial effects of this application are: This invention introduces a polyetherimide (PEI) toughening phase and utilizes nano-silica (SiO2) for interface regulation to construct a ternary synergistic structure: PPEK continuous phase—PEI toughening phase—nano-SiO2 interface layer, thereby improving the material's plastic deformation capacity and interfacial bonding ability, and achieving high toughness of PPEK resin. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the PEI / SiO2 pre-dispersion structure. Detailed Implementation

[0011] To facilitate understanding of the technical content of this invention by those skilled in the art, the invention will be further described in detail below with reference to the accompanying drawings and specific examples. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the scope of the invention.

[0012] Raw material composition description: The raw materials used in this embodiment include: PPEK resin: 80–95 wt%; Polyetherimide (PEI): 5–20 wt% Nano-silica (SiO2): 0.1–5 wt% The particle size of nano-SiO2 is controlled to be 10–80 nm; PEI uses high-temperature resistant polyetherimide resin, with a glass transition temperature higher than 200℃ and a processing window similar to PPEK.

[0013] A toughening method for naphthalene-biphenyl polyetherketone resin includes the following steps: S1: Raw material pretreatment; Since both PPEK and PEI are high-temperature engineering plastics, they are quite sensitive to moisture. Therefore, drying treatment is required before processing. Details are as follows: PPEK resin: Vacuum dry at 150℃ for 8–12 hours; PEI resin: Vacuum dry at 150℃ for 8–12 hours; Nano-SiO2: Vacuum dried at 120℃ for 4 hours.

[0014] S2: PEI / SiO2 pre-dispersion, the specific steps are as follows: Nano-SiO2 was added to PEI, with the nano-SiO2 accounting for 1–20 wt% of PEI. Mixing was performed using a high-speed mixer at 1000–3000 rpm for 5–20 min to obtain PEI / SiO2 composite powder. During processing, the polar groups of PEI formed an interface with the hydroxyl groups on the SiO2 surface, and the nano-SiO2 preferentially migrated to the PPEK / PEI interface region, thereby inhibiting PEI agglomeration and refining the size of the second phase. The PEI / SiO2 pre-dispersion process is as follows: Figure 1 As shown.

[0015] S3: Melt-co-linked toughening; A Coperion ZSK 26 Mc18 high-temperature co-rotating parallel twin-screw extruder was used to melt-blend the composite powder and polyetherketone (PEI) resin. The temperature settings were as follows: Zone 1: 350℃; Zone 2: 355℃; Zone 3: 360℃; Die head: 365–370℃. Screw speed: 50–150 rpm. Under high-temperature shearing, PEI gradually formed a tough dispersed phase; nano-SiO2 migrated to the two-phase interface; ultimately constructing a stable interface layer. S4: Injection molding; The blended material is granulated by twin-screw extrusion and then directly used to prepare the inner liner of the hydrogen storage bottle via injection molding. The inner liner of the hydrogen storage bottle is preferably manufactured using an integrated injection molding process, and the injection molding equipment is preferably a high-temperature resistant engineering plastic injection molding machine, specifically an ARBURG ALLROUNDER 470 H high-temperature engineering plastic injection molding machine. The injection molding process parameters are as follows: The temperature of the first zone of the barrel is 350℃, the temperature of the second zone of the barrel is 355℃, the temperature of the third zone of the barrel is 360℃, and the nozzle temperature is 365–370℃; the mold temperature is controlled at 150–200℃, preferably 180℃; the injection pressure is 80–150MPa, preferably 100MPa; the holding time is 10–30s, preferably 20s; and the cooling time is 30–90s, preferably 60s.

[0016] By controlling melt flow behavior and cooling rate, residual stress inside the product is reduced, improving the dimensional stability and long-term cycling reliability of the inner liner. A PPEK composite hydrogen storage cylinder inner liner is ultimately obtained. One end of the inner liner comprises a bottle neck connection area, a cylindrical hydrogen storage area, and a bottom transition area, with the cylindrical hydrogen storage area serving as the main hydrogen storage region. The bottom transition area employs a rounded corner transition structure to reduce stress concentration during high-pressure cycling. The bottle neck area is equipped with a connection structure for valve assembly, such as a threaded interface. The resulting PPEK hydrogen storage cylinder inner liner exhibits high gas barrier performance, excellent heat resistance, good dimensional stability, and fatigue resistance, making it suitable for use in high-pressure hydrogen storage systems.

[0017] This application employs a synergistic toughening system for PPEK using polyetherimide (PEI) and nano-silica (SiO2). Traditional PPEK toughening primarily utilizes rubber systems such as SEBS, TPU, and EPDM, achieving toughening by introducing a soft phase to absorb impact energy. However, the processing temperatures of these rubber materials are typically below 300℃, making it difficult to meet the high-temperature processing requirements of PPEK resin (340–380℃). Furthermore, the introduction of the soft phase can easily reduce the material's heat resistance and dimensional stability. This application uses PEI to replace the traditional rubber system, leveraging the similar processing window and higher glass transition temperature of PEI and PPEK. This ensures the system's heat resistance while simultaneously constructing a toughening dispersed phase, improving the material's plastic deformation capacity and achieving synergistic toughening at high temperatures.

[0018] This application also employs a PEI / SiO2 pre-dispersion process to achieve interface control. Traditional nano-SiO2 is typically added directly; however, due to the high surface energy of nanoparticles, they are prone to agglomeration during melt blending, forming localized defect regions. This leads to decreased interfacial bonding, increased stress concentration, and reduced toughening efficiency. This application first pre-mixes nano-SiO2 with PEI at high speed to prepare a PEI / SiO2 composite powder, which is then melt-blended with PPEK. This method enables nano-SiO2 to preferentially migrate to the PPEK / PEI interface region, improving interfacial bonding while inhibiting PEI agglomeration and refining the second-phase size, thus differing from the traditional direct nanoparticle addition method.

[0019] This application further constructs a ternary synergistic structure of "PPEK continuous phase – PEI toughening phase – SiO2 interface layer" through interface regulation. Traditional resin blends typically form simple two-phase structures, which are prone to problems such as large second-phase size, insufficient interfacial bonding, and crack propagation along the interface. In this application, PEI exists as a toughening dispersed phase, and nano-SiO2 preferentially accumulates in the two-phase interface region to form an interface stabilizing layer, achieving interface enhancement and phase structure refinement. The PEI phase size is preferably controlled within the range of 0.5–2 μm, which is significantly different from the traditional coarse phase separation structure, thereby improving the toughness and fatigue resistance of the system.

[0020] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for toughening naphthalene-biphenyl polyetherketone resin, characterized in that, Includes the following steps: S1: Vacuum drying treatment of naphthalene-biphenyl polyetherketone resin, polyetherimide resin and nano silica; S2: Nano-silica is added to polyetherimide resin and mixed to obtain composite powder; S3: The composite powder and naphthalene-biphenyl polyetherketone resin are fed into a twin-screw extruder for melt blending. The temperature of the first, second, and third zones of the twin-screw extruder, as well as the die head, increases in a stepwise manner. The twin-screw extruder outputs the granulated blend. S4: Use injection molding process to prepare the inner liner of hydrogen storage cylinders from the blended materials.

2. The toughening method for a naphthalene-biphenyl polyetherketone resin according to claim 1, characterized in that, In S1, both the naphthalene-biphenyl polyetherketone resin and the polyetherimide resin were vacuum dried at 150°C for 8-12 hours, and the nano-silica was vacuum dried at 120°C for 4 hours.

3. The toughening method for a naphthalene-biphenyl polyetherketone resin according to claim 1, characterized in that, The particle size of nano-silica is 10-80 nm.

4. The toughening method for a naphthalene-biphenyl polyetherketone resin according to claim 1, characterized in that, In S2, nano-silica accounts for 1-20 wt% of the mass of polyetherimide resin.

5. The toughening method for a naphthalene-biphenyl polyetherketone resin according to claim 1, characterized in that, In S2, the mixed operation is specifically as follows: Mixing is performed using a mixer at a speed of 1000-3000 rpm for 5-20 minutes.

6. The toughening method for a naphthalene-biphenyl polyetherketone resin according to claim 1, characterized in that, In S3, the temperatures of the first, second, and third zones of the twin-screw extruder, as well as the die head, are set to 350℃, 355℃, 360℃, and 365-370℃, respectively.

7. The toughening method for a naphthalene-biphenyl polyetherketone resin according to claim 6, characterized in that, The screw speed of the twin-screw extruder is set to 50-150 rpm.

8. The toughening method for a naphthalene-biphenyl polyetherketone resin according to claim 1, characterized in that, In S4, the injection molding equipment used in the injection molding process is an engineering plastic injection molding machine, and the temperature of the first zone of the barrel, the second zone of the barrel, the third zone of the barrel, and the nozzle temperature of the engineering plastic injection molding machine increase in a stepwise manner.

9. The toughening method for a naphthalene-biphenyl polyetherketone resin according to claim 8, characterized in that, The barrel temperature of the engineering plastic injection molding machine is 350℃ in zone 1, 355℃ in zone 2, 360℃ in zone 3, and 365–370℃ in nozzle.

10. The toughening method for a naphthalene-biphenyl polyetherketone resin according to claim 9, characterized in that, During the injection molding process, the mold temperature is controlled at 150-200℃; the injection pressure is 80-150MPa; the holding time is 10-30s; and the cooling time is 30-90s.

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